Colorado Space Grant Consortium, The University of Colorado at Boulder Department of Aerospace Engineering Sciences, and the Edge of Space Sciences BalloonSat Missions to the Edge of Space Team Solkraft Revision D Thomas Buck, Kyle Garner, Alexandra Jung, Quinn McGehan, Mark Sakaguchi, and Scott Taylor Fall 2010 BalloonSat Mission to the Edge of Space Design Document Revision D 1.0 Mission Overview .............................................................................................................. 3 2.0 Requirements Flow Down ................................................Error! Bookmark not defined. 3.0 Design ................................................................................................................................ 5 3.1 Strucutre 3.2 Thermal 3.3 Electronics and Data Collection 3.4 How Team Solkraft Will Achieve Their Mission 3.5 Data Retrieval 3.6 Features 3.7 Illustrations 3.8 Block Diagram 3.9 Parts List 3.10 RFP Requirements 4.0 Management ..................................................................................................................... 13 4.1 Schedule 5.0 Budget .............................................................................................................................. 15 5.1 Budget Management 6.0 Test Plan and Results ....................................................................................................... 16 6.1 Safety 7.0 Expected Results .............................................................................................................. 20 8.0 Launch and Recovery ...................................................................................................... 20 9.0 Results, Analysis, and Conclusions ................................................................................. 22 9.1 Flight Data 9.2 Ground Tests 9.3 Summary 10.0 Ready for Flight ............................................................................................................. 28 11.0 Conclusions and Lessons Learned ................................................................................. 29 12.0 Message to Next Semester ............................................................................................. 29 References ............................................................................................................................... 29 Bios ......................................................................................................................................... 30 2 Team Solkraft BalloonSat Mission to the Edge of Space Design Document Revision D 1.0 MISSION STATEMENT The mission of team Solkraft is to test the effectiveness of monocrystalline and polycrystalline solar panels under near space conditions up to approximately 30 km. This will test the solar cells under varying light intensities, temperatures and altitudes. Team Solkraft shall analyze the electrical output of the solar panels to see which type is more effective in a near space environment. 1.1 OVERVIEW With a planet on the verge of destruction from global warming, the research into alternative energy sources is more important than ever before. One of the most prominent developments made over the past decade is innovative ways to capture energy from the Sun. The use of solar panels on households and businesses has become a popular way to offset energy costs and their potential for the future is even more optimistic. Solar cells are becoming more and more efficient. The National Renewable Energy Lab (NREL) set the record for the world’s most efficient solar cell in 2008 at 40.8%1. Because it is the belief of Team Solkraft that solar cells will become the main source of energy for generations to come, our mission strives to pinpoint the variables that effect solar cell output, specifically in a near-space environment. The near space environment will provide insights into solar cells being used for stratospheric platforms. Stratospheric platforms are vehicles that operate very high in the atmosphere. These are most commonly thought of for communication relays and access points to provide large areas with wireless broadband. Current stratospheric platforms are run off of fuels or batteries and can only operate for short periods of time. Team Solkraft hopes to explore the possibility of whether using solar panels on stratospheric platforms is a viable option to keep it flying for a longer period of time or even indefinitely. There is lots of testing