Leonardo Times January 2015

JANUARY 2015

Leonardo Times Journal of the Society of Aerospace Engineering Students ‘Leonardo da Vinci’

page 28

DARE

number 1

Stratos II, The story behind the rocket

Indian Aerospace Industry: An overview The story of rise of Indian aerospace industry

AIAA Aircraft design competition

Year 19

TU DELFT is the winner

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Visit klm.com/economycomfort for more information.

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Contents Table of contents

Highlights

04

Editorial

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From Leonardo’s desk

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Current affairs

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Safety at Sea - To drone or not to drone

How students designed, manufactured and almost launched a rocket to 50 km

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Wind Tunnel testing on a Hypersonic UAV

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RVD - The Orion Spacecraft

In October 2014, the first launch campaign of Stratos II took place in Spain. Even though the rocket misfired and finally failed to lift off, the campaign was considered a success, technological and operationally.

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UAV’s bringing the world closer together

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Indian Aerospace Industry: An overview

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Pipeline buckle arrestor assessment

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Load transfer around broken fibers

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Internship – Australian Lightwing Aircraft

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We Vlogen met een zucht – Waiting for a

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Design framework for high-lift systems

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Composite grid stiffened structures

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LVD - Interview Airbus A350

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Forensic engineer for a day

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Energy harvesting composites

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Column - Flying Asian style

SEBASTIAAN VAN SCHIE

AIAA Aircraft design competition

AIAA Aircraft design competition

TU DELFT is the winner In September 2014, the American Institute of Aeronautics and Astronautics (AIAA) announced the results of aircraft design competition for both undergraduate and graduate levels. TU Delft participated in both the competitions simultaneously for the first time and won!

Energy harvesting composites

AIRLINERS.NET

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36

Valhalla Study Tour

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33

ISRO

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The aerospace industry is slowly gravitating towards the east and sees India as a potential aerospace hub for the future. What are the accomplishments of the Indian aerospace industry so far? How does the future hold for the Indian aerospace industry?

DARE: Stratos II, The story behind the rocket

Indian Aerospace Industry: An overview

The story of rise of Indian aerospace industry

new revolution 28

DARE: Stratos II, The story behind the rocket

DARE

Contents

28

03

Advertisement index 02

KLM

26

De Delftse Bedrijvendagen

39

EPO

51

NLR

52

Fokker

Exploring piezoelectric composites for direct strain energy harvesting Piezoelectric energy harvesting is a quickly developing research area offering tremendous opportunities for the aerospace industry. The NovAM group investigates the fundamental behavior of piezoelectric materials and explores novel routes to improve their performance focusing on typical aerospace operational conditions.

JANUARY 2015 Leonardo Times

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Editor’s letter Dear reader, Welcome to the first edition of the year 2015. The team at Leonardo Times wishes you a happy new year.

There has been a slight change in the naming of the Leonardo Times editions from this quarter onwards. The Leonardo Times will be published now in January, April, July and October. So, the journal will now be published in the first month of every quarter.

A new editorial team has taken over the mantle of scouting for the latest research and happenings in Aerospace Engineering in Delft and beyond. The LT welcomes our new team members: Anita, Apeksha, Haider, Manfred, Martina, Victor, Vishal and Thom to the Leonardo Times team 2014-15. I see that we have a good mix of new enthusiastic editors and experienced team members from previous years who will be pooling efforts to bring out the best of news and articles in the field of Aerospace Engineering. The Leonardo Times team is planning to increase the web presence of the journal and make some improvements to the presentation style. Hopefully, these will be carried out very soon.

manufactured by students from DARE (Delft Aerospace Rocket Engineering). Stratos II rocket aims to reach an altitude of 50km and carry scientific payload. The Stratos II rocket is a 7-meter long single stage hybrid rocket. In October 2014, the team attempted to launch the rocket in Spain. However, a frozen valve caused a misfire and the rocket did not take off. The team is currently evaluating and improving the old design, which will result in the Stratos II+, and is planned to launch in the summer of 2015. In spite of the launch issues, the students consider the project a success and rightly so. The article features the story behind the project and interview with its two team managers.

We also feature an overview of the Indian Aerospace industry including its history and the outlook for future in light of changes in government policies. As promised in the last edition, a detailed look in to the AIAA aircraft design competition is included in this January edition of the Leonardo Times. TU Delft students competed in both graduate and undergraduate categories and came out on top.

Find the details of their designs from page 36 onwards.

Apart from the aforementioned articles, there are many interesting articles showcasing the top quality research being carried out by students and staff of Aerospace Engineering faculty of the TU Delft.

Sushant Gupta

DARE

The cover article for this issue of the Leonardo Times features Stratos II rocket designed and

Colophon Year Nineteen, number 1, January 2015 The ‘Leonardo Times’ is issued by the Society for Aerospace Engineering students, the VSV ‘Leonardo da Vinci’ at the Delft University of Technology. The magazine is circulated 4 times a year with a circulation of 5500 copies.

EDITOR-IN-CHIEF: Sushant Gupta FINAL EDITOR: Raphael Klein EDITORIAL STAFF: Anita Mohil, Apeksha Amarnath, Bob Roos, Haider Hussain, Joris Stolwijk, Raphael Klein, Manfred Josefsson, Martina Stavreva, Victor Gutgesell, Vishal Balakumar, Thom van Ostaijen.

THE FOLLOWING PEOPLE CONTRIBUTED: Sjoerd van Rooijen, Tommaso Mannucci, Alexandre Campino, Thijs Gritter, Konstantin Rangelov, Svilen Rangelov, Akshay Raju Kulkarni, Pradeep Pandurangi, Liang Zhang, Jack Kha-Han Tai, Jakob van den Broeke, Rob Hermsen, Tobias Knop, Lubi Spranger, Prithvi Sai, Sebastiaan van Schie, Malcom Brown, David Zaccai, Sonell Shroff, Karel Dhoore, Meander Leukfeldt Michiel Schuurman, Shahrzad Hosseini and Frederik Van Loock.

COVER IMAGE: DARE DESIGN, LAY-OUT: dafdesign, Amsterdam PRINT: Quantes Grafimedia, Rijswijk Articles sent for publishing become property of ‘Leonardo Times’. No part of this publication may be reproduced by any means without written permission of the publisher. ‘Leonardo Times’ disclaims all responsibilities to return articles and pictures. Articles endorsed by name are not necessarily endorsed editorially. By sending in an article and/ or photograph, the author is assured of being the owner of the copyright.

‘Leonardo Times’ disclaims all responsibility. The ‘Leonardo Times’ is distributed among all students, alumni and employees of the Aerospace Engineering faculty.

VSV ‘Leonardo da Vinci’ Kluyverweg 1, 2629HS Delft Phone: 015-278 32 22 Email: VSV@tudelft.nl ISSN (PRINT) : 2352-7021 ISSN (ONLINE): 2352- 703X For more information, the website can be visited at www.vsv.tudelft.nl. At this website, the ‘Leonardo Times’ can also be digitally viewed. Remarks, questions and/or suggestions can be emailed to the following address: LeoTimes-VSV@student.tudelft.nl

DARE Stratos II team

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From Leonardo’s Desk

Dear readers, 12 November 2014, Philae slowly approaches comet 67P/Churyumov-Gerasimenko. All over the world tension starts rising on whether this mission that was launched over ten years ago will succeed in creating yet another great part of space history. As you are reading this, Philae – as well as the 70th board of the VSV – has successfully touched down and is up and running. As Rosetta was the first satellite to ever orbit a comet, it is our first time as a board to run such an incredible and diverse society. The society has never been larger with more than 200 active members contributing to the society currently. This year, our 27 committees are fully prepared to organize everything that the VSV stands for.

Next to that, the VSV ‘Leonardo da Vinci’ celebrates its 70th year this year, which means that the 14th lustrum of our association will be celebrated. The lustrum was officially opened on December 12 in the city hall of Delft during an Extraordinary General Members Assembly. After a spectacular entrance from an eight-meter high platform and fly-bys by Martinair, NLR and the TU Delft, two novel Members of Honour – Michel Peters and Martin Schröder – were installed during the assembly. This was a great addition to the extraordinary group of Members of Honour of the VSV ‘Leonardo da Vinci’.

For the larger audience, a successful beer cantus was organized, for both aerospace and other Delft students, which announced that a lustrum of the VSV ‘Leonardo da Vinci’ couldn’t go unnoticed. Next to a ski trip in February, the entire month of May will be marked by unique lustrum events. A few days after the opening stunt on the first of May an eight-meter high ramp will be built on which our students and staff will be able to test their true engineering skills to see who can fly the furthest. The weekend after, our members take off again. This time however, not in simple home-built aircraft off a ramp, but in small general aviation aircraft from a very special airfield in the Netherlands.

Here, students will experience what it is like to actually fly an aircraft as opposed to just designing them. Finally, the month will be concluded with a luxurious gala at an extraordinary location, where the 71st board will be announced.

Before this exciting lustrum month takes place, we will be focused on the 3rd of March 2015. On this day, the Aviation Department has arranged a symposium considering all milestones in the life of an aircraft. While main subjects as conceptual design, operations and end-of-life solutions will be discussed; recent events in aviation will be covered as well. All together, it definitely is an interesting and inspiring day to look forward to.

Next to yearly events such as Airbase, the Belgian Beer Drink, the freshmen weekend and all the lectures and the excursions organized by the different departments, there is one upcoming event that cannot be left unmentioned. On 29 August 2015 the VSV ‘Leonardo da Vinci’ and Breda International Airport will cooperatively organize yet another Airshow. This edition will feature innovation in Dutch aviation. While highlighting 95 years of Dutch pioneering, we will take a glance at what the future holds.

Last October, we said farewell to a very characteristic three-engined aircraft: the MD-11, by many people considered as a beautiful aircraft that brings up great memories. This is exactly what we are seeking to achieve; a year for which everybody involved can be proud of, an exciting year to look forward to, but most of all, a year that brings up great memories and stories when thought back on.

All in all, make sure to keep an eye on the upcoming planned events and be prepared for some unexpected surprises.

With winged regards, Sjoerd van Rooijen President of the 70th board of the VSV ‘Leonardo da Vinci’

January 2015 Leonardo Times

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Current Affairs

A380 FUTUre UncerTAin

December 10, 2014, London, UK

deMAnd FOr F-16 TO reMAin sTrOng UsAF

BriTish AirwAYs

December 17, 2014

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irbus CFO Harland Wilhelm hinted at a potentially discontinuing the manufacture of A380s. This came to light when he revealed that Airbus might not break even in 2018 unless it offers more efficient engines for the aircraft, to make it an attractive sell. The forecasted orders for the aircraft, that cost $25 billion to develop, are not adding up since airlines are backing off. “It’s an excellent plane but it only works for the right destinations”, said Alexandre de juniac, CEO of Air France-KLM. The A380’s current standout sponsor Emirates’ President Tim Clark is pushing for Airbus to upgrade their engines rather than discontinue the aircraft entirely. In light of these developments, Airbus CEO Fabrice Bregier has confirmed plans for an A380-900 with a stretched fuselage and an A380neo. The A380neo, in which ‘neo’ stands for ‘new engine option’, will have high efficiency engines and refined aerodynamics. (H.H.)

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orty years after the first flight of the F-16 prototype, the Air Forces worldwide are increasingly counting on the F-35 to replace the planes they’re flying today. However, with F-35 being seven years behind schedule and $163 billion over budget, the Lockheed Martin F-16 Fighting Falcon is currently enjoying an unexpected renaissance. For instance, the Netherlands’ plans to buy 85 of the F-35 fighters are under review, with officials saying they may cut as many as 33 from their purchase. In the meantime, the U.S. has recently decided to cut plans for F-35 production for the upcoming 5 years by 17 aircraft. As a result, the average age of currently operated military aircraft is increasing and the machines are becoming increasingly expensive to maintain and operate. (H.H.) FL Technics Engineering

AIN Online

AirpOrT drOne cOLLisiOn risk wArning

BOeing gOes sUsTAinABLe wiTh ‘green dieseL’ BOeing

www.TesTed.cOM

December 8, 2014, London, UK

December 3, 2014, Washington, USA

oeing has completed the world’s first flight using “green diesel,” a sustainable biofuel that is widely available and used in ground transportation. The company powered its ecoDemonstrator 787 flight test airplane on December 2, 2014, with a blend of 15 percent green diesel and 85 percent petroleum jet fuel in the left engine. Sustainable green diesel is made from vegetable oils, waste cooking oil and waste animal fats. On a lifecycle basis, sustainably produced green diesel reduces carbon emissions by 50 to 90 percent compared to fossil fuel, according to Finland-based Neste Oil, which supplied green diesel for the ecoDemonstrator 787. (H.H.)

landing airliner and a drone came close to colliding at London Heathrow Airport, according to data now published the CAA (Civil Aviation Authority). It has not been confirmed which airliner operated the aircraft, nor exactly how narrow the distance between the objects concerned was, but the aircraft involved has been identified as an Airbus A320 airliner. Current legislation limits UK drone flights to a maximum altitude of 400 feet, at no more than 500 meters range from the operator. 50-meter exclusion zones exist around structures, vehicles and people, while flights encroaching on airport approach paths are severely restricted. “People using unmanned aircraft need to think, use common sense and take responsibility for them”, said a CAA representative. (H.H.)

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Airport International

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Current Affairs

Orion Flight Test

Galileo: Doresa Back on Track

December 9, 2014

ESA

NASA

December 5, 2014, Cape Canaveral, USA

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ASA has conducted its first Orion flight test. The unmanned capsule was brought to orbit by a Delta IV Heavy and stayed there for four hours. After two circulations around the Earth, the capsule started re-entering Earth’s atmosphere. It came down in the Pacific ocean and has successfully been recovered by the USS Anchorage. The data of this flight test will be used to modify the Orion for manned missions. The Orion capsules have been designed to bring astronauts to space and eventually to Mars. In 2021 NASA has planned its first manned mission in an Orion capsule and for 2023 a manned mission to an asteriod is planned. Orion is the US’ re-entry in manned space flight after the end of the Space Shuttle program in 2011. (V.G.) NASA

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oresa, one of the two Galileo satellites, which have been delivered into a wrong orbit, has started transmitting navigational data. After the partial success of the VS09 mission, the satellite was brought to a suitable orbit for navigation. With eleven maneuvers, the satellite is now on its new target trajectory, from an elliptical orbit to a more circular orbit. Its navigational payload has been turned on and first signals have been received. Circling the Earth on higher altitude, the periodical time of the satellite has changed to twenty days instead of ten days. By switching on its navigational payload, ESA can now finally begin their full “In-Orbit Test” campaign. (V.G.) ESA

Ariane 6 Approved and Unveiled

Another wake up: New Horizons

December 7, 2014

NASA

ESA

December 2, 2014, Luxembourg

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SA has unveiled the Ariane 6 (A6). A6 will be a 3-staged rocket with optionally two (A62) or four (A64) boosters.

With 63 meters of length, the A6 is about 15 meters taller than its predecessor. The payload capabilities of A6 will be similar to the capabilities of Ariane 5. However A6 aims to significantly reduce the costs to bring a satellite to space. With the approval of the completion by the Council at Ministerial Level, the first launch has been planned for 2020. On the ESA website you can now find an animation of the A6. (V.G.) ESA

et another probe has woken up from its sleep. New Horizons, a NASA probe, was sent to study Pluto, its moons and two objects in the Kuiper Belt. Since its launch in January 2006, the probe has travelled roughly 4.7 billion kilometers, flown by Jupiter and passed Uranus’ and Neptune’s orbits.

After the Voyager and Pioneer probes, New Horizons is the furthest spacecraft sent by man. The probe itself is one of the few spacecraft powered by a thermonuclear generator.

In February 2015 it will pick-up its obeservation of Pluto and in July 2015 its Pluto flyby is scheduled. Even though the mission is meant to end in 2026, scentists hope for its functionallity to last until 2038, when it will have reached the outskirts of the heliosphere, in order to study and explore it. (V.G.) NASA

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University of Southampton

Safety at sea: to drone or not to drone?

Unmanned operations in maritime environment Unmanned flight technology has developed greatly in recent years, possibly representing an alternative to traditional platforms for surveillance, patrol and reconnaissance missions. The 2seas – 3i project explores this option from an operational point of view in a maritime environment. A multipurpose, high endurance UAV platform with tailored sensors and a dedicated control interface was developed by a joint partnership of academia, industry and maritime authorities.

TEXT Tommaso Mannucci, PhD Candidate, Control & Operations

Situational awareness is, broadly speaking, the cornerstone for tasks where timely and efficient reactions are of primary importance. Law enforcers, lifeguards and firefighters heavily depend on reliable and quick delivery of information in order to be effective. Where safety is not a main element, monetary motivations may be an equally driving factor. Inspection, monitoring and safety assessment is a significant expenditure in both money and time for a number of different companies and organizations. Needless to say, an aerial point of view often offers the best in terms of delivering a comprehensive and fast situational awareness, especially in those environments where other means of performing such a task involve either a very specialized platform, or very long completion times. The fact that helicopters are a common choice in the aforementioned situations is, therefore, not surprising. But recent innovations in the ever-growing field of unmanned flight open up new and appealing scenarios. Whereas a helicopter is a complex and expensive platform, in need of costly and time consuming maintenance, requiring an expert and trained crew with a significant setup time, UAVs and RPAS offer an affordable and signifi-

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cantly simpler alternative for a number of operations. In addition, sparing human presence on the field opens up to a new range of missions where safety of the crew constitutes a major constraint.

The 3i project (standing for Integrate coastal zone management via Increased situational awareness through Innovations on unmanned aircraft systems) takes these considerations to a turning point, investigating the ground for UAV expansion in the field, assessing available technology and expanding knowledge on the key development fields. The choice of coastal zones as the operational setting of the project reflects the 3I belonging to the 2seas INTERREG Programme, involving the countries facing the North Sea and the English Channel of the Netherlands, the United Kingdom, France, and Belgium.

The project enlists a wide array of partners from academia, industry and local authorities, with TU Delft as leading partner.

A joint collaboration of the Port of Rotterdam, Politie Rotterdam Rijnmond, and Kent Police resulted in the development of three test scenarios. The scenarios embodied the functionalities that end users find desirable for operations in

a maritime environment, and span from sorting incidents on seaside locations, to detect illegal dumping at sea, or to locate, enumerate and identify hijackers of a vessel. All scenarios had a set duration of between two and three hours. These clear-cut scenarios contained clear indications on flight conditions and duration, on footage time delay and quality, and on mission typical environment. Such premises were the basis for the design of the different elements composing the system, i.e. the platform, the payload and the mobile ground station.

The platform, denominated 2SEAS20 and designed by the Computational Engineering Design Group of the University of Southampton, is the result of the team’s extensive knowledge of 3D printing. Designing the vast majority of the parts with such a production technique in mind allows for high performance results due to tailoring components in depth. The result is a lightweight platform (an Operating Empty Way (OEW) of twenty kilograms), boasting fully redundant architecture, from control surfaces, to avionics, to power and thrust generation. Such a redundancy represents an exceptional effort towards

Leonardo Times January 2015

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univerSiTy of SouThampTon

Figure 2. The Paparazzi operator at work. The 3i Van contains all the necessary room and interfaces for three operators to control every aspect of the mission.

Figure 1. The gimbal of the camera system.

safety of the platform. The 2SEaS20 is propelled with a pair of two-stroke piston engines, and this choice allows for a remarkable endurance of three and a half hours (a new prototype platform, S.P.O.T.T.E.r, upgrades both engines and fuel tank for an even higher endurance). adding to a cruising speed of 100km/h and max speed of 150km/h, this makes for a platform capable of performing long lasting missions and covering long distances without the need of ground assistance. a paparaZZi auTopiLoT is present on board for automatic control. Paparazzi is an open-source project for which Tu Delft’s Micro aerial Vehicle lab (MaVlab) is top developer. The autopilot can be equipped with tailored and adaptive flight plans, allowing for customizable, waypoint-based flights, effectively making the 2SEaS20 a multipurpose platform.

