DESIGN
SYNTHESIS
EXERCISE
2013
TEXT Ir. Joris Melkert - Coordinator Design Synthesis Exercise
The design synthesis exercise forms the closing piece of the third year of the Bachelor degree course at the Faculty of Aerospace Engineering at TU Delft. In this exercise the students learn to apply their acquired knowledge from all aerospace disciplines in one complete design. The object of this exercise is to improve the students’ design skills while working in teams with their fellow students. In the exercise Systems Engineering plays an important role.
In the design/synthesis exercise, students work in groups of ten, for a period of ten weeks full time on the design of a (part of an) aircraft, spacecraft, space mission or wind turbine. Despite the fact that the fi nal designs result from a design process executed by small groups of students with limited experience, it can be con-cluded that the designs are of good qual-ity. Not only the scientifi c staff of the Fac-ulty of Aerospace Engineering, but also
the external experts and industry, which have supported the design projects, have expressed their appreciation of the re-sults. In the spring exercise of this year, 18 groups worked on a range of topics. They ranged from designs of UAVs to large passenger aircraft and from a mis-sion to Mars to swarms of satellites. The students presented their results in the design symposium held on July 4th.
Dur-ing the symposium their presentations were judged by a jury consisting out of 21 experts from academia and industry form seven diff erent countries in Europe. At the end of the symposium the jury awarded the “Fedde Holwerda Design Challenge Trophy” to the team that worked on the design called “Swarm of hybrid MAVs”. In addition to the trophy all team members received a certifi cate, eternal fame and a group dinner spon-sored by the company ADSE. This design focused on a series of hybrid MAVs that
will take part in the IMAV competition in Toulouse this fall. A hybrid MAV is a Micro Aerial Vehicle that can take-off and land vertically, but can also perform horizon-tal fl ight. The exercise is coached by mul-tidisciplinary teams of experienced staff members. Each team has one principal tutor and two additional coaches. These guide the student through the exercise and grade them at the end. Next to that a team of six staff members coordinates the whole of the exercise. This in all makes it the largest educational activity of the faculty.
01
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he reason this switch between tech-nologies is being made can be at-tributed to several reasons: The tips of the blades from a wind turbine are the most eff ective in generating energy. By avoiding the need for all the material in between –namely the hub and the rest of the blades– the same effi ciency in energy extraction can be obtained, which will in turn reduce costs and structural needs. A kite provides the opportunity to achieve the high turning speed of the blade tips whilst reducing the material required by simply using tether lines and a bridle sys-tem. Additionally, higher altitudes with higher wind speed are easily accessible. However, a big challenge this technology has run into is the need for proper and ef-fi cient automation.As part of the Design Synthesis Exercise, an automated launch, landing and stor-age system has been developed to ac-commodate a 70m2 infl atable kite. This
system should operate fully autono-mously for a period of three months, at which point the kite and main line are scheduled to be replaced. It must be ca-pable of performing optimally in a wind speed range of 4 to 25m/s to maximize
the uptime in which the kite can extract energy from the high altitude winds. The fi nal design of such a system is based on a vertical boom of 35m height, upon which a horizontal aluminum beam is mounted with the capability to slide up and down. This horizontal beam serves as a landing platform for the kite when it is positioned at the top of the vertical boom and can then be lowered into a storage equipped with alternating sliding poles. These poles have the task to keep the entire bridle system and kite folded and in tension while stored, to avoid entanglement and damage of the system. As the operation of the kite should be maximized, a deci-sion-making tool was implemented to ensure the kite is stored only when there is the risk of a thunderstorm or if the wind speed range is not met.
The various results that were produced during the design phase lead the way for several conclusions: an optimal auto-mated launch, landing and storage sys-tem has been developed for the pumping kite. This current system generates 30kW of power in average, but can easily be scaled up to generate 150kW. Thanks to
the decision-making tool, a kite uptime of 84% was achieved, which not only ensures that energy generation is maxi-mized but also that the consumption of the system for landing, launch and stor-age is decreased to less than 1% of the produced energy. This, coupled with the fact that the entire structure is built of highly accessible and sustainable materi-als ensures that the environmental bot-tom line is met.
Finally it would be important to point out that despite the system having an initial investment cost of €53,000, this only ac-counts for 4% of the total lifetime costs. By optimizing the kite and line replace-ment procedure and scaling up the gen-erated power to have a rated power of 150kW, this system has the potential to be implemented on a much larger scale and become a common sight in the fu-ture world.
In a world where technologies evolve at a surprisingly fast pace and competition is at an all-time high, it has become
of utmost importance to push innovation to an even greater extent and break through into the unthinkable. This
way, as technologies for wind energy extraction are developed, revolutionizing methods are created that improve
the way in which power is generated. Even though wind turbines have been the core idea of wind power generation,
a trend of using power kites is gaining interest among many research groups and companies all around the world.
The Kite Power Group of the TU Delft has jumped in the bandwagon to use this pumping kite system to harvest high
altitude wind energy.
