LT 2013 december by Anouk Scholtes

DECEMBER 2013

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

page 22

Mission to Mars : MSL and Mars 2020

number 4

Interview with Gerhard Kruizinga, JPL

Hypersonic re-entry technology

Insights into new advances in re-entry vehicles and materials

Audi: the cost of enlightenment

On the cost and performance of CFRP in the passenger car industry

Study Tour ‘Limitless’

Year 17

Study tour through the U.S.A. and Canada

Come on board.

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Contents Table of contents

Cover articles

Contents

Editorial

From Leonardo’s desk

Current affairs

Automating wiring formboard design

Interview with AE Alumnus Gerhard Kruizinga working at JPL

Audi: the cost of enlightenment

Hypersonic re-entry technology

LVD - Prandtl’s best wing system

Gerhard Kruizinga is an alumnus of Aerospace Engineering faculty of TU Delft working on various interplanetary missions at Jet Propulsion Laboratory (JPL). LT caught up with him about how he got to his job, current and future missions to Mars.

TU students sweep UAV design

Missions to Mars: MSL and Mars 2020

Hypersonic re-entry technology

competition 22

Interview - Missions to Mars: MSL and Mars 2020

Insights into new advances in re-entry vehicles and materials

Internship report - From Moscow to the Moon RVD - Space Debris

Study Tour ‘Limitless’

Student project - MAVLAB

We vlogen met een zucht... - VTOL

Insights into developments in technology in re-usable launchers aimed at reducing enormous costs involved in new age solutions for hypersonic re-entry vehicles.

Audi: the cost of enlightenment

aircraft 40

Column - Ariane 6: ESA at a Crossroads

On the cost and performance of CFRP in the passenger car industry

Advertisement index Fokker

Deerns

EPO

NLR

Delftse Bedrijven Dagen

KLM

Carbon composites are well established for limited edition supercars. What will it take for composites to be applied in passenger cars? An insight in combined internship and thesis project at Audi Germany.

Study Tour ‘Limitless’

Study tour through the U.S.A. and Canada The VSV organizes a study tour for the students every year. This year it was an intercontinental tour to USA and Canada. A report on the 2013 study tour ‘Limitless’.

DECEMBER 2013 Leonardo Times

Editor’s letter Dear reader, It gives me a great pleasure to be presenting this edition of the Leonardo Times to you readers. It’s a privilege to be writing this editorial, as this is the first issue for me as editor-in-chief of the respected journal Leonardo Times. Since the first time I have read this journal, I always thought it’s a very professional effort put together by students from the Faculty of Aerospace Engineering and I feel honored to be involved in the team that brings it all together. I have big shoes to fill in and the pun is intentional! My predecessor, Benjamin has been instrumental in putting it all together for the last year. He has been very inspiring and a very helpful guide for the whole team. This task falls upon me now, I am confident that with our editorial team, we will live up to expectations and I hope the readers will be able to savor the different flavors being put on their plate as Benjamin mentioned in his last editorial. And yes, since my origins are from India, there is bound to be a dash of spice and color in the way the story unfolds! This year, we have had some team members leaving the team in pursuit of their dreams. I had a wonderful experience working on the Leonardo Times with Pattareeya, Alisa, Nout,

The Leonardo Times team 2013-14

Colophon Robert-Vincent and Stefan, I wish them the best in their endeavours elsewhere. I would also like to welcome the new additions to our very International editorial team: Bob, Joris, Lakshmi, Nikita, Prithvi, Raphael and Shahrzad. I can already see that they bring new ideas, I see that we have a good mix of new enthusiastic editors and experienced team members from previous years who will be pooling efforts to bring out the best of news and articles in the field of Aerospace Engineering for you, the reader for the next 4 issues.

Year seventeen, number 4, December 2013

Aerospace Engineering is such an interesting world to say the least. I had a great opportunity to see this first hand this year being a participant in the VSV study tour “Limitless” to US and Canada this year. Travelling through the country that can easily be said to be a pillar in Aerospace manufacturing and development, I got immense inspiration to see how what we study as students is being put into actual developments in the industry while visiting companies like Boeing, Northrop Grumman, Embraer, XCOR etc. We hope the reader will be able to get insights into developments at these companies in the coming issues with articles featuring these organizations.

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

This issue includes an article on ”Limitless” on page 32. This issue also notably includes an Interview with Gerard Kruizinga of JPL about his involvement in NASA missions to Mars, developments at Audi, Hypersonic re-entry materials and many more interesting topics.

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 repsonsibilities 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 an employees of the Aerospace Engineering faculty.

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

THE FOLLOWING PEOPLE CONTRIBUTED: Tobie van den Berg, Mark Booij, K.J. Sudmeijer, Tom Pruijsers, Raphael Klein, Steve Brust, Malcolm Brown, Dr. ir. Roelof Vos (FPP), Ewoud Smeur, Sjoerd Tijmons, Ingo Gerth DESIGN,LAYOUT: dafdesign, Amsetrdam PRINT: DeltaHage B.V., Den Haag

VSV ‘Leonardo da Vinci’ Kluyverweg 1, 2629 HS Delft Phone: 015 - 278 53 66 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

Leonardo Times DECEMBER 2013

FROM LEONARDO’S DESK

Dear readers, A lot has happened since the beginning of the new educational year. Not only in the Aerospace world, where the Boeing 787 Dreamliners are again airborne, but also at this faculty. We have received more first year students than last year, and the pressure is higher than ever to get your ECTS with a BSA of 45 ECTS according to the regulations from the government. They will no longer give a grant to the Master’s students, but this will become a loan. The month of September was a special month for Leonardo’s desk due to a couple of things. Just like every year the board changed at the beginning of September. On the 3rd of September, seven enthusiastic students started their journey to guide the VSV ‘Leonardo da Vinci’ for a year and make the VSV even better than it is today. Next to the board, the previously mentioned 380 new aerospace students also started their journey at this faculty to claim their place as the best engineers in this world. For a lot of the new students their adventure already started at the end of August when they came to the freshman’s weekend. During this weekend, 237 freshmen had the chance to get to know each other, the VSV, and make a quick start for the upcoming year. At the end of the weekend a lot of freshmen were enthusiastic and motivated to start their studies as much as the board

was looking forward to start with their VSV year. Two days after the changing of the board, 2 of the 7 board members, including myself, left as a part of the organising committee on the study tour named ‘Limitless’. The study tour departed on the 5th of September to the United States of America and Canada to visit Aerospace companies. During this tour, 30 students and 2 professors had the opportunity to visit companies like Boeing, Northrop Grumman, NASA JPL, Bell Helicopters and Gulfstream, to name a few. In the meantime, on the other side of the world, the board was working hard to guide the VSV as well as possible. Along with some excursions and drinks at ‘De Atmosfeer’, the VSV also had the interest drink for new active members. After a successful drink, we are happy to welcome 70 new enthusiastic VSV members. Together with all the members of the VSV, we will try to make this year even better than the previous years. On the 4th of October, the study tour group returned from their trip and all members of Leonardo’s desk were back working on a beautiful VSV year. At the time of writing this Leonardo’s desk, a few activities have already taken place but a lot are still ahead of us. One of the most important activities is the Symposium. Every year either the Aviation or Space department organises a big symposium with a topical

theme. This year the space department will be organising the symposium on the 4th of March, where the main subject will be manned missions to Mars and unmanned ones to the moons of Jupiter. Only a week after the symposium another big event will be happen at our faculty. On the 18th of March the faculty will transform for one night from a university into a vibrant clubbing area, where 1000 students can enjoy drinks and dance to live DJ’s. Next year in September, a new study tour ‘Valhalla’ will depart, but this time they will stay in the Europe. Combining the wind energy and space applications in the Scandinavian area with the beauty of north Italian design at companies such as Piaggio and Lamborghini, it guarantees to become successful once again. As you can see, this new academic year will bring many activities and exciting times. Not only for us, at the board, but also for our new and old members and all the students at this faculty. Thus, I am very motivated and ready to grasp all the possibilities that this year will bring and I will keep you all updated in the following Leonardo Times editions! With winged regards, Jef Michielssen President of the 69th board of the VSV ‘Leonardo da Vinci’ DECEMBER 2013 Leonardo Times

Current Affairs

STRETCHING THE A350

October 22, 2012, Toulouse

idier Evrard recently announced that Airbus has launched a detailed technical study into further stretching the A350. The current studies focus on how much additional engineering work would be needed for the aircraft’s structure and systems to allow the fuselage to be extended beyond that of the A350-1000, a stretched version of the baseline A350-900. Evrard points out that the landing gear for the A350-1000 is already different from the A350-900, and has an upward potential of multiple tons. The amount of engineering work needed to stretch the A350 would largely depend on the extent of the stretch and the kind of missions that the aircraft would have to fly. A stretched version that does not include significant upgrades is likely to lose range. (J.L.) Aviation News

FROM MILITARY TO CIVIL USE

October 23, 2013, Cordoba, Spain

irbus Military is working on a new civilian application for its C295 medium transport aircraft, having performed an initial test of its suitability as a fire-fighting platform. Airbus released an image of a C295 aircraft taking part in a recent water bombing trial, near Cordoba, Spain. The image shows the transport aircraft releasing water from a tank installed within its fuselage, as part of an assessment of the act’s effect on its aerodynamic performance and centre of gravity. According to Airbus Military, the flights went well, and further tests are planned in the near future to make a more detailed analysis of the C295 as a fire-fighter aircraft. Derived from the smaller CN235 and with a maximum payload capacity of around 9000kg, C295 has already been adapted for use as a maritime patrol and anti-surface/anti-submarine warfare aircraft. (J.L.) Airbus

NASA PLANS BIG LAUNCHER

October 21, 2013, Huntsville, Alabama

A319 CJ FITTED WITH SHARKLETS

October 23, 2013, Las Vegas

ASA is planning a new heavy payload launcher, called the Space Launch System (SLS). SLS will have a payload capability of 70 tons to LEO. Four RS-25 engines, the same engines also used on the core stage of the Space Shuttle, will power it. Like the Space Shuttle, the core stage of SLS will also run on a liquid hydrogen/liquid oxygen mixture. The 70-ton configuration will have a height of 98m, close to the height of Saturn V (111m), and approximately double the height of ESA’s Ariane 5. NASA is planning to conduct the first test flight in 2017. (B.R.)

irbus recently delivered the first A319 corporate jet equipped with sharklets to an undisclosed, private customer. The sharklet ACJ319 now matches the range of the 737-700-derived Boeing Business Jet, which has a range of 11,500km. All A320 family ACJs will be provisioned for sharklets, but not as a standard item. Corporate jet customers will need to order them from a list of optional equipment. Sharklets improve the fuel efficiency and the range of the aircraft. By obstructing high-pressure air under the wing from mixing with low-pressure air at the wingtip, the sharklet diminishes vortices that create drag. This effect makes the wing more aerodynamically efficient, allowing the aircraft to fly further with the same amount of fuel. (J.L.)

NASA

Flight Global

Leonardo Times DECEMBER 2013

Current Affairs

BOEING 787 STILL IN TROUBLE?

October 9, 2013, Tokyo

SPACEX FLIES UPGRADED FALCON 9

September 29, 2013, Vandenberg AFC, California

apan Airlines had to divert two Boeing 787 aircraft bound for Tokyo back to their departure airports on October 9 because of different technical issues encountered after takeoff. The first aircraft had to return to Moscow’s Domodedovo International airport when pilots discovered a failure in the aircraft’s electrical system after take-off. The failure affected power to the aircraft’s lavatories and galleys, says a JAL spokesman. The other jet returned to San Diego when an alert indicating failure in the right engine’s anti-ice system was activated. Both aircraft have since returned to service after undergoing the required maintenance work, according to JAL. However, both flights were severely delayed. In relation to the recent battery issues occurring in the 787, this is yet another negative connotation to the 787 program. (J.L.) Flight Global

PLANCK SATELLITE RETIRED

October 23, 2013, Space

paceX has completed its demonstration mission of its upgraded Falcon 9 launcher and launched four satellites into their targeted orbits. The upgrades include more powerful engines, a more robust support structure, a stronger heat shield to allow re-entry and ultimately landing of the rocket, and a new payload fairing. SpaceX managed several engine relights during flight, one of which was the retro propulsion restart on the first stage featuring supersonic retro propulsion. The first stage managed to re-enter successfully but did not manage to sufficiently control the roll motion, losing part of the stage in the water. SpaceX believes that the experience, together with their grasshopper tests allows them to fully recover their booster stages in the future. (B.R.) SpaceX

GOCE MISSION ENDS

October 21, 2013, Low Earth Orbit

SA’s Planck space telescope has completed its final burns to completely deplete its fuel tanks. The burn is one of the steps to leave the Plank in a permanently safe configuration. The Planck retired because its helium coolant supply has depleted. Planck has done a total of eight full sky surveys of the Cosmic Microwave Background from its earth-sun L2 orbit, five surveys using both its high frequency and low-frequency instruments, and subsequently three surveys using only its low-frequency instrument to refine the data. ESA launched Planck in May 2009 on an Ariane 5 launcher together with the Herschel space telescope, which retired in June 2013. (B.R.)

SA’s GOCE satellite has run out of fuel after mapping the gravity field of the Earth for over four years. Launched in March 2009, the GOCE mission was originally planned to last until April 2011, but unexpected low solar activity meant fuel was consumed slower than anticipated. At the time of writing, GOCE is planned to re-enter the atmosphere in early November. While most of GOCE will disintegrate in the atmosphere, some parts are expected to reach the Earth surface. ESA does not yet know exactly where these parts will come down, but the possible footprint is expected to become narrower as the time to re-entry decreases. (B.R.)

ESA

DECEMBER 2013 Leonardo Times

AUTOMATING WIRING FORMBOARD DESIGN Knowledge Based Engineering to support wiring harness manufacturing design at Fokker Elmo Increase in aircraft wiring complexity call for manufacturing design improvements to reduce cost and lead-time. To achieve such improvements, a joint research project was performed by the Flight Performance and Propulsion (FPP) group and Fokker Elmo BV, the second largest aircraft wiring harness manufacturer in the world. The project objective was to largely automate the creation of manufacturing drawings using Knowledge Based Engineering techniques. TEXT Tobie van den Berg, PhD candidate at Flight Performance and Propulsion

WIRING HARNESS DESIGN & MANUFACTURING Aircraft wiring harnesses are designed in a 3D digital environment such as CATIA. Figure 1 shows the digital wiring model for the Airbus A350. To efficiently manufacture wiring harnesses, flat tables are used as shown in Figure 2. A wiring harness is represented on these tables by means of 1:1 scale production drawings called formboards. PAST In the past, before the availability of 3D digital mock-ups, formboard drawings were created by manufacturing a prototype wiring harness in the 3D physical mock-up of the airplane. This prototype harness was then physically flattened (by force) on a table and a drawing of photo of the contours was made as a blueprint for series production. As the prototype could fit in the physical mock-up, harnesses built with these drawings would fit in the aircraft as well.