The Wi-Fi connection enables a range up to forty kilometers. The 2SEaS20 can be commanded manually via remote as well, to comply with flight regulations and to provide an additional level of safety. aS payLoaD, the Tu Delft selected a camera system for the 2SEaS20, which is independent from its platform with the exception of powering. The main element of the system is its gimbal, i.e. a moving head for the sensors (in Figure 1). The gimbal has two axes of rotation. Its high performance design allows for 105˚/sec rotation rate, an accuracy of 0.02˚ and almost complete rotational freedom. The sensors are equally sophisticated: a Sony FCB-H11 for HD daylight footage (offering a 10x optical zoom) and a FLIr Quark 336 for thermal imaging (useful for recognition and rescue opera-

Figure 3. The navigator deciding the route for the uaV. With intuitive gesture recognition, the touchscreen of the Human Machine Interface makes navigation an easy task.

tions). The gimbal also includes an array of sensors - including barometers and GPS - allowing for more refined control options. For instance, it is possible to focus the gaze of the sensors on a fixed point on ground. a high frequency Wi-Fi link allows control of the camera and transmission of real-time SD video on range between four and ten kilometers, depending on environmental conditions, while a digital recorder can be added as a separate module to allow on-board HD-ready footage. Such a module can come in handy during inspection missions, or when flying beyond the reach of the transmission system. If the recording module is not added, a sixhour lasting battery can be added instead, effectively making the camera system a stand-alone unit.

The mobiLe GrounD STaTion allows a fast deployment of the system and a fully comprehensive control environment.

This sturdy van (in Figure 2) acts as a mobile control room for three operators. The Camera Operator has control over the camera system. He can steer the camera manually by mean of a control pad, but also has access to the sensor information to engage in more sophisticated control.

The operator is also in charge of guaranteeing the correct retrieval, storage and replay of footage. The Paparazzi Operator is in charge of the automatic flight of the uaV – especially during complex manoeuvres such as take-off and landing – with a focus on safety. This operator has access to the full capabilities of the Paparazzi interface, also providing status of the uaV in terms of position, speed, flight height and other vital information. The navigator, as the name suggests, is responsible for plan-

ning and executing the mission. He can do so by means of the highly interactive Human Machine Interface (HMI), shown in Figure 3 and realized by Telecom Bretagne and Deev Interaction. By performing basic gestures on a touchscreen, the navigator can instruct both the uaV and the camera system to perform multiple basic manoeuvers, each designed for a precise goal. Monitoring an area from above, inspecting a particular building or location, or focusing the camera on a straight line, are feasible operations with the HMI that anybody could immediately grasp. Each manoeuver is immediately reported to Paparazzi Operator for approval or denial, therefore guaranteeing safety of flight under all circumstances. The navigator’s role is particularly befitting to all professionals with high experience in mission management but lacking the skill or the time to familiarize with the more complex control interfaces of the other operators. In the words of Marcel Mattheijer of Digital & Media Solutions, designer of the van, controlling the system with the HMI “is easier than playing angry Birds”. reSuLTS of the project have shown that the current technological level is sufficient to provide efficient, multipurpose and relatively inexpensive platforms like the 2SEaS20, powered with a reliable payload, and made simple to use by increasingly ergonomic interfaces. although national flight legislations still struggle to make room for unmanned autonomous flight, projects like the 3i are bound to speed up the process.

(For more information: www.2seas-uav. com)

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ALEXANDRE CAMPINO

WIND-TUNNEL TESTING ON A HYPERSONIC UAV Subsonic Aerodynamic Characteristics of a Hypersonically Shaped Vehicle The HypResearch project has as mission to break the world record on the longest sustained hypersonic flight. It is aimed to sustain Mach 6 for 500 seconds and then proceed to land autonomously. For that purpose the HypResearch vehicle was designed, developed, built and tested at the TU Delft’s LTT for its subsonic aerodynamic characteristics.

TEXT Alexandre Campino, MSc. Student Aerospace Engineering, Flight Performance and Propulsion

ll commercial airliners nowadays have a definite limit on the time they take to connect two points in the globe. For that reason flying at hypersonic speeds will bring a new paradigm to commercial flights in the future. The groundbreaking design of the Concorde back in the 70’s was the first attempt of an airliner going supersonic. Although it is success in terms of engineering, it has failed on the business side of the project thus being terminated due to lack of profit. This is why developing a sustainable manner of flying hypersonically must be researched.

The HypResearch projected can be considered the first step leading that way. This article is based on an MSc thesis where the model, shown on background image on the top of this page, was tested at the low-speed low-turbulence wind tunnel.

Alongside the experimental approach, a numerical approach is also evaluated and the results are compared.

The aircraft’s shape is optimized for hypersonic flight, with its low aspect ratio, thin and sharp leading edges and very low overall width. Since part of its flight

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envelope will be the subsonic descent and landing, its characteristics during this portion of the flight are of paramount importance.

EXPERIMENTAL SET-UP: The testing set-up is shown on the background image on the top of this page. The model is mounted upside-down with a rear support structure. This is done such that the aerodynamic interference between the support and model is trimmed down to a minimum. The structure fairing,

which covers the structure rod that connects the model to the wind-tunnel balance, is aerodynamically shaped to minimize its wake. Sweeps of angle of attack and sideslip were made and the aerodynamic forces acting on the model were registered at each different attitude. The measurements were made at constant Reynolds number of 7,5 million, which determined the speed of the wind tunnel to be between 85m/s and 95m/s. The control surfaces of the aircraft were also tested to investigate if they were correctly sized, ALEXANDRE CAMPINO

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Figure 1. PIV Vortex Field located perpendicularly to the wing’s upper surface at the trailing edge.

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ALEXANDRE CAMPINO

meaning that if a certain deflection has enough power to change the aircraft’s attitude. The HypResearch has two different control surfaces, elevons that span the entire wing’s trailing edge and an all-moving rudder.

VORTEX FLOW Highly swept wings are dominated by a different kind of flow condition. The boundary layer on the downside of the wing’s surface will meet the sharp leading edge. It will not be able to negotiate with the very adverse pressure gradient, thus separating. The separated flow will roll-up over the wing’s upper suface, creating a vortex, which can span the entire length of the leading-edge. The incoming flow will see this as a apparent wing with a very large leading-edge radius. It will deflect around it, thus accelarating the flow, and re-attaching on the leeward wing’s surface. This aerodynamic phenomena greatly increases the lift of the wing and its called vortex lift. The additional lift created by the vortex’s presence over the wing is of very hard prediction. This is due to the highly unstable nature of vortices and its inherent difficult of representing it theoretically or numerically.

PIV AND OIL FLOW ANALYSIS Particle Image Velocimetry is an experimental technique used to visualise the flow field. It was very useful for the present case due to the vortex’s presence over the wing. Figure 1 shows the vector field of a plane perpendicular to the wing’s upper surface. This plane is located at the wing’s trailing edge. It is possible to see the vortex’s core and where it is located with respect to the vehicle. In addition to this test, also an oil flow analysis was perfomed. This allows to see surface flow contours as it is shown in Figure 2. It is possible to see the vortex’s core line all over the wing’s length, running parallel to the leading edge over the surface. The vor-

ALEXANDRE CAMPINO

ALEXANDRE CAMPINO

Figure 3. Lift coefficient curve for the HypResearch.

Figure 2. Oil Flow analysis

tex’s presence also causes the flow over the surface to have a velocity component directed to the leading edge.

RESULTING AERODYNAMIC FORCES Figure 3 shows the lift curve as function of the angle of attack for this aircraft. This is the typical outcome of the force measurements performed by the wind-tunnel’s balance. A typical straight wing’s lift curve will be linear with the angle of attack, for low angles of attack, which are here being taken under consideration. The linearity is represented in green on the graph. What is seen is that the result obtained for the HypResearch is far from linear. This additional lift is due to the vortex’s presence and its denominated by vortex lift. The vortex lift is what allows highly swept wing aircrafts to produce enough lift at low to moderate angles of attack.

NUMERICAL APPROACH A numerical approach to predict the aerodynamic forces on the aircraft was also undertaken. Many high-fidelity CFD codes try to predict with accuracy these types of flow conditions and the resulting forces. Some have success at the cost of high-computational time and very complicated pre-processing. A low-fidelity approach was attempted, which has a very low computational time to output a result, only takes a matter of minutes, and the meshing is quite straightforward with a very useful GUI to assist throughout the process. The code is based on a VLMVortex Lattice Method enhanced with a leading-edge suction analogy, which predicts the influence of the vortex on the wing’s aerodynamic forces. This was coded in Matlab having as its basis a preexistent code called Tornado. The results matched within a 2-5% margin of error the experimental results. The prediction of longitudinal forces and moments was rather good, even when control surfaces were deployed. There are a few limita-

tions concerning higher angles of attack, when the vortex influence is not so simpe to calculate. Nevertheless the approach taken was quite succesful and can be later used in the design phase of these kind of vehicles due to its reliability and low computational time.

CONCLUSIONS Subsonic wind-tunnel tests were preformed on a chined delta wing aircraft where the aerodynamic characteristics were investigated. The values obtained will be used later to build the automatic control system of the aircraft, which is completely essential and must be very robust due to the natural unstableness of the aircraft. It was observed that the aircraft is unstable in pitch. Although this was expected, since the aircraft is designed for hypersonic flight, where the aerodynamic centre will shift back, closer to the centre of gravity, eventually rendering the aircraft stable. During subsonic flight the control system must actuate, making the necessary control deflections to bring the aircraft back to the trimmed condition. The same was found out about the rolling stability. Lack of surface control power was oberserved due to incorrect sizing. Going back to the drawing table and re-designing them or impose strict conditions to the control system can mitigate this problem.

FUTURE WORK The HypResearch project has been around for a couple of years, but just now it is making the first steps on becoming a reality. Although there is still plenty of work to be done. This was the first part of wind-tunnel testing done on the model, but more is planned to the future where a dynamic testing rig is being developed.

Additionaly, hypersonic wind-tunnel testing is also to be performed.

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RVD ESA

THE ORION SPACECRAFT Successor of the Space Shuttle

On July 8, 2011, after a little more than thirty years of service, the Space Shuttle program came to an end with the final landing of the Space Shuttle Atlantis at NASA’s Kennedy Space Centre in Florida. At that time, NASA was already busy with developing a follow-up to the Space Shuttle that is called Orion. Its first unmanned multi-hour test flight is scheduled for December this year.

TEXT Thijs Gritter, BSc Student Aerospace Engineering, President of the 29th Space Department

HISTORY During a press conference on January 14, 2004, President George W. Bush announced the follow-up to the Space Shuttle: ‘’Our second goal is to develop and test a new spacecraft, the Crew Exploration Vehicle (CEV), by 2008, and to conduct the first manned mission no later than 2014 [...] This will be the first spacecraft of its kind since the Apollo Command Module’’.

The proposal, which would later be called Orion, was a reaction to the Space Shuttle Columbia accident and the White House’s review of the American space program.

The CEV was a capsule designed for a moon landing as part of the Constellation space program. This program, including the Ares I and Ares V rockets, was cancelled by Barack Obama in 2010 because of budgetary concerns. However, Obama continued the development of the CEV and in October 2010, the NASA Authorization Act passed into law. It stipulated that NASA should develop a Multi-Purpose Crew Vehicle (MPCV) to operate beyond Low Earth Orbit. On May 24, 2011, NASA announced the Multi-Purpose Crew Vehicle Orion. It is a new spacecraft based on

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the CEV, which is focused on transporting astronauts to the moon and return them to earth, as well as deep space missions.

REQUIREMENTS The Orion spacecraft is an Apollo-like spacecraft that has to host a crew of two to four members for an active duration of 21 days and a total duration of up to six months. This requirement is designed to provide for the following capabilities: It has to provide the crew for launch, return and operation in deep space, as well as being fully capable of performing missions in cis-lunar space. This is the space between the earth and the moon’s orbit.

Furthermore, it has to be evolvable to serve as the primary crew vehicle for missions beyond this cis-lunar space. Next to this the Orion MCPV will provide the possibility to bring astronauts and cargo from and to the International Space Station.

The beyond-LEO design does not include volume in the service module for large unpressurized cargo items for the ISS, but removing consumables tanks, which are not needed for back-up ISS transportation, and replacing this volume with cargo capability could carry cargo carried

by Orion.

Furthermore, other mission-specific design variations can be designed and implemented. In contradiction to the space shuttle, which was designed as a lifting body, it will not be possible for the Orion to land like an aircraft, instead it will be able to land in the sea, like the Apollo capsules. Next to this, NASA is aiming at making Orion reusable. However, the reusability of Orion will be limited to about ten times, while the space Shuttle could be used over 100 times. This is a challenge, caused by the deterioration of the salty water. Finally, Orion has to provide for Extra-Vehicular Activities, through depressurization of the crew compartment. The Space Launch System, or SLS will launch it. As said before, initially Orion had to be designed and tested by 2008. The first manned mission had to be conducted by 2014. However today, the testing of Orion is still not completed and at this moment, there is already a delay of six years.

DESIGN The design of the Orion is based on space capsules of the past, but it takes

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The second part is the crew module (CW), which is the capsule where a safe habitat for the crew is provided. Furthermore, it provides storage for consumables and research instruments and next to that, it serves as the docking port for crew transfers. The crew module is the only part of the Orion that will be reused. The CW will have a volume of almost nine cubic meters and capabilities of carrying four astronauts for the active duration of 21 days.

The third part is the service module (SM).

This component carries the main rocket engine, furthermore it carries large solar panels and when coupled to the crew module, it provides the water and oxygen needed to create a habitable environment. Furthermore, it maintains the temperature of the vehicle’s systems and components. When no astronauts are carried, the service module can also transport unpressurized cargo and scientific payloads. The SM supports the crew module from launch through separation prior to re-entry.

SPACE LAUNCH SYSTEM The NASA Space Launch System is a multipurpose heavy-lift launch vehicle system designed to bring cargo and astronauts into space. Therefore, it will be used to bring the Orion MPCV into space. It follows the cancellation of the Constellation Program and the NASA Authorization Act of 2010, which envisions the transformation of the Ares I and Ares V into a single launch vehicle. It can be configured for specific mission needs and it uses an

Figure 1. Different versions of the Space Launch System

evolvable development approach, which allows NASA to address high-cost development activities early on in the program.

The SLS will combine technological investments from the Space Shuttle Program and the Constellation Program, so it can take advantage of proven hardware and tooling and manufacturing technology. This will significantly reduce development and operations cost. It will consist of a core stage and two solid rocket boosters.

It will also be evolvable, ultimately carrying 130 metric tons of crew and/or cargo into space, meaning it will be bigger than the famous Saturn V rocket (Figure 1).

TESTING The first tests of Orion were performed in 2007. From this year to 2011, NASA performed environmental testing in the world’s largest thermal vacuum chamber at the Glenn Research Centre in Sandusky, Ohio. On 20 November, 2008, Alliant Techsystems successfully completed the first Orion launch abort test.

In 2009, the pathfinder, which is a combination of the Orion Boilerplate and LAS module, was tested at the White Sands Missile Range in New Mexico. On May tenth 2010, NASA successfully executed the PAD-Abort-1 test at White Sands New Mexico, launching a boilerplate Orion capsule to an altitude of approximately 1800 meters. This December, its first unmanned multi-hour test flight is scheduled.

NASA has already spent trillions of US dollars on space exploration. While in the 60s and 70s space exploration was seen as a national duty in the cold war, it is nowadays difficult to justify these kinds of spending, not only in the US. The Orion shows that despite this difficulty, the United States still aims to be the leading nation in space exploration.

NASA

The MPCV will consist of three main parts.

The first part is the launch abort system (LAS), which rockets fire to pull the astronauts to safety if a problem occurs with the booster early in flight. It will be placed on a tower on the top of the crew module.

It will be activated within milliseconds in order to bring the crew module to safety in the event of an emergency during launch or climb to orbit. It also protects the crew module from dangerous atmospheric loads and heating. It will be jettisoned after the MPCV is ascended into orbit.

NASA

advantage of the latest technology in computers, electronics, life support, and propulsion and heat protection systems.

Like the Apollo module, it has a conical shape, which is the safest and most reliable solution for re-entering the Earth’s atmosphere, especially at the velocities reached by a direct return from the moon.

It will be a bit more than five meter in diameter and its mass will be around 25 tons. Inside, its volume will be almost twenty cubic meters, which is more than 2.5 times the volume of an Apollo capsule.

Figure 2. Cut-out view of the Orion Crew Module

REFERENCES http://www.nasa.gov http://www.spaceflightnow.com NASA, ‘’Preliminary Report Regarding NASA’s Space Launch System and Multi-Purpose Crew Vehicle’’; NASA; January 2011; http://www.nasa.gov Griffin, Acosta; News Conference Exploration systems architecture study; NASA; September 19, 2005; http://www. nasa.gov George W. Bush; Announcement on new vision for Space Exploration Program; The White House January 14, 2004; http://georgewbush-whitehouse.archives.gov http://www.aerospaceguide.net http://www.space-travel.com SPACE DEPARTMENT The Space Department promotes astronautics among the students and employees of the faculty of Aerospace Engineering at Delft University of Technology by organizing lectures and excursions.

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DRONAMICS Ltd.

UAVs: Bringing the World Closer Together

It is hard to imagine global commerce without cars and roads. One startup wants to make use of the advances in UAV technology and create a “car for the skies”.

Accelerator-backed DRONAMICS taps into its ties with the TU Delft community and the vibrant startup ecosystem of Sofia, Bulgaria to create a product that will make air cargo faster, cheaper and more efficient, and will open previously unviable routes to communities worldwide.

TEXT Konstantin Rangelov, Student Aerospace Engineering, TU Delft, Co-Founder of DRONAMICS Ltd. Svilen Rangelov, B.A. in Economics, Davidson College, Co-Founder of DRONAMICS Ltd.

C

argo drones have been a hot topic ever since Amazon showcased its door-to-door delivery system. But don’t put a landing pad on your front porch just yet – it turns out that UAVs might replace other parts of your package’s journey long before they replace your mailman.

Or at least that’s the goal of DRONAMICS – a startup that got funded by the EIFbacked accelerator Eleven (www.11.me).

Led by the Rangelov brothers, DRONAMICS is building a prototype that can carry a car’s load of cargo between small airports as much as 2,500km away. The goal is to optimize supply chains on less-trafficked routes and to open up routes which were previously underserved due to the prohibitively expensive economics of manned flight.

THE ORIGINS OF THE IDEA When Amazon showcased their drones last December, both authors of this article were excited and knew a big change was coming to the world. Living 2,000km apart, “send it by drone” became an inside joke they would throw at each other. For

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months, they toyed with different UAV ideas and use cases, and soon they knew they had a front-runner to bet on – the DX-1 Legionnaire cargo UAV. Svilen gave up his show business career to work on their startup, Konstantin finished up at Airborne and DRONAMICS was born.

JOINING AN ACCELERATOR Self-funding quickly proved limiting for a project of such scale, so the Rangelov brothers decided to apply to a startup accelerator. While most startups apply to every single accelerator program to raise their chances of funding, Svilen and Konstantin decided they would submit just one application, and chose Eleven – since it was based in Sofia, Bulgaria, and combined funding from the European Investment Fund as well as private investors.