TEXT
DSE group 1
03
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he objective was to design a control-lable system architecture for the guided atmosphere-assisted deceleration of a vehicle employing an infl atable aeroshell – NASA’s response to the challenge of de-celerating an exploration-class (unprec-edentedly massive) vehicle in the thin Mar-tian atmosphere – to arrive at a particular location in Martian atmosphere with a par-ticular energy level before landing. Unlike a conventional rigid aeroshell whose thermal protection system is too heavy to make the launch economically viable, an infl atable aeroshell can be deployed to diameters far exceeding the limiting dimension – the di-ameter of the launcher fairing. The increase in the surface area that interacts with the atmosphere also makes the aeroshell much more eff ective at decelerating the craft – al-lowing conventional supersonic decelera-tion methods to be used at higher altitudes. To dissipate enough energy, the vehicle needs to interact with the atmosphere more than once. Designing a human-rated system, however, means that reliability and safety are top priorities and the number of interactions should be minimized, reduc-ing the possibility of error and subsequent mission failure. This leads to a maximum of two interactions: aerocapture followed by Entry, Descent and Landing (EDL). Aero-capture reduces the energy frominterplan-etary fl ight to orbital levels while EDL (sans “Landing”) decelerates the vehicle to super-sonic speeds.
Having determined the entrance and exit conditions for the aerocapture maneuver leading to the target orbit from which the vehicle proceeds to EDL, the challenge is to fl y through a 300m x 75m ellipse 13km above Martian sea level at Mach 1.8. Given a maximum lift to drag ratio of 0.3 (as pro-duced by a model that uses the Modifi ed Newtonian method) the aerocapture and EDL trajectories were optimized (with re-spect to heat load in aerocapture and peak g-loads in EDL) by allowing the vehicle’s at-titude to the fl ow to vary within the allow-able angles of attack (dictated by the loca-tion of the stagnaloca-tion point), varying the magnitude of the lift and drag vectors. The resulting aerocapture maneuver dissipates 55% of the vehicle’s total energy, leaving the atmosphere at 4,715m/s to proceed into a 1-sol orbit before descending to the target ellipse in 400 seconds.
An extensive trade-off process led to a concept that creates a double-axis center of gravity off set by displacing the aft cen-ter body to change the vehicle’s attitude to the fl ow through moment equilibrium. The mechanism that displaces the aft body is a double-rail system that provides a total lon-gitudinal displacement of 0.9m and a total
lateral displacement of 0.2m with a mass of 370kg (including driving motors and gear boxes but excluding energy sources). Progressive mass estimates suggest that the control and deceleration system mass fraction (includes thermal protection sys-tem and aeroshell structural mass) can be reduced from 20% to circa 15%.
The controller showed that following the reference trajectory for aerocapture (atmo-spheric anomalies and normal variability excluded) was possible with an error mar-gin of 0.17° allowing the spacecraft to pro-ceed accurately to the target orbit. Despite 5Hz oscillations encountered in some con-trollers for EDL (that are thought to stem from the fact that those controllers are underdeveloped and the reference signal has kinks), the simulation results back the feasibility of this system – hitting the target ellipse at Mach 1.8 is possible with the cho-sen architecture.
Given more time, the project would have led to a more complete design, especially in terms of the vehicle’s structural proper-ties and the reliability of the EDL control-lers. Still, the groundwork has been laid for future endeavors in the hope that mankind can break free from its earthly bounds. For further info, contact the author at alex.minich@gmail.com
From the moment when man fi rst looked up at the stars he has dreamed about the unknown that lies beyond.
According to legend, the articulated ambition to explore the universe fi rst appeared somewhere around 1500 in
China – a Ming Dynasty offi cial Wan Hu attached 47 small rockets to a chair and sat down holding the strings of
two kites to guide his vehicle in fl ight. The explosion that followed led to the loss of a promising spacecraft and an
ambitious man, but the mission that this project builds towards is more ambitious yet – to put man on Mars.
TEXT
DSE group 3
CONTROLLABLE INFLATABLE AEROSHELL
KEES
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oday, wingsuits are more popular than ever. Especially since the development of portable cameras, online wingsuiting videos have inspired many to try the sport. And, where many try, there are also many who fail. The number of fatalities has in-creased dramatically, and since 2008 has even doubled. In 2012, thirteen people lost their lives pursuing Icarus’ dream. Given the small size of the wingsuiting community at about 4000 strong, these numbers are con-siderable.“Almost everyone in the close-knit com-munity has lost someone they cared about to the sport, and many even saw it happen with their own eyes”, says Matthijs Beek-man, responsible for the survey sent to almost seventy parachuting enthusiasts. “We’ve learnt a lot from this survey, espe-cially about which aspects of wingsuiting can be improved”, he continues. The ma-jor issues were stuck zippers when freeing your hands to steer the parachute, lack of stall awareness, and shoulder fatigue after prolonged fl ight. All these issues were due to the unconventional way a wingsuit ‘fl ies’. Like a wise Space Ranger once said: “It’s not fl ying, it’s falling with style.” (Lightyear, 1995)
Wingsuits are designed on a trial-and-error basis, and no-one had a clue of the
associ-ated fl ow behavior. This project is the fi rst scientifi c approach to this design process and the specifi cs of wingsuits had to be dis-covered. The team contacted Phoenix-Fly, a major wingsuit manufacturer, for advice. Fortunately, Dutch top-dog wingsuit fl yer Jarno Cordia was able to provide a solid ba-sis of knowledge for the group to build on. To get an understanding of the fl ow around a wingsuit, the group set up a qualitative windtunnel test. Using smoke and tufts, the fl ow separation became clearly visible on a portion of the leg wing, as well as be-hind the parachute. The discovery of a sec-ond leading edge on the wingsuiter’s arm, which arises due to leading edge morph-ing, was also surprising.