of solar cells on the ground and data on how normal ground temperatures affect solar cells. It seems to be agreed upon that under conditions on the ground solar cells decrease in efficiency with an increase in temperature.1 However, there is much less exploration of how solar cells operate under the more extreme conditions of a near space environment. Team Solkraft shall test how well two different types of solar cells (monocrystalline and polycrystalline) function at different altitudes with varying light intensities and under different temperatures. As a control for the experiment the solar cells will be tested under different temperatures on the ground at a constant altitude before the launch day. The solar panels will be tested on similar weather days with different temperatures and similar temperature with different cloud cover that will provide different light intensities. From this initial testing of the solar cells Team Solkraft will compare this data to the data we receive on launch day to see which factor, light intensity or temperature, affects the solar cells. 3 Team Solkraft BalloonSat Mission to the Edge of Space Design Document Revision D To plot the effectiveness of the solar cells versus altitude we will use data from the GPS attached to the weather balloon after getting approval from EOSS. Light intensity shall also be measured using photodiodes to see how that affects the functionality of the solar cells. Team Solkraft is doing this to analyze the effects of near space on monocrystalline and polycrystalline solar cells. From the information acquired Team Solkraft will decide which type of solar cell is more efficient in a near space environment. 2.0 MISSION REQUIREMENTS To give the mission the best possible prerequisites to succeed certain requirements need to be fulfilled. Below is the Mission Objective, the Level 0 requirements which come off the Mission Objective and at last the Level 1 requirements which come off the Level 0 requirements. The Level 1 requirements state the actions necessary to complete/fulfill the Level 0 requirements. The relationship between a requirement and its parent requirement (or Mission Objective) is stated in the last column of our table. OBJECTIVE The mission of Team Solkraft is to test the effectiveness of different types of solar panels (monocrystalline and polycrystalline) under conditions on the ground and up to near-space conditions of approximately 30 km. MISSION REQUIREMENTS LEVEL 0 Requirement Requirement Number M 0.1 The solar panels on the BalloonSat shall be exposed to nearspace conditions M 0.2 Team Solkraft shall measure the internal and external temperature with varying altitude M 0.3 Team Solkraft shall measure the light intensity with varying altitude M 0.4 Team Solkraft shall test for variations in solar cell output under varying climate conditions M 0.5 Team Solkraft shall meet the requirements for the request for proposal M 0.6 Team Solkraft shall make sure no one is hurt during construction and testing Where it comes from Mission Objective Mission Objective Mission Objective Mission Objective MISSION REQUIREMENTS LEVEL 1 4 Team Solkraft BalloonSat Mission to the Edge of Space Design Document Revision D Requirement Requirement Number M 1.1 The solar panels shall be attached to the angled sides of the BalloonSat M 1.2 Team Solkraft shall be able to record the altitude of the BalloonSat using data from EOSS GPS M 1.3 Team Solkraft shall be able to record and save data during the flight M 1.4 Team Solkraft shall maintain a minimum internal temperature of -10 degrees Celsius. M 1.5 Team Solkraft shall program the Arduino microcontroller to record solar cell output data to a micro SD card M 1.6 Team Solkraft shall take in-flight pictures using a Canon A5701S camera and save them to the camera’s 2 GB memory card. M 1.7 Team Solkraft shall record science data to the Arduino Microcontroller M 1.8 Team Solkraft shall build a structure for the BalloonSat capable of withstanding near space conditions Where it comes from M 0.1 M 0.4 M 0.2, M 0.3 M 0.2, M 0.3, M 0.4 M 0.5 M 0.2, M 0.3, M 0.4 M 0.5 M 0.2, M 0.3 M 0.4 M 0.1, M 0.5 3.0 DESIGN 3.1 STRUCTURE To achieve our goal of measuring the functionality of solar panels in a near space environment we will mount eight solar panels on the exterior of a BalloonSat. Four of these cells will be monocrystalline and four will be polycrystalline. The frame of the BalloonSat will be a square pyramid with the top cut off so that the 3D structure