LT March 2014 by Anouk Scholtes

march 2014

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

page 26

Design Synthesis Exercise An overview of the Fall Design Synthesis Exercise 2013 ATMOS UAV

number 1

Hi-tech startup with game-changing ideas

Optimal topology of future composites

A new optimization approach for future composite materials

Student Project – Human Power Team

Year 18

A year with the Human Power Team Delft & Amsterdam

A little more room, a lot more comfort YouĂ ll be amazed what extra legroom and a seat that reclines more can do for your journey. Get comfortable with Economy Comfort, available on all KLM ights. Visit klm.com/economycomfort for more information.

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Contents

Editorial

From Leonardoâ&#x20AC;&#x2122;s desk

Current affairs

ATMOS UAV

Post-impact performance of composites

Optimal topology of future composites

LVD - Commercial Supersonic flight

Student Project - Human Power Team

RVD - Fifteen years of International Space Station

Pylon Blowing on Pusher Propellers

Design Synthesis Exercise Fall 2013

Digital Radiographic Technology

Internship Report - V2G Thermal Coupling Analysis

Start-Up Company - Revolutionary composite joining method

We vlogen met een zucht... - History of Aviation safety

DESDEMONA and a ticket to Space

Column - The other drones

Contents

The DSE is the final phase of the Bachelor degree course. This requires weeks of hard work by the students organized in groups. In this DSE Special issue, the results of their efforts are featured.

ATMOS UAV has successfully applied VTOL with horizontal cruise flight resulting in a portable, lightweight and practical system with unprecedented specifications.

ASML

Dynaflow

Dutch Aviation Group

TWD

Ministerie van Defensie

NLR

Fokker

Optimal topology of future composites

A new optimization approach for future composite materials Composites have replaced aluminium because of their weight advantages. Research on variable stiffness composites which have the promise to further reduce the structural weight.

KLM

ATMOS UAV

Hi-tech startup with game-changing ideas

Advertisement index 02

DSE Special

An overview of the Fall Design Synthesis Exercise 2013

Cover articles

Table of contents

Student Project â&#x20AC;&#x201C; Human Power Team

A year with the Human Power Team Delft & Amsterdam The fastest man on earth is from the Netherlands. Thanks to a team of 10 TU Delft students and 5 students from Amsterdam who designed, built and tested a superfast aerodynamic bicycle to break the sprint record in deserts of Nevada.

MARCH 2014 Leonardo Times

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Editor’s letter Dear reader, The month of March starts with a good news for TU Delft. In the recently released World Reputation Rankings of Times Higher Education magazine, TU Delft has risen a number of places in various lists and has secured the highest rank amongst Dutch universities as well as the third highest European university of technology. Although there are a number of such rankings and lists, it can be said that compiling these lists is not an exact science; yet they do serve as a compliment to the hard work of the researchers and students at the University. The Faculty of Aerospace Engineering has also been abuzz with activity with a number of Bachelor students working hard for weeks on the Design Synthesis Exercise the last quarter. From page 26 onwards, this issue features the results of the hard work and effort put in by the student groups. The cover features the winning design ‘The SkyDowser’ which is an autonomous UAV with the idea of scanning large areas looking for ground water. In other news, the MOOC’s online course in cooperation with the faculty: ‘Introduction to Aeronautical Engineering’ has had a good start with over 6000 students from all over the world joining in. Every Bachelor’s student remembers a more extensive version of this course at the start of the studies at the faculty.

times. Lots of speculation has been going on as to what happened on board. Why was the ACARS system disabled? Why was it diverted from its route and where is the plane right now? Twenty-six countries have joined in on the search for the missing plane. A satellite operator claims three million people have participated in search for the ill-fated flight, searching through satellite images to locate the plane. The answers to this mystery are essential in learning lessons for future aviation safety. As students, we have indeed a lot to learn and contribute to the future of aviation safety. There have been a lot of opportunities in this aspect at TU Delft. In January this year, we had ‘Green versus Safe?’ symposium on air traffic safety at the faculty with a guest lecture from Deborah Hersman, chairperson NTSB, where she was also awarded an honorary doctorate at TU Delft. Again in March, we had the very successful ‘SAFE: Safeguarding Aviation in the Future Effectively ’ symposium with speakers from industry and research institutes. At Leonardo Times, we continue to strive to explore various aspects of aviation and space technology. This issue includes an article in our regular feature ‘We vlogen met een zucht’ on history of aviation safety by Prof.dr.ir. John Stoop, who is retiring after being a foremost advocate for aviation safety for 38 years. Also featured are articles on research in fields of composites, propeller performance and turbine blades along with our regular features. I hope you as the reader enjoy reading the Leonardo Times. Any remarks, questions or suggestions from you, the reader are very much welcome. Sushant Gupta

AFP/ CHAIDEER MAHYUDDIN

As I write this editorial, Malaysian Airlines flight MH370 has still not been located. It is turning out to be one of the most perplexing aviation-intelligence mysteries of recent

Colophon Year eighteen, number 1, March 2014 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: Jeroen Wink EDITORIAL STAFF: Aryadad Fattahyani, Bob Roos, Jasper van Gorcum, Joris Stolwijk, Jules L’Ortye, Lakshmi Sabbapathy, Lubi Spranger, Nikita Mahto, Prithvi Penumadu, Raphael Klein, Shahrzad Hosseini THE FOLLOWING PEOPLE CONTRIBUTED: Jef Michielssen, Sander Hulsman, Jurjen de Groot, Dirk Dokter, Fardin Esrail, Daniël Peeters, Martijn van Moorselaar, Menco Schuurman, Elias Allegaert, Geertjan Roks, Bas Verhagen, Tolga Celebi, Tomas Sinnige, Vincent Maes, Ir. Anande Bergman, Prof.dr.ir. John Stoop, Marijn Wouters, DSE Groups and Antanas Melaika. DESIGN, LAYOUT: dafdesign, Amsterdam PRINT: DeltaHage B.V., Den Haag 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, 2629 HS Delft Phone: 015 - 278 53 66 Fax: 015 – 278 12 43 Email: VSV@tudelft.nl 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

MH370 – Missing from the Radar

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FROM LEONARDO’S DESK

“Hello world” These were the words that were tweeted by the Rosetta space mission when she woke up after a sleep of 31 months. Not only were a lot of ESA employees very happy, the mission was also still working and on its way to explore a new part of space. By landing a spacecraft on the comet 67 P/Churyumov-Gerasimenko, ESA will write a new chapter in space mission history. During the first week of January, the same phenomenon could be observed at Leonardo’s Desk, when we came back from the Christmas holiday. Along with the active members, the board was happy to be back and to resume our work. With a lot of large upcoming activities and the help of the active members, we were on track to write a new piece of VSV history. During the last weeks, the 69th board has noticed that the enthusiasm of the board and its members did not fade away since the Christmas vacation. Due to some new computers and the makeover of the committee room, members can work as much as they want without any limiting factors. This was also visible in the work they delivered and the agenda of the VSV from January until the end of March. A combination of aerospace related lectures and excursions alternated with parties was the agenda of every VSV member. Some activities during this period were marked in everyone’s agenda, starting with the Ski trip to St. Sorlin d’Arves in

France. Together with 80 enthusiastic members, the board changed Leonardo’s Desk for snow, skiing and après-skiing. During the vacation, a lot of hours were spent on the slopes and in the evening with the group, to get to know each other a little bit better. After 10 days of skiing and having a lot of fun and meeting a lot of students, it was time to take the bus back to what we call our home since September, Leonardo’s Desk. Back at the boardroom, everyone was excited to go back to work with the largest technical career fair of the Benelux, De Delftse Bedrijvendagen, as the next event. With 140 companies in a timespan of two days, the DDB is the way to find a dream internship, graduation project or even a job. At the moment of writing, the career fair still still has to happen but with a team like this year I am sure that it will even be a bigger success compared to last year. The same is the case for the Symposium and Airbase. On time of writing, the board and committee members are working hard to make sure that the symposium and Airbase will be a big success. On March 4th, we will welcome prominent speakers at the auditorium for the spacetheme symposium ‘planetary exploration’. With speakers such as Andre Kuipers and Johann-Dietrich Wörner, the symposium will be of great professional quality. One week after the symposium, the faculty is being prepared to welcome 1000 students. On March 14, the doors of the faculty will be open in the evening to give a

lot of students the night of the year. During this night, 1000 students will have the opportunity to dance in the center hall of the faculty on the tunes of Oliver Weiter. Despite of the fact that that I cannot predict the future, I am sure that these events will be a great success and we, the board, are looking forward to it. Next to our activities for bachelor and master students, we are also working to keep the education quality. Some changes are happening within the programs at the faculty. From next year, the commissioner of educational affairs from the VSV board will be a part of the Bachelor Educational Management Team of the faculty. This means that we will help the faculty to sustain the quality of the Bachelors program in a different way as we do it at this moment. From now on we will not not only be evaluating the bachelor program but also give our opinion when decisions have to be made. At the moment, there is a lot of enthusiasm at Leonardo’s Desk and the motivation to make this a beautiful is year. Due to the work of our member, I have a good feeling that we will complete our mission to write a new piece of VSV history. With winged regards, Jef Michielssen President of the 69th board of the VSV ‘Leonardo da Vinci’ MARCH 2014 Leonardo Times

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Current Affairs

STRETCHING THE SUPERJET

January 24, 2014, Moscow, Russia

COMET CHASER WAKE-UP

January 20, 2014, Solar Orbit

ukhoi ‘s civil aircraft division is putting out the word that the likelihood of a near-term emergence for a stretched Superjet is small, although the proposal remains under examination. It announced that a Superjet featuring increased passenger capacity is running through the project definition study, but it was indicated that there is no pressure to develop the aircraft, and it was said that “The first prototype might be presented to the market in a few years,”. It has not stated the probable accommodation of such an aircraft. Russian authorities have pointed to a potential demand for a 130-seat aircraft to address a capacity gap between the 98-seat Superjet 100 and the 150-seat Irkut MC-21 (J.L.) Flight Global

PHOBOS FLYBY

he Rosetta Satellite of ESA has woken up again after 31 months of hibernation. Already launched in 2004, Rosetta has made three flybys of Earth and one flyby of Mars to build up enough speed to reach its chasing orbit. After its wakeup, Rosetta will chase comet 67P/Churyumov–Gerasimenko and eventually land on it in November 2014, making the first pictures ever from a comets surface. The Rosetta lander will make initial measurements during the first 65 hours on the surface, and will extend the mission up to three months depending on how long the lander survives on the surface. Scientists hope that by learning more about comets, our knowledge on the origin of the solar system will improve. (B.R.) ESA / NASA

DELTA SAYS NO TO ONBOARD PHONE CALLS

December 18, 2013, Atlanta, US

December 29, 2013, Martian orbit

SA’s Mars Express satellite has performed a very close flyby of Martian moon Phobos. Mars Express approached Phobos to an altitude of only 45km, the closest approach yet. ESA measured the change in orbital velocity (in order of cm/s) of Mars Express in order to learn more about the gravitational field of Phobos. While both the mass and the volume of Phobos were already accurately known, scientists hope that this flyby will generate data accurate enough determine the gravitational coefficient known as J2, one of the parameters which indicates how much the gravity field deviates from the perfect spherical shape. Scientists estimate that it will take several months to analyze the obtained data. (B.R.)

elta Airlines boss Richard Anderson said the airline would ban mobile phone calls on planes even if US regulators allow mobile phone calls during flight. The Federal Communications Commission (FCC) stated it would consider lifting its ban on in-flight calls. Anderson claimed a majority of Delta’s customers who were surveyed indicated phone calls would be a disruption to comfort of other passengers. He added inflight crews also objected to allowing mobile phones to be used. “Even as technology advances and as regulations are changed, we will not only consider what we can do, but as importantly we will also consider what is right for our customers and our employees,” Anderson said in a memo to staff. (J.L.)

ESA

BBC UK

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Current Affairs

OPPORTUNITY ANNIVERSARY

January 25, 2014, Mars

CHINA TESTS HYPERSONIC MISSILE

January 16, 2014, China

ars exploration rover Opportunity has celebrated its 10th anniversary on the red planet. Opportunity landed on January 25, 2004 in Eagle Crater on Mars to complete a mission originally planned to last three months. Opportunity also achieved all of its mission goals within those three months, and against all odds Opportunity is still operational after ten years, still advancing science way beyond originally planned for. At Eagle Crater Opportunity found evidence of acidic ground water. Later in its mission, Opportunity found evidence that the area near Endeavor Crater has been wet with non-acidic water for a prolonged time. According to data gathered by Opportunity, conditions may have been able to sustain microbiological life near Endeavor Crater, confirming the conclusion found by Mars rover Curiosity. (B.R.)

hina has tested for the first time a hypersonic missile capable of reaching several times the speed of sound, according to the Pentagon. The test makes China the second country after the United States to conduct experimental flights with hypersonic vehicles. This technology could allow armies to rapidly strike distant targets anywhere around the world. The flight was conducted on January 9 and the Chinese vehicle, dubbed the WU-14, is supposed to travel at 10 times the speed of sound according to a report in the Washington Free Beacon, an online publication. Meanwhile, the US has placed a high priority on hypersonic projects, spending $200m in the 2013 fiscal year on three programs while conducting a number of test flights. (J.L.) The Guardian

COMMERCIALLY TO THE MOON

January 16, 2014, Washington DC

NASA

COLD-WEATHER TESTS A350

Iqaluit, Nunavut, Canada

irbusâ&#x20AC;&#x2122; second flight-test A350 aircraft, MSN3, has departed Toulouse on a transatlantic trip to Canada where it will undergo cold-weather testing. The Rolls-Royce Trent XWB-powered aircraft is heading for Iqaluit, Canada where temperatures can reach minus 30 degrees Celsius. Airbus says the twin-engine jet will spend about a week at the airport Iqaluit while exposed to the freezing environment. In some 200 flights, the two flying prototypes have accumulated around 900 flight hours, about a third of the certification total. The first test aircraft, MSN1, is continuing with development tests but will shortly move towards formal certification tests. Over the next few weeks Airbus will introduce MSN4 as well as the cabin-equipped MSN2 to the flight-test fleet, followed by MSN5 in spring. (J.L.) Flight Global

ow that commercial parties transporting payloads to Low Earth Orbit seems successful, NASA wants to take commercial transportation further. NASA believes the moon holds value for commercial exploitation in harvesting resources and scientific exploration. NASA challenges commercial parties in its Lunar CArgo Transportation And Landing bY Soft Touchdown (CATALYST) programme to design a reliable and cost-effective transportation system to the moon capable of transporting small to medium payloads up to 500kg. This transportation system would enable the scientific and commercial exploitation of the moon. In return for the commercial support, NASA offers involved parties access to their testing facilities as well as their experience from previous missions, loans of equipment, and contribute specific software for development and testing of the transportation system. (B.R.) NASA

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ATMOS UAV

High-tech startup with game-changing ideas Since the early years of aviation, aircraft manufacturers have taken multiple shots at aircraft that combine vertical take-off and landing (VTOL) with horizontal cruise flight - an idea that to this day continues to be technologically challenging. ATMOS UAV successfully applied this concept to unmanned aerial vehicles (UAVs) resulting in a portable, lightweight and practical system with unprecedented specifications. TEXT Sander Hulsman, Jurjen de Groot & Dirk Dokter (Founding Partners, ATMOS UAV B.V.)

igh-tech start-up ATMOS UAV is developing a new type of small-unmanned aircraft that distinguishes itself from current market offerings in both design and capabilities. The unique design is best described as a clever combination of a fixed-wing aircraft and a helicopter, utilizing the advantages of both. The ability to take off and land vertically removes the need for a runway or other additional infrastructure for launch or recovery. Furthermore, the system is able to fly at very low speeds or hover for stationary measurements and observations, while the mission area can still be traversed quickly with a relatively high cruise speed. Since wing-borne horizontal flight is a substantially more efficient means of flight than hovering, the range and flight endurance of the vehicle are greatly increased. An additional advantage of the ATMOS system is its ability to handle rough weather and high winds much better in comparison to other VTOL UAVs of similar size and mass. Despite the efforts of several aircraft manufacturers and research institutes, combining VTOL with horizontal flight still proves to be a technological challenge:

only a small number of VTOL aircraft are in operation today, with the Harrier Jump Jet and the Bell-Boeing V-22 Osprey being the best known examples. Both have had a development process known for numerous setbacks, resulting in substantial unanticipated costs and delays. Part of the technological difficulties associated with VTOL aircraft can be overcome by using unmanned aircraft. Flight dynamics and control are no longer limited to human comfort and the system can have lower mass and higher agility. This allows for a fundamentally different design for the ATMOS UAV. Instead of tilting the thrust units (as it is applied in the V-22), the entire aircraft tilts forward in order to make the transition to horizontal flight. This reduces the mechanical and structural complexity considerably. This unique design leads to a UAV with unprecedented operational flexibility and favorable specifications. This concept capitalizes perfectly on the current trend that requires UAVs to be capable of performing an increasingly wide range of different, but complementary operations within a single mission. A depiction of the concept of the ATMOS system is illustrated in Figure 1.

