CSU DemoSAT-B 2010 Preliminary Design Review

CSU DemoSAT-B 2010Critical Design ReviewColorado State UniversityPaul Scholz, Tyler Faucett, Abby Wilbourn, Michael Somers

June 14 201011This is Paul from CSU demosat-B and this is our PDRMission OverviewObjective: to study alternative energy collection at different altitudesFind the ideal altitude for alternative (wind & solar) energy collection.

Is high altitude energy collection worthwhile?Can the added cost of high altitude energy collection be made up for with increases in efficiency?

2Paul - The objective of our study is to find the ideal altitude for wind and solar energy collection. The data we collect could help a company determine if the added cost of high altitude energy collection, can be overcome by increases in efficiency. 2Current ProductsMARS Maggen Air Rotor System

3Paul - There are many current products that are in development to collect energy from the sun or wind at high altitudes. The one shown on slide 3 is the Maggen Air Rotor System. This product is a balloon tethered to the ground that will spin as air flows across it spinning a generator and sending energy back down to the ground. 3

CoolEarth Solar Balloon MARS turbine4Paul - On slide 4 we can see the CoolEarth solar balloon. This product is a solar panel with a balloon shape that is lightweight and very mobile. It uses its shape to focus the suns energy onto its solar panels. This makes it very efficient and could possibly be used in an airborne application.4How we can helpOur test could provide useful data to someone wishing to put up a similar system on Earth or MarsAn airborne solar/wind power farm could be very useful for remote area power generationOur test vehicle will provide data to give an altitude of maximum power generation.

5Paul - After the launch day, we hope to use our data to be able to provide an altitude of maximum energy collection for both solar power and wind energy, as well as a combination of the two. This data could be very helpful to anyone trying to perform airborne alternative energy collection, whether it be in a remote location somewhere here on earth, or even on Mars where efficient power generation is needed. 5Mission Requirements6REQUIREMENTMETH ODSTATUSPayload mass must be 1.5 kg or lessDesign and use of lightweight materialsPayload must accommodate flight string per the users guideDesign and testPayload must pass all structural tests in users guideDesign and testPayload must successfully complete all functional and environmental testsDesign and testPayload must have the capability to complete all mission objectivesDesign and testPayload must cost under $1000Budget carefullyMichael- Our top priorities are to measure wind speed and solar panel power. We have added in other sensors to gather an increase in accuracy in our two primary measurements. With temperature and pressure the altitude of the balloon can be found, as well as the air density. This is important because air density plays a large role in the amount of power that can be produced from wind. We will use an accelerometer to know the speed of the balloon. With this data the total wind speed will be known and not just the speed relative to the balloon.6Concept of OperationsJust before launch power to the heaters and microcontroller will be turned on via switches on the top of the payloadThe microcontroller will run its program which includes taking input from 5 different sources and transmit the data serially back to the SD card at a rate which we will specify for each sensorAfter the program has run for 150 minutes, the program will end so that we do not write over our flight information with data collected on the ground7SubsystemsStructuralThermalDataStorageProcessingElectricalSensing

8Michael- We have 5 major subsystems in our payload8Subsystem StructuralMust have cylindrical shapeAllows for even and constant sun exposure to solar faces

Must have center core flight string pass throughPass through design must comply with all DemoSAT-B regulations

Pressure differences inside and outside the payload must not exceed 10 psid

9Michael- The first subsystem were looking at is structural. We designed the overall structure to have a cylindrical shape, so that the total sun exposure on the panels is equal regardless of the orientation of the payload on the string. We designed for a center string pass through which complies with all of the demosat-b criteria. Lastly we hope to keep the pressure difference from inside to outside the payload under 10 psi.9Subsystem - ThermalThe internals of the payload must remain above 0C to prevent failures of electrical componentsThe internal electrical components must be placed as close to the center of the payload as possible Internal flexible heaters will be installed to maintain required internal temps. Flexible heaters allow for easy placement near critical components (battery)

Temp. DistributionFlux10Michael-Most of the payload structure is made from foam board insulation that is at least one inch thick in all areas and 1 in most. From our models we know that the center of the payload will most likely be the warmest area, so we hope to keep most of our critical components there. We have also purchased flexible heaters that can be used to heat certain components as well as the inside cavity of the payload.10Subsystem - DataProcessingAll sensor data shall be processed on a PIC 16F884 microcontrollerStorageThe PIC shall send data from the sensors to the data storage unit every 5 secondsThe data storage device shall be removable and portable and must allow for computer interface

11 Michael-All of our measurement sensors are going to be attached to a PIC16F884 microcontroller. The data gathered from the sensors will be processed using the microcontroller, and the data will be sent to and recorded by external data storage unit every five seconds. In order to retrieve our launch data most easily, we decided on using an external SD card reader. That way we have a removable card that attaches easily to a computer interface.11Subsystem - ElectricalAll electrical components must be powered by a 5V sourceThe power supply must be able to produce 4.8V to 6V for at least 2 hoursSwitches for electrical components must be mounted on the external of the payload