is formed using four trapezoidal pieces of equal size, one larger square as the base, and one smaller square as the top. This structure will be made out of foam core cut from a single piece in order to help the structural integrity. We will use hot glue and aluminum tape to secure the structure. The structure of the BalloonSat will be attached to a weather balloon using 2.4mm Dacron line by running the line vertically through a non-metal tube at the center. The structure of the BalloonSat will be set in one place along the cord by tying a figure-eight knot in the line at the top and bottom of the BalloonSat. We will also put an American Flag on the BalloonSat to identify it. 3.2 THERMAL 5 Team Solkraft BalloonSat Mission to the Edge of Space Design Document Revision D In order to keep our experiment warm during the flight the satellite will be insulated with foam. In addition to this we will use a heater on the inside of BalloonSat powered by three 9V batteries to help keep the internal temperature of the BalloonSat above -10oC. 3.3 ELECTRONICS/DATA COLLECTION Data from the solar panels will be recorded using an Arduino Microcontroller hooked up in a circuit with the eight solar panels. We will be able to record all of the solar panels through two analog inputs by using a sixteen channel multiplexer. The multiplexer will alternate from which solar panel the Arduino is taking data. It will do this every half second however, so we do not need to worry about the time difference as a factor in our data. The voltage will also be recorded with a load on the circuit created by a resistor that is not very affected by temperature to make sure that is not affecting the results of our experiment. Through doing this we can find the power output on the resistor. The measurements for the temperature will be taken by a HOBO data logger with the internal temperature sensor and an external temperature. This will allow the data to be easily taken off of the data logger and onto a computer for easy evaluation. We will also use four thermistors connected to the Arduino Microcontroller through a multiplexer to record temperature on each side of the BalloonSat. To measure the light intensity we will use a photodiode on each face of the BalloonSat that the solar cells will be on. The data for which will be recorded by our Arduino Microcontroller again using the multiplexer and then going to an analog input. In addition to the data we collect using sensors on our satellite we will also collect altitude data from the GPS attached to the weather balloon at the end of the flight string after getting permission from EOSS. 3.4 HOW TEAM SOLKRAFT WILL ACHIEVE OUR MISSION First we will look at the structure of our satellite. Team Solkraft will design the sides of our pyramid structure to fit four of the solar cells which are 76mm x 83mm x 6mm, one on each side. Team Solkraft will then cut out a template of the satellite out of foam core and assemble the structure using hot glue and aluminum tape. Before integration of the solar panels into the structure Team Solkraft shall first test each one by connecting them to a voltmeter and testing each one under different amounts of light to be sure that they are working. The next step is to integrate our solar cells by soldering the positive side to a resistor and then attaching a lead to that resistor going to the multiplexer input. The negative side will be connected to the ground of the microcontroller. The microcontroller will turn the analog signals into digital and give a voltage reading of the solar cells. Also along the outside of the satellite we will mount a photodiode on each side to measure light intensity positioned between the two solar cells. This will help us determine which solar cell is facing the sun based on the intensity and we will use that specific panel’s voltage reading. We will then start mounting the components on the inside of the satellite such as the heater, HOBO, and camera. After learning how to solder in class, 6 Team Solkraft BalloonSat Mission to the Edge of Space Design Document Revision D Team Solkraft will assemble the heater and place it in the satellite ensuring that when the BalloonSat passes through the tropopause that the circuits remain at an operable temperature. Next the camera will be mounted to the BalloonSat. The camera is programmed to take pictures approximately every 20 seconds. Team Solkraft will cut out a hole for the lens in one of the sides; this will ensure ventilation to the satellite to help prevent any condensation build up. Insulation will also surround the lens from the side back to the camera so that the rest of the satellite is still insulated keeping the heat in. Our HOBO will have its external temperature sensor mounted through another hole in one of the sides of the satellite so we will have a comparable internal and external temperature reading. 