As a member of the Global Accelerator Network, Eleven partners with Google, Microsoft, Amazon, IBM and TechStars. In less than two years, it has funded over 83 startups from all over the world with more than € 6.5 million, making it one of the largest early-stage investment funds in

Central and Eastern Europe. Eleven’s rigorous 3-month program features a series of workshops, dubbed “the Entrepreneur’s MBA”, and connects startup founders with Eleven’s extensive network of mentors, professional investors and potential future customers. In addition to Eleven’s financial and mentorship support, DRONAMICS takes advantage of a growing team of technical advisors, including some at Konstantin’s home base at Delft. What’s next is completion of the first functioning prototype and raising a Series A round of financing.

TRANSFORMING AN INDUSTRY One of the main problems of the air cargo industry is that the unpredictability of orders makes it hard to optimize loads.

For years, cargo airlines have tackled that problem by diversifying their fleet to make sure they have aircraft of all sizes – from 747’s to small twin-prop Cessna’s.

But, while the cargo hold can be “shrunk” to fit, the same cannot be said for the pilot, the cockpit and the life support systems – all of which add non-cargo weight to an

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DRONAMICS LTD.

Figure 1. Impression of the design

aircraft and thus as the cargo shrinks, that weight becomes a bigger proportion than economically viable, establishing a natural threshold and a barrier to the development of smaller (and therefore more efficient) manned aircraft. This conundrum can only be solved by separating the pilot from the aircraft. This is what DrOnaMICS is doing with its “Legionnaire”. The adventurously named aircraft is to be operated remotely using the proprietary DrOnaMICS Control System (DCS) that the DrOnaMICS team is developing together with their partners.

JOB-CREATING INNOVATIONS DCS enables a further step in optimization – because a Legionnaire can only carry up to 350kg, it makes little sense for one pilot to operate it throughout the whole route.

Instead, one pilot/operator at the origin will be responsible for the take-off, while another pilot/operator at the destination will be responsible for the landing. In midair, the flight will be one of many being monitored by a team of operators, in a model resembling current air Traffic Control systems. In essence, this hybrid system would also temper the labor costs for a carrier by letting the number of aircraft in operation be several times greater than the number of occupied pilots/operators, which is a necessary compensation for the fact that the aircraft used is much smaller than the manned ones and as such, more runs are needed to fulfill the same order.

Does this mean more strikes by pilots and fewer jobs? On the contrary – by increasing the efficiency of cargo flights, a lot of new routes will open, necessitating net-

works of new operators and numerous new jobs. So, while labor costs will grow in absolute terms, their relative weight in a company’s income statement will actually become smaller, creating value for both society and the enterprise.

TAKING ADVANTAGE OF NEW TECHNOLOGIES On the technological side, the proliferation of hobby drones has been made possible in large part due to the effects of Moore’s law – devices have gotten very small, very light and very cheap. Of course, a big uaV like the Legionnaire requires a lot more advanced control systems than a $200 hobby camera-drone, but technology like the one developed by raspberry Pi, arduino and u-Blox allows for rapid prototyping and fast iteration as well as the implementation of industrygrade redundancies and the inclusion of a variety of sophisticated sensors in order to keep track of all systems of the Legionnaire in real time. Safety is another big focus for DrOnaMICS, as the chaos of the roads should not be brought up to the skies. Solid anti-collision systems are being developed, and rigorous testing is to be performed before the Legionnaire is to make its first commercial flight.

HELPING DEVELOPMENT IN EMERGING MARKETS Clearly such a model for air cargo will not be applicable to all routes – the sheer tonnage of the cargo passing through the world’s busiest airports means that there simply isn’t enough time in the day and enough runways for that cargo to be deliv-

ered via small aircraft like the Legionnaire.

This is why DrOnaMICS envision the Legionnaire, as a vehicle, is better suited for emerging markets, like ones in africa. The world’s second largest continent is home to 54 countries, most of which are also largely underdeveloped with poor road infrastructure. at the same time, africa has proven to be very open to innovation.

Consider mobile phones – african countries like Kenya were among the world’s first in developing mobile banking services. It made sense, being cheaper and more accessible than building a network of brick-and-mortar branches. Much like in many countries landlines were never built outside of big cities, the prohibitive costs of road construction and the vastness of the continent may force africa once again to skip a step and turn directly to the next frontier of ground-breaking technology – drones. Considering how global commerce is dependent on transportation, lowering its costs will make goods more affordable and this in turn will help communities grow. Villages and towns, away from the global hubs of commerce, that were previously prohibitively expensive to fly cargo to, will now be able to receive goods quickly and cheaply. It is then easy to see why DrOnaMICS and its investors are so excited about the longterm potential of all the opportunities that unmanned cargo aircraft will open to communities worldwide. “Lots of startups want to change the world, but simply changing the world is easy,” the rangelov brothers like to say, “We want to make it better”. Let’s wish them luck!

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ISRO

Indian Aerospace Industry: An overview The story of rise of Indian aerospace industry

The Indian aviation industry is critically poised today with its first footsteps in mainstream civil aviation industry. This article takes a look at the growth of Indian aerospace industry and its potential for aerospace engineers and enthusiasts.

TEXT Akshay Raju Kulkarni, Student Aerospace Engineering, Member Aryabhata Pradeep Pandurangi, Student Aerospace Engineering, President Aryabhata

The beginning It was 15th October 1932, when a single engine De-Havilland Puss Moth took off from Karachi’s Drigh Road Aerodrome (present day Pakistan) to Mumbai’s Juhu airstrip. This was a momentous occasion in Indian aviation history. It was the first commercial flight in pre-independence India that started as a division of Tata Sons, called Tata Airlines. It was a modest industry consisting of one Puss Moth aircraft, one Leopard moth, one thatched shed, one pilot, one engineer and two apprentice mechanics. To start with, the service included a weekly airmail to some major cities of India and later expanded to passenger transport.

A few years later in 1940, Hindustan Aircraft was started in cooperation with the (British) Indian Government and encouraged by a local kingdom. The British government favoured this, as it saw an opportunity to further strengthen its military power. The factory in Bangalore quickly became a major centre for maintenance, repair and overhaul. Soon, all aircraft that operated in Burma and India could be repaired at this factory.

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Post the Indian independence, it was renamed Hindustan Aeronautics Limited (HAL) in the year 1964. Around the same time, two other organisations came into being; National Aerospace Laboratories (NAL) and Indian Space Research Organization (ISRO). NAL was bequeathed the responsibility of developing civilian aircraft, while ISRO was founded to develop India’s space capabilities. Some of the notable accomplishments of ISRO in this period include the launch of India’s first satellite Aryabhata in 1975 and successfully test firing Rohini, an indigenous Satellite Launch Vehicle (SLV).

Until 1991, the trifecta of NAL, HAL and ISRO was the keystone of Indian aerospace ably supported by Defence Research and Development Organisation and a few other public and private organisations. While quite a few projects were started by these three organisations, their progress was not rapid, as a lot of restrictions were imposed on them and technology was not easily acquirable.

The Liberalization, Privatization and Globalisation era Post liberalization of the Indian economy

in 1991, there has been a discernible improvement in the development of the aerospace industry. HAL for instance, is one of the largest aerospace companies in Asia and has a turnover of over two billion USD of which over 40% comes from international deals. HAL is also developing its own aircraft and helicopters.

Some of the famous projects include the design and manufacturing of HAL Tejas (single-seater, mutli role fighter jet), HAL Dhruv (light helicopter), a trainer aircraft etc. ISRO, in the same period, developed and launched the Polar Satellite Launch Vehicle (PSLV) and the Geosynchronous Satellite Launch Vehicle (GSLV), becoming the sixth space organisation in the world to have the capability to launch satellites into geosynchronous orbit. ISRO also launched Mars orbiter mission ‘Mangalyaan’ and lunar mission ‘Chandrayaan’, both of which were unique and laudable for reasons of their own. The Mars mission was one of the most inexpensive missions of its kind, in addition to having the rare distinction of being successful in its maiden flight. The lunar mission, on the other hand, helped ascertain the presence of water on moon. NAL has had successes in this period with the maiden flight of NAL

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isro

Hansa (a two seat civilian aircraft) and naL Saras (a variable 8 to 19 seat aircraft).

Though most of the development was centred around major government owned public sector companies, the visible change could be attributed to the liberalization, globalisation and privatization policy that was brought forth by the Indian government in 1991. Many argued that the efforts of these organisations in the sixties, the seventies and the eighties bore fruit in the nineties and the introduction of the new policy was merely coincidental. nevertheless, no expert could deny the new avenues that were opened by this policy. Private companies were allowed into the aerospace market albeit just domestic ones. This helped the public sector companies to outsource part of their work. International restrictions after India’s 1998 nuclear tests, and India’s own protectionist policy prevented International companies from joining the fray and accelerating the growth and competition. This did not stop India from modernizing their defence force, which led to it buying aircraft and spare parts from other countries, very soon becoming largest importer of arms in the world. deFenCe oFFseT PoLiCY The Government of India realised the fallacy of the approach they were taking and soon enacted a rule known as Defence Offset Policy in 2005. The policy introduced 30% offset in contracts valued over fifty million uSD. under the policy, foreign vendors are required to discharge an obligation of offset either through execution of export of Indian items and services or through investments in India’s aerospace infrastructure. This policy had a twopronged motive. On one hand it would keep the fair percentage of the governments’ expenditure in Indian economy and on the other, to ensure that compe-

tence to develop cutting edge technology is created within India. One might wonder as to why companies would agree to such a contract. This principally has two advantages: India is a huge market especially in terms of its potential and relationships fostered now would mean enhanced business opportunities in the future, and the low cost of manufacturing in India makes it a viable manufacturing destination.

Many countries such as the uS, France, The netherlands, australia, Germany etc. already have an offset policy and it has almost become a common practice in aerospace and defence deals. all foreign direct investments (FDI) in India are controlled by Foreign Investment Promotion Board (FIPB) that until recently, had stipulated that foreign companies could hold equity of utmost 26% in all ventures. This necessitates the foreign investors to team up with Indian companies to start a joint venture. For long, FDI had been an issue flagged by top defence aerospace companies such as EaDS, Boeing, Lockheed Martin, British aerospace, rolls-royce, and other component makers1 who were increasingly interested in utilizing the Indian market2 to exploit the possibility of developing cutting edge technology in India.

The FUTUre Considered by many as one of the biggest decisions in the aerospace industry after the Liberalization of Indian economy in 1991, the Government of India recently announced a 49% FDI in aerospace and defence manufacturing. This aims to boost the confidence of various foreign investors in the Indian economy and spur them on to invest more in India. Companies like airbus, Boeing, General Electric, Mahindra aerospace and Honeywell already have research centres in India.

Moreover, companies like rolls royce and airbus have announced their expansion plans in India.

Tata airlines, known today as air India, boasts a modern fleet of 108 aircraft. In addition to air India, a number of other carriers are also catering to the exponentially increasing number of air travellers in India. Only recently, Indigo airlines, a low cost carrier in India, secured a deal with airbus for purchase of two hundred and fifty airbus a320 neo3. The deal is estimated at 26 billion uSD and ranks as the single largest order of jet aircraft from airbus.

Stories of most countries having a successful aerospace industry tread a familiar path. Most start off with development in the defence sector and become truly successful when they make an entrance in civil aviation industry. There are only few companies in the world, which can claim to design, develop and manufacture complete civilian aircraft on their own. With the announcement of new 90-seater civilian aircraft by naL in cooperation with other domestic and international partners, India has finally decided on a fullfledged entrance into civil aviation.

If India succeeds, knowing their ability to produce technologically advanced products at ridiculously low costs and the growing popularity of air travel in India, the world may have new player in the civil aviation market. There is a myriad of opportunities already opening up in India for aerospace engineers from world over to demonstrate their skills. The question remains though: who, when and how. For it is a twenty billion uSD market, even the pessimists among us can no longer ignore it. The writing on the wall is clear, the early bird that enters the booming Indian aviation market will catch the biggest worm!

Contact email: aryabhata@tudelft.nl

ada

references

Figure 1. Tejas operating from Leh in the winter of 2013, at an altitude of 3,524 m (11,562 ft). Leh has one of the highest commercial airports in the world.

[1] http://www.voanews.com/ content/a-13-2009-09-24voa46-68806852/362715.html [2] http://www.idsa.in/jds/3_1_2009_ EssentialElementsofIndiaDefenceOffsetPolicy_TMathew.html [3] http://timesofindia.indiatimes. com/business/india-business/rollsroyce-to-power-up-rD-in-India/articleshow/37522299.cms [4] http://forbesindia.com/article/ india-budget-2014/india-budget2014-higher-fdi-in-defence-a-stepforward/38202/1 [5] http://fortune.com/2014/10/15/ indian-airline-indigo-agrees-record250-airbus-jet-order/

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09-Feb-15 22:27:04

Pipeline Buckle Arrestor Assessment An application of finite element method

Pipelines are susceptible to local buckling which is commonly triggered by defects.

If the ambient pressure is sufficiently high, local collapse can initiate a buckle that propagates at high speed catastrophically damaging the pipeline. Buckle arrestors are used to increase the circumferential bending rigidity to stop the spreading of the collapse. The method found in the thesis study can be used to assess the performance of both J-lay single-step and double-step collars as buckle arrestors.

TEXT Liang Zhang, Graduate Aerospace Engineer, Aerospace Structures & Computational Mechanics

O

ffshore engineering is a wide area of geotechnical engineering, which includes the design, and construction of structures with functionalities in the sea.

Some of these structures are oil platforms, submarine pipelines, artificial islands and wind farms. Transportation of fluid or gas from an offshore platform is one of the biggest challenges and the construction of pipelines was proven to be the most efficient way. The most common methods for pipeline installation are J-lay, S-lay and reel-lay. Among them, J-lay installation is most suitable for deep water. Within HMC (Heerema Marine Contractors), single-step collar in combination with hang-off table was used in past projects with J-lay on DCV (Deepwater Construction Vessel) Balder as shown in Figure 1. During J-lay installation, collars can be used to hold the whole pipe string. Once the installation process is completed, the collars can also function as buckle arrestors, which are defined as circumferential load stiffeners placed periodically along the length of the pipeline.

Because the propagating pressure could be as low as about 20% of collapse pressure, it is uneconomical to design the pipe with propagating pressure, thus the cost effective way to stop buckle propagation is to put buckle arrestors periodically. Buckle arrestors locally increase the circumferen-

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tial bending rigidity of the pipe to a level that can stop the spreading of the collapse.

Once properly designed, they could arrest an incoming buckle, thus, limiting the damage to the structure to the limited distance between two adjacent arrestors. The graduation assignment provided by HMC, and presented in this article, is about the buckle arrestor assessment for the J-lay doublestep collar.

Challenge For the design of collar as buckle arrestors, within HMC the theory of S.Kyriakides (Kyriakides, Park & Netto, 1998) or C.G.Langner (Langner, 1999), which is treated as conservative, is used to assess the performance of single-step collars as buckle arrestors. To assess all types of collars, a full-scale test would be the best way but that is expensive and time-consuming. Instead of it, finite element method is a proper way to simulate buckle propagation and crossover. The question is how to make the reliable model to accurately obtain propagation pressure, crossover pressure and collapse pressure in order to assess and compare single-step and double-step collars as buckle arrestors?

FEM and validation In order to guarantee the accuracy of results, a 3D finite element model is created.

For the material model, J2 flow theory of plasticity with isotropic hardening and finite deformation is used to describe the elastoplastic behavior of the material.

When simulating buckle propagation, the calculation can be static or dynamic depending on the consideration of the purpose of calculation. In general, quasi-static analysis uses Riks method, a path-following method, which could trace the load during buckle initiation, propagation and crossover process. If one considers that pipelines are designed with collapse pressure rather than propagation pressure in mind, the dynamical propagation should be more realistic than quasi-static propagation because the ambient external pressure, which is higher than propagation pressure, is essentially constant on the sea floor. For element selection, continuum shell elements SC8R are used in Abaqus to reduce the computational cost. SC8R elements can provide solutions for both thin and thick shell problems. In this case, transverse shear effect could be significant and stacked elements together through thickness provide the better representation for the shear deformation. In addition, on account of calculation efficiency, symmetry boundaries are used and only 1/8 model is created.

Quasi-static analysis gives results that are

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Liang Zhang

hMC

Figure 3. Influence of dent ovalization on collapse pressure with different dent sizes Liang Zhang

Figure 1. The representation of J-lay pipeline installation for DCV Balder.

Figure 2. Influence of ovality on collapse with different pipe dimensions.

deFeCT inFLUenCe on CoLLaPSe PReSSURe The initiation of local collapse under certain external pressure depends on the defect size. Then the question is how to evaluate the influence of defect size quantitatively.

Geometric imperfections, such as local dent and ovality, are the most common trigger for local buckling. For the calculation in abaqus, the influence of ovality can be introduced by keywords (*imperfection) or creating the pipe section with ellipse profile. The difference is that the former only has local ovality while the latter owns ovality through whole pipes. The calculated collapse pressures are compared to results from DnV (Det norske Veritas) expressions with the definition of ovality by DnV. as can be seen from Figure 2, two models used in the calculation almost give the same prediction on the collapse pressure while the results from DnV expression is more conservative when the pipe is relatively thick (D/t=12.5, where D stands for

the diameter of the pipe and t represent the thickness of the pipe). The main reason is that with the increase of pipe thickness, the plastic collapse will rely more and more on the yield behavior of pipe while DnV expression only simply accounts for the yield stress.

Dents can occur occasionally during pipe installation especially when contacting with rollerboxes. In this case, the elastic deformation will recover once the local force is removed on the pipe while the permanent plastic deformation cannot be recovered.

Thus the unload step in abaqus is needed to account.

The collapse pressure is normalized by yield pressure P0 and is calculated with three dent sizes, 0.1 times diameter, 0.4 times diameter and 0.8 times diameter, as can be seen in Figure 3. apparently, collapse pressure decreases drastically with the increase of dent ovalization. With the increase of dent ovalization, the collapse pressure approaches the propagation pressure. The speed of decreasing with varying dent size mainly attribute to the plastic behavior.

Liang Zhang

more conservative on prediction for buckle propagation and crossover than dynamic analysis, which is preferred in the design stage. In addition, the computational cost of quasi-static analysis is much cheaper than dynamic analysis. In general, five most important phases can be seen during simulation on buckle initiation, propagation and crossover. They are local collapse, first inner contact of upstream pipe, buckle propagation, buckle crossover, and first inner contact of downstream pipe. The created finite element model is validated by one relevant paper (netto & Kyriakides, 2000). In this paper, experimental set up and finite element analysis implementation were explained and compared on both quasi-static analysis and dynamic analysis in this paper.

doUBLe-STeP CoLLaR vS SingLe-STeP CoLLaR With verified finite element model, singlestep and double-step collar are calculated separately with given dimensions from HMC as indicated in Figure 4. Since the propagation, pressure and collapse pressure is independent of collar dimensions, the comparison between double-step and single-step collar is only made with crossover pressure. The results show that the double-step collar could perform similarly with the single-step collar as long as the arrestor material occupies the same volume.

In addition, crossover pressure for both double-step collar and single-step collar changes much more significantly with thickness variation than with length variation.

ConCLUSion The methodology for finite element analysis found in the thesis can be used in the design of all kinds of collars and buckle arrestors, which provides the possibilities for HMC to design more functional collars and buckle arrestors to satisfy different installation requirements.

references [1] S.Kyriakides, T.-D.Park and T.a.netto, “On the design of integral buckle arrestors for offshore pipelines”, Proceedings of the 8th International Conference on the Behavior of offshore structures, Vol.1, pp.277-289, 1998.

[2] Carl G.Langner, “Buckle arrestors for deepwater pipelines”, Offshore technology conferences, OTC10711, pp.1-5, 1999.