An approximation of the shape was made by fi tting two airfoils on end. Several varia-tions of these shapes were made, and then run in JavaFoil and XFLR5, two potential fl ow programs, at typical wingsuiting Reynolds numbers between 1.63*106 and 5.44*106. These methods were validated with experimental data from a NACA0021 airfoil. For a more quantitative analysis, a CFD program was used for the fi nal selec-tion of the right two-airfoil model to repre-sent a wingsuit.
In addition to developing a new model, the aforementioned safety issues were
addressed with revolutionary new inven-tions. A passive fl ap, as employed by birds, splits reversed fl ow at high angles of at-tack, increasing lift. Fully deployed, it can trigger an audible stall warning to increase the pilot’s situational awareness. Another improvement is a droop leading edge, which can be directed downwards to mo-mentarily increase lift, enabling the pilot to maneuver out of dangerous situations. Furthermore, reenergizing tunnels, start-ing at the wstart-ingsuiter’s sternum and endstart-ing behind the parachute, counter the bound-ary layer moment defi cit caused by the sudden end of the parachute container. (Tilmann, 1999) Vortex generators pull the fl ow inside the boundary layer, thus ener-gizing it. In the new design, the infl atable wing parts are connected so they infl ate evenly, solving this problem during the exit. The bottom of container is also altered to lie on the wingtip. This prevents the pi-lot chute getting stuck in the low pressure region behind the wingsuit. The problem of malfunctioning zippers was solved by a smart cable release system, coupled to the parachute, the new standard.
These inventions allow one to fall in style, safely. We predict that with the necessary improvements, wingsuiting will become an extreme sport accessible to anyone. Blue skies!
04
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Similar to other amazing stories about aviation, this story starts with the famous tale of Icarus. The Greek son of
the master craftsman Daedalus dreamt of human fl ight and used feathers and wax to build his own set of wings;
his own personal wingsuit. Ever since, men have tried to imitate birdfl ight with various constructions. The fi rst
re-corded attempt of a construction similar to present wingsuits dates back to 1930. A sailcloth was used between the
legs to increase horizontal movement and maneuverability during skydiving. In the meantime, the classic wingsuit
has evolved into a ram-air infl ated extreme sports monster.
TEXT
DSE group 4
05
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As resources are depleting and worldwide consumption is increasing, human kind needs to rethink the way things
are made in order to maintain the current quality of life. Cradle to Cradle® provides the basis for designing a
self-sustaining product which positively infl uences its environment. The aim of Cradle to Cradle® is to eliminate the
concept of waste while making use of renewable energy and preserving ecological diversity. Since Cradle to Cradle
has never been applied in aerospace engineering, the goal of this DSE project was to design a Cradle to Cradle
air-craft that could enter service by 2025.
TEXT
DSE group 5
AIRCRAFT DESIGN USING CRADLE TO CRADLE
Today’s general aviation manufacturers take no eff ort into implementing proper end-of-life plans in their business plan. Instead, they focus on creating long last-ing, reliable aircraft without considering their ecological impact. The reason for this is the lack of profi tability of end-of-life operations on today’s aircraft, as they are often made from a large amount of diff er-ent materials, which can not be recycled properly due to impractical design. The Infi niCraft is a competitive, reliable, two-seater general aviation aircraft, com-parable to a Cessna Skycatcher. The In-fi niCraft looks like most high wing aircraft, has a range of 1,000 km, a cruise speed of 200 km/h and a maximum power of 103 hp. However, the Infi niCraft is 93% eco-nomically recyclable. 89% can even be re-cycled according to the Cradle to Cradle principles with today’s techniques. This means that materials regain their original qualities and properties after recycling.
PROPULSION
For the propulsion system, bio-ethanol E100 was chosen because of its high avail-ability prospects in 2025. Ethanol is made from various biological sources such as switchgrass, sugarcane, corn or waste. It is much cheaper than conventional avgas. A downside is the lower energy density,
which leads to a heavier fuel load. This is partially compensated by higher engine effi ciency. Depending on the biological source for the fuel, the eff ective CO2 emis-sion can be reduced to 0 kg/h. A three blade propeller was chosen, which gives the aircraft a far fi eld noise of 60.4dB. With this noise level, the Infi niCraft will always obtain the lowest possible landing fees.