3.5 DATA RETRIEVAL Team Solkraft BalloonSat will have an Arduino microcontroller to record the voltage output of the solar cells. This data will then be transformed from an analog to digital signal to be logged and stored for later collection on either the flash memory of the microcontroller or an external memory card hooked up to the USB port of the microcontroller. Therefore, the means of data retrieval will involve transferring the data from the microcontroller to a computer for processing after the BalloonSat has returned to the ground. The photodiode sensors will also produce a voltage based on the light intensity and the amount of voltage from those sensors will correspond to the light intensity. Team Solkraft will record this in the Arduino microcontroller. The data will then be analyzed as voltage output as a function of altitude, and also temperature recorded by the thermistors because they are closest to the solar panels for the most accurate reading. The altitude data will be retrieved from the GPS attached to the flight string, and the external temperature will be taken from the HOBO logger onboard our BalloonSat. It will then be possible to determine the efficiency of the cells as a function of altitude and temperature. The data analysis will be done using Excel. 3.6 FEATURES Photodiodes Photodiodes will measure the light intensity from the sun and convert it into voltage that will be read by the microcontroller. Team Solkraft will use this to determine specific measurements for the light intensity as it changes throughout the flight. Solar Panels 7 Team Solkraft BalloonSat Mission to the Edge of Space Design Document Revision D The solar panels are our experiment. With them Team Solkraft will determine what affects their functionality in a near space environment. We will also see which type is more effective. Structure The structure will allow Team Solkraft to use the solar cells more efficiently because they will be more directly angled towards the sun. The trapezoidal shape will also help the structural integrity when the BalloonSats land because all of the parts inside the BalloonSat will give it a lower center of gravity making it more stable and less likely to land on a side damaging a solar cell. 3.7 PICTURES 8 Team Solkraft BalloonSat Mission to the Edge of Space Design Document Revision D This is the original layout of the Balloon Satellite. Some changes were made to the layout. Changes The Arduino microcontroller was moved to the sidewall instead of on the bottom Only one battery was required for the Arduino so there are now only 4 batteries total The heater was moved more toward the center of the satellite. It was placed on the bottom of the satellite near the flight tube The batteries were laid flat against the bottom of the BalloonSat Camera Heater 220 mm Batteries 128 mm 220 mm 90 mm HOBO Arduino 110 mm 9 Team Solkraft BalloonSat Mission to the Edge of Space Design Document Revision D 3.8 BLOCK DIAGRAM 3 9V Batteries Batteries Switch Switch Heater 2 GB Memory Card Camera HOBO Power Photodiodes Switch Polycrystalline Solar Cells Provided Hardware Sensors Thermisters Multiplexer Solar Cells Battery Switch Arduino 328 Monocrystalline Solar Cells 2GB Micro SD Card 10 Team Solkraft BalloonSat Mission to the Edge of Space Design Document Revision D 3.9 FINAL PARTS LIST Part and where it is from Six Monocrystalline solar panels from Edmund’s Scientific Fourteen Polycrystalline solar panels from The Electronic Goldmine Six Photodiodes from West Florida components Arduino Duemilanove Microcontroller Starter Kit from Sparkfun Electronics 9V to barrel jack adapter from Sparkfun Electronics 5 Thermistors from Sparkfun Electronics Micro SD Shield from Sparkfun Electronics Multiplexer breakout board from Sparkfun Electronics Foam core from Colorado Space Grant Insulation from Colorado Space Grant Canon A5701S from Colorado Space Grant HOBO Datalogger from Colorado Space Grant Heater from Colorado Space Grant 9V Batteries from Colorado Space Grant Reference http://www.scientificsonline.com/lowcost-high-output-encapsulated-solarcells.html