Figure 4. Schematic diagram of single-step collar and double step collar

[3] T.a.netto and S.Kyriakides, “Dynamic performance of integral buckle arrestors for offshore pipelines. Part I: Experiments & Part II: analysis”, Int.J.Mech.Sci.42, pp.1405-1452, 2000.

January 2015 Leonardo Times

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11-Feb-15 00:53:15

LOAD TRANSFER AROUND BROKEN FIBERS

An analytical and finite element approach of damage in composites

Aircraft operation costs are very dependent on the fuel consumption, which is in turn dependent on the weight of the aircraft. To design lighter and more fuel economic aircraft, the strength-to-weight ratio is possibly the most important structural factor that needs to be taken into account.

TEXT Jack Kha-Han Tai, MSc. Graduate Aerospace Engineering, Aerospace Structures and Computational Mechanics

C

omposite materials are advantageous compared to metallic materials because of their higher performance for similar weight. The definition of a composite material is stated as follows: ‘Composite materials are materials made from two or more constituent materials with significantly different physical or chemical properties, that when combined, produce a material with characteristics different from the individual components.’ The first use of composites in aircraft is earlier than you might imagine. In 1903, the Wright brothers made the first successful controlled and powered human flight, with a flying machine heavier than air. The main structure was made of wood, but the wings of their flying machine were made of doped linen, which by definition is a composite material.

Today’s composite panels are made of fibers, such as glass and carbon, and are embedded in matrix material. In general high modulus fibers and low modulus matrix are used in the aerospace industry, resulting in a material where the fibers carry the significant primary loads while the matrix’s main purpose is to keep the fibers together. In some occasions, the matrix carries secondary loads, loads the composite panel was not designed for. At

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first these fiber-reinforced plastics were introduced in commercial aircraft, only replacing small non-critical aluminum surface areas. In the 1950’s, only two percent of the weight of the Boeing 707 was made of composite material. Thirty years later, in the 1980’s the A310 of Airbus consisted of five percent composite material. Driven by a need to produce aircraft that are more efficient, the use of composite materials has increased exponentially from then on. Today 50% of the weight of the newest Boeing 787 consists of composite materials. With their relatively low density compared to metallic materials, composites perform better in terms of strength and buckling and can be seen as the future of the aerospace industry. However, a big drawback is present; damage of composites is not fully understood yet. Failure mechanisms of a composite panel can range from broken fibers, cracked matrix to delamination of plies. Fatigue damage does also occur in composite materials and the behavior is relatively unknown.

Therefore, it is difficult to predict the failure mode of a composite panel, and even more difficult to predict the life of a composite panel after damage has occurred.

Fiber bundles in composites can break due to manufacturing faults, impact or ex-

cess loading. In damaged isotropic material, like metal, the stress will be redistributed equally over the material. The load of a broken fiber in composites however will not be redistributed uniformly over the other fibers of the panel, but experiments proved that the fibers adjacent to the break will carry most of the released stress. The research presented in this article is focused on the load transfer of a broken fiber in unidirectional tape composite material loaded under tension. A top and side view of the model setup is shown in Figure 1 respectively. The model is similar to an electron microscopic picture of a composite material, shown in Figure 2 a).

The goals are to analyze the behavior of stress increase in the neighboring fibers, and to derive an equation that is able to compute the stress based on the fiber volume fraction and material properties.

As in every research, assumptions and simplifications are made to simplify the actual situation. In reality, the fibers are spread out randomly in the matrix material, as shown in Figure 2 b). In the analyzed model the distance between the fibers is assumed to be constant, resulting in a hexagonal pattern as shown in Figure 1 a). Because of the constant inter fiber distance it is possible to derive an equation

Leonardo Times JANUARY 2015

09-Feb-15 23:39:32

AUTHOR

AML ENGINEERING COLUMBIA AND CHARLES W. DAVIDSON COLLEGE OF ENGINEERING.

COPYRIGHT

Figure 2. a) Uneven fiber distribution (the black dots represent the fiber crosssections); b) Electron microscopic picture of a graphite golf club shaft.

AUTHOR

Figure 1. a) Top view of the three dimensional model; b) Side view of the model

Figure 3. a) The green and purple lines of fibers are obtained by rotating the horizontal row by 60 degrees; b) The three dimensional model is reduced to a “flat” two dimensional model

that links the inter fiber distance with fiber volume fraction; a number that shows how much volume percent of fiber is present in the composite material. In general, fibers do not fail per string but in bundles.

However, since the research starts from scratch, only one fiber is broken at a time instead of multiple.

In order to reduce the model size, symmetry is used to reduce the panel size by four.

The axes of symmetry are shown in Figure 1 b). The three-dimensional problem is simplified by decomposing the hexagonal pattern into three separate linear patterns that repeat every 60 degrees, shown in Figure 3 a). The fiber rows highlighted with green and purple can thus be obtained by rotating the horizontal fiber row by 60 degrees. Using geometry, an equation is derived to relate the stress between the simplified and original situation. The model is further reduced to two dimensions by replacing the circular fiber crosssections with square ones, and is shown in Figure 3 b). The effect of the square fibers on the stress concentration factor compared to the circular fibers is investigated using a finite element analysis. It turns out that the difference in stress is minimal.

The two-dimensional model with three intact adjacent fibers is shown in Figure 1 b) and Figure 3 b), and is analyzed using equilibrium, stress-strain, strain-displacement and compatibility equations. As result a fourth order differential equation is obtained that is able to describe the stress in every point of the model. Unfortunately, the author has not solved the co-

Figure 4. a) Axial stress in the fibers of the two-dimensional model; b) Axial stress in fiber 1 along x-direction for different fiber volume fractions

efficients of the differential equation yet.

An alternative approach using finite element analysis is applied to obtain the axial stress in the fibers of the two-dimensional model. The results are shown in Figure 4 a) and confirms that the load released by the broken fiber is indeed not distributed equally over all the intact fibers, but mostly over the adjacent fiber.

The effect of the fiber volume fraction on the decay of the axial stress in fiber 1 is investigated. The results are shown in Figure 4 b) and agree well with the expectations.

The fiber spacing does not influence the stress concentration factor significantly, which is logical because the low modulus matrix material is not able to carry significant loads. However, other authors in the past [1-6] have assumed that the axial stress stays constant inside a fiber. When investigating the stresses in x-direction, as shown in Figure 4 b), it appears that the difference of maximum and minimum stress within one fiber is approximately 30 percent. This significant difference could lead to a fiber cracking from the side closer to the break, ripping through, and breaking the fiber.

The discoveries made in this research are a step towards analyzing damage in composite materials. Fibers are not created equally strong and data exists for fiber imperfections and manufacturing faults. By combining the analytical approach presented in this article with a statistical approach the chance of failure of a random composite panel could be predicted.

The obtained data can then be used as

a building block for fatigue analysis of composite materials. A cyclic load then replaces the applied static tensile load in the model and the life of a composite panel can be predicted after every cycle, generating statistics for fatigue failure.

For more information on this topic or how you can contribute to the future research on damage in composites yourself, please contact the author through the Leonardo Times.

References [1] J. M. Hedgepeth and P. Van Dyke, “Local Stress Concentrations in Imperfect Filamentary Composite Materials,” J. Compos. Mater., vol. 1, pp. 294–309, 1967.

[2] J. Hedgepeth, “Stress Concentrations in Filamentary Structures,” 1961.

[3] W. Fichter, “Stress Concentration Around Broken Filaments in a FilamentStiffened Sheet,” NASA TN D-5453, 1969.

[4] S. V. Kulkarni, B. W. Rosen, and C. Zweben, “Load Concentration Factors for Circular Holes in Composite Laminates,” J. Compos. Mater., vol. 7, no. 3, pp. 387–393, Jul. 1973.

[5] H. Fukuda and K. Kawata, “On the Stress Concentration Factor in Fibrous Composites,” Fibre Sci. Technol., vol. 9, pp. 189–203, 1976.

[6] H. D. Wagner and A. Eitan, “Stress Concentration Factors in Two Dimensional Composites: Effects of Material and Geometrical Parameters,” Compos.

Sci. Technol., vol. 46, pp. 353–362, 1993.

JANUARY 2015 Leonardo Times

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Jakob Van den Broecke

Internship report

Internship at Australian Lightwing Aircraft 3 Months Down-Under

Australia is a country with a lot of different faces. It offers beautiful nature, astonishing marine life, and lively cities and above all: very friendly people. The company I worked at, Australian Lightwing Aircraft, breathes out this Australian spirit. The small aircraft manufacturer is located on Australia’s East Coast about ten hours drive north of Sydney and two hours south of Brisbane on a local airfield in Ballina, New South Wales.

TEXT Jakob van den Broeke, MSc Student Aerospace Engineering

T

he company, part of the Hughes Engineering Group, is a family business managed by Howard Hughes and his son Nick. The main focus of their enterprise is on the manufacturing of two-seater aircraft, but the last years a couple of new projects were initiated including the design of a flight simulator and the design of an electrical car. All of their projects are done in their own workshop, from start to finish. Together with Thijs Bouquet, another student from our faculty, I started the three-month internship in September last year. Halfway during the internship, around mid-October, a third Aerospace Engineering student from TU Delft joined us: Pieter Bauwens.

The Internship The tasks at the company were quite diversified. In the first stage, we were responsible for the redesign of the prototype of a new project that Australian Lightwing was working on: the RoadE, an electrical vehicle. The goal of this project was to develop an electrical vehicle that would inspire a broad public to travel in an ecologically responsible way. First, the internal loadbearing truss structure was redesigned

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after which the outer shape was given a complete makeover making the vehicle more aerodynamic and aesthetically attractive. The design of the truss structure was done in CATIA and some realistic loads were virtually applied to the structure in order to check whether it wouldn’t deform too much under normal conditions. While doing this, one also had to think about requirements from local authorities concerning vehicle safety. The truss was basically the only structure going through the whole cabin protecting the people in the car in case of an accident. Another requirement for this truss was that it should be able to accommodate all batteries and provide protection in case of a battery fire. Following this, a redesign of the outer shape was done and to get a realistic impression of how the car was going to look like, a fullscale mock-up was made using fiberglass and foam.

A plane for a farmer The second task at the company was to assist in the manufacturing and design of a newly ordered customized aircraft for a customer who had some special requirements. As he was going to use his aircraft

to drive cattle over his vast farm, he needed the aircraft to have a very low stall speed.

He also wanted to use the aircraft for some small transports across his farm, which meant that the load bearing capacity of the two-seater plane had to be increased compared to standard designs. Further, he was on a limited budget requiring different and less expensive production techniques.

Components that are usually made of fiberglass were made for this airplane from a textile-covered frame. However, some parts were still made of fiberglass and as interns, we were involved in the manufacturing of these parts as well as the design of a new – lighter- wing spar. The interns eventually started the manufacturing of this spar. During my work at Lightwing, the aircraft was not yet finished, but when Pieter left two months later aircraft had almost reached completion.

Test Flight During the internship – as a sidetrack - a test flight was performed with one of the experimentally certified aircraft in order to test the stability characteristics of the airplane. Nick took us into the Australian skies with the SP-2000, one of Lightwing’s

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JAkoB VAn den Broecke

JAkoB VAn den Broecke

Figure 1. View of Ballina and the Pacific Ocean from the ALW SP-2000

AfTer hoUrs During the whole duration of the internship I stayed in a youth hostel in Byron Bay, about 30 minutes drive north of Ballina. In the beginning, I was looking for a private room but I quickly realized that hostel life is just amazing. The little town attracts travellers from all over the world and has an amazing bay and a cape with a lighthouse from which you can see mountains, dolphins and whales. The beautiful cape with the lighthouse is the most eastern point of the Australian mainland. There is a living surfing scene and just offshore are beautiful scuba diving opportunities in the Julian rocks marine reserve. As Byron Bay is centrally located on the East Coast, it is the perfect basecamp for trips along the coast during the weekends. For example, I visited the cities of Melbourne, Sydney and Brisbane and did a diving trip on the Great Barrier reef from Cairns. you can easily jump on a plane after work on a Friday

afternoon and visit another city for the weekend. “Twelve Apostles”, a rock formation along the “Great Ocean road” not far from Melbourne was a great experience.

Together with Thijs and Pieter, we also climbed Mount Warning, due to its altitude and location, the first point on the Australian mainland to see rays of sunlight every morning. We climbed the mountain during the night so that we could enjoy this mythical sunrise. On another trip, we went to Fraser Island, the biggest sand island in the world, where Thijs and I did a three-day 4WD trip through its magnificent nature.

The island had its own landing strip on the beach as can be seen in figure. We were also invited twice at our boss’ place for dinner and played after-work golf. In short, there was not much time to be bored. After the internship, I went to the Fiji Islands to enjoy some more scuba diving and adventure on the remote islands. The next destination was new Zealand for a three-

week trip through the South Island, which is really worth paying a visit when you are “around” anyway. In short, the possibilities for activities inside and outside Australia are unlimited! fUTUre InTerns I can say that working at Australian Lightwing gave me a good impression of how a small aircraft manufacturer is managed.

A very good advantage of working there is that as an intern there is no need to stay stuck behind your computer. There is always the possibility to go to the workshop to see, try and do things. If you are interested in doing an internship in Australia at a company where you can gain some hands-on experience, Australian Lightwing is a good choice. They are always involved with projects in which they can use students from our faculty. you can contact Lightwing by sending an email to fly@lightwing.com.au .

JAkoB VAn den Broecke

two-seater aircraft. During the test, several manoeuvres were performed such as a Phugoid, the initiation of a spiral, a Dutch roll and some engine-off manoeuvres. This test flight showed the need for an aileron trim in the design of future airplanes and that a small adjustment had to be made on the installed angle of attack of the wing.

Figure 1 shows a picture taken right after take-off from Ballina airport. As another side project the interns could also fly the flight simulator the company was developing in order to set-up the flight controls of different aircraft in the simulator.

Figure 2. Landing strip on Fraser Island

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“We vlogen met een zucht...�

WAITING FOR A NEW REVOLUTION How aircraft design converged into blandness

Recently, the McDonnell-Douglas MD-11 served its last passengers before retiring from service. With another iconic aircraft gone, it becomes clear that distinctive aircraft designs are being replaced with more economical, optimized models. However, it seems that these optimal designs also converge to a single configuration. Will all aircraft look the same in a few years, or are there more interesting developments?

TEXT Joris Stolwijk, MSc Student Aerospace Engineering, Editor Leonardo Times

WAVING GOODBYE TO AN ICONIC AIRCRAFT On November 11, 2014 at 16:45, the McDonnell-Douglas MD-11 (see visual) performed its last commercial ever: KLM organized farewell flights on this day to give aviation enthusiasts a last chance to experience the tri-hole. Rarely ever has an aircraft going out of service gathered this much attention, but this occasion was different: many people, especially flight and cabin crew, were emotionally attached to this aircraft because it was special. The MD-11 was the only remaining wide-body passenger aircraft in the world with a trijet configuration, characterized by the iconic third engine mounted in the tail.

Also, it was the last aircraft designed and produced by McDonnell-Douglas, before the company was taken over by its big brother Boeing. Because of this, it is also the end of a long-lasting relationship between KLM and Douglas Aircraft (which merged with McDonnell Aircraft in 1967).

KLM also owned the DC-8, DC-9 and DC10 jet aircraft models and when they ordered the MD-11, they were genuinely excited about the flexibility of the aircraft:

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It was easy to reconfigure the plane between cargo, passenger and combined operations and to adjust the size of the different cabin classes, which made it easily adaptable to seasonal schedule and demand variations.

However, with ever increasing fuel prices and changing regulations, it became clear that the third engine was a real burden for airlines due to its fuel consumption. Boeing introduced the 777, an aircraft with similar range and capacity, but with only two highly efficient and more silent engines. Airbus did the same with the A330, and thus McDonnell-Douglas struggled to stay relevant in this market. Many airlines started to replace the MD-11 with said alternatives, and as it became harder to find spare parts for maintenance, even KLM was forced to put it out of service.

The MD-11 aircraft will still be in use for the foreseeable future, but only for cargo operations.

This is just one example of a recognizable trend: as aircraft designs become more efficient and reliable with each iteration, they also appear to converge into one standard configuration. Apart from the

Airbus A380, which is in a class of its own with its massive passenger capacity, nearly every mid- to long haul passenger aircraft in production today has the same layout: One deck, two aisles, 200-350 seats, two wing-mounted high bypass ratio engines and a fuselage-mounted horizontal tail.

The Boeing 767, 777, 787, as well as the Airbus A330 and A350, they all look very similar (Figure 1), and one would have to carefully inspect the dimensions of the wings, fuselage and engines to determine which aircraft is which. Only the Boeing 747-8I, the latest iteration of probably the most recognized aircraft in the world, still sports the characteristic semi-double deck configuration and four engines. But, given the lack of orders for this aircraft, it is most likely that in the coming years even the 747 series will have the same fate as the MD-11: out of production and subsequently out of service.

THE GOLDEN AGE OF AIRCRAFT DESIGN Looking further back in history; it becomes clear that the 1960s and 1970s, when the jet era reached maturity, were the real golden age for aircraft design. The first Boeing 747 was introduced in 1969 as

Leonardo Times JANUARY 2015

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09-Feb-15 22:34:52

DEAN MORLEY ON FLICKR, LICENSED UNDER CC BY-ND 2.0

THOMAS VANDERMEIREN ON FLICKR, LICENSED UNDER CC BY-NC 2.0

Figure 1. Spot the differences; the nearly identical configuration of current wide-body jet aircraft is striking. From top to bottom: Airbus A350-900, Airbus A330-300, Boeing 777-200ER, Boeing 787-8.

the first wide-body aircraft in history. Both the McDonnell Douglas DC-10 and the Lockheed TriStar L-1011 were put into service in 1970, introducing wide-body designs with a trijet configuration. And the supersonic AĂŠrospatiale-BAC Concorde (Figure 2) is, more than a decade since its last flight, still admired for its futuristic looks, even though the design is 45 years old.

Is the fact that aircraft are starting to look more and more alike a bad thing? Maybe for plane spotters and aviation enthusiasts it is a sad development, but it is most likely that airlines and passengers will only care about the end product: a comfortable and safe flight from A to B. Also, this design convergence trend does not mean that there are no more improvements taking place in this industry. The introduction of composite materials, modern avionics, wing design refinements and more silent engines have all significantly improved the efficiency and comfort on the latest aircraft from Boeing and Airbus. Reducing the aircraft weight (and thus saving fuel) is a continuous motivation for aircraft designers to reconsider every detail of the aircraft design, taking it as far as redesigning the passenger seats: For example, KLM recently introduced its new economy class seat on its Boeing 777-200 which is much thinner and lighter, and it also allows for an extra seat to be placed on each row of the aircraft [1].

FUTURE DEVELOPMENTS New seats will however not make an aircraft look any more distinctive from the

TU DELFT

NOREBBO STOCK ILLUSTRATION AND DESIGN

Figure 2. The AĂŠrospatiale-BAC Concorde, seen here on approach to London Heathrow airport, England on October 8, 1995, was the only supersonic commercial passenger jet to ever go into service.

Figure 3. Multi-Fuel Blended Wing Body design of the AHEAD research project.

outside, and that is where radical new development has stagnated in the past two decades. Will we ever see a new passenger aircraft with an innovative, unconventional design again? Well, probably not in the coming fifteen years. Both Airbus and Boeing are not planning to develop new aircraft models in the foreseeable future; they will only re-iterate their existing portfolio [2]. However, preliminary research at TU Delft and other Aerospace institutions definitely gives a bright prospect: concepts have been published for interesting new wing configurations, new propulsion methods, and even ways to transfer between aircraft in mid-air. Many of these design concepts have been published previously in the Leonardo Times. For example, a forward swept wing constructed from composite materials is in development at DLR, which was covered in the June 2014 edition. In the same edition, research on air-to-air refuelling systems for passenger aircraft was also covered. One of the outcomes was that the tanker aircraft could feature a joint wing configuration, where the horizontal tail would be in connection to the main wing. Similar joint winghorizontal tail configurations are being explored as well, such as the Prandtl wing configuration. Also, one of the most radical design proposals currently in development is the blended wing body (BWB) design of the AHEAD-project (Figure 3).

