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Fusex 2007-2008 :LEIA (CLES-FACIL, INSA de LYON)
Fusex 2007-2008 :LEIA (CLES-FACIL, INSA de LYON)
Fusex 2007-2008 :LEIA (CLES-FACIL, INSA de LYON)
Fusex 2007-2008 :LEIA (CLES-FACIL, INSA de LYON)
Fusex 2007-2008 :LEIA (CLES-FACIL, INSA de LYON)
Fusex 2007-2008 :LEIA (CLES-FACIL, INSA de LYON)
Fusex 2007-2008 :LEIA (CLES-FACIL, INSA de LYON)
Fusex 2007-2008 :LEIA (CLES-FACIL, INSA de LYON)
Fusex 2007-2008 :LEIA (CLES-FACIL, INSA de LYON)
Fusex 2007-2008 :LEIA (CLES-FACIL, INSA de LYON)
Fusex 2007-2008 :LEIA (CLES-FACIL, INSA de LYON)
Fusex 2007-2008 :LEIA (CLES-FACIL, INSA de LYON)
Fusex 2007-2008 :LEIA (CLES-FACIL, INSA de LYON)
Fusex 2007-2008 :LEIA (CLES-FACIL, INSA de LYON)
Fusex 2007-2008 :LEIA (CLES-FACIL, INSA de LYON)
Fusex 2007-2008 :LEIA (CLES-FACIL, INSA de LYON)
Fusex 2007-2008 :LEIA (CLES-FACIL, INSA de LYON)
Fusex 2007-2008 :LEIA (CLES-FACIL, INSA de LYON)
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Fusex 2007-2008 :LEIA (CLES-FACIL, INSA de LYON)

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Dossier de clotude du projet Leia (fusee experimentale)

Dossier de clotude du projet Leia (fusee experimentale)

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  • 1. LEIAClosing Document CLES-FACIL 2008 http://cles-facil.insa-lyon.fr cles-facil@insa-lyon.fr
  • 2. Table of ContentsProject Goals................................................................................................4 1.1 Cansat.................................................................................................4 1.2 Recuperation System..........................................................................5 1.3 In-Rocket Measurements....................................................................5 1.4 Integration of the New Motor..............................................................5Developed Solutions....................................................................................6 1.5 Cansat.................................................................................................6 1.5.1 Structure..........................................................................................6 1.5.2 Ejection............................................................................................7 1.5.3 Original Parachute System...............................................................7 1.5.4 Radio Link........................................................................................8 1.5.5 Control.............................................................................................9 1.5.6 Recuperation....................................................................................9 1.6Recuperation system.........................................................................10 1.6.1 Ejection Mechanism.......................................................................10 1.6.2 Double Parachute System..............................................................11 1.6.3 Timer..............................................................................................11 1.7 Measure in the rocket.......................................................................12 1.7.1 Accelerometer................................................................................12 1.7.2 Pressure Sensor.............................................................................12 1.7.3 Camera..........................................................................................13 1.8 Integration of the new motor............................................................13Results and analyses..................................................................................15 1.9 Cansat...............................................................................................15 1.10 Recuperation System......................................................................16 1.11 Measurements in the Rocket..........................................................16 1.12 Integration of the New Motor..........................................................17 1.13 Unexpected Result..........................................................................17 2/18
  • 3. Project Members Gabriel Arnold- Nicolas Praly Dulac Project Lead President Florent Gabriel Arnold-Nicolas Praly Bouchoux DulacMechanics Lead Electronics Software Lead Lead  Séverine Belloir Michal Ruzek BertrandSylvain Tanguy Mathieu Mandrin Rafic Meziani Riedinger Fernando Jérôme Bégel André Machado Mattioli Jean-Mathieu Raphael Antoine Damien Malric Cousin Philippe Roudot   With help of:Sylvain Rouard Marc Dal-Molin Spas Balinov Former Project President (2007) President (2006) Lead 3/18