AUTOMATED FLIGHT A high level of flight automation is an important design objective for ATMOS UAV, as this decreases the operatorâ&#x20AC;&#x2122;s workload, thereby increasing situational awareness and focus on the mission. Since auxiliary equipment (e.g. a catapult) is not required for take-off and landing, it furthermore allows routine flights to be executed without intensive human interaction. Finally, flight automation increases the overall system safety. Studies show that human errors - not only control errors but also misperceptions and decision-making errors - are currently one of the main causes for UAV crashes (Asim et al., 2010 and Thompson, 2005). When operating the ATMOS UAV system, the end user does not control the aircraftâ&#x20AC;&#x2122;s actuators directly. Instead, the user enters the desired mission objectives into the ground control station. A complete mission can be planned beforehand and executed automatically, while real time alterations to the mission plan remain possible at all times. Subsequently, the vehicle translates this human input into a complex set of low level commands that

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ATMOS UAV BV

HAALBEELD FOTOGRAFIE

Figure 1. Schematic depiction of a typical mission of the ATMOS system.

determine the actual flight path. As a result, the user does not have to focus on keeping the vehicle safely airborne, without forming a hazard to other air traffic, interfering with airspace regulations or escaping the safe flight corridor. The user can fully focus on the received imagery, process the information in it and carefully devise the next step in the observation mission. The ground control station furthermore provides an easy interface to control the payload (e.g. pan/tilt of a camera), and allows multiple vehicles to be easily controlled by one operator. HISTORY & FOUNDING OF THE COMPANY The company was founded in June 2013; however, the six founders have been working on the technology for over two years. Originating from a Design Synthesis Exercise (DSE), a bachelor graduation project at the Delft University of Technology, the ATMOS team initially elaborated the conceptual design for participation in the UAVForge challenge, an international competition with the goal of performing a complex surveillance mission with a UAV. The design was promising and the team was selected to compete in the final fly-off held in May 2012 to put the system to the test. In four short months the design was transformed into functional prototypes and the novel control theory was further developed and implemented in the autopilot software. The challenge, organized by the US research institution DARPA, was in fact so

complex and demanding that none of the competing teams were able to complete the entire course without complications. Nevertheless, the ATMOS team left quite an impression with the transitioning vehicle that was different from the other more conventional designs and also turned out to be the only vehicle able to fly fully automated. The flights performed during the challenge were in fact, to the best of the teamâ&#x20AC;&#x2122;s knowledge, the first fully automated flights of a multi-modal UAV ever. The final result for the ATMOS team was a respectable third place out of the 140 initial contestants. This valuable result, together with the striking appearance and distinctive transition flight of the vehicle, led to a growing interest from the university, the media, but also the industry. After the competition, ATMOS UAV was additionally rewarded with the UfD Bachelor Grant and the UfD Teamwork prize. Furthermore, the Dutch Aerospace Fund (NLF) acknowledged the company with the Dutch Aerospace Award in November 2013. The team consists of six aerospace engineers, each with a specialty in a different field, resulting in a complete and complementary set of disciplines required for the design and production of unmanned aerial systems. This unique combination of inhouse knowledge is one of the preconditions for a successful high-tech company. Coupled with the growing demand from the market it was a logical decision for the team to bring the project to a higher level and commercialize the technology.

EMERGING CIVIL DRONE MARKET The first unmanned aerial vehicles were already used during World War I, starting with the development of Hewitt-Sperryâ&#x20AC;&#x2122;s automatic airplane (Pearson, 1997). Up until the last decade, research and development of UAVs was mostly performed for military purposes. Currently, however, the civil market segment is rapidly expanding (Teal Group, 2012). Ongoing technological developments in the area of electronics, sensors, propulsion and energy storage result in increasingly lower cost and higher performance of those components and allow UAVs to become available to civil users. This technological revolution, together with growing public acceptance, is accompanied by a wide range of new opportunities and applications. In many situations, unmanned aircraft are a cheaper alternative for manned aircraft, and can even add additional capabilities. This allows them to be deployed more often and for multiple purposes, with much higher flexibility compared to traditional methods. Unmanned systems are beneficial for search and rescue teams, firefighters, and other emergency response teams as they can have an overview of a situation instantaneously. In addition, the surveillance of industrial areas (e.g. refineries or power plants) can be performed at relatively low cost and effort with UAVs. Also, inspections of industrial assets like windmills or gas-flares can be performed in a safer and cost efficient manner. A promising application is precision agriculture: a UAV equipped with a multi-

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Besides using unmanned aircraft for observation purposes, scenarios are being investigated where UAVs are deployed as a means of cargo transportation. The delivery of consumer packages on demand is an example. However, it will take years before the regulatory and procedural framework has evolved sufficiently to integrate such infrastructure in the airspace. Moreover, delivery in urban areas is still technologically challenging. However, this concept is definitely a promising solution for cost-efficient transportation of emergency supplies to areas afflicted by (natural) disaster or for distributing vaccines or medication to regions without proper infrastructure.

The Netherlands has a great opportunity to become a significant player in the global drone market, as it has a leading position in related industries, such as high-tech sensor and data processing technology. The current (lack of ) legislation, however, negatively affects development and proliferation of UAV technology. This contrasts with neighboring countries, where a more adequate and straightforward legislation is in effect. Possibly, Dutch companies will feel compelled to move their operations abroad for this particular reason. That is one of the reasons why the Dutch Association for Remotely Piloted Aircraft Systems (DARPAS) was founded, representing the interests of the professional Dutch UAV community.

ATMOS UAV BV

LEGISLATION Entrepreneurs and companies have noticed the fact that this new market offers great potential globally. In the Netherlands alone, some 150 companies have

already been founded that are exploring the opportunities of the technology. The problem they are facing, however, is that putting the legal aspect of their operations in order is currently remarkably complicated. As it is often the case for newly introduced technology, a regulatory and procedural framework has not been fully defined yet. Currently, it is only possible to fly small unmanned systems legally by requesting exemptions on laws of both local and national authorities, a cumbersome and time-consuming procedure, that is moreover poorly and inconsistently documented. UAV operators, designers, researchers and manufacturers are spending too much time and effort in getting familiar with them and satisfying accompanying administrative obligations.

Figure2. Artist impression of the ATMOS system performing coastal inspection

It pleads for easier procedures and better communication and incites the legislators to accelerate the generation of a workable and safe regulatory framework that stimulates and supports the expansion of the industry. KEY APPLICATIONS OF ATMOS UAV Small UAVs, and especially multi-rotors, are being used at an increasing rate for civil applications, yet end users claim to repeatedly experience the same set of drawbacks of current systems. One of the often-heard complaints about these systems is the limited flight time. Although many manufacturers of VTOL UAVs of this size claim flight times of up to 40 minutes, in practice these UAVs even struggle to reach 10 minutes of consecutive flight. For a lot of applications however, switching to fixed wing systems is not an option, since fixed wings do not offer stationary observation and often come with cumbersome operations for deployment or recovery, requiring a runway, catapult and/or catching mechanism. Furthermore, most of the existing systems highly depend on the communication link; a lost link often results in a crash. Since all flight control of the ATMOS UAV is executed on-board, the vehicle is not dependent on a stable communication link. All of the above make the ATMOS UAV the preferred option in many applications. The key specifications of the system are shown in table 1. ATMOS UAV has a strong focus on inspection and surveillance applications where quick response time, reliability and mobil-

HAALBEELD FOTOGRAFIE

spectral camera captures detailed images of crops. This allows the farmer to detect local lack of nutrients, lack of irrigation or disease afflicted plants and take appropriate and targeted actions, resulting in an increased crop yield. UAVs offer valuable possibilities in other sectors as well. In geodesy, UAVs are used for performing land surveys and volumetric analyses of bulk materials. In wildlife conservation, they are being deployed for localizing poachers. In the television and film industry, they shoot a scene from a birds-eye view, and in real estate they take appealing photos of a property for sale.

Figure 3. Team members conducting final flight checks on the sixth prototype

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HAALBEELD FOTOGRAFIE

Figure 4. Flight-test of the sixth ATMOS prototype

ity are important aspects. Targeted end users are companies with large industrial assets, emergency response organizations and security companies. The ATMOS system can also be used as replacement for existing fixed-wing UAVs of a similar size, reducing deployment time and complications during take-off and landing. An example of such a surveillance application is the automatic routine scanning of large industrial areas such as port areas, producing high-resolution maps at scheduled intervals. These maps subsequently can be used for the detection of unwanted disturbances, monitoring of construction site progression or documenting changes in large container storage areas. Furthermore, the system would be very suitable for inspections of critical infrastructure, such as dikes or coastal areas. In Figure 2 the ATMOS UAV is illustrated performing a coastal inspection. Another surveillance application worth mentioning is the deployment of ATMOS UAV on ships and other offshore assets. The VTOL capability ensures that the vehicle can easily take off from ships, while

the forward flight capabilities allow the vehicle to withstand windy sea conditions and quickly travel the required distances. A feature that is especially useful in supporting security teams on freighters operating in and near pirate hot spots. The problem these teams face is distinguishing pirate vessels from fishing boats or trade ships. Although the detection of neighboring boats is already possible, the identification of those vessels and the level of threat are still hard to determine (Gard AS, 2012). The ATMOS system can be used as a flexible tool to identify those possible threats considerably quicker. FUTURE Currently ATMOS UAV is in the stage of product development. The next milestone is a product pilot in the summer of 2014 that will showcase the full functionality of the system and demonstrates its benefits to interested parties and potential customers. The product launch is planned in spring 2015. It is the goal of ATMOS UAV to establish a high-end brand recognized for reliable and practical unmanned aerial sys-

Table 1. Design specifications

Design cruise speed

70km/h

Design top speed

100km/h

Range (max)

60km

Hover endurance (max)

20min

Horizontal flight endurance (max)

65min

Payload capacity

500gr

Maximum take-off weight

2500gr

Wingspan

1.5m

tems and to grow the company into one of the major players in the industry. Key ingredients for realizing this are a highly flexible and efficient development team, a strong, shared focus, an ambitious business plan and a unique selling point. For questions about the team, the product, the company or career opportunities, feel free to contact us at: ATMOS UAV B.V. Kluyverweg 1, Room 2.20 2629HS Delft The Netherlands tel: +31 (0) 15 – 744 03 21 info@atmosuav.com www.atmosuav.com References 1. Gard AS, “Piracy – Recent NSC/UKMTO advice concerning fishing vessels”, April 2012, http://www.gard.no/ 2. Pearson, L., “Developing the Flying Bomb”, 1997, http://www.history.navy. mil/ 3. Asim, M., Ehsan, N., Rafique, K., “Probable Causal Factors In UAV Accidents Based On Human Factor Analysis And Classification System”, Center for Advanced Studies in Engineering, 2010 4. Thompson, W.T., “U.S. Military Unmanned Aerial Vehicle Mishaps: Assessment of the Role of Human Factors Using Human Factors Analysis and Classification System (HFACS)”, 2005 5. World Unmanned Aerial Vehicle Systems – 2012 Market Profile and Forecast, Teal Group Corporation, 2012

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POST-IMPACT PERFORMANCE OF COMPOSITES

Predicting Predicting compression Compression after after impact Impact (CAI) (CAI) in in composite composite laminates laminates

Impact damage has been known to seriously limit the performance of composite aircraft structures. In the preliminary design phase, tens of thousands of subparts need to be analyzed for impact. Over the years, many approaches have been proposed to study the creation of impact damage and to determine the residual strength of the structure. Although the progress has been significant, most of the existent methods are too prohibitive for large-scale implementation in the industry. In this thesis study, efficient analytical models were developed to study impact damage. These models will help the designer in the preliminary design phase to perform quick trade-offs and multiple analyses. TEXT Fardin Esrail, MSc. Graduate Aerospace Engineering, Aerospace Structures & Computational Mechanics

THE CHALLENGE Impact damage modeling in composites is challenging for two reasons: The overall damage state is very complex and different types of failure must be modeled. Furthermore, the problem is dynamic, which means that after onset of damage the stiffness properties must be updated, after which the load is increased. The thesis was broken into two parts: damage resistance and damage tolerance. “Please, think it over well, if you really want to get into this thesis”, said my supervisor. He emphasized that this was not going to be the average kind of work. DAMAGE RESISTANCE AND DAMAGE TOLERANCE In the seventies, Cairns and Lagacé (Cairns & Lagacé, 1989) developed the notion of damage resistance and damage tolerance at MIT. Damage resistance in this context deals with the amount of damage a com-

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posite structure sustains for a given impact load. Damage tolerance deals with the residual failure load of the damaged structure. Previous work on these two topics included work done by Sun and Chattopadhyay (Sun & Chattopadhyay, 1975), Cairns and Lagacé (Cairns & Lagacé, 1989), Olsson (Olsson, 2001) and Talagani (Talagani, 2013). These efforts ranged from simple curve fits to very detail finite element analyses using cohesive elements. Simple curve fits do not really add to the understanding of the problem and previous work showed that a detailed finite element analyses could take a couple of days to run (Talagani, 2013). ANALYTICAL METHODS TO MODEL IMPACT DAMAGE In this thesis, analytical methods were developed for two purposes: To model the types, amount and location of impact damage (damage resistance) and

to determine the residual compression strength of a composite laminate (damage tolerance). These analytical models should be used in the preliminary design phase avoiding expensive finite element analyses and/or test programs. When developing analytical methods, one needs to be aware of the following: out of ten potential methods, only one or none actually works. Analytical methods are simplified involving many assumptions. The question is: how valid are the assumptions made? This question is answered by verifying the model with numerical methods and/or by validating the model using test data. What makes a good engineer is being ready to make the proper assumptions. What makes a great engineer is being ready to abandon these assumptions and search for the right ones. Although different kinds of impact problems exist, this work is limited to quasi-static impact. This is the case when the impactor mass is

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much larger than the mass of the laminate and the impactor velocity is low (one to five m/s). Furthermore, it is assumed that the laminate is quasi-isotropic and the impactor is a steel sphere. IMPACT LOAD AND STRESSES Considering a composite plate impacted by a spherical object, the impact load is typically modeled as a point load. This load is applied in out-of-plane direction and will cause stresses through the thickness of the plate. By the principle of energy balance, the impact load can be determined. One can now solve for the stresses using the finite element method. This can be computationally expensive requiring a fine mesh with element dimensions in the order of 0.05mm in the contact area (Talagani, 2013). In this thesis study, exponential functions were used in an assumed form for the out-of-plane stresses. Using energy minimization, the other stresses and unknowns were solved for. The analytical method as implemented in MATLAB takes three seconds to run and it showed to agree well with finite element results. This means that one can avoid long finite element simulations by using this model. The assumptions made here seemed to be valid for a wide range of parameters. DAMAGE SIZE DETERMINATION Moving on to impact damage modeling, simple failure criterion was used to determine different types of damage. Any damage creation before the peak impact load reached was neglected here. By the principle of energy balance, the damage created at the peak impact load was determined by modifying the previously determined stresses according to their strength allowables. The big question was: Is this assumption a reasonable one? If it is, it means a simple model can be used to determine impact damage accurately neglecting damage creation and stiffness loss before the peak load is reached. From a validation with test results published by Dost et al. (Dost, 1991) it was found that the damage contours, for example delaminations at the interfaces of plies, fiber breakage, and transverse matrix cracks,

FARDIN ESRAIL

Figure 1. A comparison of the damage contours as obtained from an ultrasonic scan from (Dost,1991) (left) and the predicted damage contours (right) for a quasi-isotropic laminate, laminate material: IM7/8551-7.

Figure 2. Comparison of the local stress distribution (the stress parallel to the applied displacement) from the analysis model with finite element results in the impact damaged region for an orthotropic laminate ([0/0/0/0]s AS4-8552). At the boundary of each ellipse, a sudden drop in the local stress can be seen.

were captured quite accurately. Figure 1 for a comparison of the analysis model prediction with the damage contours obtained from an ultrasonic C-scan of a damaged quasi-isotropic laminate. For some cases however, the discrepancies were significant. RESIDUAL STRENGTH DETERMINATION It is recognized that the models that have been developed so far in the thesis study were simplified and as such, they were not valid for all cases. At that point, three to four months passed from the kick-off meeting, taking into account that two months were only spent on an approach that eventually did not work. Only two months of the actual work resulted into a damage resistance model. A decision had to be made here: Do we start refining the damage resistance model to make it more versatile? As the model refinement seemed to be out of the scope of this thesis, the answer was obvious and we moved on to set up a damage tolerance model in order to determine the residual strength of the damaged composite. The damaged region of the laminate was modeled as several concentric ellipses of different stiffness and strength. This difference in stiffness will give rise to stress concentrations when the laminate is loaded under uni-axial compression. Figure 2 depicts the stress concentration in the damaged region consisting of three elliptical inclusions. As the elliptical boundaries are reached, a drop in the stress can be observed. This is attributed to the lower stiffness encountered in these regions. One can imagine that the difference in strength may cause some ellipses to fail and redistribute the load to other ellipses until the entire laminate fails as a whole. To determine the failure load, or the residual strength, of the damaged laminate, a progressive damage analysis was carried out. PROGRESSIVE DAMAGE ANALYSIS At the damage site, delaminations and transverse matrix cracks can coalesce in individual smaller laminates, or sub laminates. As the laminate is loaded un-

der compression, the sub laminates can buckle, ultimately leading to final failure. In the analysis model, local buckling was not captured and this would have implications on the failure load predictions when compared to test data. The failure load was determined in an iterative procedure: Apply a small compression load, check which ellipse fails, adjust stiffness/ strength properties, increase the load and continue the iteration until the laminate fails as a whole. When an ellipse fails, it becomes equivalent to an open hole, increasing the local stress concentrations. Failure of an ellipse was assessed by using a first ply failure criterion. See figure 4 for the comparison of the predicted failure load with published test results from Dost et al. (Dost, 1991) for a quasi-isotropic laminate. CONCLUSIONS The efficiency of the models created make them prime candidates, when refined further, for trade studies and optimization. They can form the basis to accurately predict the compression after impact strength of quasi-isotropic laminates. References [1] Cairns, D.S., Lagacé, P.A., “Transient Response of Graphite/Epoxy and Kevlar/ Epoxy to Impact”, AIAA Journal, Vol. 27, No. 11, pp.1590-1596, 1989. [2] Sun, C.T., Chattopadhyay, S., “Dynamic Response of Anisotropic Laminated Plates under Initial Stress to Impact of a Mass”, Journal of Applied Mechanics, Vol. 42, pp. 693-698, 1975. [3] Olsson, R., “Analytical Prediction of Large Mass Impact Damage in Composite Laminates”, Elsevier Science Ltd., Composites: Part A 32, pp. 1207-1215, 2001. [4] Talagani, M.R., A PhD. Dissertation, Chair of Aerospace Structures & Computational Mechanics, TU Delft, 2013. [5] Dost, E.F., Ilcewicz, L.B., Avery, W.B., “The Effects of Stacking Sequence on Impact Damage Resistance and Residual Strength for Quasi-Isotropic Laminates”, ASTM STP 1110, Orlando, FL, 1991.