Not only does this aircraft have an unconventional look with the payload compartment morphed into the wing surface, it also features a canard configuration, no vertical tail and two large rear-mounted

dual fuel combustion engines [3].

AS ALWAYS, COSTS ARE THE MAIN ISSUE Such designs have the potential to have a revolutionary impact on the efficiency of aircraft operations, but introducing such concepts to the vastly regulated and conservative civil aviation market of today would require major investment.

New production facilities, completely redesigned airport terminals and adapted regulatory measures would all have to be realized before radical new developments are feasible. And currently, those are commitments which nobody is willing to make. But, as the motivation to keep saving fuel and to decrease operational costs continues to drive the industry, even such large investments might be worthwhile.

We will just have to wait.

References [1] KLM Introduces New Cabin Interior and Inflight Entertainment System Aboard 777-200 Fleet, http://news.klm. com/klm-introduces-new-cabin-interior-and-inflight--entertainment-systemaboard-777-200-fleet/, KLM, November 14, 2014 [2] Want major new aircraft designs?

Wait until 2030, http://www.cnet.com/ news/want-major-new-aircraft-designswait-until-2030/, Cnet Sci-Tech, July 23, 2014 [3] Advanced Hybrid Engines For Aircraft Development (AHEAD), http:// www.ahead-euproject.eu/, accessed on November 28, 2014

JANUARY 2015 Leonardo Times

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09-Feb-15 22:34:58

APPLICATION TRAININGS 10th, 11th and 12th of February

PRESENTATION DAYS 17th and 18th of February

SIGN UP FROM 5 JANUARY ONWARDS!

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IN-HOUSE DAYS 16th of March till 3rd of April

INTERVIEW DAYS 22nd of April till 8th of May

WWW.DDB.TUDELFT.NL 11-Feb-15 01:22:26

Kick start your career!

Find your job, internship or thesis project via DDB. Every year ‘De Delftse Bedrijvendagen’ (DDB) leads more than 2500 students to the start of their career. If you want to hit the ground running this year, make sure you do not miss this event. Whether you are job hunting or in need of an internship, DDB offers an unique opportunity to get to know a wide variety of high-profile companies.

APPLICATION TRAININGS

DDB is the largest technology oriented career event in the Netherlands, and takes place each year in the Aula Conference Centre of the TU Delft. This career event is specifically aimed at the students of Delft University of Technology and offers them a wide range of companies and institutions.

PRESENTATION DAYS

Prepare yourself for your job interview

Get to know 130 national and international companies

DDB will this year kick-off with the Application Trainings. During these trainings the companies will provide you with both general tips and tricks as well as detailed personal advice. Newly introduced this year: during the Application Trainings you will be able to have your résumé checked as well as during the Presentation Days!

During the Presentation Days, DDB will give you the opportunity to get to know almost 130 national and international companies.

You can meet these companies by visiting their information stand or view their company presentation. There is also the opportunity to have your résumé checked again and to talk to the recruiters during the drink.

10th, 11th and 12th of February

17th and 18th of February

IN-HOUSE DAYS

INTERVIEW DAYS

Take a look behind the scenes at the companies

Take part in one-on-one interviews with the companies

The In-house Days will be organized by the companies on location and give you the opportunity to form a more complete idea of the companies you are interested in. Your résumé will be forwarded to the companies of your choice, based on which the companies will select participants. On March the 31st an In-House Day will be held in the Aula Congress Centre in Delft for companies situated far away from Delft.

During this period, companies are free to invite students for an interview or simply to get to know the company in more depth.

For the Interview Days your résumé will be sent to companies you are interested in, but also to companies that are interested in your master’s programme specifically. You will receive an overview of which companies are interested, and from these you can make a selection.

16th of March till 3rd of April

22nd of April till 8th of May

PARTICIPATION

ORGANIZATION

All activities described above are included in a single price when participating in DDB. On top of this, you also receive a full-color company guide with information about all participating companies.

DDB is organized by five student societies, that together from ‘The Pentagon’: Vereniging voor Technische Physica Applied Physics Gezelschap Leeghwater Mechanical Engineering Technologisch Gezelschap Chemical Engineering VSV ‘Leonardo da Vinci’ Aerospace Engineering W.I.S.V. ‘Christiaan Huygens’ Applied Mathematics and Computer Science

You can participate by signing up via our website, www.ddb.tudelft.nl, or by coming to the Aula Congress Centre on the 20th, 21st or 22nd of January. Participation is only € 10,- if you register before January 23rd. From January 23rd and onwards participation will cost € 15,-. All personal information will be treated strictly confidential. So if you are looking for a job, an internship or a graduation project, subscribe now at www.ddb.tudelft.nl.

IMPORTANT DATES Deadline reduced entree fee Deadline registration for In-House Days and Interview Days

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11-Feb-15 01:22:37

DARE

STRATOS II, THE STORY BEHIND THE ROCKET

How students designed, manufactured and almost launched a rocket to 50 km

For more than four years, the students of DARE have been working towards the launch campaign of Stratos II. Finally, when the campaign took place, technical flaws prevented the rocket from even lifting off. The goal of 50 kilometers altitude has yet again been postponed. Why did that happen? Why do the students still consider the launch campaign a success?

TEXT Rob Hermsen and Tobias Knop, Students MSc. Aerospace Engineering, Project Stratos Team DARE

THE LAUNCH CAMPAIGN, LOGISTICS AND THE CEDEA LAUNCH SITE: The Stratos II project started in 2010, right after the launch of Stratos I to an altitude of 12.5 km in 2009. The first two years of the project were spent mostly on technological developments and small-scale tests. Towards the end of 2012, the construction and testing of the main systems started. From this point on the students used all their technical knowledge to get the system functional. A completely other side of the project is however often being forgotten by students and spectators; the project’s organization, logistics, safety procedures, planning and the arrangement of a launch site. Without this, it would be impossible to launch a rocket halfway to space.

Already at the start of the project the team was searching for an appropriate launch site, which would be able to accommodate the launch. If you want to

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launch a rocket to 50 kilometers altitude, you will find that having the right launch site is paramount to the success of the launch. To make sure that a launch can be conducted safely, the possible landing sites and the airspace through which the rocket travels need to be cleared from sea and air traffic. These amongst others are the many possibilities the launch site offers.

For Stratos II the launch site CEDEA (Centro de experimentación de El Arenosillo) was contacted. El Arenosillo is a launch site in the Southwest of Spain that is operated by the Spanish space agency INTA (Instituto Nacional de Técnica Aeroespacial). INTA is the same organisation that also operates the deep space communication stations in Madrid. At the CEDEA launch site, a large number of sounding rockets were launched during the ‘60s, ‘70s and ‘80s, with the last sounding rocket launched in 1992. Stratos II should have

been the first sounding rocket launch on the base for more than 20 years. Only a handful of people were left on the base, who had experience with launching rockets. With them, and with the help of old launch procedures, the joint procedures and operations between INTA and Stratos II were established. But still there was a lot to learn on both sides, since Stratos II differs significantly from the design of classical sounding rockets formerly launched at the base. In comparison, Stratos II features more advanced electronics and a hybrid engine, instead of an engine with purely solid propellant.

Together with the INTA, the ground stations were selected and the human resources were divided amongst the different stations. These stations included an optical tracking system, a station near the launch pad, the control room, and two telemetry stations. Communications channels were established between

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DARE

DARE

Figure 1. The rocket body partially froze due to a leak in a sealing valve.

these stations as they all needed to work through the same procedures and maintain the same countdown clock. The work required for an operation like the launch of Stratos II is often underestimated. The unexpected is bound to happen and you need personnel, who can handle stress and who are able to improvise to smoothen the necessary hick-ups. The fact that this year’s launch campaign went so smoothly, it should therefore already be considered a major success for the team.

THE ELECTRONICS AND THE FLIGHT TERMINATION SYSTEM: A variety of electronic systems were mounted on Stratos II. The systems were developed by the project team, as well as by external parties, that wanted to fly their experiments aboard of the rocket.

The flight computer was fully designed by students of DARE. They designed their own printed circuit boards to carry out a multitude of tasks, such as measurements of position and attitude of the rocket, the actuation of parachutes and engine valves, the control of the payload, data management and power management.

Next to these tasks that are carried out fully aboard of the rocket, a number of systems is in contact with the ground via a radio frequency (RF) transmission.

One of these downlinked systems features

the camera feed, which utilizes a GoPro camera to capture live footage. The camera was looking outwards through a small glass window in the skin of the rocket. Another system is a small telemetry downlink that sends back the current state and housekeeping data of the rocket. This system enables the ground station to analyze the status of the rocket and lets the team draw conclusions on whether everything was going as planned.

The flight termination system (FTS) was another system to be linked by a RF transmission. The FTS consists of an uplink from the base to the rocket, which is in contrast with the other two that are downlinks. The FTS ensures that the flight of the rocket can be terminated by a command from the ground. This is necessary in case the range safety officer considers the safety of the mission endangered. This is the case if the rocket is pushed away from its expected trajectory by the winds or if there is a mechanical failure of the fins. In that situation, the rocket could potentially land outside the planned safety zone and put people at risk. If the command is send through the FTS, the rocket will terminate its flight. As a safety redundancy, the rocket will also self terminate if it stops being in contact with the base for more than three seconds.

The FTS was one of the systems causing the most troubles during the preparation and the launch attempts. The problems occurred because the receiver in the rocket needed to work together properly with the antenna of the ground station. As the rocket had never been at the launch site before, problems occurred while testing the functionality of the FTS. Eventually the problems with the FTS were solved but not after losing considerable time. In the end, the rocket failed to launch because the work on the FTS system required the team to take it out of the rocket and reintegrate it after maintenance. The seal of the valve, which regulated the oxidizer flow into the combustion chamber, was fatally damaged in this process. This caused the valve to leak and while doing so, it froze a part of the rocket (Figure 1).

DHX-200 AURORA; THE HYBRID PROPULSION SYSTEM: Stratos II uses a single-stage hybrid rocket propulsion system by the name of “DHX200 Aurora” which was completely produced and tested by students at DARE. As opposed to the liquid and solid propulsion systems, which are more commonly used in governmental and commercial spaceflight, a hybrid propulsion system differs from these. The point that it has both components of the propellant, that is fuel and oxidizer, present in different JANUARY 2015 Leonardo Times

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DARE DARE

Figure 2. The disassembled hybrid motor of the Morning Star in the DARE laboratory

Rob Hermsen

STRATOS II INTERVIEW LT interviewed Rob Hermsen and Tobias Knop about their respective work on the Stratos II project. Both were asked questions about their roles and their views on the project.

Rob Hermsen is the team manager of the Stratos II project and Tobias Knop is the leader of the Propulsion team. They had similar answers on what motivated them

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to join the Stratos II project, a combination of challenge and need within the student team. “It seemed like the best challenge and the nicest way for me to continue. At that point there were many alumni from Stratos I that were graduating and there was kind of a gap, a vacuum that needed to be filled by new people, something like that I kind of expect to happen now after Stratos II. I felt I could be a suitable person to step in and help the student team.” said Rob. Tobias in particular emphasized the notion that it was a genuinely novel challenge that appealed: “In 2010 when I first joined the project I was generally excited about even the small-scale project of making a hybrid engine fire, which had not been done before. It sort of sparked the “if you can make this, you can make anything mindset.” That was quite appealing to me.” The two encountered many challenges they had to face while working on the project. Rob Hermsen emphasized that the main challenge lay not in engineering, but in working with people: “It is eventually people who do the job and you need to make sure that they stay motivated and they actually do their job, that they all work together and that they have good

relationship between each other.”

Tobias iterated a similar opinion that the biggest challenge lay not with the technical but with a organizational aspect: “I think the main challenge would not be a technical one but especially as a team leader was to combine the energies of different people and channel them into one direction. Everybody was excited about different little bits but some bits were sort of left out so I had to make sure they were not left unaddressed and would not come back and stab us in the back.”

Rob explained part of the cause was ambitious young engineers: “Coordination is very important. In order to work more efficiently, people want clear structure, clear tasks and why the task is needed. The latter is especially true for engineering people, as everybody here is rather smart, and require a clear explanation on the reasons behind the tasks.”

Management of the around fifty individuals involved in the project was a recurring topic in Leonardo Times’ interview with the two, who admitted it was hard work

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The oxidizer used for the DHX-200 Aurora is nitrous oxide, also known as laughing gas. It can easily be obtained in industrial gas cylinders. It is stable at room temperature and conveniently pressurizes itself to up to 60 bars, ideal for the use in a rocket.

The fuel grain is based on sorbitol, a solid

and had shifted during the project. While Rob on paper is the ‘team leader’, he admitted this was not an ideal setup: “Originally, two people were imagined: One for logistics and one for technical tasks, but at the end it kind of turned into one person, which was me. Although, I do think such a division should be done on the next big project, as the team will benefit a lot more of it and the people who are responsible, will feel a lot less pressure.” Eventually, Tobias stepped in to assist him: “In direct preparations of and during the launch campaign, I sort of slowly moved into the position of, I would not call it technical manager, but more an operations manager to support Rob. Colloquially, he had too much on his plate and I took over the operational side and the safety management from him. It sort of changed as we went along and got into our positions.”

On a more technical standpoint, an interesting fact is that Stratos II was originally conceived as a two-stage rocket powered by solid rocket motors, but actually turned into a single-stage hybrid. Rob shed some light on this: “We found that for the hybrid

DARE

sugar alcohol. It is augmented by additives of energetic aluminum particles and paraffin wax, each of them with a ten percent mass fraction. This combination was found during a test campaign of fuel characterization tests on small scale (400N, 3s burn time). The combination shows an ideal combination of beneficial properties such as combustion stability, high specific impulse, fuel density and regression rate.

The developed lab scale system was adapted to a lightweight airframe and flight tested in the Summers of 2012 and 2013 to altitudes of one kilometer. The “Morning Star” rocket (Figure 2) served as a demonstrator for both flight-proving the hybrid rocket technology as well as a rehearsal for eventual ground operations of the Stratos II rocket.

The Morning Star rocket and the lab scale static system featured a 40mm diameter combustion chamber and a one-liter tank of nitrous oxide, both fitting into an envelope of 100mm diameter and 800mm length (Figure 3). It features the same amount of components as the eventual up scaled DHX-200 Aurora.

After successfully demonstrating the necessary technology and operations the Morning Star design was selected to be up scaled by a factor of 25 on thrust and a factor 10 on burn time leading to the DHX-200 Aurora propulsion system, sat-

Figure 3. The Morning Star rocket in the launch tower

team there was a group of new people who were already quite experienced with their own system and they were very hard working. Although the solids group was also quite a good team, they were leaving after Stratos I. We thought that the hybrids would be more productive in the occasion of the problems that would inevitably occur.” Tobias also stressed that the team made the difference: “Had this team been developing a solid motor, it would have been a solid motor.”

Rob also added an important logistical constraint of avoiding solid-fuel engines: “Logistics: Try transporting 80 kg of explosives across borders” to which Tobias added, “Our propellant combination is in different phases- a solid fuel and a liquid oxidizer so it is physically impossible to mix everything at the same time. There have been no problems whatsoever with the Dutch law.”

Both hold high hopes for the future of DARE and a possible Stratos III project, that they are confident will happen. Tobias answered confidently: “Yes, definite-

DARE

phases, makes it safer for use. A liquid propulsion system uses both liquid fuel and liquid oxidizer that are burned in a combustion chamber. For example, a liquid hydrogen and liquid oxygen is used in the core stage of the European launcher Ariane 5. A solid rocket uses a premixed solid mixture of fuel and oxidizer components, for example, the Space Shuttle Solid Rocket Boosters with ammonium perchlorate and Aluminium powder in a synthetic matrix.

From a safety point of view, these types of propulsion systems are relatively dangerous as the two propellant components can easily mix in case of an emergency and therefore explode. A hybrid propulsion system on the other hand typically has a solid fuel grain already located in the combustion chamber, while the liquid oxidizer is stored in a separate tank. The finite surface area of the fuel grain does not allow a complete mixing of the two propellants making an explosive reaction impossible. This higher safety aspect makes hybrid rockets perfectly suited for experiments by amateurs and student groups such as DARE.

Tobias Knop

ly. We will go to space.” Rob was equally optimistic, and hoped the success would create new opportunities: “[DARE] may even go further than that by breaking the world record. In that way, I hope we will be able to have a more professional attitude in communication and cooperation with companies, especially international ones, that is the launch site in Spain, Italian and German Aerospace companies, Hungarian payload, or working with other student teams”

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DARE

Figure 4. The static test of the DHX-200 Aurora conducted in Rijswijk.

isfying the needs of Stratos II. It features commercial off-the-shelf components and student-designed custom parts that are manufactured in house.

Good combustion stability was achieved with five and ten seconds firings, extrapolation of thermal data however hinted at a necessary redesign of the internal ablative cooling layout. Another important issue was discovered during two tests: potential grain cracking during the motor startup. Due to the shock load of the sharply increasing combustion pressure during the ignition phase the solid fuel grain can develop cracks that directly expose the vulnerable aluminum pressure vessel containing the combustion.

In order to solve both problems and implement newly acquired knowledge on increasing overall efficiency a second iteration of the engine was developed by spring 2014. In the summer of 2014, a second set of five tests was performed at DLR

in Trauen (Germany). These tests validated the new thermal protection concept and its impact on retaining structural integrity as well as the design change to ensure no more grain cracking to occur upon motor start-up and newly designed injectors and post combustion chamber devices to improve efficiency.

For the integration into the Stratos II rocket, the proven statically fired system was stripped of all unnecessary sensory equipment and high weight components that were not absolutely necessary for a safe and successful operation. Fins, a remote umbilical disconnect, the mechanical interface to the launch rail and other separately tested subsystems were added before the propulsion system and the capsule could be integrated into the final rocket.

DARE

The diameter of all major components and ultimately the rocket was set to 200mm. In order to perform static tests the motor needed to be oriented horizontally, while the total tank volume was split into two vertical vessels. All feed system parts resemble the flight system as close as possible in order to validate as many design choices as possible in a realistic firing situation. The static test system is also augmented with extra controls and sensory equipment that are not present on the Stratos II vehicle. The static test setup and the first test motors were finished in spring 2013. Testing short combustion times and overall thermal behavior commenced in May at TNO, Rijswijk (Figure 4).

At the time it was the largest propulsion

project DARE had seen by an order of magnitude so valuable experience was gained on working with large scale systems.

Figure 5. The gound station at CEDEA during the first launch window.

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Suhas Shyamsundar

VSV Study Tour ‘Valhalla’ Visiting Aerospace Engineering related companies in Germany, Scandinavia and Italy

In September 2014, thirty Aerospace Engineering students departed for an exciting trip across Europe to visit some of its major players in the Aerospace Industry. From icy winds in the polar circle to sunny beaches in Northern Italy, this year’s study tour was probably the most diverse trip through Europe the participants had experienced.