Leonardo Times DECEMBER 2013

PRESENT At date, preparing a wiring harness design for manufacturing is a repetitive, timeconsuming and mostly manual, experience-based process. This is mainly due to the fact that several manual quality checks and adjustments are required to ensure that the 2D drawing matches the 3D digital model such that the manufactured wiring harness (in a flat plane) can be installed in the (3D) airplane without causing damage or requiring excessive force from the installation operator. Creating a single drawing may take from a few hours up to several days. The formboard design process consists of the following steps: 1. Analysis. Check on quality and completeness of the 3D design definition. 2. Flattening. Transformation of the 3D model to a flat plane. 3. Fitting. Rearrangement of the flat model to fit the given dimensions of a table frame. 4. Dress-up. Addition of manufacturing instructions. Considering the time currently required to create a high quality formboard, the productivity of the formboard designers could be improved by eliminating manual, repetitive development steps through automation. Knowledge Based Engineering (KBE) is proposed as the design automation technology to increase the process productivity.

KNOWLEDGE BASED ENGINEERING Dr. ir. G. La Rocca (FPP chair, Faculty of Aerospace Engineering, TU Delft) defines KBE as: â&#x20AC;&#x153;a technology based on dedicated software tools called KBE systems that can capture and reuse product and process engineering knowledgeâ&#x20AC;? (La Rocca, 2011). A KBE system allows a user to develop expert systems with geometry handling and data processing capabilities. As such it can be described as the merger of Artificial Intelligence (AI) and Computer Aided Design (CAD) technologies. The KBE system used at FPP is GDL by Genworks. BUILDING BLOCKS KBE applications can be constructed using flexible parametric building blocks called FLIGHT MAGAZINE

ENGINEERING PRODUCTIVITY An increase in productivity is required for the European aviation industry to remain competitive in a world with more competition, shorter development timescales, products that are more complex and decreasing numbers of technically skilled personnel. The development of aircraft electrical wiring harnesses at Fokker Elmo could benefit from an increase in productivity.

Figure 1. Wiring in the Airbus A350 digital mock-up.

FOKKER ELMO B.V.

3D design

3. Design analysis

CAD exchange 2.

Figure 2. Manufacturing a wiring harness on a formboard at Fokker Elmo

High Level Primitives (HLP). As opposed to (low-level) CAD primitives such as points, lines and solids, a HLP is a functional element or parametric building block, incorporating and reusing relevant knowledge. HLPs have been defined and implemented for the main wiring harness components. Although the wiring harness is a single product, it needs to be represented in both the 3D design definition and the 2D production state. To allow this, wiring harness HLPs are defined featuring geometry attributes corresponding to multiple geometric states.

DEVELOPMENT The research was performed by working for few days a week at Fokker Elmo and with support from the FPP spin-off company KE-works, which specializes in developing KBE applications. Expert knowledge on wiring harnesses and the formboard design process was provided by a team or â&#x20AC;&#x2DC;Task Forceâ&#x20AC;&#x2122; consisting of senior Fokker Elmo engineers from the design engineering and manufacturing engineering departments. Development of the KBE solutions was done by iteratively identifying key process steps and requirements, acquiring, formalizing, implementing (in a KBE application) and verifying knowledge in collaboration with the Task Force members. This resulted in three KBE applications: a CAD import application to reparameterize CATIA generated STEP files (step 1 in Figure 3), an application for analysis and flattening and an application for fitting, dress-up and export of a drawing. ANALYSIS & FLATTENING The capabilities of current analysis and flattening tools are limited, requiring time-consuming, repetitive manual work. The automatic flattening provided by the CAD system electrical workbench is unreliable and requires additional checks and adjustments. Procedures have been developed and implemented in a KBE application to automatically evaluate the 3D

Flattening

Fitting

Dress-up

Production

Figure 3. A wiring harness going through the steps of the KBE supported formboard design workflow

wiring harness state for potential flexibility violations with respect to the 2D manufacturing state (step 2 in Figure 3). Flexibility evaluations are performed by means of experiment-based rules, validated by years of industrial practice at Fokker Elmo. A new method for wiring harness flattening was devised that aligns the 2D geometry states of the wiring harness HLPs with respect to each other. This returns 2D models with deformations within allowed limits and the minimum amount of bundle twisting (step 3 in Figure 3).

FITTING & DRESS-UP A flattened wiring harness model is currently adjusted manually to make it fit within a standard formboard frame size. In the KBE implementation this translates to a search problem with multiple quality and manufacturing efficiency objectives such as minimize frame size, eliminate crossings and optimize for manufacturing ergonomics. To ensure that the fitted wiring harness state can be deformed to the 3D installation state, the flattened model is discretized into bendable sections for which bending limits are established. Both manual fitting by an engineer and automatic fitting using search methods are constrained by these limits, eliminating the need for time-consuming checks and adjustments. From experimentations with different automatic fitting approaches, the so-called alignment method, based on manual fitting heuristics, is selected and implemented. This method attempts to align branches of bundles with respect to each other according to a limited set of bending and flipping strategies (step 4 in Figure 3). A formboard frame is automatically selected, the layout is adjusted with respect to manufacturing ergonomics and production instructions are added (step 5 in Figure 3). Finally, the resulting drawing can be exported to a 1:1 scale PDF file. THE POTENTIAL OF APPLYING KBE The developed KBE applications were

tested using twenty-five 3D digital wiring harness models from a current commercial aircraft program at Fokker Elmo. Formboard design experts approved the quality of the output formboard drawings. The time spent on formboard design tasks was demonstrated to reduce from values in the order of hours to minutes. A conservative calculation indicates that in practice a five-fold productivity increase can be obtained. The developed formboard KBE suite offers functionalities that are not present in conventional CAD systems. The applications can considerably reduce the amount of repetitive work, while ensuring compliance to physical constraints and manufacturing guidelines.

FURTHER WORK There are many opportunities to improve and extend the developed KBE applications. Some of the topics that are of interest are different optimization techniques for fitting, flattening so-called closed-loop wiring harnesses, change identification and generating semi-3D formboard tooling (e.g. with 3D-printed moulds). Work has already started on some of these topics by students doing their Master thesis work. ACKNOWLEDGEMENTS This research was made possible by the expertise of and close cooperation with Fokker Elmo BV and support from KEworks. References 1. G. La Rocca, Knowledge Based Engineering to support aircraft design and optimization, PhD thesis, TU Delft, 2011 2. T. van den Berg, Harnessing the potential of Knowledge Based Engineering in manufacturing design, PhD thesis, TU Delft, 2013, to be published

DECEMBER 2013 Leonardo Times

AUDI: THE COST OF ENLIGHTENMENT On the cost and performance of CFRP in the passenger car industry

Being one of the premium German car brands, Audi has a long-standing “Leichtbau” tradition. Living up to the company motto “Vorsprung durch Technik”, Audi is currently working on implementing CFRP in cars such as the S7, A8 and R8. In a combined internship and thesis project in Neckarsulm, Germany, I assessed the performance and cost of Automated Fiber Placed composites, a new technology, opening up possibilities for cost effective manufacturing of highly efficient structures. TEXT Mark Booij, MSc Student Aerospace Structures and Computational Mechanics

he average weight of passenger car vehicles has increased over the last decades as a result of improving passenger comfort levels and the rise of ever-strict crash safety regulations. Rising fuel prices, environmental awareness and governmental regulations on the other hand require a decrease in the structural weight of a car, instead of an increase. One way to reduce the vehicle weight without sacrificing safety or comfort is the use of lightweight materials. Hence, the interest in Carbon Fiber Reinforced Composites (CFRP) technology was borne. The current use of structural composites in the automotive sector is confined to ultrahigh performance, small series supercars such as the Ferrari F430 Scuderia, Lexus LFA and Lamborghini Murcielago where cost is not an issue. The Lexus LFA for instance has been designed with a carbon fiber cabin that weighs 100 kg less than a comparable aluminum one whilst retaining the same rigidity (Reinforced Plastics, 2010). In a way, this sector can be compared to the space industry, where a one

Leonardo Times DECEMBER 2013

kg weight saving can lead to a €7,50015,000 fuel cost reduction depending on the mission. For the passenger aircraft industry, this number lies somewhere between 800-1,200€/kg. Passenger cars are more sensitive to the manufacturing costs with a 7.5€ /kg weight to cost ratio. Profit margins are generally small and a difference in cost of a few cents per part can make or break a design. This means, that if CFRP is to be implemented successfully on a large scale in passenger cars, it must not only be lighter, it must also be cost competitive with traditional metal designs. CURRENT SITUATION The most common example of the use of structural composites in passenger car vehicles today is the all-electric BMW i3. Other cars, such as the current Audi R8 and BMW M3, employ carbon accessories such as roofs or spoilers, but the primary reason for these CFRP components is the cosmetic appearance and not the weight. The majority of supercars today are manufactured using epoxy prepreg hand lay-up

and autoclave curing. Originating from the field of Aerospace engineering, this is a low volume, expensive production process which yields excellent strength and stiffness characteristics. More cost sensitive cars such as the i3 are manufactured using Resin Transfer Moulding (RTM) where dry fabrics are preformed and afterwards impregnated with resin under high pressure using a two-sided mould. This semi- to fully automated process is used for medium volume series. Current problem areas are speed, material scrap, performance consistency and formability. In essence, the automotive industry uses aerospace technology, leader in the field of lightweight construction and the use of CFRPs, and strives to apply this in a costeffective manner. It can be said that lightweight car construction is all about bringing aerospace technology down to earth by making it more cost-effective. AUTOMATED FIBER PLACEMENT PROCESS The need for automation, low scrap rates and affordable prices led to the develop-

ment of the AFP process, currently used to manufacture large sections of the Boeing 787 Dreamliner as well as the Airbus A350 XWB. The AFP process (Figure 1) builds up a laminate by placing bands of multiple narrow tows, which are compacted on the substrate whilst controlling fiber directionality and steering. This means that the conventional approach of building up a laminate, by stacking prefabricated angled plies by hand can be replaced by a fully automated process. Being able to cut and restart each of these tows, the process allows for a high degree of control, precision, and minimum material waste. The individual pay-out of the small tows enables in-plane steering of the fibers leading to curved fiber paths. The amount of in-plane fiber steering that is allowable is limited by the material and processing conditions as excessive curvature leads to manufacturing defects such as waviness, tow buckling and deviation of tow-paths. The majority of advanced composite structures that are manufactured today are built using thermoset epoxy prepreg tows. Both industry and scientists are currently working hard to make the AFP process suitable for processing dry fiber and thermoplastic material as well. The main reason for this is the potential to use cheaper materials and reduce cycle times and investment costs. Thermoplastic binder material inside dry fiber tows is activated by the application of heat just prior to the placement to provide tack, making it possible to build up a preform for the RTM process using AFP. The use of AFP in combination with RTM processing has the potential to reduce process cycle times to minutes rather than hours when compared to autoclave curing. This has brought Dry Fiber Placement (DFP) to the attention of the automotive sector.

J.M.J.F. VAN CAMPEN

CORIOLIS COMPOSITES

AUDI AG GERMANY

Figure 1. Automated fibre placement machine

Figure 2. Fibre paths for a curved panel with a hole loaded in compression and shear (van Campen, 2011)

OPTIMISATION The in-plane steering capabilities of AFP make it possible to vary the lay-up or stacking sequence over the planar direction of the composite component. This results in a non-uniform stiffness distribution, hence the name variable stiffness (VS) or steered fiber composites. This allows the designer to utilize the anisotropic nature of the composite material to its full potential by tailoring the stacking sequence to the internal loading state at each point in the laminate. Research at the AS&CM group has shown that fiber steering can be applied successfully to improve the stiffness, buckling and fundamental eigen frequency of composite structures. Figure 2 provides an example of the use of fiber steering on a curved panel with a hole loaded in compression and shear, in order to improve the buckling characteristics by moving the load away from the unsupported hole region of the panel to the supported edges. Fiber steering can thus be used as a means to design more efficient structures that make for lighter cars. THESIS PROJECT Audi, my supervisor dr. Christos Kassapoglou and me together formulated a project to investigate the potential of automated steered fiber placement. Due to the confidential nature of the project only a rough outline is given here. The first goal of the project was to find the maximum potential of steered fiber composite structure by means of mechanical testing. For the optimization, various software packages such as MATLAB and MSC Nastran were used in combination with user-defined codes and routines. Manufacturing took place in France and Germany, whilst the mechanical testing was conducted in the DASML lab at the Aerospace faculty.

The second part of the project focused on generating insight in the cost of manufacturing of straight- and steered fiber reinforced structures for the dry-, thermoplastic- and thermoset fiber placement processes by performing a manufacturing cost analysis in order to see if the improved performance is worth the cost. This information, together with the data on achievable performance gains, was used to evaluate the feasibility of steered fiber placement being applied on the next generation of Audi cars. EVALUATION AND OUTLOOK Finishing up my thesis, I can look back at a challenging but very worthwhile period in my life. Working at one of the largest car manufacturing companies in Germany on a hands-on project and being able to manufacture and test my own designs has been a great experience. In retrospect, the practical experience I gained from joining the Formula Student team Delft in 2010 and 2011 has been very valuable and is highly recommended for people looking for a job or internship position in the German automotive sector. The next two decades will tell if and when the automotive sector will shift to composites as a means of â&#x20AC;&#x153;enlighteningâ&#x20AC;? the car. If so, the AFP process is likely to play a vital role.

References [1] Car makers look closer at carbon fibre, http://www.reinforcedplastics. com, Reinforced Plastics, 2010. [2] J.M.J.F. van Campen. Optimum lay-up design of variable stiffness composite structures. PhD thesis, Delft University of Technology, 2011.

