DESIGN
SYNTHESIS
EXERCISE
2012
TEXT Ir. J.A. Melkert - Coordinator Design Synthesis Exercise
T
he design synthesis exercise formsthe closing piece of the third year of the Bachelor degree curriculum of 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 stu-dents. In the exercise Systems Engineer-ing plays an important role.
In the design/synthesis exercise, students work in groups of ten, for a period of ap-proximately ten weeks full time on the de-sign of a (part of an) aircraft or spacecraft. Despite the fact that the fi nal designs result from a design process executed by small groups of students with limited experience, it may be concluded that the designs are of good quality. Not only the
scientifi c staff of the Faculty of Aerospace Engineering, but also the external ex-perts and industry which have supported the design projects, have expressed their appreciation of the results. In the fall ex-ercise of this year eleven groups worked on a range of topics. They ranged from designs in the fi eld of aeronautics and space to earth observation and wind en-ergy. The students presented their results in the design symposium held on January 31. During the symposium their presen-tations were judged by a jury consisting out of eight experts from academia and industry.
At the end of the symposium the jury awarded the “Fedde Holwerda Design Challenge Trophy” to the team that worked on the design called “Design of a Jumbo City Flyer”. In addition to the trophy, all team members received a
cer-tifi cate proving this, eternal fame and a group dinner sponsored by the company ADSE. This design focused on the devel-opment of a large short range aircraft primarily aimed at the Asian market. The exercise is coached by multidisciplinary 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.
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he original Rutan Long EZ is ahome-built aircraft with a canard confi gura-tion, designed by Rutan Aircraft Factory in the late seventies. In the previous de-cades, it has served as a General Aviation aircraft bringing pleasure to those who fl y it and their accompanying passengers. In this period, several derivative aircrafts are built, based on the Long EZ. It can be seen as a commonly used, innovative small aircraft typically used for medium range fl ights with a maximum range up to 3,000km.
So why would somebody try to redesign something that is working perfectly fi ne? The answer is simple: To prove that zero emission General Aviation is no longer science fi ction and can be accomplished with currently available technology. With this reasoning, this DSE project regarding the Zero EZE has been initiated. Within a timeframe of ten weeks, numerous ad-justments have been made to the origi-nal Long EZ, which can be summarized by splitting them into three main topics: Propulsion, Aerodynamics and Materials & Structures.
PROPULSION
While aiming at sustainable fl ight, the pro-pulsion system is the most important part
of the aircraft that has to be redesigned. Several options are currently available: Batteries, such as ion, Lithium-Zinc and diff erent types of Air batteries, all promise sustainability. The problem withbatteries, however, is the high weight penalty, the availability of materials and the End of Life disposal issues. Using an alternative fuel such as biodiesel leads to a more sustainable way of fl ying, but this DSE group had something completely dif-ferent and more innovative in mind. In cooperation with the Process and En-ergy department of the University, several options about implementing a Hydrogen based fuel cell have been discussed. When asked if we were joking about putting two human beings into this aircraft, we knew we were onto something new and excit-ing. With an in-house developed program called Cycle-Tempo, two fuel cells have been designed, capable of delivering 70kW each with an effi ciency of 49% and a combined weight of just 90kg. The water produced will be used to cool the fuel cell system, while the excess heat will be used to control the temperature in the cabin. To perform a fl ight of around 1200km with a cruise speed of 155kts, 15kg of Hydrogen will be stored in specially designed 700bar pressure tanks.
AERODYNAMICS
To increase the performance of the air-craft, a low drag body has been designed to store the fuel cell system, the pressure tanks, the electrical motor, the retractable landing gear and all other subsystems, while leaving enough room to provide the pilot and passenger with a comfortable, spacious cockpit. The wings and canard are designed in order to generate more lift to cope with the added weight of the storage tanks and have higher stability during the entire fl ight envelope.