STRUCTURES & MATERIALS
The primary structure of the Infi niCraft is built from the automotive aluminium al-loy, Al-6022. In this way, the market for re-cycled aluminium is much larger. Further advantages of this choice are the alloy’s low cost, good corrosion resistance and formability. After an analysis, it appeared very feasible to design an aircraft with this alloy. The design life of the Infi niCraft is 15 years, in order to account for the lower fa-tigue resistance. The secondary structures of the Infi niCraft are made from thermo-plastic composites and polycarbonate. The front window and doors are made from polycarbonate, a material that is of-ten used for the canopy of fi ghter aircraft. The use of this material allows for a trans-parent design, which is a distinctive fea-ture of the Infi niCraft. Finally, the interior design is customer based, using Cradle to Cradle materials.
AVIONICS
The Infi niCraft will be installed with the basic six: altimeter, airspeed indicator, turn and bank indicator, vertical speed indicator, artifi cial horizon and heading indicator. For the other instruments and fl ight documents the pilot uses a portable device, such as an iPad. This reduces the weight of the aircraft and allows for easy updates and changes to the layout.
LEASE STRUCTURE
Instead of selling the aircraft, a lease con-struction is set up. The aircraft can be leased for 2, 8, 10 or 15 years. This gives pilots more freedom at lower fi nancial risk, while it gives the manufacturer more control over the end-of-life phase of the aircraft. An operator culture is established where pilots do not own the aircraft, but operate it for a specifi ed amount of time, after which the manufacturer is respon-sible for its further operations. Where a comparable aircraft would have an hourly cost of $137, the Infi niCraft costs $130 per fl ying hour (total cost of ownership) based on a 15-year lease contract. The Infi niCraft is therefore competitive with current gen-eral aviation aircraft, and serves as an in-spiration for the aerospace industry. With Infi niCraft, Cradle to Cradle in aircraft design has become reality!
M O D EL : K O EN V A N D EN K IE B O O M , B A CK G RO U N D : K EY SH O T
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Since the aerospace industry continuously focuses on effi ciency improvement, new technologies are constantly
under development. Innovative Active Flow Control (AFC) systems have the potential to increase the performance
of aircraft in terms of lift enhancement, drag reduction, and noise reduction, contributing to a more sustainable
aviation industry. Currently there is no platform available on which these can be tested cost-effi ciently in real fl
y-ing conditions. To this end, this project was initiated to “develop an experimental cost-effi cient platform, aimed at
testing current and future fl ow control technologies in real life conditions, by ten students in eleven weeks”.
TEXT
DSE group 6
FLOW CONTROL X-PLANE
O
ne of the challenges was to accom-modate both present and future AFC systems. To this end an elaborate litera-ture study has been performed, focusing on state of the art AFC actuators and cur-rent experimental developments. AFC systems manipulate the airfl ow around an aerodynamic body under the constant supply of energy, as opposed to for exam-ple wing fl aps, which are considered pas-sive fl ow control. Cutting edge measure-ment systems have been investigated as well. Particle Image Velocimetry (PIV) is a technique to visualise the boundary layer over an aerodynamic shape. Our design features such a system in fl ight, which is ground-breaking.To make the testing aircraft as costeffi -cient as possible, the system should be able to test all kinds of active fl ow control systems on one aircraft. Simultaneously, to maximise testing versatility, the aircraft should be able to test on various wing shapes, such as varying sweep and taper. The resulting design consists of a modi-fi ed Boeing 737-500. The 737-500 has a structurally overdesigned wing and tail for its fuselage size, allowing cost-effi cient modifi cations. The wings have been rede-signed to accommodate modular testing panels. These test panels contain
mea-surement equipment and active fl ow con-trol systems. They can easily be taken out and replaced by panels that contain diff er-ent systems. The test panels themselves are designed to be non-load carrying, so the structural load is carried by a new top skin of the wing box, located 5cm below the upper surface. Each panel location on the wing provides for plugs for high volt-age power, low voltvolt-age power, pressure, PIV laser, and data handling cables. To test diff erent wing shapes or more de-manding active fl ow systems, a second wing is mounted on a pylon structure on top of the fuselage. The wing is replace-able, allowing for testing of any wing shape with a surface area below 8m² and a wing span of up to 8m. Unconventional wing confi gurations and even morphing wings can be mounted. Structurally de-pendent actuators, like rotating wing sur-faces, can effi ciently be tested on top of the pylon. The supporting structure allows rotation of the testing wing so that the test wing angle of attack can be changed independently of the angle of attack of the entire aircraft. The pylon structure is mounted directly to the reinforced fuse-lage frames to prevent excessive stress in the fuselage skin. It is detachable, so tests on the main wing can be performed
without interference. One disadvantage of using this wing is that the maximum cruise Mach number is restricted to 0.5, so any transonic testing has to be done on the main wing. Also, due to its smaller size, the Reynolds numbers achieved are signifi cantly lower than on the main wing. The interior of the aircraft is stripped of passenger seats and contains an engi-neering booth for engineers to analyse data in-fl ight. The fuselage also holds ex-tra fuel removed from the main wings in the cargo hold, and it contains systems to provide power, data storage, diff erential pressure, and data processing for sup-porting active fl ow control systems and measurements.