DECEMBER 2013 Leonardo Times

HYPERSONIC RE-ENTRY TECHNOLOGY Insights into new advances in re-entry vehicles and materials We are already used to a widespread commercial utilization of spaceflight, particularly with satellites for communication, earth observation, navigation, weather forecast and many other applications. Launching satellites is a rather costly affair, particularly because twenty minutes after lift-off the greater part of the expensive part of the launcher is transferred into scrap on the bottom of the ocean. TEXT K.J. Sudmeijer

t stands for a reason that early stage of development of spaceflight focuses on reducing the high launch costs of satellites and spacecrafts. Reuse of the launcher was identified as the most promising way to obtain a really drastic reduction in launch costs but this appeared to be an enormous technological challenge, particularly the atmospheric re-entry at hypersonic speed. A major and impressive step forward was the design and development of the Space Shuttle that also became fully operational during more than thirty years. NASA aimed at a spectacular reduction in launch costs by launching each shuttle every fourteen days. It caused a lot of concern in Europe where we just started the operational phase of the Ariane launcher. Unfortunately, for NASA the technically successful Space Shuttle appeared to be an economical failure and this was mainly caused by the extremely high maintenance and refurbishment costs. Figure 1 shows the damage of the thermal protection tiles that occurred af-

Leonardo Times DECEMBER 2013

ter every flight. Repair was difficult and time consuming because the tiles were bonded to a layer of felt underneath and could not be easily removed. Rather than launching every two weeks each shuttle was launched every ten months and sometimes even more. It became clear that the vulnerable thermal protection tiles should be protected by a robust but low mass containment and should also be easily removable. Research was done in the US, Germany and the Netherlands to develop better tiles based on the application of metallic heat resisting materials that develop a protective self-healing oxide scale against hot oxygen. An example of such a design is shown in Figure 2. HYPERSONIC FLOW A re-entry vehicle has to pass several different flow regimes: free molecular flow, transitional flow and continuum flow. In the continuum flow we have hypersonic,

transonic and subsonic flow. The highest heat and mechanical loads for a Reusable Launch Vehicle (RLV) occurs in the hypersonic regime, usually a Mach number greater than 6. In the hypersonic regime, there is a very strong bow shock with a discontinuous jump in pressure, density and temperature. Behind the bow shock the temperature is raised to about 10,000K, bi-atomic gasses like oxygen and nitrogen rapidly dissociate and the temperature decreases to about 6,000K. The dissociated gasses may chemically react with other atmospheric components and as a result, the chemical composition along a streamline is not constant. Also, the chemical reaction and the diffusion rate are important parameters that are a function of temperature and density. All these effects shall be included in a hypersonic computer code and as a result these codes become much more complicated than the subsonic and supersonic codes. The verification of the hypersonic codes is another problem. Duplication of a hy-

NASA

Figure 1. Damage of the thermal protection tiles found after re-entry

Figure 2. Removable thermal protection tile, designed by NASA Langley.

Figures 3L and 3R. Conceptual design of the experimental re-entry vehicles Hyperion-1 (left) and Hyperion-2 (right)

personic flow in a ground-based facility is presently not possible. The available wind tunnels can reproduce some parameters but not all of them at the same time. So, we have to work with a number of test facilities that can each reproduce some aspects of hypersonic flow and try to synthesize all the results. It stands for reason that there is a high demand for flight tests because it assures a real hypersonic environment. However, flight tests are expensive and the associated hypersonic database is limited. In addition to this it is not possible to correct for scale difference of the test model by similarity parameters like the dimensionless Reynolds and Mach numbers because the additional hypersonic similarity parameters are not dimensionless. Hypersonic boundary layer theory and particular transition phenomena are poorly understood and so hypersonic flight tests are needed to support ground based facilities and validate the hypersonic computer codes. Already in the early nineties, the first studies were done at the Aerospace faculty and a conceptual design was made of a small experimental re-entry vehicle that could be used for aerodynamic research (see Figure 3 left). Such a vehicle was actually developed by ESA (IXV depicted in Figure 4). IXV is expected to be launched by the new VEGA launcher at the end of

this year. Hyperion-1 and IXV have both have a rather large blunted nose in order to reduce the stagnation point heat flux and keep the nose temperature down to acceptable values. The stagnation point heat flux is inversely proportional to the square root of the nose radius and as a result of which, the IXV has got a large nose radius, a relatively high drag, and a low L/D. The maneuverability and the experimental utility of the vehicle could be increased considerably if we reduce the nose radius to 2.5cm. There are no materials available that can withstand the extremely high temperature and as a consequence of this, active cooling is required. Such a design is depicted in Figure 3 right. Recent studies at the Aerospace faculty demonstrated that new experiments are possible that cannot be done with blunt nosed vehicles like Hyperion-1. An example of this is the capability of Hyperion-2 to fly controlled suborbital flights with a constant Mach number during about thirty seconds with a large variation of Reynolds number [4]. That allows for transition measurements at a fixed Mach number that is possible with blunt lifting bodies like Hyperion-1 and IXV. Next step in our research will be to add wings with sharp leading edges in the Hyperion-2 design with the aim to in-

crease the L/D ratio even further. Such a re-entry vehicle will be able to fly longer at high altitudes and enter the denser atmosphere at lower altitudes at a lower speed to reduce heat fluxes. This is a completely new re-entry strategy. The atmospheric part of the re-entry will last much longer (one and a half to two hours) rather than twenty to thirty minutes as is presently normal for winged re-entry vehicles. Other interesting features are the low angel of attack (Îą < ten degrees) rather than thirty to forty degrees as was usual for the Space Shuttle as well as Îą-control instead of bank angle control. The accelerations during a high L/D re-entry are low and so the return flight back to earth is quite comfortable. The specific properties of this new re-entry strategy must be investigated by simulations and optimization of the re-entry trajectories to find the advantages and disadvantages of such high L/D designs. THE EXPERT RE-ENTRY VEHICLE In 1989, the Faculty of Aerospace Engineering started a daring project that aimed to design, development and flight of a small and low cost re-entry vehicle that would be launched from a submarine with the Russian Volna rocket. The re-entry module had a full metallic thermal protection system with active cooling of the nose by nucleate boiling and enDECEMBER 2013 Leonardo Times

ESA

Figures 4L & 4R. ESA’s experimental re-entry vehicle IXV

Figure 5. The Delft Aerodynamic R-entry Test bed, DART

hanced radiation cooling of the flare. The shape of the vehicle depicted in Figure 5, was a blunted bi-cone obtained after a numerical optimization process taking into account all relevant constraints and requirements. Within two years after the inception of the project, ESA took over the project and started a much bigger project under the name EXPERT with important European space industries like Alenia (main contractor), Astrium, Dutch Space and institutes like DLR, ONERA and IRT. The new re-entry vehicle became bigger (450kg) and longer (1.5m) and much more expensive (40 million Euro). The outer skin is made of a Nickel based alloy (PM1000), an Oxide Dispersion Strengthened material produced by powder metallurgy, except for the nose cap and dummy flaps that are made of a ceramic composite (C-SiC) consisting of carbon fibers with a matrix of silicon carbide. The metallic skin is pre-oxidized during one hour at 1100ºC in laboratory air that naturally develops a 5μm thick self-healing chromium oxide scale. An exploded view of EXPERT is depicted in Figure 6, showing the hot Thermal Protection System (left), the internal cold structure (right), and the interface structure with the Russian Volna launcher. Dutch Space builds the metallic outer skin in The Netherlands and they were also re-

Leonardo Times DECEMBER 2013

Figure 6. Exploded view of the EXPERT re-entry vehicle. Left the Thermal Protection System TPS

sponsible for the thermal protection system. The complete TPS including internal insulation is shown in Figure 7 as integrated in the Dutch Space facility in Leiden. The EXPERT re-entry vehicle is now fully integrated in the Alenia facilities in Turin, Italy and waiting for launch. HEAT RESISTING MATERIALS The main obstacle in the development of reusable re-entry vehicles is the availability of heat resisting materials. The environment during re-entry is very harsh and so are the material requirements: high yield and rupture strength, good ductility over the whole temperature range, resistant to hot oxygen particularly to atomic oxygen, self healing oxide scale with high emissivity and low catalicity to reduce recombination of atomic gasses at the outer wall of the re-entry vehicle. These requirements are is particularly difficult to meet if we want to apply sharp noses and leading edges in order to obtain a high L/D ratio. A material that meets all these requirements is “unobtainium” but this wonderful material has not yet been found or developed. As a consequence, we have to work with the available heat resisting materials and apply active cooling in the sharp noses and leading edges. Only a limited number of heat resistant materials are presently available for temperatures over 1,000ºC. Ceramic composites can withstand the highest tem-

peratures; Carbon-carbon (C-C) materials consisting of carbon fibers in a matrix of graphite can be used to nearly 1,800 ºC. Such C-C composites are applied in the nose and wing leading edges of the Space Shuttle. It stands for reason that carbon cannot be exposed to hot oxygen and thus a protective coating is required. C-C components that are exposed to the extremely hot hypersonic boundary layer shall be treated very carefully because the slightest damage of the coating may cause serious damage during re-entry. That is why much work has been done to develop self-healing coatings that can automatically repair damage. The results of this work that was also done in our faculty had only limited success. Small crack in the coating were actually closed but larger cracks and scratched could not automatically be repaired. These coatings must be carefully inspected after every flight and every crack that is found must be repaired. Such properties cause high maintenance and refurbishment costs that are not desirable for application in reusable launchers. Other ceramic composites like C-SiC that can be used up to 1,400ºC also need self-healing coatings and suffer from the same disadvantage. There are a few metallic materials that may be useful, particularly two ODS materials (PM1000 and PM200) where strength and stiffness at temperatures up to 1200 ºC are improved by dispersion strengthening. PM1000 is a Nickel based material

that naturally develops a chromium oxide scale at elevated temperatures and PM2000 is an iron based alloy that develops an aluminum oxide scale. Both materials appeared to have a stable and self healing oxide scale when tested at temperatures up to 1250 ยบC in laboratory air. These materials where also tested in the plasmatron (Figure 8) of the Von Karman Institute in Brussels, Belgium where in the hot plasma flow nearly all the oxygen is dissociated. Several heat resisting alloys were tested in the Plasmatron, among them also PM1000 and PM2000. For PM1000 the results were disappointing as can be seen in Figure 9. The left picture shows the surface of the chromia scale after the pre-oxidation and before the exposure to the hot plasma. The right picture shows the results after 15 minutes exposure to the plasma flow at a temperature of 1300 ยบC. The chromia scale is completely restructured and even partly destroyed by reactive evaporation. Large conglomerations of Nickel oxide were observed and it became clear that

the protective function of the oxide scale was strongly reduced. PM1000 is not a good material for the outer skin of a reusable launcher; a single use is the only option. The alumina scale of PM2000 on the other hand appeared to be very successful in the Plasmatron tests. Even after exposures of 30 minutes no degradation of the oxide scale was found and also the self healing property of the oxide scale with respect to scratches was outstanding. All scratches applied to the pre-oxidized test samples were closed by oxidation during the Plasmatron test and hardly visible anymore. So a self healing alumina scale is the preferred coating for the outer skin of a reusable re-entry vehicle. A remaining problem is the rather low emissivity and high catalicity of the alumina scale. A useful alternative may be the application of a new brand of ceramic materials: the MAX phases that are made up of three elements in the general form:

M n+1 AXn

n=1,2 or 2

where M is an early transition metal, A is

a group A element and X is carbon or nitrogen in the periodic table of elements (see Figure 10). There are three groups of MAX phases with n=1,2,3 respectively indicated by 211, 312 and 413. Particularly interesting are Ti 2 AlC and Ti3AlC2 because they naturally develop a protecting alumina scale at elevated temperatures. These materials can be used at high temperatures (up to 1,200ยบC), not brittle and can easily be machined. They posses a relatively high conductivity both for heat and electricity quite similar to metals. However, the MAX phases are much stronger in compression than in tension and that is a serious constraint for structural applications of these materials but when used in the extremely hot nose of re-entry vehicles the occurring stress will mainly consist of compression if well designed. Nevertheless, useful work has been done to improve the mechanical properties of a MAX phase by a ZrC particle reinforcement of Ti3AlC2 [9]. There are two interesting MAX phases that develop an alumina scale at elevated

Figure 7. The thermal Protection system of EXPERT, integrated in the Dutch Space facilities in Leiden

Figure 8. The Plasmatron facility of the Von Karman Institute in Brussels

Figures 9A & 9B. Microphotographs of the Nickel based ODS material PM1000. Up (9A) the surface after pre-oxidation at 1150 deg. Celsius during one hour. Down (9B) after 15 minutes exposure at 1100 deg. Celsius in the Plasmatron

DECEMBER 2013 Leonardo Times

Figure 10. Periodic table of elements with the three groups of elements that constitute the MAX phase materials, ref[8].

Figure 11. Summary of presently known MAX phase materials [8].

Figure 12L & 12R. Microphotograph of Maxthal 211. Left a fractograph showing the alumina scale after 48 hours of pre-oxidation at 1200ºC in laboratory air and right a micrograph showing the characteristic kink bands of this material.

temperatures: Ti 2 AlC and Ti3AlC2 . But the oxide scale does not only contain the stable Al2 O3 but also the unstable TiO 2 (Rutile). It has been observed by Song et al [11] that during the oxidation process at 1100 ºC in laboratory air a porous layer was formed in the oxide scale with an outer layer of TiO 2 . In our Plasmatron tests with PM2000, we found small rutile crystals on the surface of the samples that were not stable and did fall apart after an exposure time of 15 minutes. Thus, we preferred the 211 phase Ti 2 AlC because of the lower Ti content rather than the 312 phase Ti3AlC2 . A good quality of Ti 2 AlC material is produced by the Swedish company Kanthal under the name Maxthal 211. A small amount of Maxthal 211 was made available by Kanthal for the first investigation of the oxide scale. Some results are shown in Figure 12, left the alumina scale with a columnar structure and a constant thickness of 3 micron and right the characteristic kinkbands of the MAX phases. Even though the material seems promising, it is necessary to test Maxthal 211 in a plasma wind tunnel in a chemically reactive environment with hot atomic oxygen. A proposal for such tests has already been presented to ESA.