12Michael-The PIC16F884 microcontroller that we are using can only be powered by a 5V source, otherwise we will fry the microcontroller and lose our data. All sensors and electrical components will be wired in a fashion that each can run on 5V. Also, the solar panels and wind anemometer will be producing a voltage that must be stepped down to 5V before the data enters the microcontroller to be processed. The power supply we use must be able to produce 4.8 to 6V for at least 2 hours to ensure each component receives the required voltage to operate for the entire flight period.The switches will be mounted externally on the payload, one for all sensors and the PIC, and a separate one for the heaters (also a separate power supply). This complies with the Demosat-B guidelines for quick activation immediately before launch.12Subsystem SensingWind Speed SensingAnemometer must be at least 2in from the flight cordAt least 2 axis of acceleration must be sensed to accurately measure wind speed Altitude SensingPayload must contain at least 1 pressure sensor and 1 temperature sensorPressure and Temp must be measured externally for accurate dataSolar PanelsSolar panels must cover at least 90% of the rounded faces of the payloadAll external sensors must be able to operate at temperatures ranging from -80C to 30C

13Michael-Here are some of the constraints and guidelines for our sensors. The photographs at the right show what each sensor looks like as well. The cup-type anemometer is going to be mounted on the top of the payload, and must be at least 2 inches from the flight string. *Briefly go through other guidelines*13Subsystems Block Diagram14

Michael- Here is our subsystems block diagram. A more detailed schematic is presented on the next slide. In addition to these subsystems, there are heaters attached to a separate power source included in the payload, but not shown in these diagrams.14Schematics/Drawings/Analysis15

Michael-This is a more detailed electrical schematic that shows the pin layout of the PIC microcontroller we are using. It also shows the circuitry required for each sensor.15

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100mph winds at -80C

5W internal heat generation

Steady state.20Tyler20

100mph winds at -80C

5W internal heat generation

Steady state.21Tyler21Commands and SensorsSample RateSample Duration# of samplesBytes/Sample (estimated)Min Required MemoryFor data storageAvailable Memory1 sample every 5 seconds2 hours 1440 (samples/ sensor) * 6(sensors) = 8640 samples4 bytes34560 bytes2Gb SD (less due to formatting, etc.)Data transferred serially from PIC microcontroller to SD card mounted in SD card reader. 22Paul Here on slide 24 you can see how we calculated how much storage our data will take up. These are very rough estimates and we left a lot of room for error. Based on our calculations we are confident that 2Gb will be sufficient to store 2 hours worth of data sampled every 5 seconds or less if we decide. 22

23Paul Here on slide 25 you can see a block diagram showing how data is transferred from the sensors to the SD card and what type of programming is required to make this happen. Our Temperature and Pressure Sensors as well as the Solar Panels and each axis of acceleration will communication with the PIC through A/D conversion, while the anemometer will communication through pulse counting, where the microcontroller will count the number of rotations of the cup anemometer over a certain time period. All of this data will then be transferred serially to the SD card for data storage. 23Sensor SpecificationsSensorOperational VoltageOperational TemperatureMeasurement RangeNotesTemperature3.0 to 5.5V -55C to +125C-55C to +125CConverts Temperature to 12-bit Digital Word in 750 msPressure5.0V0C to 85C0 psi to 1 psi through 0 psi to 100 psiResponse time of 8 msAccelerometer (2-axis)2.4V to 5.25V-20C to 70C+/- 18g-----Cup Anemometer----------3 mph to 125+ mph2.5 mph per Hz (1 Hz=1 pulse/sec)Solar Panels (3)----------Voltage: 7.2 VWatts: 1.44 WAmperage: 200 mA24Paul We chose each of our sensors based on a few key specifications. We knew that any external sensors had to be able to operate in very cold temperatures, so we chose a temperature sensor that measures down to -55C, which is the best we could find due to our budget constraints. We also knew that we could see wind speeds of 60 to 100mph in the jet stream, so we purchased a cup anemometer that could measure speeds up to and exceeding 125mph. We also needed to find a pressure sensor with a fairly quick response time and the right measurement ranges, as well as an accelerometer with a wide enough measurement range. 24Accelerometer Math

25 X and Y out were generated randomlySamples were taken every second for this exampleTest PlansTesting TypesStructural TestWhip testDrop testStair pitch testEnvironmental TestCooler TestFunctional TestsBench Test26Paul We will be performing the standard tests that are laid out in the DemoSAT user guide. 26Structural TestsTest StructureMade in the same fashion as actual structure with minor differencesHeavier outer shell with no carbon fiber around the foamThicker (2x) mounting plateBallast taped to mounting plate on insideAccelerometer bracket attachedAluminum square screwed to top to simulate the anemometer.Total weight was 3.25 lbs