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OPTIMAL TOPOLOGY OF FUTURE COMPOSITES

A new optimisation approach for future composite materials

Weight reduction has been a driving factor in aerospace engineering for a long time. Recently, the first composite-dominated airplanes (e.g., A-380, B-787) have been taken into use. Composites have replaced aluminium because of their higher strength-to-weight and stiffness-to-weight ratio. Currently, research is ongoing on variable stiffness composites which have the promise to further reduce the weight of composites. TEXT DaniĂŤl Peeters, PhD student, Aerospace Structures and Materials, Aerospace Structures and Computational Mechanics

he high strength-to-weight and stiffness-to-weight ratio of composites are due to the build-up of the material: it consists of very strong fibres that are embedded in a matrix. These fibres are very strong in tension while the matrix takes up most of the compression load, comparable to reinforced concrete but on the micro-level. A combination of fibres and matrix is called a ply and is very strong in the direction of the fibres, but weaker in the other directions. By stacking multiple plies with the fibres in different directions on top of each other, one gets a composite laminate. A graphical representation of such a laminate can be seen in Figure 1. These composites are designed to be relatively strong in all directions, and particularly strong in the direction of the largest loads. By changing the fibre angle orientation one can tailor the strength and stiffness of the composite in different directions. The orientations of the fibres in the different plies are written down in a so-called stacking sequence.

VARIABLE STIFFNESS COMPOSITES Building composite materials used to be manual labour, which led to extremely high costs and limited accuracy. However, over the past years fibre placement machines were developed to automate the process and nowadays these fibre placement machines have evolved far enough that they can lay down fibres in any direction, not just straight. This opens up a lot of new possibilities to tailor the material properties: the fibre direction can now change inside a layer and thus also the material properties (strength, stiffness etc.) can change from one point to the next. Hence, these composites are called variable stiffness composites. Variable stiffness composites give a lot of new possibilities, so much even that it is no longer possible to find the optimal fibre angle distribution without an optimisation algorithm. Such an algorithm has been developed at TU Delft and it uses a three-step approach (Ijsselmuiden, 2011). In the first step the material properties are

represented by lamination parameters. The advantage is that only four lamination parameters are needed to define the material properties; when the composite has a symmetric stacking sequence with respect to the mid-plane of the laminate, only two lamination parameters are needed. In this step, the theoretical optimal performance (e.g., buckling load) is found, but the lamination parameters give no information about the stacking sequence. This stacking sequence is found at all nodes of the finite element model in the second step of the optimisation algorithm. The difference between the angles in adjacent nodes is constrained to be sure the composite can be made by a fibre placement machine: these machines cannot make very sharp turns. Due to this constraint the lamination parameters cannot be matched exactly at each point and the performance decreases a bit. In the third step the actual fibre paths are found. This is done to match the fibre angles at the nodes as closely as possible.

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(CHAMIS, 1983), PG. 13

Figure 2. Example of the four-step optimization approach WWW.LR.TUDELFT.NL

NGCRAFT.COM/CATEGORY/COMPOSITES

AIRBUS S.A.S. (PHOTO BY EXM COMPANY/ H. GOUSSĂ&#x2030;)

Figure 1. Graphical representation of a composite laminate

Figure 3. Variable stiffness composite with thickness build-up

TOPOLOGY OPTIMISATION A popular optimisation algorithm for isotropic materials is topology optimisation. This approach optimises the material distribution by giving each node of the finite element model a fictitious density. If this density is zero, there is a void; if it is one, the material is present at that node. A maximum allowed volume of the structure is specified and then the stiffness, strength or buckling load of a structure under a certain load can be optimised. By combining topology optimisation with the first step of the variable stiffness optimisation approach, both the material distribution and material properties are optimised at the same time. The result of this optimisation consists of a lamination parameter distribution and a material presence distribution, as can be seen in the left of Figure 2. Before the fibre angles and paths can be determined, first the contour of the optimal structure is determined. This is necessary because the elements used are usually either triangular or rectangular and thus the edges are wavy. By linearly interpolating the density distribution and smoothing the edges found in that way, a smooth contour line is found. Once the contour is determined, the fibre angles and paths are determined in the same way as was done in the variable stiffness optimisation. When optimising the stiffness of a cantilever beam clamped in on the left, with a downward force on the right, the optimal topology and fibre paths can be seen in Figure 2. This gives a 58% increase with respect to a quasiisotropic lay-up. POSSIBLE IMPROVEMENTS The results obtained using this approach

are promising, but improvements can still be made. One of these improvements is that the maximum curvature mentioned above is currently the global curvature, which means the curvature can locally be too high leading to a laminate that cannot be built. Furthermore, what has been referred to as fibre paths so far is in fact only a good impression of what the fibre paths will look like. A typical fibre placement machine lays down bands of 6 to 50mm while the example shown is 300mm wide. Furthermore, the distance between fibre paths is not constant anymore and the bands laid down only differ by about 6mm. This implies one will have to make a choice: place fibres on top of each other, or leave parts â&#x20AC;&#x2DC;emptyâ&#x20AC;&#x2122;. The first case causes a variable thickness solution as can be seen in Figure 3; the second case leads to regions with only matrix material and no fibres. In the aviation industry the second case, with a constant thickness, is generally preferred to keep the aerodynamic shape of the structure. As a final improvement it should be possible to also change the thickness of the laminate: by dropping certain plies, the material properties will change, even if the fibre angle inside a ply stays constant. By having both varying fibre angles and variable thickness it is expected that even larger weight savings can be accomplished. By changing both fibre angle and thickness, the potential change in stiffness will also be larger from one point to the next: only one or two plies can be dropped at once, and the fibre angle can not change a lot locally, but by combining both, the stiffness variation can be large.

Figure 4. Example of wing panel with stiffeners

panel, about 2m by 3m in size, with the fibre paths optimised, change in thickness and reduced number of stiffeners compared to current designs. An example of a current wing panel can be seen in Figure 4. Compared to the current state of the art wings, this will reduce the structural weight and, since less stiffeners will have to be used, the production time and cost will also be reduced. Some of the possible improvements will be made by TU Delft, but this work is also supported by the European Seventh Framework Program, and is part of the CANAL project (CreAting Non-conventionAl Laminates) where also commercial companies, aerospace research institutes and other universities are involved. Concluding, even though a lot of improvements are still possible, it is already clear variable stiffness laminates can reduce the structural weight of aerospace structures. If you have further ideas or want to contribute to this research as a graduate student, contact the author for further information. References [1] Ijsselmuiden, S. T., Optimal design of variable stiffness composite structures using lamination parameters, Ph. D. Thesis, Delft University of Technology, Delft, Netherlands, 2011. [2] Chamis, C.C. , Simplified composite micromechanics equations for hygral, thermal and mechanical properties, Society of Plastics Industry Conference, NASA Technical Memorandum 83320: pp. 1 - 17, 1983.

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COMMERCIAL SUPERSONIC FLIGHT The past and the future

BOEING/NASA

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Contemporary world is all about going faster than ever before. Various communication technologies allow us to interact and trade almost instantly with the entire world. Computers are faster than ever before. One thing, however, has slowed down, the speed at which we travel. Supersonic travel is no longer possible. What was it like and where are we heading next? TEXT Martijn van Moorselaar, Treasurer of Aviation Department, Student Aerospace Engineering

AN ERA BYGONE Unlike today, traveling at supersonic speeds used to be possible not so long ago. Two supersonic passenger airliners used to be in commercial use, the AĂŠrospatiale-BAC Concorde and the Tupolev Tu-144, with the Concorde being the much more successful one of the two. The Concorde has been in use for almost 27 years, predominantly by Air France and British Airways. Although no longer in service, the Concorde is still one of the most iconic and well-known aircraft that have flown on the Earth. Featuring a very sleek fuselage and its double delta shaped wings, it looks unlike any other passenger jet currently in use. The Concorde is almost always seen in a predominantly white livery. The highly reflective white paint was used to prevent the aircraft from overheating when flying at supersonic speeds. Making its first commercial flight with British Airways on January 21, 1976 the Concorde was capable of transporting 100 passengers at twice the speed of sound. This allowed the aircraft to perform transatlantic flights in half the time

it takes today, namely three and a half hours. Its fastest crossing only took 2 hrs 52 min 59 sec, from New York to London. The Concorde not only flew faster than any other current aircraft but also higher, having a cruising altitude of 17,000m. At these altitudes, the passengers could even experience looking at the curvature of the earth. Flying the Concorde was an experience like no other, something very few people experienced. It did, however, come at a price, since the average price for a round trip was upwards of $12,000 [van der Linden, 2004].

both Air France and British Airways announced that they would withdraw the Concorde from service. On November 26, 2003, the Concorde made its last flight, marking the end of an era.

The beginning of the end of the Concorde was on July 25, 2000, when Air France Flight 4590 crashed. Crashing just minutes after take-off, killing everyone on board and four more on the ground, Flight 4590 was the first crash of a Concorde. However, due to the fact that the Concorde flew a lot less than any other aircraft, it immediately had more fatal incidents per million flights than any other aircraft. After safety updates, the Concorde did return for commercial usage in November 2001. Passenger numbers however dropped, following the crash and the 9/11 attacks. In 2003,

Even though it is still seen as a marvel of engineering, the Concorde had its share of problems. Its biggest problem was the noise it produced, both in flight and on the ground. When taking off, the Concorde was one of the loudest aircrafts ever manufactured. A bigger problem however was the sonic boom it produced, which was so loud that the Concorde was not allowed to fly over land at supersonic speeds. This greatly restricted the amount of routes the aircraft could fly, thereby reducing is usability. The Concorde was also very expensive to fly. It consumed

FIXING THE BOOM Today, the only supersonic aircraft are military aircraft. For commercial flight, there is no longer an option to travel at supersonic speeds. With the demise of the Concorde and as of yet, an unfilled gap has been left. Research however is being done and supersonic travel might return.

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AERION CORP.

twice the amount of fuel as the Boeing 747, while transporting only a quarter of the passengers [Black, 2012]. Even though British Airways has always claimed to have made a profit on the Concorde, it must be clear that any new design must overcome the noise and fuel consumption problems faced by the Concorde. Currently a lot of research is being done on supersonic transport jets. Much of this research is focused on the reducing the noise produced by the sonic boom. As Peter Coen, supersonic projects manager at NASA’s Aeronautics Research Directorate’s Fundamental Aeronautics Program, says “If we can’t solve the boom problem there is no sense working the other issues because the airlines won’t buy an aircraft they can’t fly wherever they want to fly” [Wilson, 2013]. Research is being done at, amongst others, NASA and Japan Aerospace Exploration Agency (JAXA). Both for NASA and JAXA the sonic boom is a very important issue. At JAXA, their current project is the NEXST, National Experimental Supersonic Transport. Launched in 1997, the program is now in its second phase. The goals of the first phase were to acquire design technologies to reduce drag when cruising at supersonic speeds. A scale model of the design was tested in 2005 in Australia. The model, which did not have an engine, was accelerated to Mach 2.0 by a solid rocket booster. Launched to an altitude of 19km, the aircraft separated and flew at Mach 2.0. The flight test confirmed that the design reduced Aerodynamic drag. The second phase of the program focuses on noise reduction, while maintaining aerodynamic performance. Numerical simulations and wind tunnel tests are being done to gain a better understanding of how the sonic boom is related to the aircraft configuration. However, in reality the sonic boom is also influenced by the atmosphere, as Ohnuki, leader of the Supersonic Transport Team at JAXA, also states. To address this JAXA is planning a flight test, which will hopefully be conducted in the mid 2010’s [Ohnuki, 2012]. Alt NASA too a lot of research is being done with the N+2 and N+3 programs. N+2 focuses upon an 80-passenger vehicle, traveling at supersonic speeds with transatlantic range, which should reach a technology readiness level in 2025. The envisioned aircraft has to be able to operate with an environmental impact on par with that of current subsonic aircraft. N+3 is a step further, reaching a technology readiness level in 2035. The N+3 aircraft is envisioned to be in the 100-to200-passenger class and to have transpacific range. For NASA the focus is also upon reducing the sonic booms, with ex-

periments already showing a much lower sound level than that of the Concorde. THE FUTURE With a lot of research being done, it is time to look at what the future might bring for travellers wanting to travel at supersonic speeds. One of the frontrunners of bringing supersonic travel back is Aerion. Aerion is working on the Aerion SBJ, a supersonic business jet capable of carrying 8-12 passengers at Mach numbers up to 1.6. Although this seems futuristic, Aerion expects the SBJ to be tested and in service by the end of the decade. Another proposed future supersonic business jet is the HyperMach SonicStar. With a cruising Mach number of 3.6, it can transport 24 to 32 passengers at supersonic speeds. Announced in 2011 the SonicStar is expected to fly in June 2024. Both the SJB and the SonicStar promise to produce less noise and be more fuel efficient than the Concorde. This would enable them to fly over land and to be economically viable. Richard Lugg, CEO of HyperMach even boasts ‘The aircraft is six times faster than the Gulfstream G650 and you are still paying less for fuel’ [Andrews 2013]. Boeing and Lockheed Martin together with NASA are also working upon larger supersonic aircraft. Both companies are working on aircrafts for NASA’s N+3 program. Although these aircraft would truly be a ‘Son of Concorde’, it will still be years before these aircraft reach the market, if ever. Although all concepts sound promising, they still have to get off the shelf and into the air, something the Concorde achieved 44 years ago. Only time will tell what is going to happen, but for supersonic travel, the future seems promising.

References 1. HyperMach in talks with manufacturers over supersonic jet, http://www. corporatejetinvestor.com, Alex Andews, 2013 2. My Ride on the Concorde, http:// www.airspacemag.com, Robert van der Linden, 2004 3. Race to be first with ‘son of supersonic’, http://edition.cnn.com, Jones, 2011 4. Aerion corporate site, http://www. aerioncorp.com, Aerion, 2013 5. Celebrating Concorde, http://www. britishairways.com, British Airways, 2013 6. Beyond Concorde: The next generation of supersonic flight, http://edition. cnn.com, Hume, 2012 7. The SST of the Future: Interview With NASA’s Peter Coen, http://www.defensemedianetwork.com, Wilson, 2013 8. Concorde Aircraft Facts, http://www. flightlevel350.com, Flightlevel350, 2013 9. Sonic Boom Heads for a Thump, http://www.nasa.gov, NASA, 2012 10. For Flight Demonstration of Quiet Supersonic Aircraft Technology, http:// www.jaxa.jp, Ohnuki and Makino, 2012 11. Supersonic flight inches closer to reality, http://www.independent.co.uk, Thomas Black, 2012

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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Student project

BUILDING THE FASTEST BICYCLE IN THE WORLD A year with the Human Power Team Delft & Amsterdam

“Third time lucky” is the saying, but for the third Human Power Team it almost turned out as a year for nothing. The team has been attempting to set the world record for the fastest bicycle powered only by human muscles for two years already. This endeavor to let a Dutchman be the fastest human on earth resulted in a marvelous year with many ups and downs and a world record. TEXT Menco Schuurman, Student Aerospace Engineering, Chief engineer/ Aerodynamics Human Power Team 3.0, Elias Allegaert, Student Aerospace Engineering, Aerodynamics Human Power Team 3.0, Geertjan Roks, Student Mechanical Engineering, Mechanical engineer Human Power Team 3.0

he third Human Power team set off in September 2012, and consisted of students from Aerospace Engineering and Mechanical Engineering from Delft University of Technology. Because of the importance of the engine, a human being, students from the faculty of Kinesiology from the Vrije Universiteit Amsterdam were also part of the team. The goal of the year was to achieve a new human powered world speed record of over 133.28km/h. In order to do so, a special recumbent bicycle with an aerodynamic monocoque structure had to be developed. In line with the previous years, the bicycle would this time be called VeloX3. The design process started with an eightweek research phase, where the work of the previous teams was studied and opportunities for the next year were investigated. A Numerical model was created to compare the influences of the main parameters. It could be concluded that aerodynamic drag causes approximately 75% of the total resistance. Rolling resistance of the tires was responsible for 20% of the losses. A remarkable outcome was that the weight of the vehicle affects the

top speed very little. This is due to the fact that the world record course has a small downward slope of less than 0.6%. CONCEPTUAL DESIGN In the following period, design decisions on the main components of the bicycle were made. Some components remained the same as in the previous year; the main layout stayed similar to a conventional recumbent bicycle, and the monocoque. The monocoque construction of the second year was incorporated as well. This concept proved its performance on safety several times in the past. Another concept that was continued was the camera system. The VeloX2, which was the predecessor, had a camera system with a monitor in front of the rider. Cyclists were very positive about the clear display. An important change was made for the drive train, which was moved from the front wheel to the rear. This change resulted in a more comfortable steering behavior and a better driving position for the rider. DETAILED DESIGN The detailed design phase started with making decisions about how the sub-

systems would be implemented. An important aspect in this phase was the aerodynamic monocoque. The largest resistance was aerodynamic. Hence, it was desirable to have the best aerodynamic shape that was able to contain all the subsystems. Multiple wind-tunnel tests were performed with genuine pleasure for the Aerospace Engineering students (see Figure 1). During this phase, extensive structural calculations were performed on the frame and the monocoque. Based on the results the team set up a comprehensive production plan. Drawings of all subsystems were made in CATIA to be sure that every subsystem would fit inside the bicycle, and renders of the drawings were used in the design presentation at the end of this phase. The presentation was given to show sponsors, former team members and other people interested the team’s progress and the final design. PRODUCTION AND TESTING The production started with ordering components and manufacturing carbon composite and metal parts. This turned out to be very intensive and time consuming. It became clear that there was a