Leonardo Times DECEMBER 2013

References [1] E.mooij, A.G.M.Maree, K.J.Sudmeijer,Aerodynamic controllability of a selected reentry test vehicle. IAF, 1995. [2] E.mooij, F.G.J.Kremer, K.J.Sudmeijer, Conceptual design of a small re-entry test vehicle. AIAA, 1989. [3] E.mooij, F.G.J.Kremer, K.J.Sudmeijer, Aerodynamic design of a low-cost re-entry test vehicle using a Taguchi approach. AIAA, 1999 [4] M.Dijkstra, Trajectory optimization of Hyperion-2 for the study of hypersonic aerothermodynamic phenomena, Final Thesis 2013. [5] R.Monti, D.M.Paterna, A low risk reentry: looking backward to step forward, Aerosp. Science and techn. 2006. [6] k.j. Sudmeijer, J. Buursink, C. Lopes, Enhanced Radiation Cooling for Metallic TPS, 4th European Workshop on Thermal Protection Systems for Space Vehicles, Palermo 2002. [7] J.Buursink, K.J. Sudmeijer, “Experimental studies of an Enhanced Radiation Cooling System”, AIAA 2004[8] M.W. Barsoumi, T. El Raghy, The MAX phases: Unique New Carbide and Nitride Materials, American Scientist, Volume 89. [9] G.M.Song, W.G.Sloof, S.B.Li, S.Van der Zwaag. Fabrication and mechanical properties of electroconductive high temperature ZrC particle-reinforced composites. Journal of computational and theoretical nanoscience, vol5, 2008 [10] G.M.Song, Y.T.Pei, W.G.Sloof, S.B.Li, J.Th.M.De Hosson, S.Van der Zwaag. Oxidation induced crack healing in composites. Scripta Materialia, 2008 [11] G.M.Song, Y.T.Pei, W.G.Sloof, S.B.Li, J.Th.M.De Hosson, S.Van der Zwaag. Early stages of oxidation of ceramics, Materials, Chemistry and Physics, 2008

Duurzaam transformeren

Beeld: OPL Architecten

...brengt idee禱n tot leven

B議dragen aan een optimaal duurzame en comfortabele leef- en werkomgeving is de kern van onze missie. Dat doen we door de ontwikkeling en duurzame transformatie van innovatieve en energiezuinige gebouwconcepten zoals b議 De Daalse Kwint in Utrecht. Deerns is het grootste onafhankel議ke adviesbureau op het gebied van installatietechniek in Nederland. Met projecten over de hele wereld en zestien vestigingen in Europa, Dubai en de Verenigde Staten is Deerns bovendien een toonaangevend internationaal bureau. www.deerns.nl

PRANDTL’S BEST WING SYSTEM

NICK KALOTERAKIS

LVD

Minimizing induced drag

Innovation in the field of Aerospace Engineering is driven by the need for more sustainable aircraft with lower emissions, lower operating costs and lower noise pollution: ‘sustainable growth’. These goals for the future have never been more relevant than now with the weak economy, global warming and the ever-growing need for air travel. That is why engineers are beginning to look for unconventional solutions for the future of aviation. TEXT Tom Pruijsers, BSc student Aerospace Engineering, member of the Aviation Department

SUSTAINABLE GROWTH There are multiple fields in Aerospace Engineering where there is room for innovation to attain sustainable growth. The most prominent fields are propulsion and material technology, but also innovation in air traffic management, accident survivabilty, passenger comfort and many others play a role. A more drastic way to achieve sustainable growth would be to look at completely new aircraft configurations. A lot of research is already being done on several new concepts, the possibly most well known is the blended wing body. There are, however, many more innovative concepts under development, one of the most interesting being the Prandtl plane. REDUCING DRAG Reducing the drag on aircraft is one of the most important ways to create more fuel efficient and therefore more economically competitive aircraft. A drag reduction of just one percent can save 400,000 litres of fuel and 5000 kg of emissions per year (W. Schneider, 2000). The two most important types of drag for aircraft are parasitic drag and induced drag. Parasitic drag is created by air hitting the front of an aircraft. Induced drag is created when a wing pro-

Leonardo Times DECEMBER 2013

duces lift and the high-pressure air from beneath the wing and low-pressure air from the top of the meet, generating a vortex at the wing tip. This effect depends mostly on the shape of the wing and the lift coefficient. Currently on many aircraft, winglets are used to reduce the effect of wing tip vortices. The Prandtl plane takes the concept of these winglets to a whole new level in an attempt to eliminate the wing tip vortices. THE CONCEPT The key attributes of the Prandtl plane are its wings, which form a closed box-wing system. The two wings are connected to each other with long winglets and are attached to the fuselage at the front and at the tail of the aircraft. This configuration is named after the German scientist Ludwig Prandtl whose research in the early 20th century formed the basis for (in)compressible aerodynamics. In 1924, Prandtl published a paper in which he described that the box-wing configuration could reach much lower values for induced drag than equivalent monoplanes (Figure 2). Additionally, an optimum equivalent triplane will have a lower induced drag than the biplane version. This effect holds when the number of wings is increased towards

infinity. Prandtl called this the ‘best wing system’ (L. Prandtl, 1924). However, when the number of wings is increased the design becomes increasingly more impractical due to problems with the manufacturing and parasitic drag. Therefore current research only focuses on biplane configurations. To obtain this minimimum induced drag several conditions must be satisfied. The lift distribution and the total lift must be equal on both wings and the vertical wings should have a butterfly shaped lift distribution. The efficiency can be further improved by decreasing the vertical distance between the wings and increasing the wingspan (L. Prandtl, 1924). Researchers from multiple universities in Italy have done extensive research on Prandtl planes in the early 2000’s. Their research led to several results. For example, to satisfy the aforementioned condition of equal lift on both wings the high rear wing should be connected to the top of the vertical tail. Another conclusion was that the reduction of induced drag still occurs with highlift devices extended, as long as they are extended equally on both wings. Most importantly the researchers concluded that that the Prandtl plane configuration

could reduce the amount of induced drag up to thirty per cent with respect to an optimum monoplane, which is quite significant (A. Frediani, 2005). Currently, TU Delft is also doing research on the Prandtl plane. The design also has several other advantages besides the reduction in drag. It provides much more room for high-lift devices, its box-shaped wings provide high strength against torsion and high stability of flight. But there are also some disadvantages that come with this design, most importantly the problems with storing the landing gear and fuel and a complicated pitch control system (A. Frediani, 2005). APPLICATIONS The Prandtl plane is a versatile aircraft concept and can be adapted for various aircraft designs. The design is well suited to be used for small sporting aircraft as they fly at lower airspeeds where the effect of induced drag is much more important than at high airspeeds. The extra parasitic drag this concept experiences from its larger frontal area due to its biplane configuration also has a smaller impact at lower airspeeds. The AOK Spacejet, brainchild of the French aircraft designer Remi Cuvelier, is a great example. Its maiden flight is scheduled later this year. A mockup was presented during the Paris airshow 2013 and it can be seen in Figure 1. Another example of a single-seater Prandtl plane is the Finnish FlyNano Nano. It has succesfully completed its first flight in 2012, but is not yet in production. Even though well suited for smaller, slower aircraft the Prandtl plane can just as well be used for large aircraft. In fact, the Prandtl plane has the potential to easily outclass the Airbus A380 in terms of capacity. This is significant as current generation aircraft are limited in dimension to a 80x80 m square surface area to be com-

PUBLIC DOMAIN

PATRICK PERRIER

Figure 1. A mockup of the AOK_Spacejet as on display at the Paris Airshow 2013.

Figure 2. Ludwig Prandtl with his fluid test channel.

patible with current airports. For that reason, current aircaft cannot be bigger than the A380 (A. Frediani, 2005). The Prandtl plane has the possibility to increase the width of its fuselage where the A380 has not, for the biplane configuration allows for shorter individual wings. Because of this quality the Prandtl plane is also very suitable to be adapted to a cargo aircraft. It can be designed as a wide-body aircraft that is close to the ground such that it provides lots of room for cargo and is easily loaded. Probably the most effective design would be a combined passenger/ cargo aircraft. OTHER CLOSED WING CONCEPTS The box-wing is not the only shape of a closed wing system that has been explored; there have been several different types that have been suggested throughout the history of aviation. The earliest example would be the Blériot 3 built by French aircraft builders Louis Blériot and Gabriel Voisin in 1906. It consisted of two elliptical wings, one in the front and one in the back. Unfortunately, the aircraft was never able to succesfully lift off. Famous aircraft designer Ernst Heinkel and the French company SNECMA both researched the coleopter design, which can only be described as a fuselage built straight through a ducted fan. It has the capability to lift off vertically and then fly horizontally using the duct as a circle-shaped wing. However, after SNECMA tested the design it proved to be too unstable and dangerous to fly so the development was halted. Lockheed also worked on an aircraft with a circular wing called the ‘Lockheed Ringwing’. The wing of this aircraft forms a swept back ring around the aircraft. The wing is connected to the fuselage at the bottom, and to a taller than normal, forward swept vertical tail at the top. The design, however, proved to be quite impractical and research was discontinued. A recently patented new type of winglet called the

spiroid also aims to reduce the amount of induced drag by forming a closed loop winglet at the wingtip. It is currently being tested by the company Aviation Partners, based in Seattle. ENGINEERING THE FUTURE The Prandtl plane is a concepts that will change the future of aircraft design. But it is far from being the only one. Even though designs as the Prandtl plane and the blended wing body are still far from being realised as passenger aircraft, it is good to learn that innovation in the aerospace world is still thriving. CONTACT LVD-VSV@student.tudelft.nl References [1] W. W. Schneider “The importance of Aerodynamics in the development of commercially successful transport aircraft”, Aerodynamic Drag Reduction Technology. Proceeding of CEAS/ DRAGNET European Drag Reduction Conference, 19-21 June, 2000,pp 9-16, Potsdam, Germany. [2] L. Prandtl, “Induced drag of multiplanes” NACA TN 182, 1924. [3] A. Frediani, lecture series: “Innovative Configurations and Advanced Concepts for Future Civil Transport Aircraft”, June 06-10, 2005, Pisa University, Italy.

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.

DECEMBER 2013 Leonardo Times

TU STUDENTS SWEEP UAV DESIGN COMPETITION

To design a high-altitude long-endurance UAV to fly a twenty-hour reconnaissance mission at an altitude of 80,000ft, was the assignment for this yearâ&#x20AC;&#x2122;s undergraduate design competition. The competition was organized by the American Institute of Aeronautics and Astronautics (AIAA). Three students from Delft demonstrated superior design skills, winning the first, second, and third prizes. TEXT Raphael Klein, Steve Brust, Malcolm Brown and Dr. ir. Roelof Vos (FPP)

very year the American Institute of Aeronautics and Astronautics (AIAA) organizes an airplane design competition aimed towards undergraduate students from all over the world. All participants are asked to propose an airplane design in response to a given design specification. This yearâ&#x20AC;&#x2122;s specification asked individuals to develop an extremely flexible lightweight aircraft to carry out twentyhour reconnaissance missions at an altitude of 80,000ft. Additional requirements included a payload weight of 400lb, a maximum take-off weight below 7500lb, a landing distance below 3600ft, and a wing span of no more than 300ft. Furthermore, the airplane structure had to be sized for the gust spectra of MIL-F-8785B and the steady maneuver loads defined in FAR 25.331, 25.349, and 25.351. As a final requirement, the airplane had to be transportable within a standard shipping container. Three third-year students (Raphael Klein, Malcolm Brown and Steve Brust) took up this challenge and started in the fall

Leonardo Times DECEMBER 2013

of 2012 on their individual designs. All designs turned out very differently, but each of them ranked in the top three. We present an overview of the three winning designs. HELP (1ST PLACE) High Endurance Lightweight Program (H.E.L.P.) has been designed by Raphael Klein. It has a peculiar configuration: it is a twin-boom tail dragger with an inverted V-tail (see background image). This configuration came very late into the design

process. It was only two weeks before the deadline that the configuration was finalized. The H.E.L.P. started as a flying wing. In the initial weeks, only the performance requirements were considered. The idea was to make a highly efficient flying wing with a very large aspect ratio that would perform well at very high altitude and would allow a large lift to drag ratio. However, several weeks into the design, new and more specific requirements were provided by AIAA. Two of these requirements became crucial: the aircraft should be able RAPHAEL KLEIN

Figure 1. HELP UAV boxed in standard shipping container

MALCOLM BROWN

JOSH HOLLAND AND STEVE BRUST

Figure 2. Isometric view of Rukh UAV

to fit in a forty feet-shipping container and it should be structurally designed to meet jet fighter military requirements. These new requirements led to drastic changes in the configuration as the flying wing configuration would not allow for storage in the specified container and would most certainly not meet military specifications. Slowly the span of the H.E.L.P. was shortened, the wing sweep was reduced and new features were added on to the aircraft. To maintain stability and controllability of the aircraft, a large tail was added at the end of twin booms and the engine was moved forward. The centerpiece of the H.E.L.P. was kept just long enough to fit as a whole in a container while carrying a payload of 400lb and having a large down-facing window. The other parts of the aircraft were all attached to this centerpiece by means of easily removable fixtures. Finally, the booms were connected through the tail for an increased flutter resistance. The result is an aircraft that can withstand load factors of 9g’s that can fit in a container (see Figure 1) while performing all the other requirements provided by the AIAA. RUKH (2ND PLACE) In an effort to reduce lift-induced drag at the operating altitude, the Rukh HALE UAV (Figure 2) was designed with a very high aspect ratio wing. This was achieved structurally with a partially joined wing, undoubtedly the aircraft’s most striking visual feature. In using a derivative of a joined wing configuration the aircraft benefits from dual lifting surfaces; deciding on a safe but within bounds set of stability margins proves challenging. Strength of winds aloft, variations in the gust spectra, and requirements for safety and operability in military standards all

Figure 3. Structural layout of Sky-I UAV

hold significance when deciding various margins for the aircraft. Structurally, the joined wing poses the biggest design obstacle. Differences in internal forces and moments experienced within the wing differ significantly between the inboard and outboard sections relative to the joint; meaning in certain portions of the wing the design could get away with using less structural weight. Facing stringent weight requirements, these possibilities are fully utilized. The internal structure of both the front and rear wings along with the fuselage is fully vetted by way of a FEM structural analysis tool. A structural component of particular interest and frustration is the wing joint that joins front and rear sections because it is also the point of attachment for the landing gear. Designing for maximum landing loads on one landing gear quickly sees the allowable loads near the limit. An added challenge in itself was the distance between teammates and the shear amount of data and analysis to be shared as the Rukh UAV has been designed by Steve Brust (TU Delft) and Josh Holland (University of Kansas). Doing the work and making decisions is one thing, attempting to convey an interpretation of that data to someone in an e-mail or Skype conversation is another. SKY-I (3RD PLACE) The Sky-I as shown in Figure 3 was designed by Malcom Brown. It is a canard concept with high-aspect-ratio, sweptback wings and a central, airfoil-shaped fuselage with a pusher-mounted turbocharged piston propeller engine. The canard is chosen since it adds to the lift created while the aircraft remains stable, and, since the wings are very long, its wake influence is relatively small. It is also placed below the wing to reduce the downwash on the wing. Due to the short rear fuse-

lage, it is chosen to use the winglets as vertical stabilizers with rudders. This requires the wings to be swept backwards, also adding to aeroelastic stability and the aircraft’s innovative appearance. A propeller is used due to the very large loss in jet engine thrust at 80,000ft and the very long, slow loiters. The Rotax piston engine is also cheaper and easier to procure, even though it needs to be triple turbocharged, as well as being more efficient. In terms of structure, the aircraft has a very minimal, lightweight composite structure. To reduce production costs the wings have a taper ratio of one and no twist, making the mold constant along the span, allowing smaller and simpler molds to be used. The spars are formed from closed tubes on the leading edge and trailing edge, already in the shape of the airfoil, allowing for perfect leading edge and trailing edge flow. The hollow ribs connect the spars and are covered with a lightweight flexible plastic film, allowing the wing to be extremely flexible but still strong. In order to not interrupt the leading-edge and trailing-edge spars, differential spoilers are used for roll control and high lift devices are not needed due to the light wing loading. The wings easily split into an outboard section and a fused center section to allow for transport. Finally the bicycle landing gear is inspired by the Lockheed U-2 setup with wing-mounted outrigger wheels. FUTURE ENDEAVORS The three wins demonstrate the excellent airplane design capability of Aerospace Engineering students from TU Delft. We intend to participate in this competition in the coming year. Interested students who want to compete can look up the design specification at www.aiaa.org or send an email to r.vos@tudelft.nl. DECEMBER 2013 Leonardo Times

Interview

MISSIONS TO MARS: MSL AND MARS 2020 Interview with AE Alumnus Gerhard Kruizinga working at JPL

The Jet Propulsion Laboratory (JPL) located in Pasadena, California is the leading organisation for planetary missions and a point of attraction for many Aerospace Engineers. The Leonardo Times interviewed a former student of our faculty who made the big leap overseas and dedicated his career to planetary exploration from JPL. We talk to him about his job, current and future Mars projects he is involved in. TEXT Jeroen Wink, Bob Roos and Sushant Gupta, Students Aerospace Engineering, Editors Leonardo Times

Can you tell us something on your time at our faculty, were you involved in any societies and what was the focus of your program?