TEXT Lubi Spranger, Student Aerospace Engineering, Editor Leonardo Times Prithvi Sai, Student Aerospace Engineering, Editor Leonardo Times

Bremen, Germany The first destination of the ‘Valhalla’ Studytour 2014 through Germany, Scandinavia and Italy was Airbus Defence & Space (former EADS Astrium, Cassidian and Airbus Military) in Bremen. The group was received by the Executive Assistant for Orbital Systems and Space Exploration and given a company presentation with a special video message of the Dutch Bremen site manager. The programme then continued with a guided tour including the clean room integration facilities where the upper stages of the Ariane V launch vehicle were assembled. Other highlights of the tour included the mission control room for the Automated Transfer Vehicle (ATV) and a one-to-one model of the European unit of the ISS. Hamburg, Germany Day two of the study tour continued with more insights into Airbus with a visit to the company’s German headquarters in Hamburg. The site is responsible for the assembly of the A320 family and is home to the A380’s major component assembly

hall. It also deals with the final acceptance and delivery of the world’s largest passenger aircraft to customers in Europe and the Middle East. After a company presentation and a number of technical presentations from engineers with a TU Delft background, the group was taken on a factory tour. Besides the impressive assembly halls, another highlight of the programme was to see one of Airbus’ five supersized transportation aircraft, the Beluga take off from the site’s own runway.

The day at Airbus was rounded off with a dinner at a German brewery and a stroll through the Reeperbahn, a going out quarter in Hamburg. On the next day, there was no company visit planned, only a group bonding activity at ‘Dialog im Dunkeln’, Dialogue in the Darkness.

Subdivided into smaller groups, we were guided through a sealed off building by a visually impaired tour guide who introduced us into the world of sensing without vision. This was a whole new experience for everyone and brought us closer to the way blind people experience their environment.

Brande, Denmark After the short stop in Aarhus the next company to be visited was Siemens Windpower in Brande. A former aerospace alumnus from Delft had put together a diverse program for the day including three interesting presentations covering a short introduction into wind power, R&D of deicing/ anti-icing systems and aerodynamic flow control systems. The guided tour around the facilities was the highlight of the visit, featuring 3MW and Siemens’ largest 6MW wind turbine nacelles.

The blade manufacture site was located in Aalborg, but we were still able to see a 6MW turbine blade at the site in Brande and even able to walk inside it. Thereafter, one of the Siemens Wind Power technician trainers gave us some insight into the safety trainings and showed us around the training facilities.

Grenaa, Denmark Terma, in Grenaa, produces advanced aerostructures both for civil and military aircrafts around the globe and belongs January 2015 Leonardo Times

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SuHaS SHyamSundar

Figure 1. KSaT in Tromsø.

to the Danish Terma group consisting of three divisions: aerostructures, Defence & Security and Space. The Granaa site produces highly complex composite parts used for example on the F-16, the G450 and the F-35. Some of the parts produced

by Terma include leading edges and center fuselage panels, horizontal and vertical tail skins and spars. Since a number of parts produced by Terma are destined for military purposes, the company requires the Danish government to approve of its customers. The visit included a company presentation and an interesting factory tour..

two different case studies on an incident and an accident. For both happenings, we had to investigate the cause. One of the case studies dealt with the HaZE01 crash in 2012 during a practice maneuver by the norwegian airforce, where a C-130J crashed into Sweden’s highest mountain Kebnekaise. The reason for the crash was a too low flight level. In the second case, a serious incident was investigated where a plane slipped off the runway. For these study cases, we learned a lot about the importance of fine distinctions between findings, facts and causes for an incident/ accident.

LInkÖPInG, SWeden after an adventurous search for our hostel with nokia offline maps in linköping and late night arrival, we woke up on the 10th of September at a beautiful little holiday resort surrounded by fields and white houses with red frames: we had arrived in Sweden. The planned visit to Saab was cancelled, but the organizing committee quickly decided on an aerospace alternative: the ‘Flygvapenmuseum’, which featured many interesting aircraft, exhibits put into historical context.

GÖTeBOrG, SWeden: Halfway through the tour, it was time to visit Göteborg, Sweden. It is the second largest city in Sweden and home to the company Volvo. We arrived by train from Stockholm after our first train journey through the Scandinavian countries and spent the rest of the day exploring the city. The next morning, we visited GKn aerospace Engine systems, formerly called Volvo aero engines in Trollhattan.

The company is known for their rM series engines. We visited their facilities such as the research and development wing, maintenance hangars, assembly halls, and nondestructive testing laboratories.

STOCkHOLm, SWeden On our first morning in Stockholm, we visited the Swedish accident Investigation authority, a government agency of Sweden that is part of the Ministry of Defence. The programme was very interactive: after a general presentation we were split up into two groups to perform

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TrOmSØ, nOrWay: From Göteborg, we travelled to Oslo by train. From there, our flight departed to Tromsø and in the early evening we landed on the arctic island. The city was beauti-

ful with the norwegian Sea surrounding it from all sides, many underground tunnels and tall bridges. The sky was clear and as night fell, we gaped at the night sky admiring the northern lights. The next morning, we visited Kongsberg Spacetec and KSaT. These two companies are subsidiaries under the Kongsberg group. Except for the students from a space background, most concepts were new to everyone and by the end of the day we had learnt a lot.

The main areas of business of both companies are Earth observation systems and satellite antenna systems. The next day, a group activity was planned to go by cable car to the top of a mountain in Tromsø and from there we went on a hike around to another peak. The time flew by in this beautiful scenery.

OSLO, nOrWay: The Gardermoen airbase is one of the oldest airbases in Europe. German forces destroyed the airbase during World War II and it has gone through a number of changes since then. The main attraction was a lockheed C130-J, popularly known as the Super Hercules. We went around the base visiting the repair shop, rescue preparations and operations and coincidently, we saw a troop of Dutch military forces at the base to perform some military exercises. We went around the Super Hercules, had a detailed look into the cockpit, its avionics and propellers. We also had the opportunity to talk to lockheed and rolls-royce experts about this massive military aircraft. after the visit, we

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Figure 2. Ferrari in Maranello.

in the field of aerospace and automobile engineering welcomed us with a presentation about their current research topics, past experience, academics and their departments. We also toured around the aerospace department laboratories to see the wind tunnels. mOdena, ITaLy: The last destination of our company tour was Modena, the home to Ferrari and Maserati. We went around the assembly unit of Maserati where models ordered from various parts of the world are manufactured. The next day, it was our final company visit and a grand closing ceremony with Ferrari at Maranello. We visited the engine assembly facility, the chassis and power trains assembly of 458 Italia, the FF variant and many more. We had the opportunity to see every stage of the

production process from the customized car interior design to the wheel mounting and testing. The visit reached up to our high expectations and the well-organized program, which was specifically tailored to our group’s interests, particularly impressed us. Before returning to the netherlands, we spent our last day in riccione, a holiday resort in Italy: the perfect location to end our tour. The next day we took our flight from Bologna to Eindhoven where our journey came to an end.

To all the enthusiastic people, participants and faculty staff who helped us in making this tour happen and to the organizing committee members who successfully planned this amazing trip, we would like to say thank you. Our experiences and memories will be relived at one of the (hopefully!) many revival drinks to come.

SuHaS SHyamSundar

TurIn, ITaLy: Turin was our first destination in Italy, the sixth largest city in Italy. It’s a beautiful city surrounded by the alps and is well known for its automotive industry with manufacturers such as Fiat and alfa romeo. We arrived from Milan by bus in the afternoon and we took a long walk though Turin, visiting the city’s main areas. Everyone was excited to taste the endless combinations of gelato. We visited Thales alenia and alenia aermacchi on the next day.

First, we went to Thales alenia where we had a brief presentation about the company activities, and then we visited their facilities, including the clean rooms where they manufacture modules for the International Space Station and control rooms. afterwards, we were seated in a 3D theater to watch a demonstration of operations in space. The second half of the day, we went to alenia aermacchi. alenia is known for its Eurofighter Typhoon and C27J Spartan aircraft. We visited the wing manufacturing plant of the Eurofighter and assembly hall of the C-27J Spartan.

Our guide showed us around both aircraft and we were offered to sit in the cockpit. although we extended our visit, there were too many interesting things to see. The next day, we went to avio aero engines. The company manufactures lowpressure turbines for aircraft engines. avio aero used to manufacture whole engines, but decided to confine to their expertise.

We went around their manufacturing facility, to obtain an insight into avio’s special manufacturing techniques. after visiting avio aero, we had the opportunity to visit Politecnico di Torino, one of the oldest universities in Italy. Two professors

maaIke WeerdeSTeyn

had some free time to go around the city visit the Opera and other historical locations.

Figure 3. Flygvapenmuseum in linköping.

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TEAM SMART

AIAA AIRCRAFT DESIGN COMPETITION TU DELFT is the winner

In September 2014, the American Institute of Aeronautics and Astronautics (AIAA) announced the results of the aircraft design competition for both undergraduate and graduate levels. The undergraduate design competition called for the design of a transonic trainer while the graduate competition called for the design of a supersonic test-bed. TU Delft participated in both the competitions simultaneously for the first time and won, and it was first time the master student team from Delft won the graduate competition.

TEXT Sebastiaan van Schie, Bachelor Student Aerospace Engineering Malcom Brown, Master Student Flight Propulsion and Performance

T

he American Institute of Aeronautics and Astronautics (AIAA) aircraft design competition is held every year by the largest technical aerospace society in the world. Three aircraft design competitions are usually organized: individual undergraduate, team undergraduate, and team graduate. This year the TU Delft participated in the individual undergraduate (Sebastiaan van Schie - second year bachelor) and the team graduate (Malcom Brown, Koen van de Kerkhof, Raphael Klein, Martijn Roelofs, Niels Singh, and Daan Westerveld) competitions. Dr. Roelof Vos of the TU Delft supervised both teams, while the graduate team was additionally supervised by Dr. Barrett from The University of Kansas and advised by Prof. Egbert Torenbeek.

THE DELFT ADVANCED TRANSONIC TRAINER (DATT) Although the T-38 has received its fair share of updates, its hardware is start-

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ing to become outdated. Due to changing needs in pilot training, an increasing number of training tasks are currently performed in two-seater F-16’s, but these will be phased out in the coming years.

In order to be ready for the future, the USAF has issued a program to find a suitable replacement for the T-38’s. This new aircraft is planned to enter service by 2023 (Air Force Times, 2013). The undergraduate competition built on that, and aimed at the design of a replacement for the T-38 trainer. The primary aim of this new trainer is to educate and prepare pilots who transition to the F-22 Raptor or the F-35 Lightning II, featuring state-of-the-art electronics and cockpit hardware. Training tasks that have to be performed include in-air refueling, highg operations, air-to-air and air-to-ground deployment, night vision imaging systems operations and data-link operations.

To achieve all these goals, the AIAA set stringent requirements for the competi-

tion. Primary requirements stipulated (AIAA, 2013): Employ a commercial offthe-shelf engine; crew of 2, one student pilot and one instructor; both crew members need to have adequate visibility to perform all tasks, including landing and take-off ; cruise Mach number of 0.9; dash (unsustained) Mach number of 1.2; sustained 9-g turns; combined runway distance for single-engine designs of no more than 6,000ft; unit flyaway cost of no more than USD$20 million, preferably under USD$10 million.

One can deduce the following from looking at the aircraft used by military aerobatic display teams: many employ fighter trainer jets because of their agility. For these reasons it was decided to employ an all-moving canard configurations. Since canards can be inherently unstable configuration, it is possible to reach higher levels of maneuverability (Whitford, 1987). Combining this with a

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LOCKHEED MARTIN

TEAM SMART

TEAM SMART

TEAM SMART

Figure 1. The Quiet Spike™ mounted on SMART

Figure 2. Presentation of the four configurations of the SMART

negative static margin, elevons all along the trailing edge of the main wing and differential all-moving canard control allows for a very agile aircraft, allowing the student pilots to experience sustained high-g turns before transitioning to their operational fighter. To avoid an excessive amount of wave drag in the transonic flow regime a sweep angle of 41.2 degrees was applied to both the canard and main wing, along with a chord thickness of 6%.

In order to provide as much commonality with the F-22 and F-35 as possible, the decision was made to use all of the Government Furnished Equipment (GFE) specified (AIAA, 2013). The GFE includes everything from avionics to ejection seats, electrical systems and vehicle management systems. Using these systems allows the student pilot to become familiar with the cockpit layout and systems implemented in the aforementioned aircraft before he flies his operational fighter.

While searching for a power plant, the choice was made to go for a singleengine configuration, as this offers several advantages. First, the maintenance complexity of the aircraft is reduced, since there are less moving parts, tubes and wires. Secondly, the size of the fuselage is reduced, since there is only space needed for one single engine instead of two. Thirdly, the runway length requirements stipulate that multi-engine designs need to take balanced field length into account instead of runway distance. The

Figure 3. Front view of the cockpit of a F-35 Lightning II

choice was made for the General Electric F110-GE-400. This afterburning turbofan found service in several variants of the F-14 Tomcat and was selected for being the one engine that combined acquisition cost, fuel consumption and size in the most favorable way. Providing 26,800lbs of thrust in static afterburning conditions this leads to an aircraft thrust-toweight ratio of 1.23. To provide the engine with enough mass flow, two air intakes were placed at either side of the cockpit.

Mach Numbers in excess of 1.2 with the aim of testing flutter behavior, tailless control and low boom supersonic concepts. Finally, the aircraft was to be able to accommodate the standard, tailless delta configuration and delta-canard configurations. The final goal was to improve on the X-56 program, an aeroelastic test aircraft with interchangeable wings, to perform the same type of experiments at supersonic speeds.

In order to keep the costs low, conventional technologies have been employed.

The aircraft is made mainly out of metal rather than composites, no new technologies have been implemented, the engine has already proven itself in another aircraft and all of the electronics are currently being developed as part of the F-35 program. A production run of 600 aircraft would result in a unit flyaway cost of $11,650,000, with an operating cost of only $5,713 per hour of flight. In 2012, the operational cost per flight hour for the T-38 was $9,233 (Time, 2012). This comparison shows that it is sensible for USAF to switch to the DATT also from a financial point of view, as the T-38 will continue to cost more each year as its maintenance increases.

The requirements were very demanding.

Basic supersonic aircraft design has become relatively straightforward with modern understanding of supersonic wave drag and improvement of engine thrust to weight ratios. However, how does one area rule an aircraft that has to change configuration? Additionally, since the wings could be seen as sacrificial to this aircraft due to the hazards of aeroelastic testing, it was not possible to store fuel or other vital systems in the wings. Furthermore, how does one make changes to the aircraft shape to influence the strength of the sonic boom and which aircraft sections are affected? These are a few of the complicated challenges the team faced at an early stage in the design. Through many hours spent discussing and researching, smart yet simplistic solutions were found.

THE SUPERSONIC MULTI-UTILITY AEROELASTIC RECONFIGURABLE TESTBED (S.M.A.R.T.) The graduate competition required a design of an aircraft test-bed capable of

First, all the design options were brainstormed. Aircraft concepts that incorporated each of these options were envisaged. Following this, an initial trade-off was made to eliminate obviously unviable JANUARY 2015 Leonardo Times

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SGT JEFFREY ALLEN, USAF

SEBASTIAAN VAN SCHIE

Figure 4. Rendering of the DATT

options based on literature research, expert opinion and common sense. This resulted in four possible aircraft, with different wing connection systems, engine(s) and intake placement, gear configurations and fuselage shape going further into the conceptual design. These concepts were then fully formed with the necessary systems and sized on first order methods. A second trade-off was also made incorporating the strongest ideas from the other concepts and the resulting aircraft was the S.M.A.R.T. (see Figure 2).

Since multiple configurations needed to be applied to the S.M.A.R.T the preliminary design process needed to be executed in such a manner that all of these configurations were feasible from an aerodynamic, structural and stability and control standpoint. This necessitated a complicated script, which used Roskam’s empirical sizing rules [5] and the DATCOM method to size the aircraft for a range of different wing planforms and surface configurations. Each configuration influences the others due to changes in weight estimations and engine thrust, thus a design convergence was run to converge to the best solution for all configurations. In order to estimate the wave drag of the aircraft at supersonic speeds, the CATIA model of each chosen configuration was sliced in MATLAB at angles from 0-180 degrees (allowed due to symmetry) to determine the cross sectional area distribution within each Mach cone for the range of Mach numbers. For the structural calculations the main design wing was modeled and analyzed in Patran/Nastran at the required 9g load and other load cases. A preliminary aeroelastic analysis was then

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Figure 5. Two Northrop Grumman T-38 Talons

also carried out on this model, resulting in the natural frequencies and eigenmodes.

The end result of all of this work was the final aircraft, the S.M.A.R.T. Why is this aircraft special and how does it satisfy the project requirements? Never before, has there been such a versatile supersonic test aircraft. There is no other supersonic aircraft that can change its configuration, from a conventional swept wing and empennage to a delta wing with canard, among other configurations. Using the innovative aluminum fuselage structure and wing attachment methods, an extremely large array of wings and structural layouts can be tested. The wing can completely or partially detach from the aircraft and it is recoverable from supersonic speeds by way of the drogue and main parachutes, saving the fuselage and all flight required and costly systems. Aeroelastic phenomena can be tested safely with small changes to the inertial properties of the wing with water ballast tanks and structural stiffness changes with a new slightly modified wing structure. The chosen carry through wing-fuselage junction allows for accurate flutter testing since this type of junction only slightly influences overall structural stiffness compared to other methods. Human lives are never placed at risk, with the aircraft being unmanned and having triple redundant systems and safety measures such as the fuel storage in the fuselage reducing the chance of fire and failure among others. It was identified that the nose shape and fineness determined, to a large degree, the strength of the sonic boom and as such, the entire nose section of the aircraft can be removed and replaced with one of a different shape also incorporating Quiet Spike™ technology (see Figure 1).

THE FUTURE OF THE AIAA COMPETITION The Aerospace faculty intends to continue this series of two years of winners of the AIAA competition. The competition can be very time consuming and so far, the students that have participated in it, have done so by dedicating their free time over a period of six months. However, using the complete TU Delft aircraft design education, any second year, third year or master student can participate and aim to score a top place. The new proposals have already been given out and you can go check them out on www.aiaa.org. If you are interested in participating in the competition, do not hesitate to contact Dr. Roelof Vos at r.vos@tudelft.nl.

References [1] Budget constraints delay new trainer, http://www.airforcetimes.com/ article/20130515/NEWS/305150023/ Budget-constraints-delay-new-trainer, Air Force Times, 2013 [2] 2013-2014 AIAA Foundation Individual Undergraduate Aircraft Competition, https://www.aiaa.org/uploadedFiles/ Events/Other/Student_Competitions/2013-2014%20RFP%20Ugrad%20 Ind%20Aircraft.pdf, AIAA, 2013 [3] Whitford, R., “Design for Air Combat”, 1987, Printed and distributed by TU Delft with permission of Jane’s Publishing Company Limited, London, United Kingdom [4] Costly flying hours, http://nation. time.com/2013/04/02/costly-flighthours/, Time, 2012 [5] J. Roskam, Airplane Design Part I-VIII, Airplane Design (DARcorporation,1985).

Leonardo Times JANUARY 2015

11-Feb-15 00:58:20

DLR

DESIGN FRAMEWORK FOR HIGH-LIFT SYSTEMS A Knowledge Based Engineering Application

In today’s competitive aviation industry, continuous efforts are being directed towards reducing design time system complexity and costs. Especially for high-lift systems, a potential gain in design efficiency can be obtained by considering their impact early on in the design process. In this master thesis, Knowledge Based Engineering (KBE) techniques are applied to increase efficient in the high-lift system design for trailing edge, single-slotted flaps.

TEXT David Zaccai, MSc. Graduate, Flight Performance and Propulsion

n the pioneering age of the jet, higher cruise speeds and wing loadings associated with fast jet aircraft called for powerful high-lift devices (HLD) to keep take-off and landing speeds within safe limits, as well as suitable approach attitudes. The level of complexity of these systems was relatively high, as proven by the doubleand triple-slotted flaps of the early Boeing and McDonnell-Douglas aircraft (Figure 1).