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Paul- The structural tests we will perform are the whip test, drop test, and stair pitch test. In all of these cases our main possible point of failure, is the central carbon fiber tube breaking or damage to the foam insulation or the carbon fiber outer shell. It is also possible that the studs in the foam insulation could pull out, in which case we might have to redesign their shape and size to hold better. We already have extra material and have budgeted time for possible redesigns such as this. 27Test Structure Photos

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Assembled test structurePieces of ballast used

Removable FrameWhip TestPerformed 5 whip tests and took video of all of them.Payload was spun overhead as fast as possibleAfter being at speed for several revolutions the experimenter pulled in on the string as hard as possible to simulate a high g-load.The length of rope from the hand of the experimenter to the payload cg was 80 inchesFrom the video the calculated angular velocity was 60 RPMThe calculated g load at these conditions was 8.2g with the peak during the pull being higher29Potenial Damage/AssessmentTop plate could have been bentEpoxy interface between the tube and fitting could failAcrylic posts imbedded in the foam could pull out or breakNo damage was observed during this test

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Stair Pitch TestStructure was kicked down a flight of 13 concrete stepsStep profile was 7.25 inches tall and 10.5 inches long

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Potential Damage/ AssessmentCF tube could breakFoam could fractureAcrylic posts breaking or pulling outTop plate bendingOne Acrylic post was broken during the tumble at the base of the nutAll other parts were unharmedPossible fix would be to shorten the posts to be only as tall as the nuts to lessen the moment on impact33Drop TestStructure was thrown off a balcony from a height of 22.63 ft. above the concrete groundIt landed almost sideways but angled enough that the top plate took the initial impact

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Potential Damage/ AssessmentBroken CF tubeAcrylic posts breaking or pulling outFoam breakageTop plate bendingThe top plate was bent from impactThe foam fractured and broke from impactThe foam layers separated near the region of impactThe fix for the foam is that it will be encased in a carbon fiber outer shell

35Structural Test SummaryNo repairs were made during testingWeak points were discovered to be the acrylic posts and the top aluminum plateOf the five pieces of ballast originally taped to the mounting plate before the tests 3 were still attachedThe plate may have bent less from the drop test if the third post had still been thereFrom the tests we are confident that the electronics on our payload will survive the extreme conditions they may encounter and our data will be recoverable36Secondary Whip TestThis test was added after the other tests had been completed and analyzedIn this version of the whip test, we dropped the payload attached to a 10 foot ropeThe sudden stop the payload experienced as the rope came to its full length was a better way to impart a sudden directional change in order to determine if the posts would hold, and if the internal electronics would stay secureAll other tests had been performed previously, and the damage was repaired37Potential Damage/AssessmentThe post that previously broke and was re-glued broke againMinor foam fractures around the postsNo internal ballast pieces separated from the mounting plateOverall, there was no significant additional damage to the structure. We are still confident that the top plate will remain secure, as well as the internal electronicsVibration testing may be analyzed when all electronics are in place to verify that our data will be retrievable

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Environmental TestsCooler TestMust purchase Dry Ice and CoolerPotential Point of Failure:Payload: Insulation design may be flawed and low internal temps may cause freezing/condensation on electrical components.Adjustments may need to be made to heater placement and insulation

40Paul The Environmental tests we will conduct will be the Cooler test. We are going to do this test on the payload as a whole when assembly and manufacturing is complete, however will are also going to test the solar panels in the cooler test. By testing the solar panels we are hoping to gather some data that will tell us if the power output from the solar panels is affected purely by a temperature drop. If we find that we need to account for a temperature change, we will be able to use the data from this test to help do that. 40Solar Panel Cold TestThe solar panel output will be tested for variations in temperatureThe panel, a 90 W light source above the panel, and a thermocouple will be placed inside a refrigerator originally at room temperatureThe refrigerator will then be turned on to its highest settingThe solar panel output and temperature will be recorded at a constant temperature interval of 2 degrees Celsius41Setup

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ResultsThe starting temperature was 22 CFinal temperature was -18 CVoltage readings were taken with a multimeter every two degreesThe voltage readings combined with known resistance values yielded current and powerDry ice was added to the refrigerator to reach the lowest temperature43Temperature Relationships44Functional TestBench TestPotential Points of Failure:Overheating of internal electrical componentsNo data transmission to SD CardNo data transmission from sensorsWiring failure

45Paul The possible point of failure on our functional test is mainly electrical. It is possible that we may see overheating of the internal electrical components. It is also possible that we dont see any data transfer onto the SD card or even any communication between the microcontroller and the sensors. We plan on getting all of these tests done very early on so we have time to make any necessary changes in our electrical design or programming. 45Parts List46

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