A lot of students in Delft would like to work at JPL. However due to ITAR this is very difficult. Can you elaborate a bit, on how you got to work at JPL?

‘I was secretary of the second RVD and I was involved in the Study Tour to Russia that sadly did not work out. For my Masters, I was in the group of Professor Wakker and I graduated on the simulation a validation of Eddy currents in the oceans using altimetry. Since the Eddy currents change rather quickly in time, it was hard to measure it. I did simulations on how to better determine the shape and the movement of these currents using data of multiple satellites.’

‘To work at JPL you need a Green card. Therefore, my idea was to go to the USA as a PhD student and try to find a sponsor for my Green card there. After my graduation, I went to the University of Texas to do a PhD, where I specialized on orbital mechanics of radar altimetry missions. Apart from a sponsor, I also met my wife in that time, so that solved the whole green card issue! Also, I got to know a post-doc at the University of Texas who later went to JPL. He was the one that actually hired

Leonardo Times DECEMBER 2013

me at JPL and is still my boss. So, my advice to students would be to pursue at PhD in the USA, because this maximizes your time there such that people get to know you. But you need patience as well. I spend more than seven years at the University of Texas before I could actually go to JPL. So, it is possible but it takes time, perseverance and a bit of luck.’ Your specialization within JPL is on navigation for interplanetary missions. Can you describe the biggest challenges for navigation and orbit determination for interplanetary missions and how they differ from earth orbiting missions?

NASA

Figure 1. Gerhard Kruizinga

‘The last interplanetary mission I worked on was Mars Science Laboratory (MSL) rover, Curiosity. The biggest challenge would not be to determine the position in the orbit, but to predict the position in time. Especially for MSL, where we wanted to land inside the crater, predicting were you will be in a later time is extremely important. On Mars, there is of course no GPS, so you will have to tell the computer where he is now, what the uncertainty in that position is such that it can adjust its trajectory to land on the position. The uncertainty we had for MSL was around one kilometer in position and two meters per second in velocity. So, the emphasis for our navigation and orbit determination is in the prediction of the path. In the end, we were only 200 meters off from our target. Partly, this amazing accuracy was due to the fact that the spacecraft was rotating on its journey to Mars. The rotation cancels out a lot of perturbing forces that are hard to quantify. So basically, we only needed to worry

Figure 2. Composite image of Mars Science Laboratory on the surface of Mars

about the perturbations in the direction of the rotating axis.

ture but for now, we are still doing most of the navigation on ground.’

It is important to note that there was actually no onboard navigation on MSL. All the navigation was made on the ground. There is no onboard processing of the sensor data with regard to flying. Everything is downlinked to earth. It is like you are navigation to Mars by looking in the rear view mirror. You look always back. First, we do an uplink to the spacecraft and we can measure very accurately the position and the velocity of the spacecraft. All the information collected on Earth because the onboard processing power for spacecraft is not nearly sufficient to model its trajectory with the required accuracy. However, there are some new developments for onboard navigation like Autonav. A first version of this was used on the Deep Impact mission. Since they did not know actually were the comet would be, they included an onboard navigation to correct for the large uncertainties. I think that developments like this will be the fu-

What would be the biggest challenges in developing the Autonav? Is it mainly computational power, or are there also other fundamental issues involved? ‘I think it’s making or getting the right measurements, because the thing is, if you want to interpret data on-board, you also need to know, where is the earth, because that’s where all your signals are coming from, so it’s probably computational, but also some things like the Earth’s orientation. Remember the Earth is wobbling a bit as it rotates. We need to take all those things into account, and the spacecraft would not know anything about that. For instance when you are flying to Mars, there are other spacecraft orbiting around Mars, and what we could use is use a link from the spacecraft in orbit around Mars talking to the spacecraft that is coming in, for instance Curiosity. People here are thinking about that, but it DECEMBER 2013 Leonardo Times

NASA

Figure 3. Mars Science Laboratory on its way to Mars

has not been fully worked out yet, I think mainly because we don’t have the right measurement devices on-board.’ And I guess those spacecraft orbiting Mars are also not designed to do that. ‘We are using the current Mars orbiters with the Delta measurement, which is the measurement perpendicular to the line of sight. We are actually making delta door measurements to Mars Reconnaissance Orbiter (MRO) and Mars Odyssey to see where Mars is. When we are flying to Mars, we are looking in the rear-view mirror; we are not looking ahead. So we don’t really look at Mars, in no way or shape or form are we detecting Mars, as we travel. So, we need to know from models, or in this case the measurements from MRO or Odyssey where Mars really is, to make sure that we hit Mars at the right spot. But you can also do a delta door between MRO and MSL, and then you can get some idea of where is MSL relative to Mars. That’s an example where we do use it, but we still go through Earth to do it. I’m sure in the future, it can be done directly. That’s the best way, because then you’re really looking forward, then you’re sensing where Mars really is, because that really matters. Remember people are saying we are flying to Mars, that’s not really the case, what’s happening is, we’re flying in space, and Mars is just catching up with us, and we have to hit it just at the right time. Otherwise, you are coming in too late and you miss the whole thing. Or if you’re coming too early, you probably crash into it. MSL arrived

Leonardo Times DECEMBER 2013

at a velocity of about 5.9km/s relative to Mars; you need to be very accurate. Especially for Curiosity, we had a very narrow corridor. That was quite a challenge. So knowing the position of Mars was actually one of our big challenges too. But because we had MRO and Odyssey and they were making measurements too, we had a really good model for Mars, and where it was. And as I said, we were only about 200m off, so that was pretty good.’ And comparing this to Viking spacecrafts, that were kilometers off… ‘Well the Vikings also first went into orbit around Mars; they spent some time taking pictures of where they wanted to land. Here it is like, you don’t go in orbit around Mars, you just land immediately and so you’re coming at a hyperbolic trajectory into Mars. There is no going back, and that’s it. For Viking at least, like you said, that was kilometers at least, tens of kilometers, but remember if you first go in orbit, if you’re a little bit high or a little bit low, that doesn’t hurt anything. Once you’re in orbit around Mars, you can actually improve your orbit around Mars, then you have better information again, and that’s what they did for Viking.’ Until now, MSL has been quite a success, but are there things, especially in field navigation, things that could be improved for future similar missions, for example, the Mars 2020 mission? ‘It’s funny that you mention that, because

I am working on 2020. I’m working on the navigation for 2020. I would say, from a navigation point of view, this was by far the best mission that I worked on in terms of our success of modeling everything that’s happening. Just to give you an idea, Curiosity has a Radioisotope Thermoelectric Generator (RTG) , which is basically using the decay of plutonium to generate heat, so we can actually make electricity on-board. We could actually see that heat coming out of the spacecraft putting a little propelling force on the spacecraft. Based on the measurements that we got, we could actually model the force that was acting because of that. There were just a few minor things that we could’ve improved on, but in general, it was really, quite remarkable how well this went. I’ve been on other missions, like for instance Phoenix, which is also a lander, which went to the North Pole of Mars, or near to it. There, we had continuously thrusting, little thrusting, I always compared it to like you’re driving a car and then a little baby seems to be pulling on your steering wheel trying to veer you off course. That was much more difficult to predict, and much more work to actually get to the same result. For MSL, I think it was one of the cleanest spacecraft that I’ve flown at this point, so for 2020 we’re basically going to use exactly the same modeling, and the same assumptions, so not much in that particular changed as far as navigation, as far as improvements. Curiosity has been operational on Mars for little over a year now, Are you satisfied

You mentioned, you are also working on the Mars 2020 mission, could you maybe tell a little bit about its objectives? ‘I can kind of give you the philosophy of the mission, the first thing is, it’s called ‘build to print’. What we mean basically is, we’re not going to change the design of the Sky Crane, or the rover, to save money, makes the mission cheaper. So it will look very much like Curiosity, the only difference is of course all the instruments on-board, and right now, there’s just an opportunity, NASA has announced, that they ask for proposals, for people to actually propose instruments that they would fly to Mars. They’ve given some guidance from a team called the SDT, the ‘Science Definitions Team’. One of the objectives

Figure 4. The Gravity and Interior Laboratory

NASA

‘Well, there was no methane at Gale crater, it could be that at other places on Mars there is methane, but Gale crater so far, they have found very little. But the other interesting thing for me was, where we landed in Gale crater, I always call it a parking lot. We just landed on a nice flat piece, so that we can drive to something that is about 10km away that is very interesting. And then there is, the first thing the scientists do, we’re supposed to take a right, they take a left. And that was kind of puzzling to us, like here we spend as this time trying to get as close as possible to the mountain, from a navigation point of view, and then they go left, going away from it. But it turned out, that was really, I guess, the best move so far, because they went about 500m the other direction and they found clay deposits. And that really suggests that it was neutral water. And that was the main goal that they were trying to go for, find clay deposits, and from that they can conclude that in the environment around that time, life could have existed, because it was in a neutral situation, neutral water amp. Essentially, MSL already has kind of done what it needed to do, to demonstrate that. But no, we’re now on our way, we’ve now driven about a little more than 3km, we still have about 6km to go, but then we’re going to get into a mini ‘Grand canyon’, driving up this mountain that’s about 5-6km high, and I think just the pictures are going to be just amazing. But there, supposedly, are all these layers, clay layers, and so now they started at the bottom of history and work their way up. I’m looking forward really to see that, but probably still, probably, it’s going to take a year before they get there. They’re trying to get there really fast right now, but still, they’ve found some interesting stuff on the way, so that they’re stopping now and then, to check some other stuff as well.’

NASA

with the scientific findings so far?

Figure 5. Artist impression of the Gravity Recovery and Climate Experiment (GRACE)

is for instance, we may want to get some samples that we store for a later mission and take little samples and store them. Another later mission may actually go pick it up, that may be one of the goals of this mission. Also, Curiosity really went there to see, is the environment suitable for life. I think for 2020 they’re trying more to see, if there are really signs of life. But go online, search for where they actually describe what the goals are for that mission. Currently, it states that people are actually proposing instruments, so that’s all I know at this point.’ So, it will be more focused on astrobiology, especially now that this water has been found.

‘Right, basically the next step, and maybe work on sample return. You know, as I said, it’s all maybe, because maybe it may

be too expensive, and then they might not do it, so it’s really up in the air right now. But from a navigation point of view, it will be virtually the same. As I said, we’re going to basically do the same thing.’ Since the focus of your career has been on unmanned spaceflight and exploration using unmanned spacecraft. What would your opinion on manned spaceflight. Are the manned attempts of the possible future worth the effort, from a science point of view? ‘Oh, that’s a good one. I’m a big fan on manned spaceflight. You can build robots and they can do all kinds of things, but in general, a robot is only going to do what you tell it to do. When you put a human into a certain situation, put him on Mars, they will see things that a computer will never thought of, or do things that a comDECEMBER 2013 Leonardo Times

puter doesn’t have the ability to. So I actually hope to see in my lifetime that we will for instance, will fly to Mars, and someone will land on Mars. Of course, it’s extremely expensive, so that’s the drawback. It’s a lot cheaper to go with robots in general than with people. But I think for certain things you really need humans to go somewhere and really find things out.’

are a little bit more than four years away and that’s very short. So things are not there yet. So technically, I think it’s feasible.’

On a kind of follow-up question on this, you and your colleagues at JPL, they are kind of the experts on getting to Mars. How do you see the chances of success of these manned exploration missions? In the US, you have Inspiration Mars; on the other side of the ocean, you have Mars One. How do you see their chances of success, is this taken seriously by the space community?

‘JPL has been asked by the Indian Space organization, ISRO, to share navigation. So we are going to help them, as they fly we are going to process the same measurements as they do and just help them with the navigation to Mars. I have also worked on the Indian moon mission called the Chandrayaan, when they went to the moon. It is the same thing we did for them; we did the” shadow navigation” because they had never gone to moon at that time and it’s the same now. They have never gone to Mars and there are some unique aspects flying to Mars. They just want us to kind of do shadow navigation so that there will be a mission success and they will make it to Mars. That’s why we are doing it. You know there is more and more co-operation between the International space agencies and I think JPL wants to fly an American instrument on one of the Indian spacecraft later. Its called Mars Orbiter Mission (MOM).’

‘I am also finishing up GRAIL, that was a mission around the moon very much like GRACE where we produced a very highresolution gravity field and we are almost done finishing crossing of all the measurements. These measurements will be the inputs for the scientists. GRACE and GRAIL are two spacecraft flying behind each other about 200km apart and we measure the relative velocity between them to less than μ/sec. With that, you can very accurately measure the gravitational model of the Moon or the Earth. Of course, for GRACE it’s designed to produce a gravitational field for the Earth every month. We can see the ice-caps melting in Greenland or Antarctica. We also monitor any glaciers in Alaska, Patagonia. That is basically an Earth science mission. I am also working on something that’s going to be called GRACE follow-on. So I am working on five things right now: GRACE, GRACE follow-on, GRAIL, MOM and 2020!’ That’s quite a lot! ‘Too much actually!’

Can you also tell us something about fu-

ISRO

‘Its funny that you mention it, I did some work for Inspiration Mars actually. We look at the navigation, how much propellant you need to bring in order to do the flight. So, from that point of view, it’s definitely possible. The thing though is Inspiration Mars, I don’t know about the European effort, a lot of hardware still needs to be made or hasn’t been flown and they are running out of time fast. I think their challenge will be getting all the hardware in time ready to make the flight. For instance, I think Inspiration Mars wants to launch in January 2018 and you know we

You mentioned that you are also working on the Indian Mars orbiter mission that launches at the end of this month can you elaborate a bit on your involvement?

ture NASA missions you are working on now? You already mentioned 2020.