With the increasing need to reduce aircraft costs and noise levels, and improved aerodynamic analysis tools, modern aircraft are fitted with simpler HLDs of reduced system complexity. Amongst others, this can be seen in single-slotted flaps of the B787 and nearly all Airbus models. Furthermore, a trend towards simpler and less maintenance-intensive kinematic mechanisms can be found, noting the simple flap hinges on the B787 and A350. This article summarizes the development of a high-lift system design tool by reviewing the perks of KBE applications, typical design constraints and the used analysis methods.

WHY KBE? KBE techniques essentially transform the designer’s knowledge and experience into a set of rules. Combined with a parametric model, the designer can quickly alter the product geometry. When disciplinary analysis tools are then integrated as

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well (e.g. stress analysis), the designer can rapidly iterate between different “what-if” scenarios and save time by the automated analysis process.

Current methods for weight and power estimation of high-lift systems rely on empirical data, which are not sensitive to design variables and different load cases.

The developed KBE application integrates the preliminary wing geometry with flap deployment mechanisms that account for three-dimensional flap motion. The highlift system in the developed application includes the kinematic synthesis of four common mechanisms, an initial actuation architecture, weight and power estimate.

DESIGN CONSTRAINTS The architecture and integration of highlift systems is multi-disciplinary and iterative in nature, due to tight dependencies between aerodynamics, mechanism kinematics and structures. Generally, the main constraints on high-lift systems are fourfold (Flaig et al., 1993).

Firstly, the flap’s maximum chord extension is dictated by the wing box’s front and rear spar position (Figure 2). Since the wing stiffness and internal fuel volume should not be compromised, the spar positions are fixed. This leaves a limited space for the flap and the transmission system that leads from the fuselage all the way along the spar (see visual on top).

AIRBUS (RECKSIEK, 2009), EXTENDED BY DAVID ZACCAI

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Figure 1. Trend in trailing edge flap configuration.

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DAVID ZACCAI

AIRBUS (FLAIG ET AL., 1993)

DLR

Figure 2. Geometrical constraints in flap design.

A second constraint is the geometrical limit for flap shape optimization. The main goal here is to increase the flap deflection at which separation occurs. The close-coupling between the leading edge pressure peak and trailing edge pressure gradients require a careful optimization process.

Thin trailing edges, such on modern transonic airfoils, do not always allow a generous nose radius of the flap, which further complicates to delay separation.

Thirdly, the support structure and relative thickness influence the flap’s bending stiffness. The flap’s resistance against bending is traded with the number of support stations.

Finally, mechanism kinematics determines if the aerodynamic targets can be met. A mechanism type allows for a specific dEployment path. Fowler motion, flap angles and structural properties (actuator type, torque, pylons, weight) influence this design trade-off.

DESIGN PROCESS The starting point of the proposed design process is the clean wing optimized for cruise, as well as the low speed aerodynamic requirements. Next, the developed application is used to model the high-lift layout (flap span, chord, settings) and choose the kinematic mechanism. The resulting configuration can then be analyzed aerodynamically and mechanically, following a weight and power estimate.

WING MODEL Former graduate students within the FPP department have developed a parametric wing model, called DARwing, which is developed using Genworks GDL. The model is generated using lofts for lifting and non-lifting surfaces, and accommodates leading and trailing edge devices. For the purpose of this thesis, the code for singleslotted flaps has been reshaped to allow realistic user inputs and more accurate flap motion.

STEP 1: KINEMATIC SYNTHESIS In line with the trend in HLDs, four kinematic mechanisms are modeled: the

Figure 3. Resulting geometry of a A320 wing design cycle in the devel oped KBE application. (a) Retracted flaps, link-track mechanisms synthesized and sized. (b) Retracted flaps, top view. Flaps in land ing configuration top view (c) and isometric (d).

dropped-hinge, four-bar linkage, linktrack and hooked-track. The first three are extended versions of previously developed models by a former FPP graduate (Bertels, 2008). All mechanisms are trusstype structures and actuated by a rotary or linear actuator. The synthesis of kinematic mechanisms is performed using geometric methods, rather than analytical. Since parametric models are at the core of KBE applications, it makes sense to use the geometric data readily available. However, a distinction is made between 2D and 3D kinematics. A flap deployment mechanism acts in-plane, thus being synthesized in two dimensions. It uses the retracted, take-off and landing position of the local flap section. At the other hand, the complete flap model is a 3D, rigid surface, which is rotates and translates as a whole.

Therefore, each deployment mechanism allows for out-of-plane flap motion during the 2D synthesis. This strategy permits so-called conical flap deployment, which is common for outboard flaps on swept, tapered wings.

STEP 2: AERODYNAMIC ANALYSIS When all kinematic syntheses have been completed, the static normal loads on the flap are obtained. For this purpose, an empirical estimation method from ESDU is used. Based on measurement series for Fowler flaps, it relates the relative flap chord and deflection to its normal load coefficient. By simple interpolation of the data, a crude normal load over the flap is found.

Naturally, taking into account the airfoil shape and Reynolds number, more accurate results can be obtained. However, a comparison to pressure measurements of a Fokker 28 flap indicates a maximum error of 20% for deflections greater than 18 degrees.

STEP 3: MECHANICAL ANALYSIS By combining the mechanisms dimensions from the kinematic synthesis and the obtained aerodynamic loads, a multibody simulation is initiated. By generating a SimMechanics model in Matlab, the flap-mechanism structure is deployed,

collecting the quasi-static internal loads for each link member. Next, the normalloaded members are sized with ultimate tensional stress and buckling stability using the chosen material properties. Once executed, the structural weight and actuation load are obtained. Finally, the drive motor power and transmission system weight (i.e. series of torque tubes driving the mechanisms) are computed.

TEST CASE: VFW-614 To understand the accuracy of the implemented methods better, the wing and outboard flap track (Figure 4) of a VFW614 are modeled. The faculty’s aircraft hangar is in possession of a VFW-614 wing structure including such a flap track. The predicted weight is 13% lower than the results.

RESULT The final KBE application implements a design process which results in a preliminary geometric and kinematic design of trailing edge flap mechanisms, complying to a given set of design requirements: mechanism position, dimensions and orientation, flap gaps, overlaps and deflection angles, choice of materials and finally, the flap limit speed. The application is capable of determining the three-dimensional flap motion, in addition to estimating the system weight and required power of both the kinematic mechanisms and a simplified actuation architecture.

Recommendations for future research include the inclusion of higher-fidelity analysis tools, such that estimate accuracies can be increased. Extending this tool for leading edge high-lift systems will also greatly increase the application’s functionality.

References [1] A. Flaig and R. Hilbig, “High-Lift Design For Large Civil Aircraft”, AGARD-CP 515, paper 31, 1993.

[2] F.G.A. Bertels, “Design Framework For Flap System Kinematics”, Master’s thesis, TU Delft, 2012.

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COMPOSITE GRID STIFFENED STRUCTURES Validation of a finite element based damage prediction model

The recent growth in composite application is now being implemented in aircraft primary structures such as the fuselage of large civil aircraft such as B787 and the A350. One of the front-runners in cylindrical stiffened shells for applications that undergo pressurization and therefore, in-plane bi-axial stresses, is the grid-stiffened or lattice structure. Although extremely weight-efficient and damage tolerant, the lack of automated economical manufacturing techniques caused this concept to be neglected thus far. The recent advances in automated manufacturing have made it an attractive candidate.

TEXT Dr Sonell Shroff, Assistant Professor Aerospace Structure and Computational Mechanics, ASM

G

rid-stiffened structures are successors of geodesic structures that have been a part of aircraft and building technology for over a century. Developed by Sir Barnes Willis, for Vickers in 1938, it was eventually used to build the Vicker’s Wellington bomber as a large framework of Duralumin W-beam elements. The array of cells formed by the pattern of grids, or stiffeners, gave the fuselage of the Wellington inherent damage tolerance, making for a highly reliable aircraft. Geodesic structures have since been used in many other aircraft and spacecraft applications such as in the Douglas DC-6 and DC-7, and in rocket boosters for the Saturn, Delta and Titan launch vehicles where a specific geodesic structure called a grid stiffened structure was used. In aircraft, principally a grid-stiffened structure provides increased resistance to the buckling related failure modes in an aircraft skin. In addition to the membrane stiffness provided by a thick skin, using struts of higher material concentrations in the form of ribs in an aircraft skin also adds bending stiffness, making the structure more buckling resistant. The

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grid can be orthogonal, isogrid (equilateral triangles), or anisogrid. Apart from providing high torsion and shear resistance, the interconnected grid pattern gives multiple load paths and redundant stiffening leading to increased damage tolerance [1].

The unidirectional mechanical properties of a fibre-reinforced composite are highly suited to grid stiffening patterns because ribs are mainly loaded unidirectionally in tension or compression along their length.

Therefore, the minimum mass design of a grid stiffened structure has been a subject of interest for a number of decades with various studies providing useful insights into the failure mechanisms of such structures, and their sensitivity to design parameters such as the grid spacing, grid angle and skin thickness [2]. To apply this technology to an aircraft fuselage, the lifetime requirement predicates a robust structure with sufficient impact and damage resistance, stability against buckling, and ease of inspection and repair to make it usable and cost efficient. Hence, the gridstiffened structure has to be evaluated for situations such as fatigue, localized loads,

residual strength after impact and interfacial connections. The research was funded by the European Union Framework 7 project ALaSCA, Advanced Lattice Structure for Composite Aircraft. At the end of the project, the prototype fuselage designed with the help of the consortium, that included, DLR, Airbus, TSaGI, CRISM-B, University of Leeds, Mendelev Insititute of Moscow, and TUDelft, would be fabricated and tested at the partnering Russia research institutes.

A significant part of the PhD work was dedicated to the evaluation of this structure under localized loads such as impact and the residual strength of the structure after impact. It was decided to investigate a variety of composite failure theories to determine a combination for which the impact damage can be predicted reasonably accurately, and the growth of the damage can also be predicted up to final failure in a computationally less expensive manner.

The World Wide failure exercise concluded that there are no universally accepted failure criteria for composites. At the same time, accepted failure criteria that attempt to model the physics of failure and isolate

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ROYAL AIR FORCE

SONELL SHROFF, TUDELFT

SONELL SHROFF, TUDELFT

SONELL SHROFF, TUDELFT

Figure 1. Fabricated carbon fiber reinforced grid stiffened panel being tested in compression

Figure 2. Examples of grid stiffening configuration

the different constituents (fiber, matrix) are amongst the most promising. I used a combination of such criteria to benefit from the advantages of each. Failure criteria based on the approach of individual failure modes and described further for tensile and compressive modes for each failure mode by Hashin and Puck, in which the general three dimensional stress states are considered are modelled separately by a quadratic polynomial containing the appropriate stress components. Hashin’s failure criterion is used to detect fibre mode failure in the composite laminate, Puck’s failure criterion is used to predict matrix cracking and crushing failure and strain energy and fracture toughness are used to predict delamination mode failure in the plies. The growth of the damage is a nonlinear material phenomenon and is modeled with a degradation factors that are applied to the stiffness of the material at the damaged regions, such that the stress state is updated accordingly all around the affected zone. A combination of these failure criteria and degradation model shows promising results in predicting damage sizes and types when compared to existing results in literature. For the details of this model, I welcome you to read the relevant part of my PhD thesis or my upcoming publications.

The model was validated by comparison with a semi-analytical model [3] developed in-house by a PhD researcher Fardin Esrail with my supervisor Christos Kassapoglou and test results for impact and compression after impact on flat laminates from known literature. A comparison of the impact damage sizes at different energy levels for the current fem method, semi-analytical method and test results for a sample laminate showed a maximum difference of

Figure 3. Geodesic construction of the Vickers Wellington Bomber

30% at low energy levels with the predictions close to the test results at high energy levels. This behaviour can be improved by reducing the dynamic effects of the model during contact between the impactor and the laminate when impacted with a low velocity. The finite element predictions are closer to the test results as compared to the semi-analytical method. The NDI scans of the tested laminate showed stair-stepped delaminations with each step seen as a π/6 wedge matching well with the finite element prediction [4].

An important part of the validation of the model involved a comparison with my own test data for the specific case of gridstiffened panels that were fabricated at our DASM Laboratory. These panels were fabricated using vacuum infusion of dry carbon fibre placed preforms. An out of autoclave curable resin was selected to reduce the complications and cost of the fabricated panel. A typical anisogrid pattern was fabricated as the grid of height roughly 20mm placed on a skin of 1.4mm thickness. The quality of the parts fabricated was investigated using destructive and NDI techniques and the finite element models were modified to match the material and geometric properties of the tested parts.

The fabrication process is another article worth! The results were extremely promising with a final failure load fem prediction with an error of 1% as compared to the test results! The most important lesson learnt from these tests is that the grid-stiffened structure is extremely damage tolerant.

Impact damaged panels tested under compression show little or no reduction in the compression strength when compared to undamaged grid stiffened panels. The grids provide alternative load paths which can bypass the impacted region to keep the final

failure load unchanged unless the damaged bays are placed too close to each other.

One of the bigger challenges in the process was the fabrication technique. I realized that something as complex as the grid stiffened panel could be fabricated with inspiration drawn from age-old handicraft methods.

All the panels were hand-made during this project; however, this research has laid the path for development of automated manufacturing techniques to produce high quality complex structures at a high speed. Taking this work forward, I am now focusing on the development of automated manufacturing of stiffened panels, steered fibre panels and curved grid-stiffened panels.

Students, who are interested in carrying out mini-projects, or thesis works related to this subject, are more than welcome for a challenging discussion.

References [1] S.M. Huybrechts, S.E. Hahn, and T.E. Meink, “Grid stiffened structures: a survey of fabrication, analysis and design methods”, in ICCM12 Conference paper 357, Paris, France, 1999.

[2] V.V. Vasiliev, V.A. Barynin, and A. Razin, “Anisogrid lattice structures - survey of development and application”, Composite Structures, pp. 361-370, 2001.

[3] F. Esrail and C. Kassapoglou, “An effcient approach for damage quantification in quasi-isotropic composite laminates under low speed impact”, Composites Part B, vol. 61, pp. 116-126, 2014.

[4] E.F. Dost, L.B. Ilcewicz, and W.B. Avery, “The effects of stacking sequence on impact damage resistance and residual strength for quasi-isotropic laminates” ASTM STP, no. 1110, 1991.

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INTERVIEW WITH BASTIAAN VAN GRIENSVEN

AIRBUS S.A.S.

LVD

Airbus A350: Means of Compliance Development (Structures)

Over the past months, the Aviation Department has been in contact with Bastiaan van Griensven, an Aerospace Engineering Alumnus now working at the structures department with Airbus. On December 4, 2014, he joined us at the faculty for a guest lecture about his work on the A350. In addition to this, LVD had an interview with him about his work at Airbus and his time as a student in Delft.

TEXT Karel Dhoore and Meander Leukfeldt, Members Aviation department, Students Aerospace Engineering Martina Stavreva, Editor, Leonardo Times, Student Aerospace Engineering

Let’s start with the beginning, why did you study aerospace engineering?

Funny you asked that, I had to try to recollect that memory! As a little boy, airplanes fascinated me, but that interest faded away when I was in high school. My field of interest became biomedical technology, however, it was a master track so I needed a BSc in another course so I chose Materials. However, during the Open Day for Materials there was an Open Day for Aerospace Engineering as well, where I rediscovered that planes still are fun!

Looking back at your time in Delft, what kind of student where you? What was your academic interest and what did you do next to studying?

I studied a lot, although a lot of people didn’t know about that because I was a morning person. That gave me time during the day to play baseball and to be at St. Jansbrug, the student society I was a member of. But most of the time, I was busy with Euroavia, the European Asso-

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ciation of Aerospace Students, where I was part of the board. With them, I visited companies all over Europe, like SAAB, Alenia, Aérospatiale and Airbus.

So, you got a little involved in the aircraft industry, but how did you end up with Airbus eventually?

By the time I was graduating, around 1995, Fokker was going bankrupt as well.

Basically, I entered a job market saturated with ex-Fokker employees. For a fresh graduate, that was an unlucky thing to have happened. Fortunately, with some contacts I had I was able to do an internship with Airbus, in Toulouse, to gain experience in the aircraft industry. At the time that I was graduating, Boeing was hiring a lot of people away from British Aerospace Airbus (now Airbus UK) and, maybe thanks to my experience in Toulouse, I was offered a job in the Fatigue and Damage Tolerance Department in the UK. I do not really call it a choice I made to work for Airbus, but I think of it as an op-

portunity that I was happy to take!

So afterwards, you did not look for another employer either?

Not really, I was offered a job once at one of the suppliers, and I have gotten a job offer from a Canadian company as well, but I did not take them. Even though they try to convince you with higher salaries, for me the working conditions at Airbus are very satisfying and there are more than enough possibilities to develop yourself within the company as well.

What are you currently working on and to what extend is this still related to the subjects you graduated in?

I graduated in “Multiple Site Damage in Flat Uniaxially Loaded and Curved Pressurized Riveted Lap Joints”, where I did a comparison study between 2024-T3 and GLARETM joints. Even though I never did something with GLARETM afterwards (I worked more on materials used for wing structures, whereas GLARETM was used for

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Right now, I am working with the certification team of the new A350-900. More specifically, I make sure that the certification rules regarding the structures group are interpreted in the same way between all the different departments working on the aircraft. It’s a coordinating job, but very technical in a way that I work with other specialists from all different groups to determine the specifications for the certification. So, comparing this to the position I started in at Airbus, it is a little different than the subject I graduated in.

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the fuselage), I had a good connection with my graduation subject at the Fatigue and Damage Tolerance Department at British Aerospace.

Figure 1. Bastiaan van Griensven giving the presentation in Aerospace Engineering faculty of TU Delft

LVD VSV

From the editor of Leonardo Times that was present during the lecture:

During his lecture at the Aerospace Engineering faculty, Mr. van Griensven also elaborated on the major difficulties in the certification process of A350.

The aircraft needs to meet both the certification requirements posed by European Aviation Safety Agency (EASA) and Federal Aviation Administration (FAA). However, additional challenges occur when it comes to a structure that is built with more than 50% of composites. All the certification procedures comply with the fact that the aircraft is mainly a metallic structure; therefore, some of the certification requirements posed by EASA and FAA are not applicable for the case of A350. The department, which dealt with the certification of the aircraft, spent a large amount of time communicating with the corresponding authorities. They needed to revise some of the requirements and at the same time provide with solid proves that the aircraft is going to be able to meet all the safety criterion.

Those include for example resistance to impact of different sections, fire under the wing, water injection from the engines and many more. For most of them special tests had to be performed. However, those cost a big amount of money to Airbus and therefore they needed to come up with a cheaper, but still sufficient way of testing their structure. Thus, they have proven that some of them can be substituted by virtual representation of the test and many of the components have been checked exactly like this. This resulted in the on time certification of A350 on the 30th of September 2014 from EASA and the statement of the Airbus President and CEO Fabrice Brégier: ”Accumulating more than 2,600 flight test hours, we created and successfully achieved one of the industry’s most thorough and efficient test programs ever developed for a jetliner”.

Are there any projects you worked in the past couple of years that you found espe-

Figure 2. Bastiaan van Griensven signing the Aerospace Wall

cially interesting?

What I find very interesting is learning.

The last 6 years I have been working in the world of regulations, specifications and their interpretation. It is a sector subject to changes and there is a lot of variety.

Six months after I started working at British Aerospace, I got involved with the inservice support group for landing gears.