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Figure 2. Testing the VeloX3 at the RDW test track

Figure 3. Preparing the VeloX3 for the qualification races

big difference compared to an university assignment. Everything that was unelaborated still required a solution. After three months, in the beginning of May 2013, the bicycle was finished. The team travelled weekly to the RDW proving ground in Lelystad to extensively test the bicycle in order to prepare it for the competition (see Figure 2). Many adjustments, repairs and replacements were added. In July, the bike competed in its first official event. An hour record attempt was performed in Germany to put the bike and the team under a stress test. On the highway in Germany a truck driving before the van with the two bicycles got a burst tire. The remains blocked the front wheel making the van uncontrollable so the van ended on its side on the shoulder of the road. Luckily, nobody was severely injured but the bicycles were partially damaged. The bikes got patched up before the hour record attempt. All in all, this week was a good preparation for the world record attempts in September. COMPETITION Finally, after many months of testing and fine-tuning, the main event for the team (World Human Powered Speed Challenge) approached. One week before the team travelled to the USA, the bicycle left Delft for its journey to Battle Mountain, a small village in Nevada. The ‘305 highway’ is situated close to Battle Mountain and is due to its specifications (minimal slope, straight, 10km in length) it is unique and suitable to perform a legal world record attempt. For this reason, the World Human Powered Vehicle Association (WH-

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Figure 1. VeloX3 for the first time in the Low Speed Windtunnel (Faculty of Aerospace Engineering)

Figure 4. Sebastiaan Bowier and some team members just after the world record race

PVA) organizes this event every year and gives teams from all over the world the opportunity to push their bicycles to their limits. All speeds are measured after approximately 8km of acceleration as a time average over 200m. In a nearby center, all teams were able to prepare (and sometimes repair) their creations (see Figure 3). From this building, it was around twenty minutes driving to the start. During the racing days, the organization closed the highway three times for half an hour. This happened every morning and every evening. Every single day for an entire week. A qualification race on the first day determined the distribution of the time slots over the teams. BAD WEATHER AND TECHNICAL PROBLEMS Just after the sun sets the wind normally drops. Since a world record attempt is only legal at wind speeds below 1.6m/s, it was preferable to race at the end of the evening slots. However, this time the weather was different from other years. Three evenings the team decided not to race because of the bad weather conditions. The unpredictable wind gusts and rain resulted in a wet road that was too dangerous for both the driver and the bicycle, especially when driving at high velocities. Despite the bad weather, the results of the team were still better than the other competitors. However, the team was still far away from the world record. During the first few races, a worrisome pattern

was discovered. One of the drivers provided more power compared to the other driver, but his maximum speed was lower. It turned out that there was a problem the driver’s riding position. This resulted in force acting on the monocoque too close to the canopy opening that caused the structure to deform slightly. It was barely visible, but it changed the aerodynamics in such a way that the bike performed far below the predictions. ALL OR NOTHING The team detected this particular problem on Friday after trying out many other technical solutions to other possible causes. That last night went by with almost no sleep. With only one racing day left and not knowing whether the solution was the correct one, the team decided to participate in both the morning and evening slots. After the morning slot, it could be concluded from racing-data that the solution to the problem was correctly detected and solved. That evening the weather seemed to be as bad as the other days, but since. Since this was the last opportunity, it was decided to race anyway. In a nerve-racking race, the driver almost decided to quit his attempt because of the wind gusts. There was almost no hope left, but from one moment to another the wind dropped. In an extreme effort the driver, Sebastiaan Bowier, set a new world record by increasing the old one with 0.5km/h to an amazing speed of 133.78km/h (see Figure 4). The second driver, Wil Baselmans reached a top speed of 127.43km/h. MARCH 2014 Leonardo Times

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‘ASML IS THE OTHER SIDE OF THE SPECTRUM’ Marijn Wouters talks about his graduation in the semiconductor industry

“I

have always been fascinated by a large variety of problems, and never been someone capable of working on a single phenomenon for years. At ASML I got to know the other side of the spectrum. Here, development goes super-fast. I’d never thought to end up in this industry, but there are clear issues here in my field.” This is what Marijn Wouters says, Master Student Aerospace Engineering subject Aerodynamics. Here’s a brief explanation for those who do not know ASML. ASML in Veldhoven makes lithography machines for the production of computer chips. The company supplies all major chip manufacturers in the world - such as Intel and Samsung and with its products defies the limits of what is physically possible. For example, with the latest generation of machines, ASML is able to print lines and components of 20 nanometres, which is comparable to printing an entire novel of 500 pages on one centimetre of a human hair. IMMERSION HOOD At ASML, Marijn is working on the optimisation of the ‘immersion hood’. This is a ring holding a small amount of water trapped between the lens column and the fast moving wafer (base material for chips) underneath. ASML uses water to get a more favourable refractive index of

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the light, which enables the company to project even smaller lines and components on chips. For a process taking place on a few nanometres, it is of vital importance that the water is as homogeneous as possible. Marijn: “The immersion hood has many tiny supply and drainage canals. Now it has been found that the removal of the water produces small pressure fluctuations. My research is focussed on this phenomenon. I visualise the fluctuations and try to determine the kind of interference they generate. Ideally, I may soon be able to provide a number of well-founded design recommendations for the next generation of ASML immersion hoods, with which ASML can further optimise the machine.” AERODYNAMICS “I chose Aerospace Engineering because I felt attracted by it. It is a comprehensive study in which you are engaged in a wide range of technical disciplines. Eventually I chose to do a Master of Aerodynamics, a tough and extremely interesting field of study: complex equations, a lot of modelling and working from assumptions. The technology, computer simulation of aerodynamics, is still lagging behind. You still can’t do many of the calculations that you’d like to do, simply because they require too much processing power. Therefore, you have to make assumptions. This

immediately yields a number of uncertainties. What kind of precision do you get in your results? And if you simplify, how should you handle that? Are you going to neglect thermal effects? And what will be the result? Do you have other choices? These are all complex issues that require a healthy dose of common sense when you start interpreting them. And that is quite similar to the practice of ASML.” SPEED To stay ahead in this industry you have to constantly innovate, take the next step. Marijn: “So here too development is done on the basis of assumptions. A scientist may well think that premature decisions are being made that can’t be substantiated well enough with calculations, models or experiments. Still, I think there is no other way for ASML. And it is also what makes the work interesting. In my temporary role as a researcher, I’m a little outside the whirlwind of deadlines. I have the time and freedom to map out and substantiate things well. ASML has an open culture in which people also listen to and think along with trainees. The subject Aerospace Engineering doesn’t immediately bring to mind the semiconductor industry, but I am very happy to have learned more about this world.” * Advertorial by ASML

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How do you make a lithography system that goes to the limit of what is physically possible? At ASML we bring together the most creative minds in science and technology to develop lithography machines that are key to producing cheaper, faster, more energy-efficient microchips. Our machines need to image billions of structures in a few seconds with an accuracy of a few silicon atoms. So if you’re a team player who enjoys the company of brilliant minds, who is passionate about solving complex technological problems, you’ll find working at ASML a highly rewarding experience. Per employee we’re one of Europe’s largest private investors in R&D, giving you the freedom to experiment and a culture that will let you get things done. Join ASML’s expanding multidisciplinary teams and help us to continue pushing the boundaries of what’s possible.

www.asml.com/careers

/ASML

@ASMLcompany

FIFTEEN YEARS OF INTERNATIONAL SPACE STATION

NASA

RVD

The International Space Station (ISS) celebrated its 15th birthday in October 2013. The ISS is the largest spaceship ever built by humans and very important for research, to understand life and physics. However, the ISS is very expensive to maintain and therefore some people argue that the ISS program should stop. The US president has decided to support the extension of the operations of the ISS to at least 2020. TEXT Bas Verhagen & Tolga Celebi, Students Aerospace Engineering, Space Department

ince the arrival of Expedition 1, on November 2, 2000, the International Space Station has been continuously occupied for more than 13 years, the longest continuous human presence in space. The ISS programme is a joint project among five participating space agencies: NASA, Roscosmos, JAXA, ESA, and CSA. The station is serviced by a variety of visiting spacecraft: Soyuz, Progress, the Automated Transfer Vehicle, the H-II Transfer Vehicle, Dragon, and Cygnus. Astronauts and cosmonauts from fifteen different nations have visited the ISS. The ISS is arguably the most expensive single item ever constructed. The total estimated cost of the space station is 100 billion dollar. CONSTRUCTION OF THE ISS The ISS is a modular structure whose first component was launched in 1998. A Proton rocket launched the first ISS module. Zarya, on November 20, 1998. Zarya provided electrical power, propulsion, storage and guidance during the initial stages of assembly. The STS-88 shuttle mission followed two weeks after Zarya was launched, bringing Unity, the first of three node modules and connecting it to

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Zarya. At that moment, the station consisted of two modules. Human presence was not possible in these two modules so the station remained unmanned for one and a half years. In July 2000, the Russians added a third module: Zvezda. After connecting this module to the station, a crew of two astronauts or cosmonauts could stay on the ISS. It is still the structural and functional center of the Russian Orbital Segment (ROS). Building the entire space station required more than 115 flights, of which forty were assembly flights. Russian elements were launched to space by proton rockets and NASA’s space shuttles brought other components into orbit. Also, more than 170 spacewalks were required to assemble and maintain the station. At this moment, the station consists of a set of communicating modules, in which the astronauts can live. These modules are connected to a truss onto which four large solar panels are attached to power the station. RESEARCH The ISS provides a unique platform on which scientific research can be con-

ducted in microgravity. At the station, the crew conducts experiments in the fields of biology, human biology, physics, astronomy, meteorology and others. Small-unmanned spacecraft can provide platforms for zero gravity and exposure to space, but the ISS offers a long-term environment where research can be done, potentially for decades combined with ready access to human researchers over periods that exceed the capabilities of manned spacecraft. NASA describes the importance of the ISS for research as follows: “The International Space Station is an unprecedented achievement in global human endeavors to conceive, plan, build, operate, and utilize a research platform in space. With the assembly of the space station at its completion and the support of a full-time crew of six, a new era of utilization for research has begun.” One of the main research subjects is the human body. Research on the ISS improves knowledge about the effects of long-term space exposure on the human body. Subjects currently under study in-

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NASA

clude muscle atrophy, bone loss, and radiation. The collected data will be used to determine whether space colonization and long human spaceflight are feasible. Another widely researched subject is physics. For example, the investigation of the physics of fluids in microgravity will allow researchers to model the behavior of fluids more accurately. At this moment, over 1,500 experiments have been performed with partners over 68 countries.

a positive, demonstrable return on investment,” he added.

FUTURE While there are currently discussions to extend the lifetime of the $100 billion International Space Station beyond 2020, there is concern about the station’s overall usefulness and operational costs, such that the station might face a fiery demise in Earth’s atmosphere at the end of this decade. The overall operational capabilities, utility, and longevity of the Earth-orbiting complex, as well as the willingness of nations to continue to take part in the program, were front-and-center topics during a meeting of the NASA Advisory Council’s (NAC) Human Exploration and Operations Committee on July 29th, 2013. During this meeting, William Gerstenmaier, NASA’s Associate Administrator for Human Exploration and Operations Mission Directorate, said space station component failure rates have been less than anticipated. “The hardware is looking pretty good overall,” he said. But micrometeoroid and orbital debris hits to the station are still considered “a major risk”, Gerstenmaier advised.

The debate over how long the International Space Station should be maintained is something that has long loomed over the program, one expert said. “This is a little bit like smoker’s cough. It’s something that nobody wants to notice”, said John Logsdon, Professor Emeritus of Political Science and International Affairs at George Washington University’s Elliott School of International Affairs in Washington, D.C. An expert in space policy and history, Logsdon said his bottom line is that “the odds are heavily against the continuation of the ISS post 2020”. Logsdon told SPACE.com that he does not think it likely that either Japan or Europe have any enthusiasm to pay for the ISS after 2020.

Concerning the attitude of the many space station partners about continuing operations through 2028, Gerstenmaier said: “I think this is probably an area where the US is going to have to lead.” International partners “are still looking more for

“For the United States, we’re seeing some benefits from the station that the partners have not yet realized. The partners are doing more traditional kinds of research. They are not quite seeing that return on investment. They still see the cost side,” Gerstenmaier added. “The cost side is very easy to measure. The benefit side is not so easy to measure.”

“That presumes that there’s no major breakthrough,” Logsdon said, referring to any potential discovery on the station with either great scientific or economic value. Furthermore, according to Logsdon, there is some talk about Russia starting a second-generation space station on their own. The professor also pointed out that China has launched two crews to its first space laboratory module, Tiangong 1, and plans to construct a 60-ton space station by 2020.

CONCLUSION The ISS provides a unique platform from which scientific research can be conducted in microgravity. Some countries mainly see the costs of maintaining the ISS and see little benefits The US thinks that the other countries are performing traditional experiments, so they do not give themselves an opportunity to see the returns on investments. If the US wants to continue the operation through 2028, they have to convince the other partners about the benefits and returns on investment in the upcoming years till 2020. REFERENCES www.russianspaceweb.com/iss_chronology.html www.space.com/22348-internationalspace-station-lifespan-2020.html www.space.com/23663-internationalspace-station-by-the-numbers. html?utm_source=feedburner&utm_ medium=feed&utm_campaign=Fee d%3A+spaceheadlines+%28SPACE. com+Headline+Feed%29 www.nasa.gov/mission_pages/station/research/index.html#.UrL7DPRDuWY curiosity.discovery.com/question/international-space-station-important

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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PYLON BLOWING ON PUSHER PROPELLERS

Focusing on Propeller Performance and Noise Emissions Propeller propulsion systems promise to offer a step change in fuel efficiency compared to turbofans. Currently, major research efforts are put into advanced propellers, with the Contra-Rotating Open Rotor as most prominent example. However, such engines suffer from relatively large noise emissions, partially due to installation effects resulting from interactions between engine and airframe. The research discussed in this article focused on the reduction of the adverse installation effects by means of pylon blowing. TEXT Tomas Sinnige, Graduate Aerospace Engineering, PhD Candidate at Flight Performance and Propulsion Department

ncreasing air traffic and rising fuel prices have led to the demand for more fuelefficient aircraft. Because of the large effective by-pass ratio achievable by propeller propulsion systems, these are much more efficient than turbofans. However, this comes at the cost of increased noise emissions, resulting from the isolated engine as well as (airframe) installation effects. One advanced propeller propulsion system is the so-called Contra-Rotating Open Rotor (CROR), an example of which is shown in Figure 1. CRORs feature two blade rows and highly swept blades to maximize efficiency and feasible aircraft operating speed. The large rotor diameter of these engines dictates an aft-fuselage mounted layout, with the propellers often positioned in a pusher configuration to reduce cabin noise (see Figure 2). For pusher propellers, a major noise source is formed by installation effects resulting from the impingement of the pylon wake on the downstream propeller disk. While cutting through the pylon wake, the inflow velocity experienced by the propeller blades is temporarily reduced compared to the undisturbed conditions outside of the pylon wake. This leads to unsteady blade load-

ing, directly resulting in additional noise emissions. Considering that the installation effects are the result of the presence of the velocity variations in the pylon wake region, it can be expected that eliminating the velocity deficit in the pylon wake can reduce them. This can be achieved by blowing air into the wake from the aft end of the pylon, a technique referred to as pylon blowing. The work discussed in this article, performed as MSc thesis at the faculty of Aerospace Engineering, involved both experimental and numerical evaluations to assess the effects of pylon blowing on the performance and noise emissions of pusher propellers. EXPERIMENTAL SETUP All experiments were performed in Delft University of Technologyâ&#x20AC;&#x2122;s Open Jet Facility, using a propeller test rig (shown in Figure 3) leased from the German-Dutch Wind Tunnels (DNW). Note that in contrast to CRORs a single-rotating tractor propeller was considered. A straight, nontapered pylon model was positioned upstream of the propeller model to simulate an installed pusher propeller. The pylon blowing system was integrated in the py-

lon, and formed by a novel Uniform Blowing Rod (UBR). The UBR consists of an interior air channel shaped such that in theory a uniform outflow distribution is obtained from the pylonâ&#x20AC;&#x2122;s trailing edge, while vanes are placed in the outflow segment to align the flow blown into the pylon wake. A Rotating Shaft Balance (RSB) is integrated in the propeller model to measure the forces and moments generated by the propeller. Finally, noise measurements were performed using two out-of-flow microphones. NUMERICAL SETUP Computations were done using a custommade program formed by a collection of existing numerical and analytic methods, as described in detail in (Sinnige and Veldhuis, 2014). The isolated performance was computed using the propeller lifting line code XROTOR, with the input blade section characteristics obtained from RFOIL. To quantify the installation effects first the pylon-wake velocity profile was obtained using a combination of 2D XFOIL analysis and the Schlichting wake model. No methods were implemented to predict the pylon wake profiles in blown condi-

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NASA

ROLLS-ROYCE PLC.