MATERIALS & STRUCTURES
Applying an Advanced Grid Stiff ened structure for the fuselage and a sandwich structure for the wings optimizes the Zero EZE. These methods are validated using a Finite Element Model computer program. The material used for both the wings and fuselage is Carbon Reinforced Fibre Poly-mer, CRFP, resulting in a weight loss of 20% for the structural part alone.
CONCLUSION
The newly designed Zero EZE is an ambi-tious, innovative project indicating that theoretically it is possible to perform me-dium range fl ights with small aircraft, all the while producing zero emissions!
Innovation, sustainability and safety are not the most commonly used words when discussing about General
Avia-tion. A declining reputation and a decrease in demand are not sketching the most fl ourishing future for this
indus-try. By changing the mentality of engineers, authorities and even pilots however, this form of transport could be
revitalized. Within ten weeks, guided by experts, this DSE group has been able to redesign Burt Rutan’s Long EZ by
optimizing its aerodynamics, structure and most importantly developing a fuel cell based propulsion system with
zero emission contributing to an extremely low nuisance factor.
TEXT DSE group 1
TAKING THE NEXT STEP TOWARDS
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n recent years, the growing interestof the space industry in nano-satellite technology has brought about new and exciting possibilities with respect to Earth observation. The idea of forming nano-satellite constellations has made cost-eff ective solutions with high temporal resolutions possible.
The goal of this DSE assignment is to de-sign a CubeSat constellation that can pro-vide competitive near real-time imagery in the visual, near infrared and far infrared spectral bands. This is to be achieved us-ing cameras that have been specifi cally developed for CubeSat use in previous DSE assignments.
The fi rst of these cameras is the ARCTIC, which excels at high sensitivity thermal infrared imagery. The other cameras are ANT-2 TMA and RCC designs, which are improved versions of the original ANT camera. These are used to provide imag-ery in the visual and near infrared spec-trum.
The outcome of this DSE assignment is a constellation named the Competitive CubeSat Constellation for Earth Obser-vation (C3EO). Market surveys on the
rel-evance and requirements of a CubeSat constellation have led to the conclusion that both high spatial and temporal reso-lution are important. To achieve these goals, a three-segment constellation is designed, comprising of 24 ANT-2 RCC satellites at an altitude of 288km and 27 ANT-2 TMA satellites at 500km in sun-syn-chronous orbits, in addition to 37 ARCTIC satellites at 443km in a polar orbit. The satellites’ technical parameters are very similar to each other, with exception of power systems and propellant mass. The constant lighting of sun-synchronous orbits permits the use of lower effi ciency thin fi lm cells in the ANT-2 platforms, while the frequent eclipses of a polar orbit con-strain the use of solar cells in the ARCTIC satellites to high effi ciency triple junction cells. All three satellite types possess elec-trospray thrusters for orbital manoeuvres, such as phasing and drag compensation, as well as an active attitude control. Fur-thermore, all subsystems are employed in a 2-by-2U CubeSat structure such that the cameras and antennas can point nadir si-multaneously. Finally, data downlink is an important driver in the constellation de-sign, given the high data volumes that are generated by the ANT-2 RCC satellites. All
imagery is downlinked by S-band trans-mitters to a total of eight ground stations, which are distributed around the Earth. Together, these segments deliver full Earth coverage in thermal infrared and near full coverage in the visual and near infrared spectrum. Additionally, a tempo-ral resolution of one day with the ANT-2 TMA and ARCTIC platforms is provided, alongside a weekly resolution with the ANT-2 RCC platform. Such a constellation has a wide range of uses, from disaster monitoring to scientifi c research and envi-ronmental protection. Both the TMA and RCC variants are powerful tools in ocean-ography, with the ability to monitor corals and phytoplankton, as well as forestry and agriculture. The ARCTIC camera, in combi-nation with its polar orbit, allows the con-stellation to map surface temperatures across the Earth as well as the ice extent. The cost analysis has shown that the aver-age imaver-age price could be as low as 0.1 €/ km2, almost an order of magnitude lower
than competitors like Rapid Eye. The pos-sibility of selling 2% of all the imagery col-lected at this price shows the economic potential of the C3EO constellation is truly
exceptional.