  • 4. Project GoalsThis year the project’s goal was to realize a reusable cansat launcher.The rocket supposed to be built in such a way that it could be launched atleast two times during the launch campaign. As a launch vehicle, itspayload was supposed to be a cansat with an approximate weight of 600g.The rocket was also supposed to integrate various sensors to betterunderstand the flight path (accelerometer, altimeter) and help in itsrecuperation (GPS, radio link).This year the rocket was launched with a new motor never used by theclub before. One of the objectives of the year was also to properlyintegrate this ne motor in the rocket. 1.1 CansatThe CANSAT (Can- Satellite)is an internationalcompetition to promotespace-oriented researchand engineering activitiesat the student level. Cansatcompetitions are veryactive in Japan and in theUnited States, but a cansatwas launched for the firsttime in France only last yearin our INESS project (pleaserefer to the closing document of CLES FACIL 2007).The objective is to embark a module of the size of a soda can in anexperimental rocket and eject it at the flight’s appex. The final objective isto bring the CANSAT towards a target on the ground by controlling itstrajectory.In our case, we chose, as last year, to conceive a cansat able to control aparafoil with an automatic pilot. The difference between the “traditional”cansats and ours is the decision that our ejected module would not be thesame size as a soda can. This choice is justified by the fact that ourcansat will carry in addition to the standard payload, a Kiwi transmitter, 2servomotors, and a camera, the sum of which require substantialadditional volume. However we remain in the ‘special category’ range ofless than 1kg.Our previous cansat had an extremely unstable flight, so in hopes ofbettering the stability of our flight this year, we chose to go with a 2 stagedeployment of the parafoil : once the cansat is ejected from the rocket, a 4/18
  • 5. first parachute opens. After a few seconds the first parachute releasesitself and acts as a drag chute for the parafoil. 1.2 Recuperation SystemThis year we choose to enhance our traditional recuperation system.Since one of our objectives was to launch the rocket twice during theweek, we needed to assure ourselves that the landing would cause as littledamage as possible. However, since the launch campaign takes place ona military base, we have a constrained space in which we can operate.Therefore, we cannot simply use a bigger parachute, as the slowerdescent speed could cause us to land too far off course (in a mine field forexample). As a compromise, we decided on a dual parachute system forthe rocket.The first parachute deploys after the cansat is ejected. This would be asmaller chute like we used in previous years. The second one would opennear the ground (approximately 200 m). We also ameliorated ourparachute door opening mechanism to replace the rubber band with asteel spring.In the hope of speeding up the recuperation process, the rocket wouldhave a GPS receiver and a telemetry system that would allow the groundstation to know the rocket’s position at all times. 1.3 In-Rocket Measurements This year we also wanted to integrate an accelerometer and a pressure sensor in the rocket to know the evolution of acceleration and the culminating altitude. We also decided to transmit the data in real time via the Kiwi transmitter (more on the Kiwi later). Since last year there was also a camera in the rocket, we decided to keep this feature. 1.4 Integration of the New MotorThere is a significant difference between the new Pro 54 motor and the oldChamoix motor. First of all, the Chamoix has a threaded rod at the top ofthe motor, so the mechanical integration is simple. Secondly, the Pro 54 ismuch longer and thinner than the Chamoix. 5/18
  • 6. Rocket s kin Thrus t Pro 54 Retaining Free zone Retaining tab ring s leeveDeveloped Solutions 1.5 Cansat 1.5.1 StructureThe CANSAT is a 105 x 115 x 220 mm box (≈2,3 L). It contains: • 2 servo motors • a parafoil stored inside a shell • a system to deploy the parafoil • a micro-controller • a GPS • an accelerometer • a magnetometer • a Li-Poly (non-rechargeable) battery • an FSK modulator • a Kiwi radio transmitter (custom transmitter provided by the CNES) • a video camera 6/18
  • 7. 1.5.2 EjectionAs described in the previous part, the cansat is ejected at the apex of theflight parabola. Since we see the cansat as a payload (and not a part ofthe rocket as we did last year), we had to design a generic payloadejection system. We based our work on our traditional parachute ejectionsystem and used it to open a side of the rocket’s fuselage through whichwe could eject the cansat. In order to eject the cansat properly we put inplace four large elastic bands to push the cansat out of the rocket.Pictures on next page:The new ejection system will be described more completely in the recuperationsystem part. 1.5.3 Original Parachute SystemLast year we had trouble controlling the cansat once ejected from therocket. One of our hypotheses was that the parafoil opened while thespeed of the cansat was too high. In order to solve the problem we choseto use a first parachute to slow the cansat before opening the parafoil.When the cansat is ejected from the rocket the parachute opens. After fivesecond the first parachute is liberated, acting as a drag chute for the 7/18