Figure 1. Rendering of Rolls-Royce geared open rotor concept engine

Figure 2. Typical aircraft configuration with rear-mounted contra-rotating open rotor engines.

Figure 3. Photograph of the isolated powered propeller setup inside the OJF

Figure 4. Tonal noise reductions due to blowing: effects of the blowing rate; blown configuration, U = 19 m/s, J = 0.9, θ = 110°, φ = 90

tions. Instead, measured blown wake profiles were used. With the pylon-wake profile known, the resulting time-dependent blade response was computed using the Sears method, which is an unsteady aerodynamic method suitable for airfoils subject to periodic sinusoidal gusts. Having determined the propeller performance, the noise emissions were computed using analytic models developed by Hanson [Hanson, 1980) and (Hanson, 1985]. RESULTS AND DISCUSSION Application of the pylon blowing system successfully decreased the velocity deficit in the pylon wake, with reductions in the integrated velocity deficit of up to 60% compared to the unblown case. However, mixing of the flow blown into the pylon wake and the external flow was not optimal. As a result, the velocity profiles did not become uniform but instead displayed a profile with one local maximum on the wake’s centerline and two local minima left and right of the centerline. In terms of the propeller performance it was found that the effects of installation are small, with a maximum difference of 2% in time-averaged thrust and torque coefficients for realistic operating points. For the same range of operating conditions, the computed time-accurate thrust and torque signals displayed peak-topeak variations of less than 4%. Application of pylon blowing further reduced the installation effects. A comparison of the measured and computed results for the isolated propeller showed very good agreement, with differences smaller than 1% for the thrust coefficient for most operating points considered. At the highest

thrust settings slightly worse agreement was obtained due to the reduced accuracy of the blade section- response computations at high angles of attack. The installation of an upstream pylon clearly increases the propeller noise emissions. The experiments showed a noise increase of up to 15dB depending on the propeller operating conditions. Application of the pylon blowing system reduced the noise penalty due to installation by up to 7dB, again depending on the propeller operating point. At this point, it should be mentioned that propeller noise is mainly of tonal nature, with tones occurring at frequencies equal to multiples of the blade passage frequency (which is the frequency at which a fixed observer would see the blades passing by). The results discussed so far considered the total sound pressure level, which was computed from the experimental data as the combination of the first ten propeller tones. Figure 4 presents the noise reduction due to blowing for the various propeller tones separately, for a single operating point and all blowing rates considered. From Figure 4, it is observed that noise reductions of 4-7dB are obtained for the first three propeller tones, while the higher tones are practically eliminated by the application of blowing. Furthermore, it can be seen that the highest noise reductions were obtained at the highest blowing rate, indicating that the most effective blowing rate might not have been reached. CONCLUSIONS AND OUTLOOK Experimental and numerical analyses of the effects of pylon blowing on pusher propeller performance and noise emis-

sions were performed. The application of the pylon blowing system was successful in reducing the velocity deficit in the pylon wake. Furthermore, it was concluded that the effects of installation on the time-averaged propeller performance are small. Finally, it was shown that the installation of an upstream pylon strongly increases the propeller noise levels, which can to a large extent be mitigated by the application of pylon blowing. Follow-up studies with larger models and more realistic velocities, executed in an anechoic wind tunnel, are scheduled to be performed around the timeframe of publication of this article. Furthermore, the implementation of propeller integration aspects in the overall aircraft design process as well as novel methods for propeller noise prediction are key subjects of future research in the Flight Performance and Propulsion department headed by prof. Leo Veldhuis. For more information (including the possibility of graduation projects) please contact the author at T.Sinnige@tudelft.nl. References [1] T. Sinnige and L.L.M. Veldhuis, 2014. “Pylon Trailing Edge Blowing Effects on the Performance and Noise Production of a Pusher Propeller”, 52nd Aerospace Sciences Meeting, AIAA-2014-0566, National Harbor, MD, USA. [2] Hanson, D. B., 1980. “Helicoidal Surface Theory for Harmonic Noise of Propellers in the Far Field”, AIAA Journal, Vol. 18, No. 10, pp. 1213-1220. [3] Hanson, D. B., 1985. “Noise of Counter-rotation Propellers”, Journal of Aircraft, Vol. 22, No. 7, pp. 609-617.

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DESIGN SYNTHESIS

EXERCISE FALL 2013

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DUNEMAV

The aviation industry has always been inspired by naturesâ&#x20AC;&#x2122; heavier than air fliers: birds. Birds make extensive use of updrafts to significantly prolong their flight time. Updrafts are caused by different natural phenomena, such as solar radiation heating of the ground, which results in thermal updrafts, and wind striking obstacles that are large and steep enough to deflect the wind upward, which creates ridge lift. Micro Air Vehicles (MAVs), which typically have a low endurance, should be able to significantly improve their flight time by exploiting updrafts. Longer endurance would greatly increase the amount of possible useful applications for MAVs. TEXT DSE group 1

DUNEMAV GOAL MAVs have a small wingspan, a low mass, and are designed to fly fully autonomous. Since MAVs have less volume available for complex control systems, and the Reynolds number of these aircraft is very low, designing such an aircraft is a real challenge. The small size of an MAV also limits the available power, and thus the maximum range, endurance and speed. These performance characteristics can be improved by exploiting updrafts during the mission of MAVs. The goal of this DSE is to implement autonomous updraft detection and exploitation technology in the design of an MAV with a maximum weight of 1kg. The mission of the DuneMAV is to perform beach surveillance along the Dutch west coast, between Hoek van Holland and Katwijk, for more than 12 hours a day for at least 70% of the days from June to August. AIRCRAFT DESIGN The DuneMAV has been designed using an optimization algorithm, which optimizes for maximum energy extraction from an updraft. This design has been fine-tuned aerodynamically by using a 3D panel method and a vortex lattice method, and structurally, using a finite element analysis. This results in an MAV, which is specifically designed for its mission. The

DuneMAV will be hand launched and will cruise at 7.7m/s. Since the mission specifies the route between Hoek van Holland and Katwijk, some urban areas will be encountered where no updrafts can be exploited. Therefore, the DuneMAV will be equipped with a small folding propeller, mounted on the back of the fuselage, to supply the necessary energy to cross the gaps. UPDRAFT DETECTION Autonomous detection of updrafts from afar has not been done before. Clearly, the geometry of the terrain determines the locations of good ridge lift. Therefore, a system has been developed which determines the terrain geometry, by making use of the principle of optical flow. When travelling at a certain velocity, objects close by appear to move faster than objects that are far away. By using a simple camera and tracking individual pixels and converting them to flow vectors, the construction of a 3D height map is possible. Using the wind velocity and the 3D map of the dune, the updraft velocities can be estimated. CONTROL AND SIMULATION Based on a 3D height map of the Dutch coastline, the design of the DuneMAV and weather data from the KNMI in the period from 1971-2010, endurance simulations

have been performed. These simulations indicate that the DuneMAV will be able to perform its mission 70% of the time between June and August, as is required. The simulation will exclude the days that the wind velocity is too low or too high to perform the mission. Furthermore, a conceptual autopilot has been developed that is able to perform fully autonomous flight, as well as waypoint navigation. In full autonomous flight, the MAV will fly along the coast, while maximizing the amount of energy extracted from the updrafts. SURVEILLANCE The DuneMAV has been equipped with a high-resolution camera (41MP) for its surveillance mission. This camera enables the operator to zoom and detect a human from more than 250m away. This great coverage enables the MAV to fly above the dunes, where the updrafts are located. CONCLUSION Concluding, the DuneMAV will contribute to a more efficient and sustainable way of providing beach surveillance, not only along the Dutch west coast, but also along coastlines all over the world. Future work may even result in an MAV flying in an urban area using the ridge lift created by skyscrapers as its free source of energy!

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FAST REAL-TIME FLOW VISUALIZATION

Imagine you have an idea of a random shape in your head. You want to show the airflow around it to fellow engineers or to a class of students. You quickly draw it on the wall and immediately see the flow around it. Add a few more shapes to see their effect on each other. Itâ&#x20AC;&#x2122;s possible!

hroughout the history of aerospace engineering, finding out the flow behavior around objects has been very important. By now there exist a lot of tools to simulate and visualize any kind of airflow behavior, with high accuracy. But what most of these programs lack, is the interactivity and speed to quickly visualize an idea. In order to improve communication with other engineers, from the same or different fields, or to educate people outside of aerospace, a new tool had to be developed. Ten students have made it their goal to design, develop and code a real-time flow visualization tool to that end. GOAL The most important feature is interactivity. The tool must allow for user-drawn input to which the flow reacts in real-time. Speed is critical for achieving a real-time tool; a minimum goal of 30 frames per second had been set for the solver while maintaining accuracy with a minimum grid size of 128x128 units. Similar tools and applets lack accuracy. The tool that has been developed by the team is based upon known methods and new research vetted by tutors and project leaders. It is therefore known to be accurate and usable by engineers for education and communication of ideas.

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CFD The Computational Fluid Dynamics (CFD) solver, the part that calculates the flow behavior, is based on several research papers regarding vortex-in-cell methods (VIC) (Poncet, 2009) (Cottet, 2003) and the work of the groupâ&#x20AC;&#x2122;s tutor, Richard Dwight. The airfoil is modelled as an immersed boundary. The result of this is faster and, for this purpose, favorable from an accuracy/stability balance compared to more classical grid-based techniques. No through-flow and no-slip boundary conditions are handled in separate parts of the code and are important for proper functioning of the solver. SPEED AND INTERACTIVITY To make the tool as fast as possible, it has been written in C++. As of writing, it works well in real-time with a steady 50-60 frames per second on a 128x128 unit grid size. A tremendous amount of effort has been put into achieving this benchmark. The team has built its own custom PC with a large graphics processing unit (GPU) for multi-threading the large matrix operations. Also a lot of effort has also been spent on applying Algebraic Multigrid (AMG) methods for solving the matrices more efficiently, as well as other smaller improvements.

TEXT DSE group 2

Meanwhile, a graphical user interface was developed that would allow drawn user input. The user can quickly draw any closed shape, modify it and see the result. The solver can also work with multiple objects, allowing e.g. for the effects of flaps and slats. Data input occurs via an interactive projector that allows for a vibrant and appealing user experience. Users can draw on the wall and see the results instantly. Displaying the results has also been custom built. The team made its own plotting system and a particle engine, allowing the examination of individual particle behavior. THE FUTURE It is the hope of the group that the tool will continue to see development by all who wish to contribute. Expanding the capabilities of the current tool can happen on many different fronts. Interactivity can be increased by adding turbulence listening, expanded input methods, or bettering current visualization techniques. Further functional expansion could come from adding compressibility, 3-dimensional capabilities, or larger grid size features.

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AIDPLANE â&#x20AC;&#x201C; A LIFESAVING SOLUTION

After natural disasters strike, people are often left helpless and without permanent shelter. To support the victims of natural catastrophes, a cargo delivery unmanned aerial vehicle (UAV) has been designed to provide help in the form of a permanent modular house. The UAV can deliver up to 3 humanitarian aid packages per day containing all components of a house for three people from any International airport to a disaster zone within a distance of 1000 km. TEXT DSE group 3

roup three of the winter 2013/2014 DSE designed an unmanned aerial vehicle (UAV) to automatically deliver cargo packages of 500kg of weight to disaster zones in need of humanitarian aid. Aimed for operation by relief organizations such as the Red Cross, the cargo was optimized to permanently provide shelter and equipment, covering more than the basic needs of a three-person household. Permanency was defined as a time span of at least 10 years and the design of both the UAV and the cargo packages were oriented along the 2010 earthquake in Haiti. Mission requirements set by the client demanded the delivery of at least two cargo units per day per UAV over a range of 2000km, the ability to operate past line of sight and the delivery of the cargo units with a precision of 50m. In addition, the UAV had to fit into the cargo hold of a Lockheed C-130 Hercules (12m x 3m x 3m) and take-off from Punta Cana International Airport in the Dominican Republic. Three initial UAV configurations were designed conceptually: an airship, a tiltrotor and a conventional airplane. After a tradeoff based on the mission requirements in terms of criteria such as delivery speed, operational efficiency and staff required to operate the aircraft, a conventional air-

plane design was identified to be the most suitable concept. Since the UAV takes off from an international airport but does not have runway access at the disaster zone, a parachute system was designed to guide the cargo package to the ground. A LAPDS (low altitude parachute delivery system) was selected as a suitable mechanism to drop off the cargo from an altitude of approximately 50m. This was the better option compared to a guided parachute, due to its economic feasibility and the possibility to collect it after drop-off and reuse it on further missions. To ensure the safe delivery of all cargo components, including sensitive solar cells and electrical systems, airbags are mounted to the bottom of the cargo. The cargo can be transformed into a permanent, hurricaneproof, watertight, modular, expandable housing solution with a complete interior including three beds, kitchen, toilet and shower on 7m2 living space. With forerunners of UAV technology- mainly used for military applications such as the Predator series developed by General Atomics- reference UAVs were analyzed to identify the required systems on board. The avionics system has been designed

with a triple redundant open-source Lisa/L Paparazzi autopilot. The UAV integrates seamlessly into the air traffic by providing position information to the Air Traffic Controller and autonomous mid-air collision avoidance. The UAV was designed to operate with a line-of-sight (LOS) link to the traffic controllers at Punta Cana International Airport and communicate with a satellite link beyond LOS. The UAV is propelled by a single turboprop at the nose with a Rolls Royce engine which is widely used in the aerospace industry. A special structure with rollers was designed to extract the cargo during the drop-off maneuver. Another structural link between the fuselage and the wings was designed to be able to detach the wings to fit the UAV into the Hercules C130 cargo hold, a mission requirement. The detailed design of the UAV resulted in a flexible aircraft, able to perform up to three missions between Punta Cana International Airport and Haiti per day. It was designed as a lifesaving solution and will hopefully be used one day on relief missions. It is unknown where the next natural disaster will strike; it is, however, certain that there will be future natural disasters with similar consequences as in Haiti in 2010.

MARCH 2014 Leonardo Times

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THE SKYDOWSER

A lack of water to meet daily needs is a reality for one in three people around the world (WHO, 2009). Not only is this currently a significant problem, but also globally the problem is getting worse as cities and populations grow, leading to an ever increasing demand for fresh water. Even Western countries such as the United States face severe water crises (Business Insider, 2003). Over the last few years several solutions have been developed to pump and desalinate water, but the critical part of the problem still persists; no one knows where to look for this groundwater. TEXT DSE group 4

urrently the most widespread method for finding ground water in Africa consists of drilling a hole and seeing what surfaces. In the Western world other methods are available such as Proton Magnetic Resonance, which is often used in the Oil industry, and Frequency-domain Electromagnetics (FEM). It is the latter, which is very promising for scanning large areas. FEM equipment is capable of sending an electromagnetic field into the soil and measuring its response, in the form of another electromagnetic field. Based on this response, the equipment maps the conductivity of the soil. This technique is not only effective for finding water, but also for finding e.g. landmines or other explosive remnants of war. Currently FEM is applied in helicopters (HEM) and handheld devices (GEM), but these platforms are either very expensive or slow and therefore unattractive for third world countries. Hence, in just ten weeks, nine bachelor students of Delft University of Technology developed a fully autonomous Unmanned Aerial Vehicle (UAV) for their client Sjoerd Dijkstra, CEO of Winddrinker. The UAV, named the SkyDowser can scan large stretches of land for ground water by applying this FEM technique. The FEM equipment uses different frequencies to

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measure at four depth levels. The SkyDowser has a range of over 700km and can scan areas up to 30km2 per day. The launch is performed by means of a simple catapult. The operator can tense the elastic bands by hand, place the aircraft on the catapult and launch the vehicle in a matter of minutes. During flight the SkyDowser uses its laser altimeter to stay at a constant altitude of thirty metres above the ground. Obstacles such as large trees or transmission towers are detected by the stereoscopic cameras placed in the wingtips and are avoided automatically. The SkyDowser navigates autonomously, running the open-source Ardupilot as an autopilot. This system allows the operator to create flight plans in Google Maps, by defining areas or setting waypoints. The landing of the UAV is done by means of a parachute and a rubber tail cone. The parachute is positioned in such a way that the SkyDowser always lands on its tail, where the rubber tail cone absorbs most of the impact. An advantage of the parachute is that it can also be deployed in case the mission has to be aborted and thus it functions as an important safety mechanism. The combination of the catapult launch system and the parachute allow the SkyDowser to operate in virtually

any environment, including remote, desert-like areas, which are plentiful in Africa. The engine of the UAV runs on a mixture of gasoline and synthetic oil and burns only sixty grams of this mixture when scanning a square kilometre. The SkyDowser can be built for less than â&#x201A;Ź15,000, and has an operational cost of â&#x201A;Ź4 per square kilometre. This low price is achieved by utilising mainly commercially available components together with open-source software. A modular design philosophy has been implemented in the development of the SkyDowser. It is therefore not only easy to manufacture and repair, but it can also easily be disassembled for transport in a car. For detailed measurements, it is even possible to take off the wing, which houses the measurement equipment, and use it as handheld scanning device. Due to its simplicity in design and operations the SkyDowser makes an attractive alternative for HEM, GEM and Proton Magnetic Resonance. Therefore, it may just be the missing link in solving the global water crisis.