The advent of Cubesats causes a paradigm shift in space exploration and Earth observation, removing the
lim-its posed by prohibitive costs and high complexity. The exponential advances in commercial-off -the-shelf (COTS)
technology over the last decade have only made this transition easier, with universities and research organisations
alike developing CubeSats and placing them into orbit. Moreover, large companies like Boeing and NASA have also
shown interest in this promising, but yet unexplored territory.
TEXT DSE group 3
CUBESAT
THE MISSION
The Dutch Caribbean Coastguard needs a solution to be able to monitor the ter-ritorial waters, up to 22 km from the coast. The Dutch Caribbean Coastguard current-ly has a fl eet of several boats, airplanes and helicopters to monitor this area. The UAV to be designed has to be able to carry out missions autonomously, while being solar powered and able to land and take off from water. It also has to be able to send real time photo and video imaging back to the ground station.
THE SOLUTION
The solution to this problem is the Drag-onfl y. Now that the fi rst steps have been taken towards solar powered fl ight, it is time to take it to the next level.
The Dragonfl y is a unique combination of solar powered and amphibious fl ight. The Dragonfl y is a tandem wing, twin-engine aircraft. The tandem wing confi guration provides a large surface area for the solar panels and excellent performance at the
22m/s cruise speed.
The Dragonfl y is not only a good perform-ing airplane, it is also a boat. The hull is de-signed in such a way that it will generate hydro-static lift during its take-off run, re-ducing the drag and shortening the take-off run.
The entire topside of the UAV is covered with solar cells, giving it the ability to fl y for 3.5 hours during daytime. On battery power, the endurance is 1 hour of cruis-ing. The wingspan and length are 2.5m. Since it is made from glass and carbon fi bre composites, it only weighs 10kg and the wings can be detached to accommo-date transport and handling.
The Dragonfl y is able to operate fully au-tonomously for an extended period of time and is able to return to base when maintenance is needed. During the time at sea, the Dragonfl y will get its power from the bright Caribbean sun. When the Dragonfl y detects a potentially interest-ing object, it will transmit live footage to the ground station, where they can de-cide what to do. The sensors to perform all this consist of one electro-optical and
one infra-red camera. In the nose there is a built-in pan-tilt camera, which is able to classify, identify and track boats as small as a Yola drug boat. The infra-red option means that even during the night, the Dragonfl y can still perform its mission on a battery load.
The Dragonfl y will be able to monitor the territorial waters of Curaçao for a lower price, while still providing more up to date information. In fact, a fl eet of 200 Dragonfl ies is able to monitor 20 000km2
per day!
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The beautiful island of Curaçao is a holiday destination for thousands of people. The Caribbean island with its
co-lourful houses, its characteristic marine life and the gentle inhabitants are facing a problem: they are located in a
region notorious for its drug traffi cking routes, the so-called Caribbean Corridor. Currently, the Dutch Caribbean
Coastguard is monitoring the region, using boats, helicopters and airplanes.
TEXT DSE group 4
DRAGONFLY
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A growing aviation market, increasing pressure to be environmentally friendly, and rising fuel costs create
busi-ness opportunities for those able to overcome these challenges. To this end, an aircraft was envisioned that can
carry around 500 passengers over a distance of 2,500km, while being cheaper to operate and with a lower
envi-ronmental impact than a Boeing 747-400 on the same mission. To stand a chance in the highly competitive market,
this aircraft needs to have its maiden fl ight by 2025.
TEXT DSE group 6
THE JUMBO CITY FLYER
A
viation is a major player in the world economy and it is growing steadily. It is expected to grow by 5 percent annu-ally in the coming decades and a major part of this increase can be attributed to routes shorter than 2500km. Add to this the rising fuel costs and the growing global pressure on the aviation industry to reduce its environmental impact and it becomes obvious there will be a huge market for short range, economically ef-fi cient, low emission aircraft.At this moment, the short high-capacity fl ights are performed by large aircraft, such as the Boeing 747 or the Airbus A380. These are designed for an entirely diff erent mission and an aircraft opti-mised for a short range high-capacity mission does not exist at this moment. An optimised design such as the Jumbo City Flyer promises lower operating costs and lower emissions.