Figure 6. The Mars Orbiter Mission being mated to the Polar Space Launch Vehicle (PSLV)

Leonardo Times DECEMBER 2013

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Internship report

FROM MOSCOW TO THE MOON

An internship at the Space Research Institute in Moscow Due to the strict implementation of the harde knip (BSc. Before MSc. Rule) I found myself with no courses or project work in the spring quarter. I decided to put this time to good use and pursue an internship abroad. This endeavor eventually brought me to the Red Square to contribute to the Russian space program. TEXT Jeroen Wink, Student BSc. Aerospace Engineering and Editor, Leonardo Times

aving an interest in Russia for a long time, I wanted to work in the Russian space industry. Since the cooperation between Roscosmos and ESA is increasing, I hoped that it might even be possible. To learn what was possible, I mailed Professor Malenkov who chaired the space robotics chair at the St. Petersburg polytechnic university. He answered that it would not be possible at his own university but that he would ask around among his colleagues in Moscow for me. A number of weeks later I got the great news that I could work at the Space Research Institute of the Russian Academy of Sciences. After e-mail contact and a dinner in Noordwijk, Netherlands (ESA ESTEC location), I found myself at the Russian consulate with my visa in hand. My Russian adventure had begun. IKI The Space Research Institute of the Russian Academy of Science (Институт космических исследований Российской Академии Наук) is the leading organization on space exploration within Russia.

Leonardo Times DECEMBER 2013

They are responsible for the design and construction of most scientific instruments on Russian spacecraft. Furthermore they have a leading role in formulating the the science goals of the Russian Space Program. Currently they employ around three hundred scientists and engineers. Apart from the Russian space program, they are also responsible for a large number of instruments on the joint ESA/ Roscosmos Exomars program. LUNA PROGRAM In recent years, Russia formulated the ambition of lunar exploration. As a first step in this endeavor a number of robotic exploration missions are to be conducted. One of these missions is Luna Resurs (Luna 27), which, amongst others has the objective to identify the water content in the lunar regolith. The mission will consist of a lunar lander vehicle and a micro rover that is deployed from the lander. The mission is set for launch in 2019. MY WORK I was placed in the department of Dr. Oleg

Kozlov, specialized in manipulators and robotic arms for spacecraft. My main task was to design the breadboard model of a lunar rover to be part of the Luna Resurs (Luna 27) mission. The breadboard model is used to develop and debug the navigation and control software for the micro rover. The breadboard model has all of the mechanical features of the flight model. The main differences are in the weight optimization and the thermal isolation. The rover features four metallic elastic wheels, separate drives for each wheel, a robotic arm with a shovel and a drill and a pair of cameras for stereovision based navigation. The breadboard model is used to test all these features both singled out as well as in combination with each other. The majority of my work consisted of the mechanical design of this rover. The initial weight and volume requirements were to be translated into a complete Solid Works assembly and a set of production drawings of each part. On top of that, limitations in terms of tolerances, precision and

Figure 1. The engineering model of the Buran in Gorky Park.

achievable radii of the available lathes and mills needed to be taken into account. An additional challenge in this process was the significant language barrier that complicated a lot of normally trivial tasks. For example, the interface of my workstation, including SolidWorks, was completely in Russian. Despite these challenges, I succeeded to deliver a production ready assembly before the end of my internship. Next to the mechanical design, I was assigned to make some first order thermal calculations for the robotic arm mounted on the Luna Resurs lander. This arm will feature a relatively large drill to take samples from a couple of centimeters beneath the surface. The preliminary thermal calculations were used to define initial requirements on the conductance, absorption and emissivity of the structural parts. Initial results suggested that a gold coating on the structural members is necessary to prevent overheating of the drives during (Lunar) daytime operations. Furthermore, it was deemed necessary that the arm would be connected to the heating system of the main lander to prevent excessive cooling during the lunar night. OUTSIDE WORK Apart from working, there was of course enough time during the nights and in the weekends for some relaxation. Moscow is one of the most beautiful and exciting cities in the world. With its marvelous

architecture and bustling nightlife, it provides the visiting student with more that enough to do. And the super efficient metro system (the stations of which are a architectural highlight by itself ) makes every corner of this huge metropolis quickly accessible. Personally, I enjoyed many afternoons at Gorki Park. Sitting next an engineering model of the Buran while drinking a beer and watching the sun set over the Kremlin is quite a unique experience. For aerospace enthusiasts in particular, Moscow features two of the most amazing museums in the world. The Cosmonautics museum is a shrine to all Space lovers with its titanium monument to spaceflight on top and its beautiful expositions underground. Furthermore the Monino Air force museum features almost every single aircraft ever used by the Soviet military, including the worldsâ&#x20AC;&#x2122; largest helicopter, the first super sonic passenger jet and a number experimental lifting body aircraft) and is unique by its sheer size and exposition. Even Caspian sea monsters (ekranoplan) are close by as a small version is on display in the suburb of Khimki. Since there were three holidays during my stay (Labor day, Victory day and Russia day) I had the opportunity to explore a bit of the rest of Russia. Russia is most conveniently traversed by train. Trains are leaving Moscow in all directions and are mostly conveniently scheduled to drive

overnight. Furthermore, Platzkart tickets (3rd class sleeping wagon with 54 beds per wagon) are quite cheap and offer a unique opportunity to meet the real Russians. Most travellers are very interested in foreigners and despite the language barrier are often in for a talk and a toast. The main downside would be the beds, as they are not really designed for a two meters tall Dutch person. Despite the minor induced back pains, I greatly enjoyed my trips to Tartarstan, Karelia and St. Petersburg during the holiday weekends. CONCLUSIONS My twelve weeks in Moscow turned out to be an extremely rewarding experience. Being able to contribute to an actual space mission on its own is already a great feeling. But the fact that it was in Russia made it extra special to me. Despite what the current media incidents might suggest, the Russians are really gently people and in general very helpful to foreigners. As a conclusion, I would encourage everyone to pursue the opportunities that you have as an Aerospace Engineering student to go abroad. If you take the chance to it turns out to be quite easy to go to some unexpected places. A year ago I would have never tough it would be possible for a European student to work in the Russian space sector, but it turned out to be a smooth process and a great experience. DECEMBER 2013 Leonardo Times

SWISS SPACE CENTRE

SPACE DEBRIS Challenges and solutions

Space debris has been a hot topic for the last few decades, ever since the space industry started growing exponentially. Everyone agrees that space debris is a growing problem and the saturation point has almost been reached. With a big risk of a chain reaction, called the Kessler syndrome, billions of euroâ&#x20AC;&#x2122;s worth of space equipment is at risk. Clearly something has to be done about this. TEXT Elwin van Beurden & Christel Prins, Students Aerospace Engineering, members of Space Department

he amount of space debris has been growing and growing since the 1950s by, for example, accidental explosions of rocket stages and crumbling paint layers. The most important events occurred in 2007 and 2009. In 2007, the Chinese government destroyed one of their satellites by means of an ASAT missile (Anti-Satellite Missile) producing 2841 observable pieces of debris. In 2009 the Kosmos-2251, an inactive Russian satellite, collided with Iridium 33 producing 1267 pieces of observable debris. NASA scientist Donald Kessler predicted that a collision between two pieces of space junk could trigger an avalanche of collisions, rendering some orbits useless for further usage. Kessler said that when the rate of debris forms is faster than the rate at which it de-orbits, then the Earth will be surrounded by permanent junk belts. This is called the Kessler syndrome and some believe we are dangerously close to this point, if we have not passed it already.

Leonardo Times DECEMBER 2013

Everyday, NASA tracks 21,000 pieces of debris larger than 10cm and estimates that there are around 500,000 objects between 1cm and 10cm. These objects are untraceable from earth and carry energy equivalent to 0.3kg to 300kg of TNT. The ISS, the most heavily shielded spacecraft ever built, can only withstand particles up to 1cm in diameter to its most critical components. This poses a growing risk to the crews in space and the multibillioneuro equipment they are operating. One of the main problems with this space debris is that the problem will not disappear in the short term all by itself. Even by suspending all future planned space missions the problem will remain for the coming hundreds of years. Clearly a solution is needed. LEGAL ISSUES One of the main challenges facing the battle against space debris is Article VIII of the Outer Space treaty. This treaty states that any space object, including space

debris and non-functional satellites, are still owned by the country that launched them. Unlike maritime law there are no salvage rights, so if a satellite is no longer functional this does not mean a nation has abandoned it. So unless a nation gives its consent to removing a satellite or space object, it cannot be disposed of or even interfered with. Another major complication is the fact that international space law defines parts of spacecraft or other objects as individual space objects. Therefore, if one would even want to remove a speck of dust, that speck would first have to be identified before it can be removed. Liability even further complicates the entire process. Article VI of the Outer Space Treaty states that any nation under whose jurisdiction the removal of the debris is carried out retain full responsibility for the operation and any accident during the operation. This of course means that nations are very reluctant to carry out any mission that will not render any profit, but which could possibly end in a very expensive ordeal.

MIT TECHNOLOGY REVIEW

CLEAN-ME PROJECT The Swiss Space Centre is developing a space program that is planning to launch a series of Nano satellites as early as 2018. The first satellite in this series, CleanSatOne, will be launched by the SOAR space plane, which is operated by S3 (Swiss Space Systems). It is predicted that the launch costs will be cut to a quarter of the current costs and drastically reduce the footprint of the mission by returning the launcher directly to earth. Figure 1. Using a LODR system space debris can be ‘zapped’ from space

Even though this is a great start and it shows the willingness of a country to take responsibility for its space debris, the entire operation is extremely difficult, pricey and will only be able to tackle big objects.

Figure 2. Space Debris forms a huge threat to current and future missions

CUBESAIL Surrey Satellite Technologies (SST) in the UK is also involved in the space cleaning business. Currently they are researching solar sails, which employ a huge sail pushed by solar pressure through space. By not having to carry any propellants and only a few moving parts, these solar sails can offer a very cheap alternative to conventional propellant powered spacecraft. SST plans however to deploy solar sails to slow down space debris and thus deorbiting it. Thus, it is possibly a much cheaper alternative to the Clean-mE project. The mission will be as follows. The CubeSail will be launched into orbit and using a harpoon or net the space debris is captured. Once the debris is caught the solar sail will be deployed and this will create massive drag, causing both the satellite and debris to burn up in the atmosphere. CubeSail could also be fitted to future satellites. This would mean that in time every single satellite could deorbit itself cheaply and effectively after it has reached its end of life. Deorbiting satellites has always been a costly affair, since every single gram of propellant can be used to extend the lifetime of the multi million-euro missions.

NASA

The first object to be cleaned by CleanSatOne will be the Nano satellite SwissCube, this in order to avoid potential legal issues surrounding the de-orbiting of a foreign satellite. A potential hazard for the system is the potential military application as an Anti-Satellite weapon. After launch the clean-up satellite will match its trajectory to the target’s orbital plane. Traveling at 28,000 km/h at an altitude of around 700 km grabbing an object is tricky and dangerous procedure, with the potential risk of breaking up the object or sending it in a collision orbit with another object. In the case of SwissCube, the system will try to stabilize it and de-orbit itself causing both satellites to burn in the atmosphere.

LASER ORBITAL DEBRIS REMOVAL (LODR) LODR uses the impulse generated by particles that are being burnt on the objects surface. For this system to be effective about 75kJ/m2 on the object in 5ns is required, since this creates a plasma jet. One pulse can slow small debris 10cm/s and only nanometers of the surface are vaporized, so the object is not really affected by the process. With a pulse rate of 10Hz and an average power of 75kW, the laser can slow targets up to 10cm in diameter in a single overhead pass. Only about 100m/s is required to slow down an object sufficiently for it to re-enter and burn up in the atmosphere. Low operating costs and high agility are the main advantages of this system. De-orbiting large objects would only cost under a million Euros and even a small LODR system will be capable of tackling objects as much 1000kg. This system would have to be operated by an international agency to avoid legal issues of the Outer Space Treaty. CONCLUSION There are many options to remove debris from space and many more concepts are being worked out every day. It is just a matter of time until something goes really wrong in space before nations will finally actively start removing debris.

REFERENCES http://stratrisks.com/geostrat/9353 http://orbitaldebris.jsc.nasa.gov/faqs. html#8 http://www.space.com/23049-spacejunk-satellite-swiss-space-plane.html http://space.epfl.ch/page-61745-en. html http://www.aerospace.org/cords/ space-debris-basics/what-are-therisks/ http://www.dailymail.co.uk/sciencetech/article-2317754/Space-sailscarrying-suicidal-satellites-destroydangerous-space-junk-good.html http://www.thespacereview.com/ article/2130/1 http://www.technologyreview.com/ view/423302/nasa-studies-laser-forremoving-space-junk/ http://spie.org/x84761.xml 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.

DECEMBER 2013 Leonardo Times

STUDY TOUR ‘LIMITLESS’

Study tour through the U.S.A. and Canada

“What was the best part of the tour?” A question often asked, both during and after the Study Tour 2013 ‘Limitless’, which took thirty students and four staff members on an amazing trip through 2 countries, 8 cities and 12 flights. The question proved very difficult to answer, the most common answer was simply “Everything”. TEXT Jasper van Gorcum, MSc Student Aerospace Engineering, member of the Board of the VSV ‘Leonardo da Vinci’

n June 2012, six students started with the organisation of the yearly study tour of the VSV ‘Leonardo da Vinci’. First order of business: determining the destination for the tour. It was already determined that the study tour would last for four weeks in September 2013 and would be inter-continental. The wildest plans were drawn up and soon the term ‘Limitless’ was coined. After heated debate, the final cities were set to be: Washington (D.C.), Montreal (QC), Boston (MA), Orlando (FL), Fort Worth (TX), Mojave (CA), Los Angeles (CA) and Seattle (WA). In the following months flights and hotel bookings were made and various companies were contacted. On September 5, the moment was there, ‘Limitless’ was ready to take-off. WASHINGTON, D.C. The tour started with the capital of USA, Washington D.C. and the first point of agenda was visiting the Netherlands Embassy in US for welcome drinks. The next day the Smithsonian National Air & Space

Leonardo Times DECEMBER 2013

museum was visited, the museum boasts of the largest collection of aviation and space related artifacts. The entire history of human flight was could be seen in the two locations at the National Mall, the heart of Smithsonian institutions and Udvar-Hazy center near Dulles International airport. The highlights of the visit were the famous SR-71 ‘Blackbird’ airplane, Space Shuttle ‘Discovery’, Wright flyer and the ‘Enola Gay’ aircraft which dropped the nuclear bomb on Hiroshima, Japan in 1945. On the following day, it was time for sightseeing around the city. We got a tour of the US Capitol building. In the vicinity were the various other war memorials along the National Mall and of course one of the most famous residences in the world; the White House. The tour had started with a bang! MONTREAL, CANADA After only three days in Washington D.C., it was time to move on to Canada. Montréal is the aerospace capital of Canada.