Leonardo Times MARCH 2014

3/25/14 22:12

INSPIRATION MARS

I.M. DELFT

Flying a manned spacecraft to Mars is a vision within the space industry which is developing gradually and inspiring more citizens and companies to take a step towards the Red Planet. In this group of enthusiasts, the Inspiration Mars project, launched by the Mars Society, has become the innovatorsâ&#x20AC;&#x2122; beacon to contribute to this extraterrestrial adventure. The mission focuses on the design of an end-to-end fly-by mission for a flight period of 500 days, while accommodating for a man and a woman on board of the spacecraft. TEXT DSE group 5

INTERNATIONAL STUDENT COMPETITION The mission is introduced by Dennis Tito, the first space tourist, who initiated an International student competition. Worldwide, student teams will present their fly-by mission design and the winner is invited to present their design at the 2014 International Mars Society convention. DSE team Inspiration Mars Delft, I.M. Delft, represents Delft in this student competition. DESIGN PROCESS As a first step, a feasible trajectory was designed and optimized for departure. This resulted in a launch date on January 4, 2018. The mission will take a total of exactly 501 days to perform a fly-by at Mars on August 20, 2018, and return to Earth on May 20, 2019. This exceptionally quick, free-return orbit opportunity occurs twice every fifteen years. After 2018, the next possibility does not occur again until the year 2031. The design process continued with the identification of different design options per sub-system. After this phase, the design options were analyzed and critical design choices led to the foundation for

the overall mission overview of this endto-end mission. Following this phase, the detailed design process began, in which, all mission specifications were thoroughly identified from launch through landing, as follows. MISSION OVERVIEW The first step of the mission is the launch of the SpaceX Dragon re-entry capsule and two extended trunks, which carry the crew and the living module to a Low Earth Orbit on board of a SpaceX Falcon Heavy launcher. After this phase, a second Falcon Heavy is launched which carries extra fuel to this orbit. Next, in-orbit docking is performed and the refueling process, assisted by the crew with an Extravehicular Activity, takes place. Thereafter, the system undocks and the spacecraft, ADRESTIA, is ready to start its interplanetary journey. This journey is initiated by an injection into a Trans Mars trajectory due to the generation of a velocity change. Since this mission marks the very first manned mission towards Mars, the Environmental Control and Life Support System is of great importance. It ensures the safety of the crew and sustains human life and workability. This opportunity allows

for a number of scientific experiments to be brought on board, bringing to life the interplanetary mission experiments that have been performed in different projects on Earth. Halfway through the 500-day mission, the first manned Martian fly-by is performed. It will have a duration of ten hours, approaching Mars at an altitude of 180km. Using the gravity of Mars, the spacecraft obtains a velocity boost to continue its trajectory and journey back to Earth. In the final phase of the mission, the spacecraft starts approaching Earth and the crew moves back to the Dragon capsule with an Extravehicular Activity. Following this process, the re-entry capsule is jettisoned and it performs a direct reentry. The living module will continue on its trajectory into a heliocentric orbit where it will be used to collect deep space environment measurements. Finally, the crew is retrieved from the capsule and this inspirational and innovative mission is completed successfully.

MARCH 2014 Leonardo Times

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RAFT: RED CROSS AERIAL FIREFIGHTING TANKER

Wildfires have been a phenomenon for as long as forests exist. Lightning strikes, the heat of the sun and human activity, all cause these devastating fires. Research by the National Interagency Fire Center has shown that during the recent decades, the impact and frequency of these fires has increased, thus increasing the risks for people living close to the forest. This is due to both climate change and biomass growth. To combat these fires, aerial firefighting missions are often set up. However, the current fleet of water bombers is aging; the latest purpose-built water bomber was designed in 1990. TEXT DSE group 6

he need for a next generation water bomber was expressed by the Red Cross, and DSE group 6 was set the challenge to design it, with hefty requirements. Whilst a take-off distance of 1000m and stall speed of 100kts seems mild – the mainstream water bomber, the Bombardier 415 capable of carrying 6.1m³ of retardant, has similar performance characteristics – the design had to be able to achieve this with a retardant capacity of 15m³. Besides that, reloading on both land and water had to be possible. Water was chosen as retardant, as it´s widely available, proving a reliable method of extinguishing flames. Combined with the requirement of reloading on water, the direction the group was steered in became clear: designing an amphibious aircraft. However, the group rejected an easy choice of platform and also investigated the advantages and disadvantages of regular aircraft, tilt-rotors and helicopters. The immense payload weight (15m³ of water equals 15,000kg) required a large power requirement, which in turn meant large rotors were needed for both the tilt-rotor and helicopter concepts. As aerodynamic lift is considerably more efficient than mechanical lift, an airplane was chosen as delivery platform. The main concern was complying with

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all set requirements, most of which were flight performance requirements. A design power of 12MW and a design wing surface area 193m² were found to be needed for the next generation water bomber. This gave input for both wing sizing and engine sizing. The design is powered by four T56 engines placed on top of the wing in order to remain clear of any water spray. An unswept, tapered wing combined with a swept T-tail design proved most optimal for lift generation, stability and controllability of the aircraft. As the design flies at low altitudes and high angles of attack, there is little room for error. A third level of controllability redundancy was introduced using control canards, which allow for deep stall recovery. Additionally, they can also be used to allow a vertical translation of the aircraft without a rotation. Inflatable floats allow for stationary stability whilst minimizing flight drag. In order to minimize turnaround times, the design choice was made to allow for in-flight scooping of water. Using small inlets mounted under the fuselage, the aircraft can skim the water surface and take in 15m³ of water within 11 seconds. In turn, this volume of water can also be dumped in four stages by opening drop doors in the bottom of the retardant tanks. Computer

Augmented Detection and Aiming System, CADAS, a tunnel-in-sky-system, allows for precise dropping, whilst also relaying information to the ground control. This makes for an optimal flight path, combatting the fire most effectively. Optionally, a hotspot can be targeted using a fuselage mounted water cannon, which concentrates 850L of water on the target. Using lifting hydrofoils, the takeoff distance is decreased considerably in the water by reducing water drag at low speeds. On land, the design will be able to take off within a 1000m whilst having 15,000kg of a combination of payload and fuel onboard. As the design has four engines of high power, it can still take off within 1000m when one engine has failed. Therefore, this aircraft can get out of any airfield, always. To make sure that the aircraft can perform other tasks besides firefighting, an emphasis was put on multi-functionality. Outside the wildfire season, the spacious fuselage area and removable firefighting equipment turn this water bomber into a highcapacity, amphibious cargo or passenger transporter. This versatility makes it an excellent aircraft for emergency relief missions. Therefore, RAFT symbolizes a true “Flying Swiss Army Knife”.

Leonardo Times MARCH 2014

3/25/14 22:12

INVADE

Corporate travel requires efficient and prompt modes of transportation. However, air travel does not meet this need as transfers, check-in lines and waiting times greatly increase the total time to travel between two business locations. A VTOL business jet would combine the advantages of a helicopter - flexibility and no need for an airstrip - with the advantages of an aircraft - fast cruise speed and a large range. InVADe offers all of these advantages at low operating costs. TEXT DSE group 7

This Design Synthesis Exercise project aims at designing an Innovative Vertical Take-off and Landing Aircraft Design (InVADe), which will be capable of operating in densely populated areas and will offer swift, point-to-point transportation. Hence, the aircraft will exhibit vertical take-off and landing (VTOL) capabilities.

flying a range of up to 2,000km, carrying a payload of 1,000kg or a shorter distance with 1,300 kg payload. Up to ten passengers will be transported at a speed of 600km/h at 75% of the maximum power rating, with a service ceiling of 7,000m. A maximum rate of climb of 11.2m/s can be attained at sea level.

Key innovations include the fan-in-wing concept, the electrical drive system and low noise levels at take-off and landing. The fan-in-wing concept and aerodynamically efficient design of InVADe resulted in a lift-to-drag ratio 63% higher than that of the Bell X-22. The electrical drive system enables the elimination of a mechanical drive system, reducing complexity and fatigue. If the generators were to fail during take-off or landing, batteries could power the fans for up to 2 minutes. Finally, noise mitigation measures including shielding, interior lining and inclined blades are applied. While taking off or landing, InVADe will generate a maximum sound level of 80.7 dB at a distance of 100m.

InVADe is expected to fly by 2030, with a cost of 1347 EUR per flight hour. This number includes depreciation, fuel, maintenance, crew salary and other costs. In comparison to business class tickets on short-haul routes, InVADe will offer direct flight at a lower cost than regular business class short-haul tickets. By eliminating the need to travel to and from the airport, the user saves times too. Since time = money (B. Franklin, 1748) and operating cost are low, InVADE is economically viable.

Next to that, the aircraft will be capable of

environment. With a CO2 emission rate of 2.04 kg/km, on par with other modern, small business aircraft, InVADe offers a significantly lower environmental impact, particularly for short flights, since it practically eliminates the need for getting to/ from the airport. In the vertical take-off and landing phases, the total noise Sound Pressure Level (SPL) produced, after abatement measures, is as low as 80.7 dB at 100 m distance. This is comparable to the noise of a passenger car as heard from alongside a highway. In conclusion, InVADe offers the business market a fast, reliable and cost effective way of transportation without compromising on comfort and sustainability.

A sharp focus on sustainability, especially on noise and CO2 emissions, pushed the design team to come up with innovative solutions and push the boundaries of the design to meet the needs of a future aerospace industry with lower impact on the

MARCH 2014 Leonardo Times

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MACHETE: ROBOTS ON MARS

After putting the first man on the moon, now the time has come to make the first steps in bringing the first man to Mars. To secure the survivability of the first Martian explorers, caves are proposed as a primary sheltering solution. This is why a swarm of Zebros (ZesBenige RObot) was developed at the EWI faculty; they will explore and map Martian caves. With the desire to bring these robots to Mars, the Martian Autonomous Critter-Housing for Extra Terrestrial Exploration (MACHETE) lander was born. TEXT DSE group 8

he goal of this DSE project is to develop the Entry, Decent, Landing, and Deployment (EDLD) phases of a Mars mission in order to deploy a swarm of Zebros on the Martian surface. To keep a clear overview on the design choices made, each phase of the EDLD will be treated and explained in separate paragraphs. ENTRY PHASE: The entry phase of the Mars mission begins when the entry vehicle reaches the thin Martian atmosphere. The entry vehicle used for the MACHETE mission has the same dimensions as the aeroshell used for the Mars Science Laboratory (MSL) mission. Until now, the MSL is the largest mass and size one can send to the Martian surface with today’s technology and thus MACHETE is sized accordingly to achieve the largest swarm on the surface as possible. The aeroshell of the MSL on its turn is modelled after the entry vehicle structure of the Viking 1 mission. This aeroshell structure has been used for every Mars mission so far. DESCENT PHASE: The descent phase begins with the deployment of a disk-gap band supersonic parachute then the heat shield will be released.

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The parachute will slow the MACHETE lander down to its terminal velocity of approximately 100m/s. The MACHETE can be manoeuvred to stay inside its landing ellipse, and approach the beacon target. This steering is done by pulling four separate winches attached to the parachute lines. Once the terminal velocity is reached the landing phase is initiated. LANDING PHASE: When the landing phase begins eight Clustered Robot Allocation SHips (CRASH), containing the Zebros, will drop out of MACHETE and start their rocket engines. Then these CRASHs will search for a beacon signal on the Martian surface that will guide them down to the target location. This beacon function can for example be fulfilled by MSL, or it can be assumed an earlier mission to Mars placed a beacon at the desired location. It was decided to go for multiple landers to spread the risk of failure, the consequence of this decision is the extra weight added due to duplicate systems like the ADCS and propulsion needed for each individual lander. On the other hand, now the crash of one lander would not mean the end of the mission since not al Zebros will be lost. By making use of a radio transmitted signal form the beacon,

the CRASHs can calculate their optimal attitude and glide slope towards the landing location and actually go there by controlling their four thrusters. The CRASHs will fly in a circular formation to the beacon to prevent collision between them. DEPLOYMENT PHASE: Once the CRASHs reach the beacon location a hovering phase of three seconds is initiated to safely release the Lander And Descent System (LADS). The system will be released thirty meters above the ground. Immediately after the release the LADS will start to inflate a vented airbag. This vented airbag will open vents at the moment of touchdown to prevent the ‘bouncing ball effect’ and remove the risk of tip over like conventional airbag systems. Once the LADS has safely touched down, the 28 Zebros each LADS carries will be released from and start forming the swarm needed for exploration of Mars.

Leonardo Times MARCH 2014

3/25/14 22:12

GRAVITY EXPLORER SATELLITE

Earth is experiencing an increase in average temperature due to the increasing amount of greenhouse gases. The ice in Greenland and Antarctica is melting at a high rate, causing changes in Earth’s gravity field. Scientifically speaking, it is very important to monitor these changes in order to keep track of the environmental developments as well as to be able to take action against global warming. Currently there are satellite systems monitoring the gravity changes, however these systems are known to be very expensive.

NASA

TEXT DSE group 9

he challenge at hand is to design a satellite system that monitors the change in Earth’s gravity field at a low cost. The Gravity Explore Satellite (GES) mission will do this by the use of tracking of navigation satellites. Various requirements were imposed, technical as well as non-technical, confining the accuracy (e.g. pointing accuracy and spatial scale) and lifetime of GES. Furthermore, the sustainability of the mission needs to be kept in mind, having the satellite re-enter within 25 years after its minimum three years lifetime. Since the biggest driver is cost, it was decided to use Commercial Off-The-Shelf components wherever possible. Also because the mission is desired to be as small as possible, it was determined to make use of CubeSats. In the conceptual design phase of the exercise, the focus was put on three different design segments; the payload, the orbit and the attitude determination and control system. For the gravity measurements are done by the use of tracking of navigation satellites the payload consists out of a GNSS (Global Navigation Satellite System) receiver and receiver antenna. The main choices where using a dual-frequency GNSS receiver, having a one satellite mis-

sion, or two single-frequency GNSS receivers on two satellites. After a trade-off, with as most prominent criteria cost, reliability and accuracy, there was decided upon the dual-frequency receiver. For the orbit the most favourable type was determined to be a dawn-dusk sun-synchronous orbit with an inclination of 97.7°, which gives an almost constant lightning and thermal condition. The height that gives the largest ground track was found to be 580 km, at this height the whole Earth is covered within a month. The attitude determination and control system was chosen to be an integrated board, containing amongst others a star tracker, reaction wheels, and attitude control algorithms. In the detailed design phase, all the subsystems were designed, as well as the system integration. The main task of the communication system is the receiving of data from the navigation satellites and communicating it to the ground station. The ground station selected for the GES mission is the one at TU Delft; GES will pass the station seven to eight times a day. The power subsystem exists out of body mounted solar cells and a battery. Five solar cells are placed on the sunlit side of GES and on the side of GES facing the Earth,

getting energy from Earth’s albedo. Also two cells are placed on the side opposed to the sun, in case the satellite starts tumbling and will have to go into safe mode. GES is coated in order to keep control of the thermal properties with 2 MIL silver Teflon and black paint. The temperature of the internal system is kept between 40 degrees in the worst hot case and -8 degrees in the worst cold case, keeping all the subsystems working properly. With all the subsystems designed and sized, it was clear that a 2U CubeSat would be needed to house all the equipment. The low cost CubeSat mission GES will be unique to the space market. No other gravity observation mission is operational within a university budget, making this a one of a kind opportunity for institutions and universities with a space programme, such as the TU Delft. CubeSats have been proven to be very popular in university research programmes for their easy use and relatively low cost. Furthermore, students can be enthused to voluntarily dedicate some of their time to the project, reducing employment costs. GES is expected to have a total mission cost of 250,000 Euros.

MARCH 2014 Leonardo Times

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DIGITAL RADIOGRAPHIC TECHNOLOGY Non-destructive testing of turbine blades

Inspection of turbine blades has always been a big challenge. Any irregularities in the blade have a huge impact on the gas turbine, so these blades have to be manufactured and inspected in the most sophisticated way possible. The evolution of digital radiographic technology took a leap forward to solve these problems in the industry environment which also enhances production quality and reduce rework. TEXT Prithvi Sai Penumadu, Editor Leonardo Times, MSc Student Flight Performance & Propulsion

ondestructive testing and inspection technologies are advancing very rapidly through the digital revolution, software development and newer imaging capabilities. Often derived from the technological community, both 2D and 3D imaging can solve complex issues in the areas of component life extension, sustainability for service, design optimization, quality control or root-cause failure analysis. High-resolution imaging has become practical, cost-effective and can save critical time when properly applied to real-world applications. However, interpretation of the radiographic images is extremely difficult due to the complex structure involved The quality specifications set for turbine blades and stators are very demanding as these blades and vanes are not only used in the aviation sector but also in power plant operations. Turbine blades become increasingly complex due to factors involving optimizing efficiency and weight reduction. In order to maintain high standards and life of turbine blades there should be an accurate method to analyze the blade irregularities such as

incompleteness during casting process, wall thickness, controlling the position of cooling holes, hole diameter, roughness etc. These properties can be analyzed with X-ray systems during production and quality control. During maintenance and repairs turbine blades are welded back together and at this instance extensive uses of digital systems are necessary. X- ray systems such as highly dynamic radioscopy, Computed Tomography (CT), automatic defect recognition and micro focus X-ray. CT is a technique which gives the user a three dimensional interface of the inspection item. This allows the user to precisely analyze pores and the wall thickness of the sample, determine geometrical tolerances and to compare the result to the target specifications. It also gives a more accurate analysis of the inspected item than radiography due to the inspection in its three dimensional interface. In addition, it offers great precision and this technique is also used for quality control of the production process. X-ray slice data is generated using an X-ray source which rotates around the object; X-ray

sensors are positioned on opposite sides from the X-ray source and the detectors are in-line detector arrays. This kind of information helps to collect the required data and to speed up the production levels by reducing operative costs and other miscellaneous costs, for instance by reducing the number of rejects by using CT data to enable the process to be corrected on a timely basis. These techniques are widely used now ranging from highly specialized tasks in inline inspection to the universal microelectronics, meteorology and aviation markets. Over the past 2 years, Highly Dynamic Radioscopy (HDR) has revolutionized inspection via X-rays. Details of thin and thick regions of the sample or specimen become visible when inspecting the specimen in motion and without constant adjustment of the X-ray parameters. This method is faster in detecting defects in the specimens. The term â&#x20AC;&#x153;highly dynamic radioscopyâ&#x20AC;? means that a high level of detector dynamics exists in relation to depth resolution on the one hand, and that a high level of dynamics is present in relation to the image refresh rate on the other.