  • 8. parafoil. This way, the parafoil deploys while the speed of the cansat isapproximately 10m/s.In order to liberate the parachute we designed a small system to absorbthe opening shock of the first parachute and then liberate the firstparachute after 5 seconds. 1.5.4 Radio LinkDue to the dense vegetation on the camp of La Courtine (where the launchcampaign takes place), both rocket and cansat are not necessarilyrecovered, so we cannot rely on onboard memory for data storage. To besure to get at least essential data from the rocket we used a radio link.Last year this system allowed us to quickly recover the cansat thanks toGPS data that had been transmitted. This year we included GPS devices inboth the rocket and the cansat, in the hope of being able to recover themeasily.Aside from the GPS coordinates, some other parameters were alsotransmitted, such as altitude data for the rocket and acceleration for thecansat.Planète Science and the CNES lent us an FM radio transmitter called theKiwi. It has a TX power of 300mW and uses space-reserved frequencybands (137MHz – 139MHz).In order to be able to transmit digital data, we needed a frequencymodulator. At first we developed a modulator built around a DDS-chip,allowing a transmission speed of 480 bytes/sec. Unfortunately, just beforethe launch, it appeared that the modulator was not working as expected,most likely due to soldering problems of the SMD DDS chip. At the lastminute we had to build another modulator using an analog IC FSKmodulator: the XR2206.The reception and demodulation process was done by the CNES. Theyhave an awesome, fully equipped truck with everything we could possiblyneed for the reception of our telemetry. It has a 3-meter extensible mastwith a high-gain antenna, which should normally have received our signalperfectly…Like every year, we had to develop our own ground station software. Theradio link is set up in such a way that it is actually transparent for us at asoftware level. It is effectively a 9600baud unidirectional serial link. Wechose to use Python with wxPython & PySerial to decode the data streamand display it in a simple window. We highly recommend the use ofPySerial for working on serial data links, as development was very rapidand the PySerial library quite robust and intuitive. 8/18
  • 9. 1.5.5 ControlThis year’s control algorithm was built on top of our previous design.Originally we were using multiple GPS coordinates to derive our velocity(both for direction and speed). The problem with this approach was thefact that our GPS was a 1Hz model; this meant that to have the 3 pointsnecessary to properly derive our velocity we ended up with a measuredvelocity that was 1-2 seconds behind our actual velocity.This year we decided to take a new approach: we integrated a 2-axismagnetometer based on a MEMS IC. With this sensor we were able to getour heading in real-time (ground speed being an information that is notvery interesting to us), thus allowing us to react much faster to suddenvelocity changes, and therefore have a much more stable flight. The GPSreceiver was still used for absolute positioning and ideal headingcalculations. We also integrated a 3-axis accelerometer (also a MEMS IC)simply to gather additional data. All data was sent back every secondover our Kiwi radio link.The control loop ran on the onboard microcontroller (AtMega 128) and wascomposed of these 5 major steps: 1. Gather all TWI sensor data (Magnetometer, Accelerometer). 2. Gather GPS data (UART). 3. Calculate ideal heading (based on current GPS coordinate and target GPS coordinate). 4. Calculate angle between ideal and current heading. This is the necessary correction. 5. Apply necessary correction on the servomotors for one second (until next iteration).This control system has absolutely no flight model, and is a simple closed-loop directional control. We either pull left or right on the parafoil for a setamount of time t (t < 1s), and the next iteration will correct the remainingoffset. We have a threshold in place so that if our heading is almostcorrect, we will not turn.Aside from the addition of the magnetometer, the control system isidentical to last year’s. We considered adding a 2nd level of control thatwould stabilize an unstable flight, but we are still not decided as to thenecessary actions to take to stabilize ourselves, nor are we completelysure of what our stability problems really are. 1.5.6 RecuperationThe cansat, due to its control system, would already transmit its GPScoordinates to us. Recuperation is therefore quite simple, as we alreadyknow approximately where it landed. 9/18
  • 10. 1.6 Recuperation system 1.6.1 Ejection Mechanism To not reinvent the wheel, we used our old ejection system with a slight evolution. The previous version used elastics to keep the latch in place. As we had to change the elastics quite often due to wear during our tests, we designed a system with a spring. Otherwise, the system functions identically to the old model. When the ejection door is latched shut, the system is in the same configuration as the picture. When the parachute or the cansat must be ejected, the motor is turned on, thus turning the cam and lifting the latch. 10/18