http://www.goldmine-elecproducts.com/prodinfo.asp?number=G1 6397 http://www.westfloridacomponents.com /mm5/merchant.mvc?Screen=PROD&St ore_Code=wfc&Product_Code=LED06 0&Category_Code= http://www.sparkfun.com/commerce/pro duct_info.php?products_id=9952 http://www.sparkfun.com/commerce/pro duct_info.php?products_id=9518 http://www.sparkfun.com/commerce/pro duct_info.php?products_id=250 http://www.sparkfun.com/commerce/pro duct_info.php?products_id=9802 http://www.sparkfun.com/commerce/pro duct_info.php?products_id=9056 Part # 3039808GRP G16397 LED060 DEV-09952 PRT-09518 NTCLE100 E3103JB0 DEV-09802 BOB-09056 3.10 HOW TEAM SOLKRAFT WILL MEET THE RFP REQUIREMENTS 1. Design shall have additional experiment(s) that collects science data and teams must analyze this data. Team Solkraft additional experiment will collect data as voltage readings from solar panels that Team Solkraft are testing. See 1.0 Mission Overview and 3.0 Design 2. After flight, BalloonSat shall be turned in working and ready to fly again. Team Solkraft will make sure the BalloonSat is able to withstand the rigors of flight through testing. See 6.0 Testing 3. Flight string interface tube shall be a non-metal tube through the center of the BalloonSat and shall be secured to the box so it will not pull through the BalloonSat or interfere with the flight string. (See flight string attachment diagram at the end of this document.) 11 Team Solkraft BalloonSat Mission to the Edge of Space Design Document Revision D See 3.1 under Design 4. Internal temperature of the BalloonSat shall remain above -10˚C during the flight. Team Solkraft will use a heater and insulation to keep the BalloonSat above -10oC. See 3.2 under Design. 5. Total weight shall not exceed 850 grams. Team Solkraft will budget our weight and plan so that our experiment shall not exceed 850 grams. See 3.0 Design and 5.0 Budget. 6. Each team shall acquire (not necessarily measure) ascent and descent rates of the flight string. Team Solkraft shall get permission from EOSS to use the data from the attached GPS. 7. Design shall allow for a HOBO H08-004-02 (provided) See 3.0 Design 8. Design shall allow for external temperature cable (provided) See 3.0 Design 9. Design shall allow for an Canon A570IS Digital Camera (provided) See 3.0 Design 10. Design shall allow for an active heater system weighing 100 grams with batteries and id 10x50x50mm (provided). Dimensions do not include 2 x 9 volt batteries. See 3.0 Design 11. BalloonSat shall be made of foam core (provided). See 3.0 Design 12. Parts list and budget shall include spare parts. See 5.0 Budget. 13. All BalloonSats shall have contact information written on the outside along with a US Flag (provided). Team Solkraft will put US Flag and contact information on bottom of satellite. 14. Proposal, design, and other documentation units shall be in metric. Yes 15. Launch is in November 6, 2010. Time and location: 6:50 AM in Windsor, CO. Launch schedule will be given later. Everyone is expected to show up for launch. Only one team member is required to participate on the recovery. Launch and recovery should be completed by 3:00 PM. Team Solkraft will all plan ahead to be at launch. 16. No one shall get hurt. See 6.1 Safety under Testing 17. All hardware is the property of the Gateway to Space program and must be returned in working order end of the semester. Team Solkraft shall make sure the BalloonSat is able to withstand the rigors of flight through testing. See 6.0 Testing 18. All parts shall be ordered and paid by Chris Koehler’s CU Mastercard by appointment to minimize reimbursement paperwork. All teams shall keep detailed budgets on every purchase and receipts shall be turned in within 48 hours of purchase with team name written on the receipt along with a copy of the Gateway order form (HW 04). See 5.0 Budget 12 Team Solkraft BalloonSat Mission to the Edge of Space Design Document Revision D 19. All purchases made by team individuals shall have receipts and must be submitted within 60 days of purchase or reimbursement will be subject to income taxes. See 5.0 Budget 20. Have fun and be creative. Will do. 21. Absolutely nothing alive will be permitted as payloads, with the exception of yellow jackets, mosquitoes, fire ants, earwigs, roaches, or anything you would squish if you found it in your bed. Nothing on our satellite will be alive. 