Concluding, we believe that the Flow Con-trol X-plane can be very valuable in test-ing active fl ow control systems. The main wing allows for testing on large Reynolds numbers and transonic testing, while the pylon test wing provides an enormous versatility in wing shapes. The removabil-ity and modularremovabil-ity of both the test pan-els on the main wing and the entire test wing on the pylon ensures a very versatile design, which together can test virtually any fl ow control system currently under research. It even ensures for extra margins to test systems developed in the future.
BOB
R
09
09
With fossil fuels depleting, the world needs new energy sources. One alternative is fusion energy using helium-3.
Helium-3 is diffi cult to obtain on Earth, but abundant on the Moon. DSE group 9 designed an end-to-end system for
lunar helium-3 mining and assessed its feasibility. The mission has to provide for ten percent of the global energy
demand in 2040. All mission elements were designed conceptually, with two transport vehicles being designed in
full engineering detail.
TEXT
DSE group 9
LUMINO
THE PROBLEM AND ITS SOLUTION
Helium-3 fusion is frequently quoted as a major reason to go back to the Moon. In-dividual aspects of lunar helium-3 mining have already been designed. However, so far no one has looked at the feasibility of the overall mission. On behalf of ESA, an end-to-end mission was designed and its feasibility was assessed.
Predictions show that in 2040 the total global energy demand will be between 2.05 to 2.26 ∙1011MWh. To supply ten
per-cent of this energy, two hundred tons of helium-3 is required per year. In the lunar regolith, this isotope is found in concentra-tions of at least twenty weight parts per billion (wppb). The reserves on the Moon could last for thousands of years.
CONCEPTUAL END-TO-END MISSION
Multiple trade-off s between various mis-sion concepts have been performed. The fi nal concept can be split into six elements: The ground segment, LEO access, LEO space dock, Continuous-Thrust Transfer Ve-hicle (CTTV), Lunar Surface Access Module (LSAM), and lunar operations. Each element handles payload canisters of 10.8 tons (2.3 tons of liquefi ed helium-3).
Payload is exchanged between Earth and a space dock in LEO via a Skylon space plane. The space dock performs maintenance and refuelling of the CTTV and stores up to
eight canisters.
The CTTV uses electromagnetic propul-sion for spiral transfers between Earth and Moon. Due to the high power demand (1.2MW), a small on-board nuclear fi ssion plant is required. The CTTV carries four can-isters.
Once the CTTV is in lunar orbit, the LSAM ascends from the lunar base and docks. Helium-3 canisters are exchanged and the LSAM returns to the base. The LSAM carries two canisters per fl ight and is powered by in-situ methane and oxygen.
To supply two hundred tons of helium-3 per year, 640 tons of regolith has to be pro-cessed per second. A total of 2000 mining vehicles are needed, such as the Mark III volatile miners designed by the University of Wisconsin. A lunar base processes the volatiles. The mining operation requires a total of 39GW, supplied by 390 autono-mous nuclear fi ssion plants.
COST ANALYSIS AND FEASIBILITY
It was found that the lunar operations and the fusion plants have the greatest impact on mission cost. Total annual mission cost is 427 to 1347B€. Resulting energy prices for fusion energy are higher than prices for energy from solar, wind, and natural gas. The expected annual profi t ranges from -720 to +260B€, for the worst and best case, respectively. To address scalability, the
mis-sion was additionally evaluated for 0.1% and 1% of the global energy demand. The expected profi t decreases if the mission size decreases and can even be negative for both best and worst case.
Technically, the mission is extremely chal-lenging, due to the unavoidable complex-ity. Most required technologies exist, with the exception of commercial fusion energy itself.
The mission may produce a positive net profi t, depending primarily on how the en-ergy price develops, and thus may be eco-nomically feasible. However, the initial in-vestments are extensive and would have a substantial impact on the world economy. Under current international law, exploita-tion of the Moon may only occur in inter-national partnerships, which have to make the mined resources available to all coun-tries. A large-scale mining operation would have severe impact on the lunar surface and atmosphere. The mining operation and the necessary use of nuclear fi ssion plants render the mission unsustainable.
CONCLUSION
Many challenges have still to be addressed to make lunar helium-3 mining possible. This end-to-end feasibility study showed that lunar helium-3 mining is unsuitable for contributing a signifi cant amount of en-ergy in 2040.