The Jumbo City Flyer has four turboprop engines mounted under its straight, low-mounted wings. The straight wings are a consequence of the fact that it fl ies at Mach 0.62. On the inside, it consists of a two-deck
passenger compartment, able to seat 514 passengers, and a lower deck cargo compartment able to fi t 32 LD1 contain-ers. The aircraft is powered by liquefi ed natural gas (LNG) and its structure is com-posed mainly of composite materials. The fact that the Jumbo City Flyer fl ies slower than current jet aircraft is because this decreases the drag and the lower fl ight speed means there is no need for swept wings. A lower fl ight speed also in-creases the fl ight time, but only marginal-ly so, since the Jumbo City Fmarginal-lyer will oper-ate on short routes. An advantage of the straight wing is that it provides more lift and has a lower structural weight com-pared to a swept wing. The lower fl ight speed also means turboprops are better suited to the aircraft than jet engines, as turboprops operate more effi ciently at Mach 0.62.
The use of LNG as a fuel means a special fuel system is required, as LNG is stored at around -160°C. The specifi c energy and energy density of LNG lead to a higher fuel volume, but a lower fuel mass, when compared to conventional jet fuel. Next
to that, LNG as fuel reduces the amount of CO2 emitted by the aircraft and the cost of LNG is lower than that of conventional jet fuels. This compensates the disadvan-tages and makes LNG a better option than conventional jet fuels.
All these improvements combined lead to a reduction in fuel consumption and CO2 emissions. The CO2 emitted per pas-senger by the Jumbo City Flyer on a fl ight between Beijing and Hong Kong is 40% lower than that by a Boeing 747-400. The Jumbo City Flyer is expected to have a cost of $170 million, whereas a Boeing 747-400 sells for $350 million. In addition, the Jumbo City Flyer is expected to lower fuel costs by 50% compared to a Boeing 747-400, which can reduce operating costs for an airliner by almost 16%.
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On October 14, 2012, Felix Baumgartner made his record-breaking free fall for the Red Bull Stratos project. This
mission inspired a DSE team of 10 students to design a comparable record-breaking mission of their own:
Strato-Blimp. The StratoBlimp is a next generation high altitude weather balloon system, featuring a UAV that is capable
of autonomous soft precision landings, whilst carrying onboard an HD camera and meteorological sensors. During
the DSE, the StratoBlimp team has designed and constructed a record attempting glider to perform this unique
mission mid-2013.
TEXT DSE group 7
STRATOBLIMP
F
or high altitude atmosphericobserva-tions, meteorological institutes such as the Dutch KNMI still rely on daily measure-ments taken by weather balloons. These balloons ascend to altitudes of up to 35km and may drift as far as 150km from the launch site before bursting. The sen-sor unit hanging under the balloon then descends with the help of a parachute. Be-cause the eff ort and cost involved in fi nd-ing these units is considerable, only the expensive units are retrieved. The cheaper models are not actively collected and only a fraction is returned by honest fi nders. Al-though the meteorological institutes are aware of the impact that the heavy metals contained in the sensor units have on the environment, up until now no sustainable alternative was available.