22. Completion of final report (extra credit if team video is included) 4.0 MANAGMENT Scott Taylor Team Lead Structure Lead Science Assist Kyle Garner Power Lead Internal Testing Data Analysis Thomas Buck Science Lead Science Testing Structure Assist Quinn Mcgehan Electrical Lead Internal Testing Programming Assist Alexandra Jung Budget/Planning Lead Structure Testing Electrical Assist Mark Sakaguchi Programming Lead Science Testing Data Analysis 4.1 SCHEDULE Team Solkraft will have a team meeting every Tuesday and Thursday at 6:00 PM. Extra meetings will be organized or rescheduled as needed. The meetings will always take place in the ITLL building in a reserved study room. Date 9/20/10 9/21/10 Tasks All Hardware needed addressed Hardware Order Form processed 10/1/10 10/5/10 10/6/10 10/8/10 Design complete Revision A/B Due Start Construction finish prototype Start Testing (Whip Test, Drop Test, Kick Test) Was this met Yes Yes, but needed to order extra multiplexer when original one broke Yes Yes Yes Yes 13 Team Solkraft BalloonSat Mission to the Edge of Space Design Document Revision D 10/09/10 10/11/10 10/12/10 10/14/10 10/19/10 10/21/10 10/25/10 Acquire all hardware and materials Finished with all structure testing Initial Programming of Arduino Start Construction of Electrical systems Start Interfacing of systems Test Electronics BalloonSat. Built 10/26/10 10/29/10 10/29/10 Final Critique Simulation Test All testing complete 11/1/10 11/2/10 11/5/10 11/6/10 11/8/10 11/30/10 12/4/10 12/7/10 Troubleshooting complete Revision C due BalloonSat Weigh-in and Turn in Launch Day Post-launch Data Review Complete Final Presentations Revision D due BalloonSat Hardware Turn In Yes Yes Yes Yes Yes Yes Not finished this day, but almost completely finished during this week Done later in the week Yes Did some ground tests after finishing completion during the following week Yes Yes Yes Yes Yes Yes Yes 5.0 BUDGET Name Purpose Canon A5701S Camera HOBO Datalogger Take Pictures Mass (g) 220 Cost Measure/record 68x48x19 temperature and humidity 30 Provided Space Grant Monocrystalline Solar Panels (6: 4 used, 2 extra) Polycrystalline Solar Panels (6) Photodiodes (6) Experiment 42x41x6 6 $4.95 (each) (each) Experiment 57x29x6 5 Heater Maintain internal temperature Provide Power 10x50x50 100 48x25x15 Amazon.com Record voltage readings from solar cells and light intensity readings from photodiodes Power Microcontroller 69x53 34 ~ $3 (each) (each) 40 $59.95 10 Sparkfun 9V Batteries (4+extra for tests) Arduino Duemilanove Microcontroller 9V to barrel jack Dimensions (mm) 45x75x90 Measure light intensity 4 Where We get it Provided Space Grant Edmund’s Scientific $1.49 (each) $.40 The Electronic Goldmine West Florida Components Provided Space Grant $2.95 Sparkfun electronics 14 Team Solkraft BalloonSat Mission to the Edge of Space adapter Switches Connecting Wires Resistors Thermistor (5 one comes with Arduino) Micro SD Shield 16 Channel Multiplexer (1) Multiplexer breakout board (1) Foamcore Shipping Totals Design Document Revision D Turn on/off electronics Provided Spacegrant/with Arduino Provided With Arduino Provided With Arduino Integrate electronics Set up circuit for solar panels Record Temperature Can put micro SD card into Arduino for extra memory Make additional readings with analog inputs on Arduino Structure of satellite 5 $1.95 Sparkfun 10 $16.95 Sparkfun 8x9 $.95 Sparkfun 40x18 $4.95 Sparkfun 53x52 (see diagrams) 163 793 Provided Space Grant ~$20 $176.54 **For those which dimensions and mass are blank, are not sure yet how much/many it will be, but Team Solkraft believe it will not put us over the weight limit. 5.1 BUDGET MANAGEMENT The budget will be managed by Alexandra Jung. Team Solkraft will keep an up to date account of spending and plan for what the experiment will need so that Team Solkraft does not go over budget. Right now Team Solkraft has a large surplus in the budget and we will try to keep a surplus in case there is anything the experiment need to order at the last minute such as a replacement part of something that has been forgotten. 6.0 TESTING Team Solkraft will make testing a priority to insure that every component will successfully contribute to the overall mission. Team Solkraft will start by making sure that the structure is capable to handle the stresses exposed during takeoff, burst, and landing. Team Solkraft shall do this by performing several structural tests on a similarly massed dummy satellite. The dummy satellite will have rocks inside of the structure of similar mass to the components but will not necessarily be in the exact position the components will be in. 1. Kick Test-The dummy was kicked down a flight of stairs to test overall strength. 