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The current economic climate requires ever-increasing aircraft performance and effi ciency. A way of achieving
this is by a smarter aerodynamic and structural design of the airframe, using novel materials and production
pro-cesses. Examples of this trend are the Boeing 787 and the Airbus A350, which feature composite wings, where the
structural deformations and the aerodynamic behaviour infl uence each other. The dynamic interaction between
the fl ow and the structure can be simulated in Fluid-Structure Interaction (FSI) solvers. Since only little validation
data is available for FSI solvers, the T-FLEX experiment is designed to provide this.
TEXT
DSE group 13
T-FLEX
F
SI solvers have become crucial in the design of modern aircraft. Therefore, it is important that these are able to solve the simulations rapidly, which could come at the price of accuracy. To validate FSI solvers for commercial airliners fl ying at transonic velocities, more data is required. This will be provided by the T-FLEX. Failing to validate an FSI solver can cre-ate an incorrect analysis, which can prove disastrous due to aeroelastic eff ects. Aeroelasticity is defi ned as the dynamic interaction between a structure and a fl ow fi eld. Several phenomena result from aeroelasticity, such as fl utter and the tran-sonic dip. Flutter is an unstable dynamic response, where the structure and the aerodynamic loads excite each other. As a result, the amplitude of the response rap-idly increases until the structure fails. The speed at which the structure fl utters is de-fi ned as the fl utter speed. The curve con-necting all the fl utter speeds for a given Mach number range is called the fl utter boundary. This fl utter boundary displays the transonic dip as a sudden decrease in the fl utter speed.EXPERIMENT
The experiment is performed in the TST-27 wind tunnel located at the TU Delft. In order to effi ciently provide data for the FSI solvers, it is important that the interaction
between the aerodynamic loads and the structure of the model is measured, and is provided to the solver. Besides the mea-surement data from the experiment, it is also important that the boundary condi-tions and the model properties are pro-vided. Furthermore, the model is tested non-destructively throughout the experi-ment.
DESIGN
The design of the model is driven by the size of the test section of the wind tunnel, due to its limited size. The behaviour of the model changes due to downscaling. Downscaling the model leads to frequen-cy increase which makes it more diffi cult to measure. The optimization process strives to decrease the fi rst natural fre-quency of the torsion and bending mode, while preventing fl utter occurrence. The fi nal structure of the model was obtained via an iterative process, where the fl utter boundary and the thickness of the model proved to be driving. The fi nal design is a hollow shell model with a skin thickness of 3mm, no sweep and a taper ratio of one. It has a length of 230mm, a chord of 150mm, a NACA 64A-010 airfoil and is manufactured from chopped roving re-inforced polyester. Additionally, a fl ap is used to actuate the model.
MEASUREMENT TECHNIQUES
Due to the limited space within the wind tunnel, mainly visual measurement tech-niques are used to obtain the valida-tion data. Furthermore, the high natural frequencies of the bending and torsion modes require high speed cameras to sample the response, such that it can be reconstructed. Particle image velocimetry is used to obtain the fl ow fi eld around the model, this is a technique that visually measures particle displacement. Model deformation data is gathered using vid-eogrammetric model deformation, which measures the displacement of targets that are placed on the model. Finally, a combination of pressure sensitive paint and pressure transducers allows the pres-sure distribution on the surface of the model to be obtained.
CONCLUSION
By providing validation data for FSI solv-ers, future numerical solvers will be able to simulate the aeroelastic eff ects with more accuracy and certainty. This will decrease the cost and eff ort for research and development and increase the per-formance and reliability of commercial airliners.
For more information about the T-FLEX experiment, please contact tfl exdse@ googlegroups.com.
14
Environmental issues have been the subject of discussions for decades. Companies all across the world have
de-veloped strategies of meeting the needs of the present without compromising the ability of future generations to
meet their own needs. One of these strategies is to invest heavily in the organization of annual events that raise
awareness of sustainability. In this sense, the Shell Eco-marathon is an event that challenges young engineers to
push the boundaries of fuel effi ciency through designing, building and testing ultra-light Fuel Effi cient Vehicles
(FEV’s).
TEXT
DSE group 14
ECO-RUNNER 4
THE GOAL
The project focuses on designing a FEV to participate in the Shell Eco-marathon of 2014 and win it. Winning implies that the vehicle consumes the least amount of en-ergy after driving ten laps on a given track around Ahoy, Rotterdam. The Eco-Runner 4 is designed to compete in the battery-elec-tric class of the competition. As one might know, there already exists a TU Delft team competing in the Shell Eco-marathon. An-other goal of the project is to improve their design (the Eco-Runner 3) and this team greatly supported the project with advice. In return, the DSE provided new insights.
BODY
The body of the Eco-Runner 4 was designed by means of a carefully carried out aero-dynamic and structural analysis. As far as the aerodynamics is concerned, the body consists of several airfoils that reduce the drag of the vehicle signifi cantly. Moreover, fairings are installed around the wheels, which decrease the drag even further. The structural performance of the body was verifi ed using fi nite element analysis, leading to a minimum body weight. It was chosen to construct the body from carbon fi bre (Toray T300) and sandwich panels (Nomex). The body should be produced by vacuum bagging.