The StratoBlimp is an autonomous UAV, equipped with an HD camera and meteo-rological sensors, that ascends hanging below a large balloon. As it fi lms its entire mission, including the blackness of space, it falls to the earth at speeds exceeding 400km/h. After four kilometers of free fall it obtains enough velocity to glide back to the initial launch spot or to a diff erent location selected prior to or during the mission. Contact will be maintained with
a station on the ground to send measure-ment data and its GPS coordinates. In return, the ground station may alter the mission target, autopilot settings or land-ing location of the return vehicle. Alterna-tive landing sites can range from roads to rooftops. The tripod-mounted self-directing antenna makes the ground sta-tion easily transportable, which allows all components required for a full mission to fi t into the back of any ordinary-sized car. Deployment takes place in minutes and with a mission time of about three hours, multiple launches a day are possible at any location the size of a soccer fi eld. UAVs today are mainly used in earth ob-servation and espionage, but like previous MAVlab projects, such as Delfl y and Atmos, the StratoBlimp project pushes the use of MAVs to new boundaries. The vehicle will come across a density more than fi fty times lower than that experienced at sea level. Temperatures will drop below -65°C, potentially freezing the electronics and causing ice to form on the wing and trol surfaces. Furthermore, jet-stream con-ditions with wind speeds of over 150km/h will have to be overcome. To comply with local regulations, the mass of the vehicle
should not exceed one kilogram. A safety parachute is ready to be deployed at any time during descent in case of malfunc-tion. With a prototype cost of €2,500, Stra-toBlimp can carry an expensive payload to high altitudes whilst sparing the environ-ment and reducing operating costs. At the Symposium in January, the prog-ress on the prototypes of the return vehi-cle and ground station was displayed. Al-though the designs were completed and the prototypes have been constructed, a lot of time and eff ort will still be required before the StratoBlimp can soar through the stratosphere. Due to the enthusiasm of the group and thanks to the support of the tutors, the project will be continued throughout 2013. The prototype will be further optimized and extensively tested before demonstrating its record-attempt-ing fl ight at the 2013 Cansat competition.
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For some decades, scientists have rigorously investigated the planet Mars. A history of satellites and landers gave
mankind more insight into the origin of the ‘Red Planet’. One question that is still unresolved is the possible
exis-tence of plate tectonics on Mars. The Ancile mission aims to provide a defi nitive answer to this question by placing
multiple probes on the Martian surface. The probes will track their own positions over a period of fi ve years and
any relative movement between these probes will prove the existence of plate tectonics.
TEXT DSE group 8
ANCILE PROBES
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he Ancile mission’s objective is toprove or disprove the existence of plate tectonics on Mars. Plate tectonics is a global phenomenon by which crustal plates slowly move with respect to each other due to a planet’s internal convection streams. The most characteristic results of this process on Earth are the formation of mountains and deep sea trenches when these plates collide. Unfortunately, on Mars these features are less pronounced. The focus of the research is the area known as Valles Marineris (VM), a straight canyon roughly 200km wide and 3,000km long and easily visible from space. It is suspected to be the result of two plates sliding along each other, known as a trans-form fault.
To make sure the mission can prove VM is due to plate tectonics, the movement of both sides of the canyon will be tracked. Knowing plate tectonics on Earth displace the surface by several millimetres each year, the accuracy of Ancile needs to be in the order of one millimetre per year. A technology suitable for the mission is called Very Long Baseline Interferometry (VLBI). The technique uses radio signals from a single source at a great distance, which can be transmitted from the Deep Space Network on Earth. Then, the delay in the arrival of the signals in between
ground stations makes it possible to track the absolute distance between these sta-tions. To map a 3D image of the ground of VM, one seismometer is placed on each station, making sure its origin is deter-mined. Now, we only need to place these ‘stations’ on Mars.
All probes will be transported to Mars housed in a transfer module, consisting of two rings of eight probes placed above each other. The module will spin up and release the probes in two stages before they arrive to Mars, to make sure all of VM is covered by the probes. Although the transfer module will crash on the surface, the individual probes de-spin and deploy infl atable heat shields before entering the atmosphere at a velocity of 5.5km/s. The probe decelerates to a speed of less than Mach 2 before deploying a parachute to further slow the probes down and align them vertically for penetrating the sur-face. The heat shield is reshaped to be stable in the subsonic region after falling through the sound barrier by defl ating specifi c sections of the shield. At 90 m/s the probe penetrates the ground and em-beds its pin into the soil.