That was really interesting because it was a very technical environment to work in with a lot of travelling and interesting investigations of in-service issues. That is where the fun actually starts for engineers: when something goes wrong there is a lot to learn and a lot to discover. What went wrong, why did an accident happen and how can we solve the problem, are questions that keep the job exciting.

Within Airbus, there are two distinct career paths you can follow from the engineering view. One is the so-called resource path that leads to Engineering Management. The second one is a more technical alternative with steps to Technical Specialists and Technologists. I was more appealed by the technical side of engineering and so I went down the technical oriented path. After six months in the fatigue research department and working on the landing gear issues for

two years, I applied for the role of Technical Specialist for landing gear structures.

What I loved about the landing gear structure is that it is very different from the rest of the plane’s structure, yet it is highly sophisticated and it has to be incorporated perfectly with the overall structure and with the electrical systems.

Do you have any plans for you future career?

I am not the type of person who plans his career ahead; I rather see what kind of opportunities present themselves and what fits with my personal life. I probably would like to do something else in life, but within Airbus, there are a lot interesting paths you can follow so I will see where the wind blows.

Aviation Department The Aviation Department of the Society of Aerospace Engineering Students ‘Leonardo da Vinci’ fulfills the needs of aviation enthousiasts by organising activities, like lectures and excursion in the Netherlands and abroad.

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ANP

A Forensic Engineer for a day An insight into ‘mock’ crash investigation

We have all seen the documentaries on air crashes. But how does it really work, and what are the skills behind the investigation of a crash? The course AE4457 Forensic Engineering has answered these questions to a number of students this year, who were put to the test at a set-up crash site, under the supervision of Michiel Schuurman, an investigator at the Dutch Safety Board and part-time lecturer at the TU Delft.

TEXT Michiel Schuurman MSc., Forensic Engineer at Dutch Safety Board, and Associate Professor TU Delft Shahrzad Hosseini BSc., Aerospace Engineering MSc. student, and Editor Leonardo Times

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n 2009, during the Turkish Airlines 1951 crash investigation in Amsterdam, Michiel Schuurman was part of the investigation team. He was chairperson of the Data Recorder team, and vice-chairman of the Systems team. In his career at the Dutch Safety Board, he has worked on numerous cases on both national and international level. With this experience, both a theoretical and practical scope of the Forensic Engineering field could be passed on to the students following the course.

To introduce this field, Forensic Engineering is the investigation of materials, products, structures or components that fail or do not operate or function as intended, causing personal injury or damage to property. Just like accident investigation, forensics looks into the event although Forensics focuses on the process of answering the questions using scientific principles. Therefore during the Forensic Engineering principles of fire investigation, systems investigation and collision investigation were discussed. Apart from the more generic engineering principles,

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also critical thinking, logic and interviewing were part of the lectures. This was to prepare the students for the field examination.

Exam description For the exam, eight teams of approximately eight students were grouped together to do the exam. Before the exam, each team received a pre-briefing with the exam rules. The groups were informed that the exam would take place on the grass field behind the Fellowship building. This meant that the field behind the fellowship was off limits during the day.

Another point that was raised during the pre-briefing was attire. The students were instructed to wear weather appropriate attire. Luckily, the weather was nice, although it could be raining next time. The investigation was confidential and students were not allowed to talk about the exam. This was a challenge as the press was present and wanted to know everything. Anthony Brickhouse, an Associate Professor from Embry-Riddle Aeronautical University, came over from the United

States to help as an instructor in the exam.

At Embry Riddle, Anthony has a crash laboratory where students get hands-on experience in investigation. Because of his experience, he was able to grade students on their performance and in the field exam.

Student approach So how did the students approach the investigation? One hour on the field is not that such, when you consider that all evidence has to be collected, pictures must be taken and the area needs to be searched for any clues. Some groups started by searching out the entire area, by spreading the group members throughout the field. Meter by meter the ground was searched for any suspicious track, bump, hole or bruise. Using simple equipment like rulers and more, all possible clues were studied closely (see Figure 1).

Following this, the two aircraft, the glider and the ultralight, were approached and searched for clues. Why was the engine detached (see Figure 2)? Why is the propeller not intact? Was it broken down dur-

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But the question remains, how deep did the students really dig? Did they find the hidden elements? a plastic bathtub duck was hidden in the cockpit of the glider, and a number of groups did find it. But what about the plastic rabbit which was hidden on the field underneath the grass?

There was not a single group that found at Embry riddle, anthony. Even though this element did not have any connection to the investigation, the students were put to a test to find out how deep they really dig and how they prioritize the time they have. dEaLinG WiTh ThE mEdia not only did the Professors put the students to a test, but the media was also present and followed the groups every step of the way. The minute a new piece of evidence was found, the cameramen would swarm around the students asking questions: “What did you find?”, and “Did you solve the case already?”. The students managed to deal with this in the most efficient way. Mostly answering concisely, yet sometimes tougher steps needed to be taken. “I would kindly ask you to step back and give us some space”, said one of the exam participants, to a journalist.

“Please watch out where you walk, and try not to step on the evidence.”, continued the student.

ThE WiTnEss in disGuisE Dr. gillian Saunders, associate Professor at Tu Delft aerospace Engineering, was asked to play the role of the witness.

“When I was approached by Michiel to act as a witness during the exam I immediately said yes. I was expecting to get a script to tell students what I saw but his brief was short: you saw nothing. For the student investigators this was a hard thing to grasp: “nothing? really?” This led to some hilarious situations. One student came back and started looking under my picnic table. When asked what he was doing, he informed me he was looking for “something suspicious”. Other students doubted my words: “really, but don’t you see those two crashed planes over there?” which led me to answer back: “Oh no, is that what it is?” But in all honesty: I saw nothing. When I got there the aircraft were already there and I went about reading my book in the sun!”

Group 4

Figure 1. Possible clues on the investigation field.

Group 4

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ing the impact of the crash, or did it detach earlier in the process? Why was there no damage on the glider whatsoever? all these questions were taken into consideration, and after the intensive sixty minutes on the field, it was time to organize the gained information and eventually it was time for sketching, and ruling out, scenarios.

Figure 2. Detached engine found at a distance from the aircraft.

WhaT causEd ThE crash?

The question everybody wants to know: ”What really did happen on June 2nd behind the Fellowship building?”. The general concept of the event was that the ultralight took-off from rotterdam-The Hague airport towing a glider. During the flight, engine and control problems meant that ultralight could not be sustained and it performed an emergency landing. The event scenario was chosen in order to expose the students to as many investigative components as possible.

With limited time (field investigation) and information, students were challenged to solve the event with information presented. a simple clue was the damage of the propeller, a clue for the question; “ Was the engine running?”. another challenge was to investigate the two aircraft in the field.

The rope behind the ultralight was a clue to a possible relation. although one could argue that the ultralight incapable of tow-

ing a glider this size should be substantiated by calculations on the performance.

The goal was to challenge students in answering the questions that needed to be answered. all in all, it has been an eye-opening experience for the participants, clarifying quite some matters on the process of an air crash investigation. Even when a number of key-clues are found, the distinction between scenarios is not straightforward, yet crucial. after ten days of putting together clues and going through different scenarios the groups handed in their investigation reports, most of them convinced to have solved the case.

The next time these junior-investigators see an investigation documentary, they will have a better feeling of the complexity of the investigation process and how deep they must dig to close the case.

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ENERGY HARVESTING COMPOSITES Exploring piezoelectric composites for direct strain energy harvesting

Energy harvesting by smart piezoelectric materials offers tremendous opportunities for the aerospace industry. Yet, the conventional ceramic and polymeric piezoelectric material systems are not compatible with typical aerospace operational environments.

This research project was conducted to investigate the energy harvesting performance of piezoelectric composite materials, which show a high, as yet unexplored, potential when deformed in shear.

TEXT Ir. Frederik Van Loock, MSc graduate at the Novel Aerospace Materials group (NovAM)

PIEZOELECTRIC ENERGY HARVESTING Energy harvesting is the twofold process of extracting waste energy present in a particular environment and subsequently transforming it into a useful energy form (e.g. mechanical vibrations to electrical energy). In recent years, the technology received an increasing amount of interest as it fits well with the current and future need for sustainable energy generation and delivery.

Potential energy harvesting applications for the aerospace industry are legion. For example, one can apply energy harvesting technology for wireless structural health monitoring on a composite aircraft. Defects in the aircraft’s structure are detected and monitored by built-in sensors that wirelessly transmit their readings to a central data unit. One can feed the power to this sensor and transmitter system by an external power source, which inevitably requires a weight increasing cable network. Alternatively, one can opt to use batteries that have to be replaced on a regular basis requiring servicing and accessibility. Ideally, one can harvest the mechanical deformation occurring in the wing’s structure and convert this into useful electrical energy by electromechanical energy harvesters as conceptually drawn in Fig. 1.

PIEZOELECTRICITY The dominant method to perform this low-power electromechanical energy harvesting is based on the piezoelectric effect (Anton, 2007). Piezoelectric materials exhibit the unique capability of converting mechanical energy into electrical energy

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and vice versa. They become electrically charged upon mechanical loading (direct effect) and deform when an external electric field is applied (inverse effect). The inverse effect is used for actuating applications including morphing aerostructures, while the direct effect is applied for sensory devices such as strain gauges or electromechanical energy harvesters.

The coupling between the mechanical and electrical physical domain is restricted to certain directions known as the piezoelectric operation modes. The dominant modes are the longitudinal (d33), transverse (d31), and shear (d15) mode.

A wide range of material systems are known to have piezoelectric properties (Bowen, 2014). Piezoelectric ceramics such as PZT (Pb(ZrxTi1-x)O3 or lead zirconium titanate) are probably the most popular and the best studied systems. They come with high piezoelectric coupling properties and temperature stabilities, though they are brittle and difficult to process. In contrast, piezoelectric polymers including PVDF (polyvinylidene fluoride) exhibit excellent processing properties and high failure strains but are characterized by relatively low piezoelectric coupling properties and temperature stabilities.

Recalling the electromechanical energy harvesting application of a self-powered structural health-monitoring concept for composite aircraft, it is clear that the aforementioned conventional piezoelectric material classes fall short. To illustrate, inher-

ently brittle PZT is problematic due to the high strain-loading environment present on the wing and PVDF is inadequate due to its limited temperature stability. Clearly, there is a need for a new material and a configuration that fits to the naturally occurring deformation modes.

A potential solution for this material selection problem is the use of two-phase particulate piezoelectric composites. These composites consist of active ceramic particles loaded into a passive polymeric matrix. The active phase enables the composite’s piezoelectric functionality, while the passive phase enhances the producibility, toughness, ductility, and flexibility of the composite with respect to the pristine ceramic material.

The smart materials team of the NovAM group investigates the fundamental behavior of these particulate piezoelectric composites and explores novel routes to enhance their properties (piezoelectric, conductivity, producibility, etc.). Earlier work by the group has demonstrated i.a. the effect of the particulate volume fraction, polymer matrix, and particle alignment by means of dielectrophoresis (van den Ende, 2012).

MSC THESIS RESEARCH PROJECT This MSc thesis research project investigated the electromechanical energy harvesting capabilities of particulate piezoelectric composites. One of the main conclusions of the preceding literature study was the poorly explored potential of piezoelectric

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SHEAR MODE CHARACTERIZATION To determine the piezoelectric coupling properties of the particulate composite materials with various ceramic volume fractions (vf [-]), the standard resonance-based measurement method was modified by employing interdigitated electrodes (IDE) (Jaffe, 1971). The novel method is adapted to the conventional piezoelectric composite production method and is particularly suitable for thin and costly composite samples as no cutting operations, leading to material losses and increased risks of sample fracture, are required.

For rigid piezoceramics, the method is a sound alternative for the standard resonance-based shear measurement method as confirmed by a rigorous numerical verification and experimental validation process (see Fig. 2).

However, the resonance-based method appeared to be unsuitable for the characterization of the shear mode properties of particulate composites as they failed to exhibit resonance behavior. Finite element effective property simulations based on a representative volume element (RVE) analysis in COMSOL as well as complementary experimental quasi-static measurements indicated that the failure of the test configuration for the investigated composite materials can be attributed to the inherently low shear coupling properties (i.e. low d15 constant) of the investigated composite material systems (see Fig. 3).

Moreover, both the numerical effective property simulations and the experimental quasi-static measurements demonstrated that, in contrast to its effective d33/d31 ratio, the particulate composite’s d15/d33 ratio at fixed ceramic material volume fractions, is lower than the bulk piezoelectric ceramic’s ratio d15/d33 ratio. Consequently, the anticipated advantage of employing the shear mode for increased electromechanical coupling efficiency for energy harvesting purposes does not apply in the case of piezoelectric particulate composites.

STRAIN-DRIVEN ENERGY HARVESTING SIMULATIONS For the second part of this work, finite element simulations in COMSOL were per-

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composites loaded in shear (d15) for direct strain-driven loading scenarios. Moreover, the literature review also demonstrated that very little is known about the shear mode properties of piezoelectric composites and how to measure it without invoking unwanted other parasitic deformation modes. Therefore, the project aimed to (1) observe and quantify experimentally the shear (d15) coupling properties of particulate piezoelectric composites and (2) simulate their energy harvesting performance for pure shear, pure normal, and complex strain states.

Figure 1. Generic overview of a wireless aircraft structural health monitoring system powered by electromechanical energy harvesters.

Figure 3. Shear strain plot of a simulated (PZT-epoxy) particulate composite representative volume element in COMSOL.

Figure 2. Validation graph showing the simulated versus measured resonance plot of an interdigitated PZT measurement sample. The inserts depict the simulated strain surface plots of the investigated sample at the first and third overtone resonance frequency.

formed to determine the influence of using IDE on the energy harvesting performance of a compliant patch. Both pure shear (d15) and normal (d33) strain-driven loading environments were investigated. Shear mode activation resulted in low absolute generated energy figures in comparison with conventional d33 operations. However, if one takes the reduced shear mode coupling of the composite material conform the aforementioned characterization study into account, the composite material is more efficiently operated in d15 mode.

Furthermore, strain-driven energy harvesting case studies for the composite IDE patch were developed and simulated.

These case studies assessed the influence of complex strain states on the patches’ energy-based performance and suggested practical experimental validation schemes for the purely numerical analysis conducted during the thesis project.

One of these studies governed focused on a cantilever beam provided with the IDE patch and bended by a single vertical tip force at its end. Although the simulated strain states of the rotated patch are conform the presumed strain transformation analogy, the (net) generated energy figures cannot be related to the imposed strain states. Further numerical simulations and experimental validation tests are required to confirm these intriguing results. It is clear that the challenge of turning this new

material concept into a working product requires not only detailed insight in material behavior, but also in mechanics, advanced modeling and unique experiments. It was great fun to combine it all within a truly international and supportive research group.

The outcomes of the MSc thesis research project are now summarized into two journal publications.

Interested in research on smart materials at the NovAM group? Contact Prof. dr. Pim Groen (W.A.Groen@tudelft.nl) or visit our website at www.novam.lr.tudelft.nl.

References [1] Anton, S. and Sodano, H., “A review of power harvesting using piezoelectric materials”, Smart Materials and Structures, vol. 28, pp. 496-509, 2008.

[2] Bowen, C.R., Kim, H.A., Weaver, P.M. and Dunn, S., “Piezoelectric and ferroelectric materials and structures for energy harvesting applications”, Energy and Environmental Science, vol. 7, pp. 25-44, 2014 [3] van den Ende, D.A., van Kempen, S.E., Wu, X., Groen, W.A., Randall, C.A. and van der Zwaag, S., “Dielectrophoretically structured piezoelectric composites with high aspect ratio piezoelectric particles inclusions”, Journal of Applied Physics, vol.

111, 124107, 2012 [4] Jaffe B., Cook, W.R. Jr. and Jaffe, H., “Piezoelectric ceramics”, London (UK): Academic Press, 1971

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Mark Esguerra

Column

Flying Asian Style A peek into Asia’s rising LCC market

TEXT Haider Hussain, Student Aerospace Engineering, Editor Leonardo Times

T

he origins of Low-cost Carriers (LCCs) in Asia can perhaps be traced back to 2001, when Tony Fernandes, the current CEO of Air Asia, bought the company. At the time, Air Asia was heavily indebted.

The purchase of the company, and its subsequent overhaul into an LCC proved to be rather beneficial. Currently, Air Asia is one of Asia’s largest LCC groups, with a fleet of 169. The LCC fleet in the Asia-Pacific region hit the 1000 mark in early 2014.

This milestone is regarded as only the first step in Asia’s emerging LCC market.

In comparison to LCCs worldwide, the Asian carriers follow many of the same practices, the most common one being a single fleet type. The Asian LCCs usually operate short-haul to medium-haul flights with a very short turnarounds. This requires them to have a rather uniform fleet with same or similar aircraft models.

These aircraft usually tend to be of the narrow-body single isle type, since they are the most economically viable for the given range. Apart from that, LCCs are known for their simplicity and ‘no-frills’ philosophy when it comes to passenger amenities. For instance, meals, if available, usually have to be purchased in-flight and are not included in the ticket price.

Three of Asia’s largest LCCs will be briefly delved into here. These are: Air Asia, Lion Air, and IndiGo. Air Asia, with headquarters in Malaysia’s Kuala Lumpur Interna-

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tional Airport, is known for being one of Asia’s largest and fastest growing LCCs. It has various subsidiaries across Asia, like Indonesia Air Asia, Philippines Air Asia, and Air Asia India. In total, it operates a fleet of 169 and flies to and from 121 destinations. Its fleet mainly consists of Airbus A320-200s and orders have been put in for A320neo aircraft as well.

Lion Air, with its main base in SoekarnoHatta International Airport, Jakarta, operates a fleet of 101 aircraft with 79 destinations. It is Indonesia’s largest airline company. Much like Air Asia, it has various subsidiaries as well, like Batik Air, Thai Lion Air, and Wings Air. Lion Air’s fleet mainly consists of variants of the Boeing 737 aircraft. However, like Air Asia, it has also put in orders for Airbus’ new A320neo aircraft.

Air Asia and Lion Air are regarded as the biggest competitors in the South-East Asian LCC market.

In the South Asian LCC market, IndiGo emerges as the largest LCC. Headquartered in Gurgaon, Haryana, India, it operates a fleet of 88 aircraft and 37 destinations. Like Air Asia, it too operates a fleet of A320-200s and has put in orders for 250 A320neos, the largest single order by number of aircraft in Airbus’ history.

The LCC market in Asia is an emerging market, and aircraft manufacturers Airbus and Boeing are very optimistic about the

future of air travel, especially for shorthaul narrow body aircraft in the region.

However, LCCs in Asia, much like their counterparts in the rest of the world, do come with their criticisms as well. The meteoric rise of low cost air travel in Asia has led to the rapid founding of multiple LCCs and the numbers are just growing every year. However, the founding of numerous companies and the rising orders of aircraft is perhaps a premature decision in some ways and is leading to overcapacity in the region. The growth of LCC’s is, some might argue, getting ahead of their demand.

Singapore based Tigerair blamed the industry’s overcapacity for their rising losses. Apart from apparent overcapacity, another criticism for some Asian LCCs is their safety. Lion Air is reported to have had at least three of its pilots arrested for the use of crystal methamphetamine. Apart from that, the recent Indonesia Air Asia Flight 8501 crash has garnered much attention to the safety of the aviation industry of the region.

Despite its criticisms, the LCC industry in Asia is a rapidly growing one, and with the continued rise of the economic prowess of the region, it doesn’t seem like it’s going to stop anytime soon. This is good news for global aviation on a whole. However, it is imperative to have the infrastructure and human power to efficiently deal with the rapid growth.

Leonardo Times jANUARY 2015

09-Feb-15 23:47:57

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