The Greater Montréal region also has the second-largest density of aerospace jobs in the world. One in 189 Québecers work in the aerospace industry, thus a perfect location for “Limitless”. We visited the Canadian Space Agency (CSA), where we could see the facilities for the future Mars Rovers and the Canadarm for International space station and an overview of all the satellites the CSA operates was given. The tour was concluded with a walk over their very own Martian landscape! After a day off, which gave everybody a chance to climb the Mont-Royal, the namesake of the city, it was time for more company visits. In the morning MDA Corporation was visited, with a nice tour of all their facilities, including their ‘noise-free’ test chamber. In the afternoon a visit to the aircraft manufacturer Bombardier and their Challenger assembly line plus a presentation on the C-Series, completed the day. The following day, the last in Montreal, we visited the International Air Transport Association (IATA) to find out the role they play

JONAS D’HAEN

Figure 2. Cape Canaveral launch facility, FL

in the Global aviation industry. BOSTON, MA After Montreal, it was time to go back to USA to Boston, MA. In Boston, we visited the famous educational institutes located in Boston; the Massachusetts Institute of Technology (MIT) and the Harvard Business School. With only two days in Boston, the next day was utilized to see the city; with a very passionate tour guide, the group walked the freedom trail and learnt about the culture and history of one of the oldest cities of US. The city was an important location in the American war of independence and events like Boston tea party took place here. In the evening, the group took the opportunity to go out in downtown Boston and got a taste of the buzzing nightlife the city offers with more than 250,000 students enrolled in the Boston area. ORLANDO, FL The pace did not slow, next up: Orlando! Located in Florida, the famous Kennedy Space Centre (KSC) in Cape Canaveral was a highlight of the study tour. Invited as ‘NASA Special Guests’ and a very enthusiastic tour guide to accompany us, the trip to KSC was one to remember. The height of the Vehicle Assembly Building towering at 160 meters is still very hard to grasp.

The building was used to assemble the Saturn V rocket for the Apollo program. The tour concluded at the Visitor’s Centre where we got to see the Space shuttle ‘Atlantis’ exhibit. After a day at the beach and a morning kayaking between alligators in Floridian swamps, it was time to visit the Brazilian aircraft manufacturer Embraer. In Melbourne, Florida, the final assembly of the Phenom 100 and 300 executive jets is done. FORT WORTH, TX Halfway through the tour it was time to move west, to Texas. Fort Worth is another major hub in aviation, in the United States of America. Immediately after the flight from Orlando it was time to visit the first company in Fort Worth: American Eurocopter. During the extensive tour, we were able to see all the facilities. This included their assembly halls, the full-motion simulators and the maintenance hangars. The next morning was planned for a visit to the Gulfstream Aerospace company. During breakfast a presentation on the past, future and vision of Gulfstream was given; truly inspiring. In Dallas, Gulfstream has the final assembly of the G150 and G280 business jets, as well as maintenance for all their products. Seeing them up close, one really appreciates what kind of engineering goes into these machines;

this was once more confirmed by a presentation at the engineering department. After a weekend with the all-Americanexperience, i.e. Rodeo, American Football and some good old western style visit to a shooting range where we had a chance to test our aim with rifles, it was time again to pack the bags and move to a different city. But not before we visited another helicopter company; Bell Helicopters. Here a tour of their renowned training facilities was given. In these training facilities, they train both the technicians and the pilots. It is very interesting to see both these sides to the training and experience their state of the art Simulator. MOJAVE AND LOS ANGELES, CA Shortly after landing in Los Angeles, a bus was waiting, ready to take the tour to the Mojave Desert. After a breakfast right on the landing strip of the Mojave Air and Spaceport, it was time to visit XCOR. XCOR is currently building their own sub-orbital, commercial reusable re-entry vehicle, the Lynx. Working from a small hangar with passionate people, this company was very inspiring. To be able to see a live test fire of their RCS rockets from up close was the cherry on the cake. In the afternoon, a tour of the flight line (with the Virgin Galactic White Knight 2 and Space Ship DECEMBER 2013 Leonardo Times

2) was made. The afternoon ended with an unexpected lecture by the famous Dick Rutan, who told about his experiences including piloting Voyager aircraft around the world in 9 days and gave us an inspirational, no holes barred talk on the future of new technology in aerospace industry. The next day, before driving to Los Angeles, it was time to visit Edwards Air Force Base and Northrop Grumman, a major defense contractor. At Edwards Air Force Base, the tour visited the USAF Test Pilot School, where Dutch test pilots gave a lecture on the F-35 and test pilot program. This interesting morning was finished at the Air Force Flight Test Museum. In the afternoon, there was a unique visit to Northrop Grumman, where assembly of the center-fuselage of the F-35 and the final assembly of the Global Hawk was done.

The last stop in Los Angeles was no less than Jet Propulsion Laboratory (JPL). There we got to see their innovation center, a test model of the Curiosity rover, their huge clean rooms and engineering center. After a very informative visit, it was time to relax during our last weekend of the study tour. This was a great opportunity to see the home of Hollywood with the Californian sun shining in all its glory. Participants of the tour took time to see famous sights like Hollywood walk of fame, Santa Monica beach, Beverley hills, Rodeo drive and the fantastic view of the whole city from the Griffith Space observatory. SEATTLE, WA On the last Sunday, it was time to fly to rainy Seattle. As the grand finale of the tour, there were two days devoted to a visit of the Boeing facilities. On Monday, it started with the 737-production facility in Renton, where they produce approximately 38 aircraft per month! Afterwards, there was a visit to the Dreamliner Gallery, where all the different options on the 787

are shown. What better place to lunch than the Boeing Delivery Centre? With a great view on the tarmac, it was a real pleasure to lunch here. Across the street was the biggest building in the world; the Everett factory. Here the final assembly on the 747, 767, 777 and 787 is done. It is very impressive to walk so close and actually in these unfinished aircraft. The next day was reserved for a full day of case study. During the day, we studied the merger between KLM and Air France and the several Boeing products and came up with our advice on the question at hand. The case study had us all very excited and gave insights into the relationship between the aircraft manufacturers and the airline industry, specially with top management of the Boeing company attending the presentations. This day was finished with a fantastic dinner hosted by Boeing on top of the Columbia Tower. To all the people who helped us during and in preparation of our tour, to all the participants and staff and to my fellow committee members; thank you for this wonderful experience, I wish I could do it again.

JONAS D’HAEN

With only a week left, the first companies visited in Los Angeles were the Los Angeles World Airports (LAWA) company at the LAX airport and Icon Aircraft. At LAX a special tour was arranged, to drive all across the airport and up close to all the airplanes; something which is not easily forgotten. Icon Aircraft was up next, this small start-up company currently builds

only one model; a small leisure amphibious aircraft. Despite the size of the company all the energy there, made it a very nice visit.

Figure 3. Space Shuttle ‘Discovery’ at Smithsonian museum

Leonardo Times DECEMBER 2013

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Student project

MAVLAB

Competing with Micro Air Vehicles (MAV) The IMAV is an annual international conference and competition involving Micro Air Vehicles (MAVs). In September, the 2013 edition was held in Toulouse, France. The MAVLab from the faculty of Aerospace Engineering, TU Delft joined the competition with a group of thirteen students (MSc/PhD) and staff members. The goal was not only to win the competition, but also to highlight recent developments and demonstrate capabilities of our group. TEXT Ewoud Smeur and Sjoerd Tijmons, MSc and PhD students at the MAVLab, Control & Operations chair, Aerospace Engineering

n order to show the developments and progresses of your research group and keeping up with other groups and getting in touch with them, visiting a scientific conference can be very fruitful. In the world of MAVs, this is not different, but at the IMAV this goes a little further. In parallel with the conference, a competition is organized where teams can compare their capabilities by accomplishing several different tasks.

cessfully completing one or more of these elements. The number of points obtained when fulfilling an element depends on the amount of human interaction and the size of the MAV; the more autonomy a MAV has and the smaller it is, the more points are scored. The outdoor mission mainly focused on doing the elements with multiple vehicles in parallel. The mission elements of the indoor competition mainly focused on collision avoidance.

The definition of when an MAV is ‘micro’ is not well defined. For the IMAV, a maximum size of 1.00m is used as a hard constraint. As a result, there is still a large variation in the size of the vehicles that show up during the competition; flying wings that use the one meter allowance up to the last millimeter, as well as mini quadrotors that are downsized that far that people don’t notice them. The latter could qualify for the term ‘Nano Air Vehicle’. This variation in size (and configuration) is driven by the different applications MAVs can be used for. For this reason two separate competitions are organized: an outdoor and an indoor competition. Both competitions are built up from different mission elements and teams can earn points by suc-

PREPARATION An overview of the MAVs that our team used during the competition is shown in figure 1. To score points at the IMAV, it was important that every MAV could autonomously complete mission elements. Achieving this took a lot of preparation. For instance, the ARDrones had to be debugged, the Quadshot was in need of guidance routines and the DelFly was not yet able to avoid obstacles, or fly through a window. The MAVLab workspace was busier than ever during this period, because quite some students were assigned to work on the competition. Some of them were already working on these vehicles for their own projects and in many

Leonardo Times DECEMBER 2013

cases creating the additional features was something they had to do anyway. And since these students worked hard on achieving the goals set for the IMAV, they were welcome to join the competition in Toulouse for a unique experience. OUTDOOR COMPETITION The second day of the conference was the day of the outdoor competition. The organizing committee rented a small airfield for the occasion, so there was enough space for safe flights. There were different mission elements located around the runway, such as a corridor that could be flown through, or a QR code that had to be detected and decoded. Since points were awarded per MAV, there was a large potential in using a lot of MAVs. However, the number of persons necessary to operate them divided the score obtained. Therefore, the MAVLab had only one operator, for a total of twelve MAVs: seven ARDrones, three Quadshots and two custom quadrotors. To achieve this every MAV was made fully autonomous to the extent that the only thing the operator had to do was put the MAV on the ground and plug in the battery.

CHRISTOPHE DEWAGTER

Figure 1. The MAVLab team

The ARDrone is the commercially most successful quadrotor at this time. It is inexpensive and safe to use and is equipped with an HD camera. This makes it a nice platform for flight-testing of new algorithms, or for flying competitions such as the IMAV. It runs its own autopilot software, but to make it really hackable, the open source autopilot software system ‘Paparazzi’ was ported to work with the ARDrone hardware. Additionally, even though everything was autonomous, a data link with every MAV was still needed to monitor the status and being able to control each MAV in case of an emergency. This required a lot of connections, so for that purpose a router was utilized. The data coming from the router was then streamed to the Internet, and by downloading an App; anyone could monitor the position and velocity of each ARDrone in real time. The Quadshot is a flying wing MAV capable of both hovering and forward flight. It is equipped with four rotors to achieve stable hover in the same way as a quadrotor. The position control for hovering rotorcraft and forward flying fixed-wing aircraft is totally different, so to make this vehicle fly autonomous the two separated controllers were interpolated in the transition region. This worked nicely in test flights. However, the day of the competition there was a really strong wind, which is why the Quadshot needed a lot of time to reach a destination whenever it was going to hover mode. Nonetheless, it managed to perform most of the mission elements and showed the benefit of having a fast forward flight mode with respect to

quadrotors. Next to this, two custom quadrotors were performing mission elements, one of which was equipped with the smallest complete autopilot in the world: the ‘Lisa/S’. Its largest dimension is 2 cm and it weighs only 2 grams, but yet it has a full IMU, radio link and GPS on board. The IMAV was the first official flight for this autopilot and it performed great. It turned out to be a very windy day, which was also reflected in the performance of the participating teams. Few teams managed to show stable flights, let alone do mission elements. The MAVLab team had less trouble with the wind, and with the sheer number of MAVs and the single operator our team won with a final score that was an order of magnitude higher than the second placed team. INDOOR COMPETITION On the third day of the conference, the indoor competition took place. For the indoor missions our self-developed platform was used: the DelFly. Two different configurations of this MAV were used. The first one is what we call the standard configuration: it has a T-tail for stabilization and steering, it is operated manually via an RC link and it has an onboard camera with live video link. This equipment allowed a single operator to perform several mission elements remotely by only looking at a small display with the live video stream: flying through an open window, flying through a field of obstacles, looking for a hidden marker and following a line on the ground. The advantage of this DelFly is its easy handling, allowing

the operator to do the mission elements smooth and quickly. The second DelFly has a completely new configuration and is called the DelFly Explorer. It can stand on its tail allowing autonomously vertical take-off, it has more precise roll control by aileron surfaces and, most importantly, it has a stereovision camera with processing onboard. In contrast to the first configuration, this particular DelFly was functioning fully autonomous: it could take-off to a predefined height above ground, follow a fixed heading, detect and avoid obstacles by using the stereo system, and detect a window by using one of its cameras. During the actual competition, flight the obstacle avoidance worked partly, the window detection turned out to be not fully robust at that time. This is why our team won the first place in the Indoor Operation ranking, and the third place in the Indoor Autonomy ranking. A compilation video of our team at the competition days can be found at the MAVLab YouTube channel. The MAVLab in Delft will organise next year’s IMAV 2014. Additionally, we are also planning to participate with our own student team. Interested students can contribute or even participate by doing their graduation work with the MAVLab. Contact us via microuav@gmail.com. References MAVLab website, www.mavlab.lr.tudelft.nl Official IMAV website, www.imavs.org MAVLab YouTube channel, www.youtube. com/user/microuav

DECEMBER 2013 Leonardo Times

“We vlogen met een zucht...”