The bottom of the housing is covered by a crushable honeycomb structure to reduce peak shocks and absorb 85% of the
kinet-ic energy. The penetrating pin is released from the probe during impact, driving it-self 60cm deep into the ground to place a seismometer out of reach from wind noise. The probes deploy fl exible solar panels by infl ating two tubes, rolling-out a solar panel of 2.7 by 0.3m on the ground. A communication link is established using a phased-array antenna on top of the box. From the point of deployment, the probes need to be operational for fi ve years. Dur-ing this time, their data will be relayed through the Mars Reconnaissance Orbiter and be analysed on Earth. Our DSE group is confi dent the gathered data will conclu-sively determine whether or not Mars is shaped by mechanics similar to the ones we see on Earth.
This mission is named after the shield of the Roman god Mars, Ancile. The myth goes that Mars sent it down from the heavens to the second king of Rome, King Numa Pompilius, as a symbol of luck.
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Looking at the expected growth in global air traffi c, it is urgent that the climate eff ects of contrails are investigated.
With this knowledge, eff ective environmental policies can be developed. Continuous local measurements on
con-trails are required to compare data from satellites, in-situ measurements and lab experiments. The ever increasing
capabilities of UAVs, their low cost, fast development times and fl exible application possibilities make them an
ideal platform to perform such scientifi c research.
TEXT DSE group 11
STRATOMAV
DESIGN PURPOSE
The purpose of this project is to develop a Micro Aerial Vehicle (MAV) that is able to perform stratospheric research on the regional infl uence of contrails on the ground surface temperature. By remain-ing continuously airborne in the strato-sphere for at least a year (which extends the current operating time of UAVs), Stra-toMAV is able to take regular measure-ments on contrails. The collected data is downlinked in near real-time. StratoMAV is constrained to have a total mass of at most fi ve kilograms, a life time of at least fi ve years and a maximum unit price of €50,000.
WING DESIGN
The result is a high effi ciency, low weight UAV with a 7m wide, high aspect ratio wing, which enables a low cruise speed of 18m/s, and a twin boom inverted V-tail. A high camber, thin airfoil has been chosen to generate suffi cient lift, as the air densi-ty is low in the stratosphere. The airframe mass is only 16% of the total aircraft mass. A D-box is placed in the front of the wing. It contains a single spar and is made out of composites to provide high stiff ness,
re-sulting in low defl ection. The aft section of the wing is composed of balsa wood ribs and the wing is covered in lightweight transparent foil.
PROPULSION AND POWER SUBSYSTEMS DESIGN
A single high effi ciency custom tractor propeller (low rpm, fi xed pitch) was cho-sen to operate in the low density condi-tions. It has a diameter of 0.87m, is located mid-wing and is foldable to allow the UAV to glide down during descent. A custom two-stage gearbox with aluminium spur gears enables the low rpm. Power is sup-plied by thin fi lm solar cells and state-of-the-art lithium ion batteries with a high specifi c density. Instead of sizing the batteries for the worst case scenario, the fl ight route was optimized by fl ying at dif-ferent latitudes. As a result, the batteries take up 44% of the total mass.
PAYLOAD AND SCIENCE MISSION
A Paparazzi autopilot system was chosen, together with a modem and a 900MHz patch antenna. A combination of active and passive thermal control is applied.
The carried payload consists of four spec-trometers, one thermal camera and a pro-cessor. Contrail detection is achieved by a pattern recognition algorithm on the thermal data. If a contrail has been de-tected, StratoMAV determines in which direction the contrail is moving and then fl ies along it, making sure that the spec-trometers are aligned with the border of the contrail. The radiation fl ux of con-trails is then determined by measuring the solar and terrestrial radiation. At the end of a contrail, StratoMAV turns around and follows the contrail again in the op-posite direction. Normally, the StratoMAV will continue taking measurements on the contrail until the contrail has faded to such an extent that it is no longer detect-ed by the contrail detection algorithm.