  • 11. 1.6.2 Double Parachute System As is explained in the project goals (p. 3-4), we used a dual parachute this year to reduce the landing shock while still staying within our authorized operating zone. The first parachute opens just after the cansat is ejected (right after the flight’s apex). The rocket’s airspeed with this first parachute is approximately 15m/s. To save place in the rocket we had to put the second parachute in the same compartment as the first one. To avoid opening the second parachute inadvertently, we put it in a bag that is kept shut until we wish to deploy it. You can see a description of our deployment system to the left. The first parachute is attached to a string (the red string in the diagram). When the rocket is at 200m over the ground this string is cut by a system using an electrical heating wire. When the string is cut, the first parachute (which is also attached to the second parachute’s bag) pulls on the bag. When the parachute pulls the bag away, the second parachute comes out and deploys. As we don’t want to lose the first parachute and the bag. They are attached to the second parachute. With the two parachutes open, the speed of the rocket is around 5m/s. Note: the system is not exactly identical to the one represented on the picture but it follows the same general principle. 1.6.3 TimerThe timer system is responsible for deploying the parachute and thecansat at the correct points in the flight (the times are based oncalculations). The timer is based on an NE555 and can be set with apotentiometer.A push button switch with a a weighted lever is triggered at liftoff with theforce of the acceleration. This switch starts the timer by sending a risingedge to the 555. After a set time, the 555 triggers with a leading edge aflip-flop that closes the door motors power supply circuit. With the intentof conserving power (in case we take time to locate the rocket, or want torelaunch it without replacing batteries), a second 555 is triggered whenthe motor starts, and takes care of cutting the power supply to the motorafter a couple seconds. 11/18
  • 12. 1.7 Measure in the rocket 1.7.1 AccelerometerA 3-axis MEMS IC accelerometer was installed in the nosecone of therocket. The intended purpose was to measure the new motor’sacceleration curve and perhaps get some attitude information during thelater stages of the flight. The accelerometer was set on a +-20G scale toavoid saturation. 1.7.2 Pressure SensorBefore the GPS era, one of the easiest ways to know the rocket’s altitudewas to use a pressure sensor. Knowing the relationship between thepressure and the height – which is a quite linear function at low altitudes –you could determine not only the altitude of your rocket, but also itsapproximate vertical speed.Even nowadays there are very few digital pressure sensors. So it’s a greatway to use some OP-amps, differential amps, filters and DACs.The sensor we used (MPX5100) is an absolute pressure sensor that doesnot need any amplifier, so it was directly connected to the microcontrollerDAC.But due to a lack of time (and importance to the project) it was calibratedat the last second, and we didn’t expect great results. 12/18
  • 13. 1.7.3 Camera2 small camcorders (FlyCamOne V.2) were taken onboard the rocket and theCANSAT. They’re lightweight camcorders usually used by RC planes, obviouslyoptimized for such a use and consequently able to start recording by themselvesafter a delay you can define. They store compressed movies on a standard SDcard you can easily read using any computer.Only the cam in the rocket worked ; the CANSATs one stopped recording at thevery moment of the launch, probably due to the proximity of the Start/Stopbutton with the structure.However the quality of the movie is far from regular camcorders movies quality.This may be caused by the size of the cam, using bad quality optical components.We’d not recommend using such cameras on a rocket flight, it would needsuitable cams that can quickly adapt their contrast to the light sourcesencountered in the sky. 1.8 Integration of the new motorIn order to integrate the motor we use a system with a thrust ring, a carbon tube,a threaded retaining ring and a threaded ring. As we can see the alignment of themotor with the rocket is made with the thrust ring and the threaded ring. In orderto make easier the integration of the motor there were strip of foam along thecarbon tube. The mass of all the system is under 750g. 13/18
  • 14. 14/18
  • 15. Results and analyses 1.9 CansatThe cansat was well ejected from the rocket. The first parachute deployedcorrectly, but due to the shock the parafoil seem to have also deployed itselfprematurely as we can see in the following picture: First Parafoil parachute CANSATThe MEMS sensors ended up being extremely sensitive to the onboard radio, andwere rendered inoperable. With the hope of at least getting some interestingdata we chose to remove the flight control algorithm, and created apredetermined set of commands. The reason is that our previous cansat had acompletely unstable flight (somersaults, 360s etc.) and we wanted first andforemost to verify that we had at least conquered that problem with our newmechanical structure. We therefore chose to have the cansat fly straight for adozen seconds, then turn right, then left, then straight again, then repeat. Wehoped we could therefore