WHEELS
Spoke wheels were chosen for the new de-sign. Although disk wheels are aerodynam-ically better, the fairings around the wheels allow the weight reduction from spokes without creating extra drag. Furthermore, the wheels are fully made from carbon fi -bre and the rear wheel has a turbine blade spoke pattern. Since an in-wheel motor is used to propel the vehicle, manufacturing could become cumbersome. To overcome these diffi culties, a specifi cally designed manufacturing process is followed, involv-ing lay-up, adhesives and curinvolv-ing. Each front wheel weighs only 800g, whereas the rear wheel weighs a mere 1,100g due to the larger wheel hub that is required for positioning of the in-wheel motor.
SUSPENSION
The front suspension of the Eco-Runner 4 is really revolutionary in the fi eld of FEV’s. The front suspension is integrated in the wheel fairings, leading to an extremely low weight of only 330g. Since the Eco-Runner 4 is rear-wheel steered, the rear suspension should allow turning of the wheel. This complicates the suspension and results in a four carbon fi bre rod system weighing 1,300g.
ELECTRONICS
As stated above, the vehicle is equipped with a customized brushless in-wheel
mo-tor from Mitsuba. The effi ciency is at least 93% and requires only 50W. Furthermore, space rated solar cells with an effi ciency of 29% are installed on the top of the body. The rules of the competition state that only 0.17m2 of the body surface may be covered
with solar panels. These cells generate an extra power of approximately 37.5W.
OVERALL VEHICLE
Assembly and integration of all subsys-tems yield the complete Eco-Runner 4. The total vehicle weight is estimated to be 23.6kg, which is a weight reduction of 45% when compared to the Eco-Runner 3. A race simulation tool was developed to esti-mate the fuel effi ciency of the vehicle. The simulation resulted in an ideal energy effi -ciency of 2,110 km/kWh which is compara-ble with a fuel effi ciency of almost 19,000 km/L of ordinary gasoline. Although this energy effi ciency is an estimation under ideal circumstances, it can be concluded that the Eco-Runner 4 is capable of per-forming very well in the upcoming edition of the Shell Eco-marathon. More impor-tantly, it can be concluded that ordinary cars can become a lot more fuel effi cient when certain concepts from FEV’s such as wheel fairings and weight optimization are employed. In this way, the ecological foot-print per car can be reduced signifi cantly and the needs of future generations can be satisfi ed.
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The miniaturization of satellites has made space accessible for universities by making use of piggy-back launch
op-portunities. The limits in budget and manpower call for the design of small spacecraft, which on their own cannot
compete with large space projects. CubeSats off er a unique opportunity for students to obtain hands-on
experi-ence by working on nano-satellite projects such as DelFFi, which consists of two 3U CubeSats in formation fl ight.
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PHI CUBESAT FOR FORMATION FLYING
F
ollowing the success of the Delfi -C3and the completion of the Delfi -n3Xt assembly, the Delft University of Technol-ogy started the development of its third nano-satellite project, DelFFi. Delta and Phi are scheduled for launch in 2015, and will form part of the QB50 network which is an initiative of the Von Karman Institute in Belgium. This network consists of fi fty CubeSats in Low Earth Orbit (320km initial altitude) performing in-situ atmospheric measurements. The mission lifetime is expected to be three months. Using com-mercial off -the-shelf (COTS) products, the Phi satellite aims to become a feasible yet novel CubeSat in terms of its unique mis-sion objectives.
FORMATION FLYING
The primary objective of DelFFi is to demonstrate formation fl ying between the two CubeSats. This has never been achieved for nano-satellites. The objective would be deemed successful if the satel-lites can maintain an along-track distance of 1000km. Two types of formation fl ight will be carried out. The fi rst is through the use of propulsion. A ΔV budget of 15m/s has been decided upon together with the Delta group to perform a variety of ma-neuvers for acquisition, formation keep-ing, as well as reconfi guration.
The second kind of formation fl ight is by using diff erential drag. The satellite design incorporates fl aps to increase the drag co-effi cient by up to a factor of three to adjust the relative decay rates. This technology is ideal to carry out moderately precise ma-neuvers of high negative ΔV and could be envisaged for the fi rst part of the ap-proach during debris removal missions. The demonstration of formation fl ight in general constitutes a stepping stone to-wards high-coverage missions with the potential for reconfi guration, such as tele-communication for remote areas.
PRIMARY PAYLOAD
To take part in the QB50 project, all par-ticipating satellites must carry and oper-ate one of two sets of selected sensory payloads for atmospheric research. The Phi satellite was assigned the FIPEX pay-load developed by TU Dresden. This sys-tem measures the atomic and molecular oxygen concentrations. Next to this, the CubeSat must carry twelve thermocou-ples which will provide data to model the fl ow fi eld around the satellite.