VTOL AIRCRAFT Go up, go forward, and go down A large percentage of the population of the Western world has at least one experience of having flown inside a conventional (e.g. non-Vertical Take-Off and Landing) airplane, but only a small percentage of this population has ever been in a helicopter. And while airplanes dominate the aviation world, helicopters only fill small and often unseen niches. Other VTOL airplanes and machines are even less visible. TEXT Jules L’Ortye, BSc Student Aerospace Engineering, Editor Leonardo Times

ver a century ago Thomas Edison stated: ‘The airplane won’t amount to a damn thing until they get a machine that will act like a hummingbird - go straight up, go forward, go backward, come straight down and alight like a hummingbird’ (Edison, 1905). It turns out he was quite wrong. Conventional aircraft like the Boeing 747 require relatively long runways, but have revolutionized air travel in a way few could ever imagine. Aircraft like the Jumbo Jet have made air travel available to the masses. Nonetheless, Vertical Take-Off and Landing (VTOL) aircraft could bring along advantages that could never be acquired with conventional aircraft. Even far before the Wright brothers performed the first powered flight in 1903, designing an aircraft that could hover was naturally one of the goals of Aeronautics. Leonardo Da Vinci was a pioneer in this field. He envisioned a platform that could be take-off vertically by means of an aerial screw spun by human-muscle power. Balloons surfaced in the time that followed, and dirigibles of the balloon were popular near the end of the 19th century. Still, heavier-than-air airplanes could only op-

Leonardo Times DECEMBER 2013

erate from long flat spaces such as runways, level fields or calm surfaces of water. However, some wondered if the same force that pulls an airplane forward could be used to pull an aircraft straight up (i.e. take off vertically). These thoughts hint at why VTOL aircraft are not as practical as they perhaps sound. The thrust and drag forces are usually quite a bit smaller than the lift and weight forces. A conventional aircraft’s thrust might only need to be 10% of its weight in order for the airplane to be pulled forward fast enough to generate enough lift to stay in the air. However, typically this ratio is close to 20%. This means an airplane that weighs 100tons might only need 20tons of thrust to stay in the air. Obviously, a VTOL aircraft that has a weight of 100tons needs 100tons of thrust to get off the ground. Since a conventional aircraft can only deliver a thrust of about 20% of its weight, a VTOL airplane needs five times the thrust of an equivalent non-VTOL aircraft. This might not seem like a difficult issue. One could argue that larger engines will provide the plane with enough thrust to take of vertically. However, the engines carried by a VTOL airplane would weigh

as much as five times or more as the engines carried by an equivalent airplane that does not take off vertically. It is important to know that the engine group is one of the heaviest component groups of an airplane. As a consequence, the useful payload is greatly reduced, and the added weight means the range of the VTOL aircraft will be small in comparison to the range of an equivalent non-VTOL aircraft. Despite this major challenge, an aircraft that could use thrust for lift seemed like a goal worthwhile achieving. Helicopters were successfully flown for the first time in the early 1930s. Similar to today, their roles were limited to situations where the ability to land anywhere and hover were important. These roles include search and rescue missions, medical evacuations, military troop transports, construction aid, and journalism. But the helicopter’s short range, relatively slow flying speed, extraordinary mechanical complexity, and extreme fuel demands designated that a regular winged airplane was used whenever possible. While an aircraft that uses thrust to lift off vertically will evidently be heavier and more complex than a regular airplane, it

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Figure 1. Leonardo Da Vinci devised plans to make a VTOL device using an aerial screw

does not have to be as bad as a helicopter. Helicopters hover all the time. If the aircraft is only required to hover during take-off and landing, while during cruise the thrust can be directed forwards for conventional flight, the aircraft can fly faster, further, and longer, without the need for much more fuel. If this kind of dual-mode VTOL technology could be developed, most of the disadvantages of the helicopter would be abolished. When turboprops were first being introduced right after World War 2, some people noticed that these engines could provide more thrust than the total weight of a conventional airplane. Some airplanes could climb vertically for a certain period of time. Hence, their weight was completely cancelled out by the thrust of the engines. Theoretically, such an airplane can be put on its tail like a rocket, and take off straight up like a rocket. These airplanes are called â&#x20AC;&#x2DC;tail-sittersâ&#x20AC;&#x2122;. In the end, the reason why the tail-sitter concept was abandoned was that any commercial application is obviously non-viable. Just try and imagine how passengers would get in and out of a vertical tube in which they are laying flat down. Furthermore, military pilots stated it would be very difficult to land such an airplane on an aircraft carrier. Now that the thrust issues were solved, engineers focussed their attention on control. But how is a VTOL aircraft controlled? In order to control any given airplane, the aircraft needs airflow over the control surfaces on the wing and tail, something a VTOL aircraft does not experience dur-

ing vertical take-off and landing. All VTOL airplanes face this problem and there are a handful of standard solutions. One could place control surfaces in the downwash airflow of the propeller, eject high-pressure air from little holes in the wingtips, nose and tail or change the angles of the blades on the propeller so that it pulls the airplane in different directions. A solution found often is to turn the orientation of the engines instead of turning the orientation of the whole aircraft. In a so-called tilt-engine design the engines are tilted forward to enable forward flight and control. This was not possible for a long time since the engines were not powerful enough to keep the plane in the air and accelerate it forwards at the same time. The tilt-engine approach was tried in many variations, including some aircraft where the wings turn upwards along with the engines. Eventually, after many accidents and failures spread over several decades, this concept became operational in 1989 in the form of the V-22 Osprey (See cover visual). Instead of moving the orientation of the entire engine, one could also direct the airflow. This was tried in propeller airplanes where the propellers were tilted up into a helicopter configuration and in jets where the engine nozzles could similarly be turned downwards instead of backwards. This thrust-vectoring approach became operational in the infamous Harrier jump jet. Instead of turning the airflow at all, one

could also deflect the air downward after the engines have expelled it. This involves placing bucket flaps behind the engines. While some experimental VTOL aircraft could take-off and land vertically with this system, the system was found most useful in short take-off and landing (STOL) aircraft like the C-17. A fan mounted inside a duct can be made much more efficient than a prop, since there are fewer blade-tip losses, and since the duct itself can act like a diffuser and nozzle, sucking air in the front and accelerating it out the back. Many VTOL airplanes use ducted fans. However, the only successful design up until this day is the Joint Strike Fighter produced by Lockheed Martin. One last approach involves having dedicated engines to produce lift. These engines turn off while flying forwards during cruise. Instead of having one massive engine and a mechanism to rotate it, the aircraft could also have one big engine or a few small ones directed vertically and a small engine mounted horizontally. This may sound like a good idea, but in practice this concept has been proven to be unsuccessful. References Lockheed Martin AirplaneDesign Wikipedia Aviation Week

DECEMBER 2013 Leonardo Times

Column

ARIANE 6: ESA AT A CROSSROADS Focusing on market needs, or maintaining heavy-lift capabilities?

TEXT Ingo Gerth, MSc Student Aerospace Engineering

BUILDING ON HERITAGE When the European Space Agency (ESA) was founded in 1975, one of its first objectives was to build a reliable European launcher. After the previous failure of the Europa rocket program under the European Launcher Development Organization (ELDO), the member states initiated the development of Ariane to ensure European autonomy for accessing space. Work on the liquid oxygen/liquid hydrogenbased launch vehicle started in the mid seventies. Ariane 1 was designed primarily to put two telecommunications satellites at a time into orbit, thus reducing costs with respect to competing launch vehicles. As the size of the satellites grew, Ariane 1 began to give way to the more powerful Ariane 2 and Ariane 3 launchers, which were both evolutions of the former. Ariane 4 was the most successful version of the Ariane 1-derived launcher family. Since its first flight on 15 June 1988 until the last, on 15 February 2003, it was successfully launched 113 times. The vehicle proved to be ideal for launching communication and Earth observation satellites, as well as scientific probes. Because Ariane 4 could be equipped with both solid and liquid rocket boosters, it proved to be versatile—the rocket could place spacecraft between 2000 kg and 4700 kg into Geostationary Transfer Orbit (GTO), nearly three times as much as its predecessor

Leonardo Times DECEMBER 2013

Ariane 3. During its operational life, Ariane 4 secured 50% of the global market for launching commercial payloads. Ariane 4 also reached the limits of the original design, still derived from Ariane 1. Having reached the boundaries of the Ariane 1 to Ariane 4 architecture, the development of Ariane 5 was started—an even heavier vehicle. The new needs proved to required an almost complete redesign with respect to the previous Ariane rockets. EVOLVING MARKETS Today, Ariane 5 is Europe’s workhorse launcher and its story is one of the biggest successes in the history of European spaceflight. But few realize just how well the launch system is performing. In fact, Ariane 5 is now the most successful launch vehicle on the commercial market, holding a share of more than 50% this year, and almost dwarfing its competitors. With a success streak of 57 launches, and twelve launches that met their time window perfectly, its reliability is nearly unrivalled. The only problem: it is expensive

But change is on the horizon. Especially SpaceX of California is of major concern to the established launch businesses around the world. And the demands of the satellite industry are continuously evolving. To remain competitive, ESA and CNES (the French space agency) are now pushing for a successor: Ariane 6.

MAINTAINING LEADERSHIP Europe’s future launcher is being designed to maintain leadership on the commercial market. The project is driven by the “triple seven” goals—seven years of development, seventy million Euros per launch, and seven tons to Geostationary Transfer Orbit (GTO) or 6.5 tons actually, as in the most recent design. Ariane 6 would replace the heavier Ariane 5 rocket, lofting ten tons to GTO, and a concurrent operation of both systems is currently not on the table. Are the triple seven goals the way to go, though? What will be the impact of reducing the maximum payload mass of Europe’s prime launcher that significantly? COMMERCIAL COMPETITION Partially, the push for Ariane 6 derives from the Falcon launcher family provided by the new player SpaceX. This launch service provider currently offers cheaper access to orbit, but must still prove reliable operation. In spite of that, SpaceX already secured an impressive number of bookings, with a current backlog of about five billion Dollars. Recently, the German military decided to have their next-generation reconnaissance satellites flown to orbit by a Falcon 9. Ariane 6 aims to react to the new market situation in three ways: cheaper prices to remain competitive, more flexibility, and indirect compatibility with other systems.

ESA

Ariane 6’s gamble: Fish in Falcon 9’s waters, while keeping the customer base of Arianespace—who trust the proven reliability and timeliness. LOSS OF SOVEREIGNTY? At what price does the “triple seven” come? Ariane is Europe’s sole heavy-lift launcher. It provides a sovereign access to space. Should the development of Ariane

6 thus focus on market needs as strongly as stipulated by these goals? Or should other government interests play a more significant role? The sheer disregarding of governmental interests is potentially dangerous. With a much-reduced capacity, critical payloads cannot be launched with European vehicles any more. Recently, Alphabus was launched at 6.7 tons the heaviest GEO satellite ever—on an Ariane 5. This would have been impossible with Ariane 6 in its current configuration. Many science and exploration missions would need to be launched by foreign partners, because they are too heavy. The James Webb Space Telescope, slated for launch in 2018 on an Ariane 5, is another example. And not to forget, any ESA involvement in human spaceflight would be massively hindered. Not only would

Europe lose the chance of a manned vehicle until a hypothetical Ariane 7 becomes operational (in the late 2030s, or even later?) Europe would even lose the capability of launching large supporting spacecraft such as the ATV. Finally, having to launch heavy European missions with foreign rockets implies significant losses to the taxpayer: Hundred millions of Euros would not be spent in the EC domestic market, but abroad. Can Ariane 6 then maintain its economically viable edge? THE ROAD AHEAD In summary, neither the status quo, nor the plans for Ariane 6 are fully satisfactory. ESA is at crossroads: Should the agency strive for market competitiveness or retain a heavy lift vehicle? The future will tell, and compelling decisions are to be made!

Note by Ingo ESA

The triple seven goals are to be fulfilled by one drastic change: Compared to Ariane 5, it will launch one large satellite at a time and eliminate the need for dual launches. The smaller payload accommodates this. Single launching is much called for, because two customers will not depend on each other for a launch slot any more. It could also enable the compatibility of payloads between Falcon 9, Ariane 6, and potentially other vehicles—an essential risk-mitigation measure for clients.

Ingo enjoys discussing space topics. Together with a group of MSc students he thus founded Vis Viva, a forum for meeting other space enthusiasts regularly. If you enjoy discussing topics just like this, you are encouraged to get involved with the society Vis Viva! You can reach him at ingo@gerth-ac.de, and Vis Viva at info@visiva.nl.

DECEMBER 2013 Leonardo Times

Kick start your career! Netherlands, and takes place each year in the Aula Conference Centre of the TU Delft. This career event is specifically aimed at the students of Delft University of Technology and offers them a wide range of companies and institutions. ‘De Delftse Bedrijvendagen’ kick starts your career with the Application Trainings, Presentations Days, In-house Days and the Interview Days.

Take a look behind the scenes

Prepare yourself for your job interview On the 11th, 12th and 13th of February ‘De Delftse Bedrijvendagen’ offers Application Trainings. The companies will provide you with both general tips and tricks as well as detailed personal advice.

Get to know over 100 national and international companies

UP SIGN FROM RY UA 1 JAN RDS A ONW

From the 17th of March until the 4th of April the In-house Days offer an opportunity to form a better, more complete idea of the companies you are interested in.Your résumé will be forwarded to the companies of your choice. Based on the résumés the companies will select the participants. As the name suggests, the In-House Days are a great way to learn on location about the culture of a company and the projects they work on. On March the 20th an inHouse Day will be held in the Aula Congress Centre in Delft for companies situated far away from Delft. You can sign up for the Inhouse days until the 25th of February - the Tuesday after the Presentation Days.

Take part in one-to-one interviews

On the 18th and 19th of February ‘De Delftse Bedrijvendagen’ hosts its most well-known event, the Presentation Days in the Aula Congress Centre. This fair gives you the opportunity to get to know more than one hundred and forty different national and international companies! There are several ways of meeting these companies. You can visit their information stand or view their company presentation. There is also the opportunity to have your résumé checked. Each day ends with informal drinks together with the recruiters.

From the 23rd of April until the 9th of May ‘De Delftse Bedrijvendagen’ will be completed with the Interview Days. During this period, companies are free to invite students for an interview or simply to get to know the company in more depth. For the Interview Days your résumé will be sent to companies you are interested in, but also to companies that are interested in your degree specifically. You will receive an overview of which companies are interested, and from these you can make a selection.

design: Studio Piraat

Every year ‘De Delftse Bedrijvendagen’ leads 2200 students to the start of their career. If you want to hit the ground running this year, make sure you do not miss this event. Whether you are job hunting or in need of an internship, ‘De Delftse Bedrijvendagen’ offers an unique opportunity to get to know a wide variety of high-profile companies. ‘De Delftse Bedrijvendagen’ is the largest technology oriented career event in the

Participation All activities described above are included in a single price when participating in ‘De Delftse Bedrijvendagen’. On top of this, you also receive a full-color company guide with information about all participating companies. You can participate by signing up via our website, www.ddb.tudelft.nl, or by coming to the Aula Congress Centre on the 21st, 22nd or 23rd of January.

Application Trainings

Presentation Days

In-house Days

Interview Days

February 11th, 12th and 13th

February 18th and 19th

March 17th through April 4th

April 23rd through May 9th

February through May 2014 Sign up from 1 January onwards!

WWW.DDB.TUDELFT.NL

Participation is only € 10,- if you register before January 23rd. From January 24th and onwards participation will cost € 15,-. All personal information will be treated strictly confidential. So if you are looking for a job, an internship or a graduation project, from January on you can subscribe at www.ddb.tudelft.nl!

Organization ‘De Delftse Bedrijvendagen’ is organized by five study societies, that together form ‘The Pentagon’: • Vereniging voor Technische Physica • Gezelschap Leeghwater • Technologisch Gezelschap

• VSV ‘Leonardo da Vinci’ • W.I.S.V. ‘Christiaan Huygens’

ort: In shour job, sis dy the

fin or se ship e Delft n r e int t via ‘D gen’! a ec proj drijvend Be

Take a look behind the scenes

Get to know over 100 national and international companies

UP SIGN FROM RY UA 1 JAN RDS A ONW

Take part in one-to-one interviews

design: Studio Piraat

Application Trainings

Presentation Days

In-house Days

Interview Days

February 11th, 12th and 13th

February 18th and 19th

March 17th through April 4th

April 23rd through May 9th

February through May 2014 Sign up from 1 January onwards!

WWW.DDB.TUDELFT.NL

• VSV ‘Leonardo da Vinci’ • W.I.S.V. ‘Christiaan Huygens’

ort: In shour job, sis dy the

fin or se ship e Delft n r e int t via ‘D gen’! a ec proj drijvend Be

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