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YXLON INDUSTRIES

Figure 1. Crack Inspection with HDR Technology

Figure 3. Wall thickness inspection using HDR Technology

Radioscopy, or inspection in motion, only works when the image refresh rate is high. Flaws are X-rayed at an optimum projection angle by moving the X-ray beam. This enables better detection. HDR-Inspection makes flaws visible in all thicknesses of the inspected itemâ&#x20AC;&#x2122;s materials right from the start using one setting, and without the inspection operator having to change the parameters. HDR-Inspect is a product that enables the inspection operator to test the entire inspection item with assurance at a glance, even in areas with different densities, by using flat-panel detectors in combination with special software. HDR is a low-noise, fast detector displaying a high level of dynamics in combination with software optimally calibrated. The structural noise that occurs even at high doses can be prevented through multi-gain calibration and a correction of non-linear detector pixels. The complex pixel correction requires very efficient conversion within the software code to be able to be used jerk-free at 30 images per second. In this way most optimum test data can be extracted for a tested specimen. This method can only be followed in a process where one item at a time can be tested for a single run. Mass production testing with this technique is time consuming. In the due course of time the problem solution for testing nondestructively in combination with mass production emerged

Figure 2. Digital live image using HDR Technology

in Germany called Automatic Defect Recognition (ADR). It is fully automatic radioscopic inspection system. ADR is designed in such a way that the system does not need any operator involvement as a result of an intelligent software system. All the inspected results can be attained automatically and can be reproduced at any time. The results obtained are highly objective and the decisions put forth to the system can be reproduced at any point of time including all the data specifications and indeed involved in high output rate. It has four levels of accessibility. Level 1 involves in the operating screen and production counters whereas level 2 is accessible to all programming functions which the operator feeds in. In level 3, the system has the capability to terminate the session and in the final level it deletes the cache memory which includes sample data, working directory, program function etc. as ADR is utilized in series production. The software obtains its image data from an X-ray system that is capable of processing very high unit volumes. Inspection decisions are always made according to the same objective criteria due to the ADR software. So there are different software packages depending on the applications. Each of these software packages is coordinated to match the special requirements posed by the inspection task. The only disadvantage is the software cost. Companies have to invest a lot of money

compared to HDR or CT techniques. Many companies use image intensifiers either with analog or digital cameras as the image source with amorphous silicon panels with 127 to 400 micron pixel pitch. The toolbar has a progressive layout which makes the system user-friendly. Its unlimited life span and very high magnification makes this technique more usable than any other systems. To conclude, the techniques used nowadays for the non-destructive testing of samples are diverse. Each company uses its own methodology but these three major principles are followed around the world. Each of the systems has its own advantages and disadvantages. Large scale industries which focus on mass production, implement ADR technology because it is time-efficient, but not all the companies can afford to buy the expensive software. Small scale industries, which act like an original equipment manufacturer (OEM), are choosing HDR technology or CT depending on their usability. With the involvement of modern computer aided manufacturing techniques, CT, ADR and HDR are emerging methods, which are followed from the past 5 years. References [1] www.yxlon.com [2] www.airwise.com [3] http://www.ge-mcs.com

MARCH 2014 Leonardo Times

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Internship report

V2G THERMAL COUPLING ANALYSIS Internship assignment at DLR Göttingen

When modelling a supersonic wind tunnel, such as the V2G (see Fig. 1), the tradeoff between affordable computations and accurate results drives much of current research. In all of DLR’s previous simulation attempts, inconsistencies were found when compared to the experimental data. To determine where the differences arose, detailed models of each stage were deemed necessary to validate boundary conditions. The first stage: the nozzle core. TEXT Vincent Maes, MSc Student Aerospace Structures and Computational Mechanics

STARTING AT THE FRONT END When results from complex CFD calculations failed to match the experimental results, the consensus was that errors in upstream boundary conditions were causing discrepancies downstream. Hence the focus was shifted from the entire flow domain to only the very first segment. The nozzle core (see Fig. 2) is a piece roughly 10.5 cm in length and contains three segments: a stagnation chamber, a neck region, and an expansion cone. Heated nitrogen gas flows from the heater into the stagnation chamber, where it is supposed to homogenise and return to subsonic speeds after being rushed through the heater. Then the subsonic flow passes through the nozzle neck, where it reaches Mach 1, and continues to accelerate as it exits through the expansion cone. The issues stem from two facts, firstly the “largest” piece has a neck diameter of only 1 cm and the maximum stagnation temperature of the flow is around 1400 K. Combining these two conditions means that the neck is at risk of being reduced in effective cross-sectional area, as increased

wall temperatures lead to increased boundary layer thickness. To solve this, active cooling is employed on part of the outer surfaces of the nozzle core. This results in a very steep thermal gradient within the nozzle core as well as a continuous heat flux caused by thermal contact with the flow. As inaccurate boundary conditions were thought to be at the root of the discrepancies between simulations and experimental results, the suggested solution was a model utilizing thermal coupling to yield a better temperature boundary conditions, based on simulated temperature fields within the nozzle core pieces. The data from this coupled model had three main questions to answer. What does the temperature profile look like? How sensitive is it to changes? And, does the flow in the stagnations chamber actually stagnate? These questions had to be answered for five different nozzle cores, each with a unique neck diameter, varying material properties and different operating conditions. ADDING PARTS TO SIMPLIFY The goal of complicating the model by

adding a coupling mechanism is to remove the uncertainty regarding the conditions of the surface being coupled. This, however, leads to additional boundaries and considerations coming into play from the integration of the structural model. To be able to generate a thermal field within the nozzle core piece (see Fig. 3) all the contact surfaces had to be accounted for. Moreover, the nozzle core is exposed to a high current which is used to power the heater and passes through the nozzle piece on its way out. Five boundary segments, induction heating and internal radiation all became active possibilities that had to be either proven negligible or incorporated into the model. The very low resistivity of the materials used to construct the nozzle cores together with the relatively large cross-sectional area of the nozzle piece (when compared to the cross-sectional area of the heater) resulted in estimated electric induction heating well below a level that could be considered to be important. Initial runs also showed wall temperatures dropped quickly to levels below 400 K at the throat

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DLR

Figure 1. Picture of the V2G wind tunnel at DLR GĂśttingen

Figure 3. Temperature field in nozzle as calculated using FEM

Figure 2. Engineering drawing of the 10 mm nozzle core

Figure 4. 3D model of flow domain with accurate heater outlet

and then remained within a bound of roughly 100 K. At such low temperatures and with such small variation in temperature it was concluded that radiation, too, could be ignored. This decision was critical as it allowed for the domain to be reduced to a semi 2D model (CFD calculations require volumes and hence always at least one element in thickness direction) which greatly reduced computational times.

high flow streams that would easily have Mach numbers above Mach 0.3. While the 2D models did confirm this suspicion, they suffered from simplified boundary conditions. The actual heater end, shown in Fig. 4, could only be properly captured in 3D models that covered at least an eighth of the total possible domain (this is the smallest piece that can be repeated to recreate the full volume).

STAGNATION IS KEY The V2G wind-tunnel is controlled with the help of a thermo-couple that is inserted into the stagnation chamber of the nozzle cores. The temperature measurement made this way is assumed to be the stagnation temperature of the flow. Hence, the power supplied to the heater is tuned to get the desired temperature from this measurement. Validity of this technique is dependent on the stagnation of the flow within the stagnation chamber. If the flow is not â&#x20AC;&#x153;fullyâ&#x20AC;? subsonic (set here to be below Mach 0.2 to 0.3), the measurement will no longer accurately represent the stagnation temperature, calling into question any post analysis done on the data.

From the 3D models it quickly became apparent that all expectations were true: the flow did enter the stagnation chamber as high speeds (above Mach 0.3) and this resulted in recirculation happening within the stagnation chamber. Based on these results a secondary study was launched into the effects of redesigning the heater end, in an attempt to improve the conditions in the stagnation chamber for the larger pieces.

The worry that the flow may not be subsonic arises from the fact that the heater exit has a combined area of roughly 35 mm2 while the largest nozzle core has a throat area of nearly 80 mm2. This gives rise to the reasoning that the flow coming in from the heater is most likely close to, if not actually, supersonic and comes in as

NARROWING DOWN THE FIELD While the research into the stagnation chamber flow field was interesting and prompted much discussion, it was not in fact the main goal for the project. The initial desired outcome was a better understanding of the behaviour of the temperature profile along the wall of the nozzle pieces. As already mentioned, there are several variables that can play a role. A total of more than fifty coupled simulations were run to assess how the temperature distribution varied. It was found that the heat passed on from the flow to the structure was relatively small and as such on

the geometry and boundary conditions set on the structural side were critical. The geometry played a crucial role as for the larger pieces the stagnation chamber is widened which removes material, causing temperatures to rise locally. As such, the geometry of the piece established a baseline shape for the temperature profile while heater contact temperature and the cooling strength dictated the actual temperatures along the wall. From these findings it was determined and later verified that a temperature profile could be effectively estimated with the use of base profiles for each of the pieces as well as reshaping functions based on the change of the heated and cooled wall conditions. LOOKING UP AHEAD Half way through the project, when the first temperature profiles and sensitivity study simulations had been achieved, a second stage project was started to run alongside this one. Another student joined the team and started running simulations of the next section of the windtunnel using the temperature profiles provided. That project made great progress and showed good initial agreement with experimental data. Results also showed that the simulation was not as sensitive to wall temperatures as expected. The question now remains that if not the downward boundary conditions caused the deviations between the initial results and the experimental results, then what else caused it? MARCH 2014 Leonardo Times

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Start-up company

REVOLUTIONARY COMPOSITE JOINING METHOD REVOLUTIONARY COMPOSITE JOINING METHODSTRUCTURES MOCS

From an aerospace thesis research to founding a new company

In 2011, Peter Madlener started his graduation thesis at the Aerospace Engineering faculty on a new joining technology for composite sandwich panels. The promising results gained in this thesis led to the foundation of MOCS: a young company with the ambitious goal of introducing a revolutionary joining technology in the market. At this moment, MOCS is introducing its technology in the composite pipe industry. In this article you will read how MOCS was founded and how the technology it invented works. TEXT Ir. Anande Bergman, R&D engineer at MOCS

WHERE IT STARTED Industries are increasingly convinced about the major advantages and endless capabilities of composite materials. This results in large-scale composite material innovation programs that are run in the aerospace and automotive industry and contribute to an increasing popularity and understanding of this material type. In a bid to push this technology forward and to increase the knowledge based about marine composite product development Damen had set up the FLIGHT R&D project, together with DSM, Teijin Aramid, Lightweight Structures, Delft University of Technology and Bureau Veritas. One of FLIGHTâ&#x20AC;&#x2122;s goals was to develop or improve production methods that could reduce the current upfront investments required for fabrication of the plugs and moulds for composite ship structures. THE NEED FOR A BETTER JOINT The panel-wise building principle is a method that could be adopted for this. The principle is based on the assumption that cost driven mono and catamaran hull

shapes can be constructed out of separate sandwich panels. These panels are produced by an automated process in a controlled environment and can be assembled at an arbitrary shipyard. Excluding the usage of a plug and mould is the philosophy behind this building principle. In addition, it reduces the production time and possible lay-up mistakes since the lay-up and impregnation process of the core and laminates, which is often done by hand, is excluded from the process. When adopting this building process, it all comes down to the connection. Large-scale implementation of existing connection methods are limited by the fact that they are vulnerable, non-reliable, time consuming and costly. FROM THESIS RESEARCH TO COMPANY Under the supervision of Dr. ir. Otto Bergsma from the Design and Production of Composite Structures research group (DPCS), Peter Madlenerâ&#x20AC;&#x2122;s master thesis research goal was to develop a sandwich panel connection method that is suit-

able for large-scale implementation. This method has to stimulate a fast assembly process without having negative effects on the structural integrity. The study on a B-stage resin type showed it has the ability to overcome the negative effects on the aforementioned criteria. Experimentally determined strength reductions are of negligible magnitude. Moreover, it can be assumed as a continuum since it is based on chemical bonding, also known as a primary bond. During the thesis, several questions were raised: can this connection technology be implemented in other industries? Can it accelerate the composite usage? These questions led Peter Madlener and Wouter Riedijk, a former classmate, to founding MOCS. MOCS is focusing on the heavy industries (civil, offshore and ship building) where structures are large and have to be made out of modules. Currently MOCS is testing the applicability of the B-stage technology in connecting fiber-reinforced pipes that are used for transportation of fluids.

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The old proverb says: “a chain is no stronger than its weakest link”, and FRP pipe systems are no exception. Despite the superior properties of composites in comparison with traditional materials, the increased interest in the combination of large diameter and high pressure is also highlighting the weak link: joints, which are responsible for more than 95% of the failures in FPR pipe systems. One of the main issues with current permanent joining technology is the lack of control on the process. Bonded and laminated joints are the most common permanent joint in the FRP pipe industry. In both cases, the first step is to prepare the pipe segments by machining and sanding the surfaces to be joined. For bonded joints, the adhesive is prepared and spread manually, after which the female and male pipe segments are fitted. To realize a laminated joint both segments are placed next to each other and are connected by manually applying and impregnating several layers of glass fiber fabrics around the two segments to be joined. In both approaches, the quality of the joint is highly dependent on the skills of the pipe fitter and repeatability of the joining process. Quality cannot be ensured as there is almost no control of critical parameters like surface roughness, thickness of the adhesive layer, curing cycle, contact pressure or fibre volume fraction of the laminated patch. MOCS’ WAY MOCS’ aim is to introduce a highly reliable joint to the market. Instead of creating a secondary joint with adhesive or a FRP patch MOCS joining technology generates a primary joint at chemical level with mechanical properties comparable with a

MOCS

THE PIPE MARKET AND THE WEAK LINK The use of Fiber Reinforced Plastic (FRP) pipe has been rapidly growing in the last ten years because of their advantages over pipes made of traditional materials like iron, concrete and plastics. Their superior mechanical and anti-corrosion properties, lower conductivity and longer life cycle make FRP pipes a natural choice both for general purpose as well as in specialty applications. FRP pipes also have shown to be competitive for the large diameter (150 mm to > 4000 mm) pipe market, which is estimated to be worth $127bn, in high-pressure areas and in elaborate pipe networks extending over several thousand kilometers.

Figure 2. Detail of the filament winding process

co-cured joint. To realize this joint special B-stage resins systems are used. The main difference between a B-stage and standard resin formulations is that the polymerization (curing) process is interrupted in an intermediate state, where a sticky and flexible polymer is obtained. The material at this phase is called B-Stage, which can be maintained at room temperature for undetermined time without curing. When the temperature of the B-stage material is raised to the appropriate level, the polymerizations process is reactivated and a solid resin is obtained. MOCS joining technology makes use of the two curing steps. The basic principle is schematically demonstrated for a plate in Figure 1. First, most of the plate is totally cured (hard-out), with exception of the ends that remain in B-stage phase. To join two plates, the uncured ends are connected and cured under pressure, resulting in one solid plate. The key to ensure a reliable joint is to maximize control over the process parameters by automation in the joint manufacturing process and the in-field joining process. For pipe connections, MOCS develops a series of tools that can be integrated in the current filament winding process (see: Figure 2) to automatically manufacture integrated pipe joints. On field the task of the pipe fitter is limited to placing the pipes and joining tools into position; however all the critical joint process parameters are controlled and registered by the tools integrated microprocessor, ensuring

a reliable and repeatable joint quality. THE FUTURE In close cooperation with TU Delft and big industrial parties, MOCS is developing the B-stage joining technology towards a market ready product. Starting from an idea for a graduation assignment in 2011, MOCS has developed into a rapidly growing company, consisting of twelve employees and graduates at this moment. The mission of MOCS is to make a strong contribution in adapting these materials in the heavy industries with the aim of contributing to the world with more durable and sustainable structures and processes. MOCS’ forecast is that the composite material market will increase but it will never replace the market of isotropic materials. The adaptation of composite materials in the offshore, shipbuilding and civil industry will be related to the replacement of specific components where composites showed to have the best business case. MOCS’ goal is to keep on building strong relationships with the heavy industries and launch several technologies where the B-stage joining technology is the first to come. If you are interested in this technology and its potential application or want to contribute to this research as an intern or graduate student, please be sure to contact the author at abergman@mocs.nl.