SECONDARY PAYLOAD
Apart from the primary payload, TU Delft was free to defi ne its own secondary
mis-sion objective. For the Phi satellite, there will be two mission objectives. The cor-responding secondary payload thus con-sists of two nano-cameras for monitoring the deployment of solar panels and an-tennas, and acoustic sensors for analyzing the satellite’s vibrations.
SUSTAINABILITY
For the sustainability aspect, the low ini-tial altitude of the Phi mission has a milder radiation environment, which allows for the use of low-cost COTS products. Care is taken in ensuring that the chosen COTS products are environmentally friendly, such that waste is reduced in the produc-tion process and no toxic materials are used. Furthermore, the low initial altitude translates into a short mission life, at the end of which the satellite will de-orbit it-self and be disposed of during re-entry, leaving no contribution to the space de-bris. All in all, the Phi satellite holds vari-ous potentials for scientifi c investigations and incorporates original elements that will contribute to educational purposes.
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Private fl ying is a hobby practised by thousands of people, a hobby which enables them to experience the ultimate
freedom of fl ight. However, private fl ight is not accessible to everyone, due to the high purchase and operating
costs of aircraft and the strict licences required to fl y them. These drawbacks are taken away by powered
para-chutes, also called paraplanes. Current paraplanes are highly uncomfortable to fl y however and are limited in their
use, due to the restriction of having to land on level ground. An improved design of the powered parachute is thus
required: enter the Parashuttle 2.
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PARASHUTTLE 2
MISSION
Parashuttle 2 has been designed to be ‘the world’s fi rst two-person, closed-cockpit, amphibious paraplane, able to compete with other microlight aircraft on the mar-ket’. This means Parashuttle 2 should of-fer superior comfort compared to cur-rent paraplanes, be cheaper than curcur-rent light sports aircraft and operate on both land and water. Parashuttle 2 has been designed keeping in mind that one per-son should be able to carry out its typical mission, consisting of transport, prepara-tion for fl ight, taxi and take-off , the actual fl ight, landing and post-fl ight activities. Design and performance aspects will be gone through in this order.
PRE-FLIGHT
Parashuttle’s two fl oats allow for transport on an internationally road-legal trailer and provide support and stability on both land and water. Wheels with diff erential brakes and back-mounted rudders allow for steering during taxi. Parashuttle’s spacious fuselage enables parafoil storage when not in use, before fl ight this parafoil is to be unfolded, connected, infl ated and placed on its back behind the vehicle. In fl ight the fuselage seats two passengers in-line. In total 180kg of payload can be carried.
FLIGHT
During take-off , the 48kW petrol engine linked to a four-bladed carbon fi bre
pro-peller accelerates the vehicle, causing the parafoil to generate lift in the process. Take-off distances are 37m and 60m on land and water respectively. During fl ight the pilot has longitudinal control by in-creasing or dein-creasing engine thrust as desired. At maximum power a climb rate of 4.7m/s is obtained. Two control levers, which the pilot controls using his hands, provide lateral control. If needed feet ped-als can be used for steeper turns and fl ar-ing. These allow for a minimum turn radius of 41m.
During such manoeuvres and during land-ing Parashuttle 2 will experience loads up to 3g. Its fuselage has been designed to handle these loads, additionally a safety factor of 1.5 was added. Using fi nite ele-ment methods an effi cient structure was designed that allows for fi ve failures be-fore a failure within the fl ight envelope. Parashuttle’s 66L fuel tank gives it a range of 200km. At a cruise speed of 55km/h this gives an endurance of 3.7 hours. Parashut-tle’s fuel consumption results in operating costs of around €30/h. Finally landing dis-tance is 37m and 70m on land and water respectively. All these performance fi gures have been found to be fully comparable to current paraplanes.
POST-FLIGHT
After fl ight the vehicle should be taxied to its storage and the parafoil should be
dried, folded and stored. Maintenance on Parashuttle 2 most often consists of visual inspection. Regular maintenance, such as an engine overhaul, is required at speci-fi ed time intervals.
POTENTIAL CUSTOMERS
Three distinct customers are foreseen for Parashuttle 2. First there are recreational fl yers, who would like to fl y more comfort-ably than in current paraplanes but don’t want to pay in excess of €50,000 for a light sports aircraft. Governmental agencies might make use of Parashuttle’s slow fl y-ing capabilities and low operaty-ing costs by using it for aerial observations. Finally commercial agencies can utilise Parashut-tle’s amphibious characteristics by using it for sightseeing activities, even at remote tropical islands.
FINANCIAL PROSPECTS
Starting the production of Parashuttle 2 requires an investment of €830,000, this investment gives the prospect of produc-ing a thousand Parashuttles over the fol-lowing ten years. Selling Parashuttle 2 at €32,660 (which is 10% above the produc-tion cost) results in breaking even at the 281st unit and a fi nal profi t of €2.15 mil-lion, which equals a return on investment of 2.6. As such, Parashuttle 2 is an attrac-tive project for investors and an attracattrac-tive prospect for customers, who see their ex-perience of fl ight move one step closer.