correlate the actions with the GPS coordinates andverify that we were indeed having an effect on the flight path of the cansat.Even after numerous integration tests and a full flight simulation that wassuccessful, our telemetry system failed catastrophically. We think the cansat’santenna may have been to blame (small home-made helical ¼ band that couldn’ttransmit far), but there is no conclusive evidence as to what happened. Weknow the system worked up the FSK modulator, so something in the actual radiolink or demodulation is to blame. Due to this failure we have absolutely nosensor data from the whole flight, which was a great disappointment for us. Wehave opted to move to a POTS radio data link for our future projects, since theKIWI demodulation truck’s system is not set up by default to handle multiplefrequencies in parallel and the overall size of the KIWI makes integrationsometimes difficult.The experience nevertheless had positive results: we succeeded in stabilizing thecansat’s flight. We also validated the rocket’s ejection mechanism. The rocket’scurrent design allows us to integrate any cansat with the following constraints:less than 105 x 115 x 300 mm and a mass of less than 1kg. 15/18
  • 16. 1.10 Recuperation SystemThe recuperation system didn’t work because the parachute bay doors didn’topen. However when we found the rocket, the string holding the first parachutein place was nearly cut due to the heat wire.Since we have not had such a problem in at least 20 years, we aren’t sure of thecauses. We know the timer was properly triggered, so we are left with thefollowing hypotheses about the door: • As we can see on some pictures, the cansat’s door was already open and may have blocked the parachute’s door. • The timer had some problem to provide sufficient power to the motor. Even with new batteries, the power may not have been sufficient to unlatch the door. • As the cansat’s door was open in mid flight, there was too much pressure on the parachute bay doors from within the rocket. This, coupled with the potential power problems, may have been enough for the door not to unlatch.As we can see on the pictures, the bottom half of the rocket resisted quite well tothe crash landing, which will allow us to reuse the bottom part to build anotherrocket. 1.11 Measurements in the RocketWe actually have no measurement results at all since both the rocket and cansatradio links failed. With our inability to get the onboard memory to functioncorrectly, all measurements are unfortunately lost.The problem with the radio link seems to be with the CNES radio receivers notreceiving a strong enough signal from our transmitters to be able to demodulateit.Several problems may have occurred:  Most probably, batteries were not powerful enough to supply the radio transmitter, which consumes a lot of power. Indeed, tons of tests were made before the launch, and the batteries – lithium-ion camera cells – were not changed before the flight. Using a transmitter near the receiver lead us to think everything is OK, while the signal couldn’t be received when we were too far away from the receiver.  The cansat antenna, which should normally have been 50cm long, was shortened to a pigtail antenna, making it less efficient. Nevertheless, with a 300mW TX power, this should not have been a real issue.  The CNES radio RX equipment was not prepared for receiving our 2 radio transmitters in parallel. It seems that one of the receivers had a sensitivity problem, which could explain why it didn’t receive the rocket’s radio signal. At least one radio link could have been received if we had chosen 16/18
  • 17. to discard the other one, but at the time of the launch we didn’t realize this.Both rocket and cansat were able to be recovered even without any GPS data.Our rocket was recovered by a Japanese team (many thanks to them!) while theywere searching for their own rocket, and the cansat was recovered thanks to atriangulation process done by Planète Sciences’ volunteers, and visual data. 1.12 Integration of the New MotorThe system was a success. As we can see on the video the motor isintegrated and blocked in the rocket in less than 15s without using anytools. 1.13 Unexpected ResultAs we can see on the video the rocket acted like a glider during the descent. Theonly explanation we can come up with is that the cansat bay’s door was actinglike a wing and caused the rocket to glide. 17/18
  • 18. ConclusionThe launch of Leia was not a total success, however we were able tovalidate some important aspects of the project: • The system to eject the cansat laterally from the rocket worked as planned. • The use of a first parachute in the cansat permitted us to stabilize the cansat’s flight. • The system designed to contain the new engine worked very well, and was easy to use by the pyrotechnician.In conclusion, we can say that even if the project did not work entirely ashoped, we have discovered good solutions to recurring problems which willallow the club to concentrate all its effort on the cansat and its control forthe 2008-2009 year. The CLES-FACIL team right before launch. 18/18

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