MARCH 2014 Leonardo Times

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TECH TALENT EVENT 23 APRIL 2014 | OUDE DELFT 57 | DELFT

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HISTORY OF AVIATION SAFETY The satisfying sighs of relief due to developments in Aviation safety

”Aviation safety is an Integral part of my career. Being part of TU Delft’s impressive record of research on Aviation safety, my career has been with a sense of purpose and a responsibility to equip students to deal with the status quo challenges on Aviation safety, developments, Investigations and Optimizations. As I retire from the faculty with a gratifying sigh of relief, It’s a pleasure for me write this article on my experience and career along the progressive stages of Aviation safety.“ TEXT Prof.dr.ir. J.A.A.M. (John) Stoop, Aerospace safety Advocate, Faculty of Aerospace Engineering, TU Delft

THE FIRST SIGH OF RELIEF By the end of the Second World War, at the Yalta conference, Churchill, Stalin and Roosevelt could not come to an agreement at the highest political level on a common blueprint for worldwide postwar commercial aviation. The first sigh of relief was when the trio found a solution on the regulatory and organizational level by establishing the International Civil Aviation Organization (ICAO). On 4th April 1947, a convention came into force to ‘’ensure the safe and orderly growth of international civil aviation throughout the world’’. Safety became embedded in the structure of international aviation as an integral aspect, dealing with air fares & fees, tariffs & treaties, certification & licensing of crews, aircraft & airports and providing air traffic services to enable interoperability and free access of any nation in the rapidly expanding aviation network. Harmonized cooperation between sovereign nations was laid down in a series of annexes, dealing with each of the elements of the aviation system as a basis for national legislation and regulations. Technology became the flywheel for progress. Safety was guar-

anteed worldwide through harmonization and standardization of technical and operational equipment, dealing with international standards, operating procedures, recommended practices, training, traffic control, navigation, communication and airport facilities. Ironically, the safety Annex became no. 13, providing a protocol for international cooperation on the investigation of major air accidents. Since then, there has been a rapid and continuous growth of aviation, expansion of global networks, rapid technology developments of metal aircrafts, jet engine technologies, and navigation & communication facilities. The first generation of jet aircraft saw steep learning curves with unanticipated midair disintegration –such as with the De Havilland Comet. Such air disasters however, also brought knowledge about metal fatigue, structural integrity and commonly applicable safety design principles. By the introduction of the second and third generation of jet aircraft with the glass cockpit, navigation displays and Flight Management Systems, safety records on accident frequency improved significantly. Air crash survivability further reduced the risk of flying, while victim care and family assistance enhanced public

confidence. The fourth generation introduced Fly by Wire, Flight Envelope Protection and Safety Management Systems during operations. Aviation became a distinct class of high tech systems: NON PLUS ULTRA safe, characterized as beyond 10-7 safe with respect to the accident rate. The introduction of the Boeing 787 and Airbus 380 has seen no hull loss yet, an unprecedented achievement towards zero defects and First Time Right principles. THE SECOND SIGH OF RELIEF A second sigh of relief could be heard when major air accidents – US Airways flight 1549 in the Hudson (see Figure 1) and Qantas flight 32 near Singapore (see Figure 2) - occurred without loss of life in situations beyond design conditions. Aviation has become a matured system where conflicting values –safety, environment, economy and sustainability-are carefully taken into consideration in complex trade-offs and risk assessments. Performance requirements on fuel economy, noise abatement, airspace and airport capacity demands, punctuality, efficiency and passenger rights prevail, laid down in European policy documents such as Flight path 2050 and framework projects on sin-

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JIGGAR SHAH

ZIMBIO

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ROYAL AERONAUTICAL SOCIETY

Figure 1. Airbus 320 flight 1549 crash into the Hudson River shortly after takeoff from LaGuardia Airport, North Carolina

Figure 2. The full damage of the R-R Trent 900 Rolls Royce engine of the Qantas flight QF32, an Airbus A380 outbound from Singapore.

gle European skies, Clean Sky and Horizon 2020. Changes in business models, shifts in global networks and new entrants in design and manufacturing became major game changers. THE THIRD SIGH However, a third sigh, this time, of disbelief went through society when a series of unanticipated major air crashes occurred in a relatively short period. Questions were raised about the inability to diagnose their causes, formulated as ‘Black Swans and Unknown Unknowns’. Inherent complexity and dynamic behavior was deemed so overwhelming that proactive analysis would become impossible, limiting safety diagnosis of such systems to their ‘’emergent’’ properties during operations. The general public wondered whether aviation had become safety complacent, whether pilots were over reliant on automation, suffering from a loss of situation awareness. Should unmanned flight provide the answer in eliminating human error or should we inevitably accept occasional losses for the common good and desirable growth? Do we inevitably proceed on the road to Hyper Taylorisation and full automation? The sector itself responded slightly differently, aware of early warnings for changes that might impact the safety integrity of the aviation system. In order to comply with a steady growth, environmental constraints, changes in global markets, intercontinental networks and new business models, ambitious plans for the future have been developed, dealing with various forms of ‘Next-Gen’ approaches with a high level of investments in new technologies.

Figure 3. Lecture by Mrs. Deborah Hersman, Chairman, NTSB, US at the ‘Green versus Safe’ air traffic safety symposium in the LR Faculty, TU Delft.

THE EXPERTS SPEAK The need for ‘Next-Gen’ also left the safety investigation community with questions on how to deal with such changes, preserving the achieved level of safety, skills and competences of the investigators, adapting them to the second age of aviation. Risk is a social construct, aiming at consensus on acceptable level of risk, balancing safety versus other values such as economy and environment. Has safety become an operational constraint instead of a critical system value? As formulated by Deborah Hersman, chair of the National Transport Safety Board in the ‘Green versus Safe’ Air traffic symposium hosted by the LR Faculty, TU Delft (see Figure 3) , ‘’aviation is all about defying gravity, safely and surely. There is no credit from the public for past achievements. Airlines are only as good as their last flight. What happens today is a given and continued improvement is expected to safely defy gravity tomorrow’’. Yannick Maligne, Senior Vice-President and Chief product safety officer of Airbus stated that we permanently must address the main threats to safety: ‘’overconfidence at all levels, maintaining highest professional standards and focus on right things to do first’’. We must capitalize from positive outcomes too like, providing feedback from reality, learning from new experiences etc. Safety investigations are problem providers for knowledge development. Design interventions can be evidence and knowledge based. Although there may be sufficient ‘’low hanging fruit’’ we must aim for the high hanging fruit as well. We should apply a consistent approach by disseminating existing and introducing new energy state/landing performing based advisory systems. For aerospace engineers, safety

is not only a virtual or social reality: safety is dealing with defying gravity, with physical energy, reality, and design tradeoffs. As Tom Haueter of NTSB said, “It’s the assumption that kills you”. Assumptions on design, modeling, performance, operations should be transparent and validated. Jean-Paul Trouadec of French BEA investigation agency said in the report on AF447: “we must reflect on the validity of human error notions and human performance models, since they did not generate expected behavior of the flight crew”. THE FINAL AND MOST SATISFYING SIGH Fortunately, as aerospace designers, we can fall back on two firewalls in the feed forward and feedback processes between design and operation: certification and investigation. We teach our own students principles of forensic engineering, safety investigation, system engineering principles, integrated and multidisciplinary design optimization methods. We have to substantiate our own responsibilities with providing industry and society with qualified designers, engineers and investigators to cope challenges of Corporate Manslaughter and Corporate Homicide Act and exorbitant claims. Finally, a personal and final sigh of relief: by the Honorary Doctorate of Deborah Hersman, our faculty has demonstrated dedication to safety that has made the aviation system NON PLUS ULTRA safe. Assured by the final sigh of relief that a responsible group of next generation students will take over, I, John Stoop (Aerospace safety advocate, 1976-2014) am retiring gracefully from the Faculty of Aerospace Engineering, TU Delft.

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NASA

DESDEMONA AND A TICKET TO SPACE Training for space flight in a 3g motion simulator On October 5, 2013, Marijn Wouters and two other contestants of a nation-wide competition ‘Nederland Innoveert’ underwent a space training exercise. One by one, the trainees were pushed to their limits in the Desdemona motion simulator, an experience that mimicked the Space Expedition Corporation (SXC) space flight envelope. The ultimate goal: training for an actual mission, the 1st prize in the aforementioned competition. TEXT Marijn Wouters, MSc Student Aerospace Engineering, Aerodynamics

SPACE TOURISM SXC, one of the major players in the space tourism market, is actively selling space tickets. SXC is also allowing future clients a chance in their space travel simulator ‘Desdemona’. This simulator, located at a TNO research institute near Utrecht, is capable of mimicking the physical phenomena that act on a human body during the launch of SXC’s space vehicle, the ‘Lynx’ [Figure 1]. Future astronauts are subject to 3G during a re-entry phase, and using smart disorientation tricks the simulator can re-create the feeling of zero gravity. Together with several other future astronauts I was allowed training for a potential trip into space. As part of a prize I won in February 2013 at a technology convention in Eindhoven I was allowed to participate in a full-day operation where we could experience what is was like to be launched to 100km, and how it felt to plunge back through the atmosphere. (DIS)ORIENTATION The day started with a detailed lecture on the exact workings of a simulator. After seeing the simulator do a trial run to warm up the systems we were ready to try it ourselves, but first a fundamental basis was created to prepare us for the

actual experience. After all, a simulator is made to reproduce the forces on a body, and in order to do that the mind has to be tricked. A centrifugal motion can be felt as an acceleration of the space ship in forward direction, as long as the brain is made to feel so.

stationary train, and the train next to you departs slowly. Purely based on your eyes it may seem as if you are moving, while the other train is stationary, creating confusion between your sensory organs as the remaining systems do not detect the movement.

During the lectures, we were introduced to the three most important attitude- and acceleration-sensing systems inside a human body: the inner ear, the eyes and the “sixth sense”, a gut feeling that can be attributed to the sensory systems spread throughout the body. While the first two are well known, the final sense is mostly relevant to people experiencing extreme disorienting movements, such as a jet fighter pilot. The interaction and cooperation of these senses allows us to determine our movements with respect to the earth’s reference frame.

This theory would become relevant later in the simulator. Since the simulator is spinning continuously to create a feeling of accelerations your actual movements do not align with your expected movement, and shaking your head results in a different inner-ear feeling than you would expect. Hence the advice: keep your head still at all times!

Should these sensory systems disagree with each other, the mind has to determine what is correct and what not. An example of this disagreement is reading a book in a car: while your eyes only observe no movement, your gut feeling and inner ears do register the car movement. As a consequence, disorientation sets in and people become nauseous. Another case is the moment you are sitting in a

To put the theoretical knowledge to the test, and show how senses could be fooled by the Desdemona, all candidates had to perform simple task of walking through a hallway, turning a corner and opening a door. The only modification is that we had to look through a special prism that inverted the eyesight, meaning that turning your head to the right looked like your head turned left. In other words, your inner ear canal started to disagree with your visual observations, leading to hilarious moments. People twisted the wrong direction, stared at the wall for minutes and could not find the door knob.

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XCOR

NASA

Figure 1. Lynx space plane

Adapting to such a changed ‘orientation’ takes most people up to 8 days, and reverting back to a regular condition takes an equal amount of time. An example was given by our instructor, describing an experiment where candidates had to play table tennis using the ‘inverted’ glasses. After a while, the candidates in the experiment were unable to play table tennis without the glasses, since they were adapted to their inverted vision. UP, UP AND AWAY After an informative morning it was time for the actual training. One by one the candidates were placed in the Desdemona simulator to undertake a virtual trip to space, while the other candidates could enjoy the view from inside the control room. After the first candidate had successfully made it back to earth, it was my turn to step up to the walkway. Stepping in the simulator felt a little like climbing on to the platform of the Apollo rockets: a retractable walkway, a huge mechanical device, a flight suit and a tiny cabin to sit in. After I am securely strapped into the seat, I could only communicate to Harry van Hulten, test pilot and COO of SXC. From the control room the whole conversation could be monitored by the others. “Are you ready, Marijn? On my count, press the red button on the controls”. The simulator is first moved into position, and slowly starts to rotate. Surprisingly, the movement does not make you nauseous in any way. The virtual Lynx slowly turns onto the runway in simulated Curacao; even the bumps in the pavement are mimicked by Desdemona.

“3… 2… 1… ignition!” With a jolt the simulator springs to life and accelerates its rotation, and in the cockpit I experiences 2g as the Lynx accelerates. It is an enormous rush, and the experience is highly immersive as every bump in the take-off strip is felt. Once the launcher reaches sufficient velocity it takes off, and the initial rockets are extinguished. I can’t help smiling: the simulator is fully drawing me in and it feels like the real deal! After a few seconds, I can push the red button again to start the final ascent to space. After pressing the button again, the rocket fires, quickly accelerating the vessel to Mach 2 as the trajectory slowly turns vertical. The sensation is phenomenal, and the simulator creates an eerie sense of actual lift-off. The initial acceleration starts to lessen, but the vessel is still gaining speed as it is propelled into the sky. After what seems like minutes the g-forces start to reduce as the blue sky starts to shift to a black, star-spotted vista. Slowly I can start to relax as the accelerations seem to vanish, and the simulator performs another trick. By tilting forward and drastically reducing rotation, a feeling of weightlessness is created, a very confusing feeling after experiencing heavy acceleration only seconds before. The sensation of ‘microgravity’ in magnified by the amazing view through the ‘cockpit’ of the Lynx. As the Lynx slowly tilts forward the Earth comes into view, revealing an amazing scene and actual sense of altitude. Harry starts pointing out various landmarks as I take control of the simulator using the internal steering column. In micro-gravity the occupant is able to control the spacecraft attitude, something that felt like a cross between a

computer game and driving a car. Quickly I take in as much as I can of the surroundings, since I’ll only have a few minutes to appreciate the view before I plunge back to Earth. Seeing everything from up high makes me wonder how it would be like to be in the ISS, and experience this view every day. Before long, the simulator takes over and I have to prepare for the hardest part of the simulation: the 3g re-entry phase. For 20 seconds the simulator spins in a mad rush, and I can only laugh; it is an amazing feeling! I had imagined it as an annoying, constricting feeling, but it closely resembles a very intense roller-coaster ride. As instructed I tighten my leg- and lower body muscles to restrict the blood flow to the upper part of my body, ensuring that a lack of blood flow won’t cause me to pass out. The sensation is incredible, and I begin to understand the term “g-junky” that was mentioned by the SXC personnel. After the pull-out manoeuvre a gliding flight back to Curacao offers a chance to relax and enjoy the last moments in the simulator. It was an amazing feeling to experience the simulator run, and what it felt like to be propelled into space. Without a doubt it was one of my best aerospacerelated experiences so far (including the Aerospace faculty parabolic flights), and it leaves a hunger for more! Time to experience the real deal. References Desdemona simulator: http://www. desdemona.eu/ Space Expedition Corporation: http:// www.spacexc.com/en/home/

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Column

THE OTHER DRONES Looking at the other drone use possibilities TEXT Raphael Klein, MSc Student Aerospace Engineering, Editor Leonardo Times

ost people will think of the MQ-9 Reaper, when mentioning drones. This is the drone that is used by the United States Air Force and the CIA in Pakistan, Yemen and Somalia to kill terrorists. Most of the time, these drones are mentioned in the news for their collateral damage. In 2013 alone, the United States estimated that 271 people died from drone strikes around the world [1]. The government claims that approximately one in every nine to 10 deaths is a civilian. But drones are not only used to kill. In fact, most drones are used for peaceful purposes around the world. MILITARY DRONES DERIVATIVES Taking the example of the MQ-9, this drone is not always used to carry weapons. The drone has been adapted for completely different missions. It is used by Homeland security for border patrol between the US and Mexico. It is also used by the Coast Guards to monitor maritime borders and ports. NASA also uses the MQ-9 for science missions along with the RQ-4 (Global Hawk). Military drones are just the tip of the iceberg. Thousands of other drones already exist. PROFESSIONAL DRONE USES Drones are used for almost any professional use. In France, the national train company (SNCF) recently announced that they would be using drones to monitor their rail network. Currently, the company

is using helicopters to monitor copper thieves on the rails all over the country. The use of drones will greatly reduce the costs of such monitoring. Drones will also be used for repairs. For rail dedicated bridges, monitoring repairs require the closure of the track and the use of professional climbers to inspect all sides of aging bridges. However, drones can do the same tasks without having to close the bridges and at lower costs. Drones can just hover over bridge to be inspected and using cameras, men can inspect the bridge from a distance. This is a tremendous cost benefit. Drones are also used in the movie industry. To film large aerial shots, helicopters are the only tool available to directors. However, they can only be used outdoors and with authorisation from the authorities. This heavily restricts their use and the possibility to realise such shots. Nowadays drones can be used for these shots. Drones can be used both in outdoors and indoors. The cameras can therefore be placed in tight locations tremendously enlarging the shot possibilities for directors. Furthermore, drones are helping to modify Hollywood. Any small budget movie, Indie movie or even YouTube movie can now use drones as a tool and does not have to spend vast amounts of money for shots that could only be filmed by helicopters.

AUTONOMOUS DRONES So far, most of the drone applications mentioned are unmanned applications. Drones can also be used autonomously. This would mean that they are programmed to do a task with no human in the loop. This is currently experimented by farmers. In large farms, the farmer can have the need to use small agricultural aircraft. From these aircraftâ&#x20AC;&#x2122;s, the farmers can survey their crops or their livestock. They can also spray pesticides over their crops. In the future, autonomous drones could survey the farms automatically. They could pinpoint locations in the farm where there is a need for more attentions from the farmers. This would ease the workload of farmers and increase their efficiency while remaining cost effective. These examples are only a few examples from thousands of other applications that are and will be possible thanks to drone technology. What drones are used for only depends on us. References [1] Fewer death from drone strikes in 2013 after Obama policy change, http:// www.theguardian.com/world/2013/ dec/31/deaths-drone-strikes-obamapolicy-change, The Guardian, January 2014

Leonardo Times MARCH 2014

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