15 Team Solkraft BalloonSat Mission to the Edge of Space Design Document Revision D Structure held well during test with only minor damages to the corners of the BalloonSat. 2. Drop Test-The dummy was dropped two stories from the ITLL second story balcony to insure the structure is capable of handing the stresses related to various landing scenarios. The BalloonSat remained intact except from minor damages to the foamcore because the structure landed on the flight tube. Team Solkraft anticipates that this will not be a problem because there will be other satellites above and below on the flight string so there will be no direct impacts as seen in the test. 3. Whip Test-The dummy was swung about a string to test the strength of vulnerable points on the spacecraft, such as the flight string tube, corners/joints, and access points. This also tested whether our system to keep the BalloonSat attached to the flight string was strong enough. This will simulate the forces exerted on the satellite during burst. This test was successful with the flight tube withstanding the forces. 16 Team Solkraft BalloonSat Mission to the Edge of Space Design Document Revision D Secondly, Team Solkraft will perform various tests on the internal components of the spacecraft. The tests to be performed include: 1. Freeze test- This test will simulate the radical temperature changes Team Solkraft’s payload will go through on its journey to near-space. In this test, Team Solkraft will put our fully functional satellite into a cooler with dry ice. To correctly simulate mission conditions, the payload will be left in the cooler for a little over an hour. The data taken during the cold test will only be temperature data due to the fact that there will be no light in the cooler. 2. Data tests- Team Solkraft will perform tests to verify that all systems are functioning correctly and the spacecraft is capable of taking data. To simulate this, Team Solkraft shall power up the payload as if it were launch day, and expose it to various environmental conditions to insure the HOBO is collecting and logging data correctly. If any issues arise, we will test individual components to make sure they are working properly. 17 Team Solkraft BalloonSat Mission to the Edge of Space Design Document Revision D Voltage Readings of Solar Cells by Arduino 0.12 0.1 Voltage 0.08 0.06 Monocrystalline 0.04 Polycrystalline 0.02 0 0 -0.02 5 10 15 20 25 Time (s) Data from a general systems test in low light. Readings are from one side of the BalloonSat. At Time~12 seconds the BalloonSat was moved into the shade. A corresponding drop was seen so we know both solar cells are giving correct readings. Also from this test we can see that the monocrystalline cells have a consistently higher voltage at a constant temperature on the ground. 3. Camera/imaging tests- These tests insured that our camera was working properly and is ready for launch day. This was accomplished by setting the programming to trigger the camera to start at certain intervals, and making sure those intervals are consistent throughout the picture taking process. We tested the camera outside and inside the satellite to ensure that the lens of the camera was not obstructed inside. The final position of the camera gives us a clear picture outside the satellite. 18 Team Solkraft BalloonSat Mission to the Edge of Space Design Document Revision D In addition, Team Solkraft will initiate tests on the experiment portion of their mission, to ensure that the experiment is capable of operation throughout the flight. These tests include: 1. Control tests- Team Solkraft will perform different ground tests to serve as a control for the experiment. For instance, because we are testing the variation of solar cell efficiency in near-space conditions, one of our control experiments will be to expose the solar cells to various temperature differences on the ground. This will enable us to possibly rule out temperature as a variable in the efficiency in solar cell output, and move us toward investigating other possible variables such as altitude. Team Solkraft will also order extra parts to ensure that the payload is capable of flying on launch day, regardless of the possible misfortunes our testing process may have on it. 6.1 SAFETY Team Solkraft will do its best at maintaining the safety of its team members and all bystanders. We will be sure to follow the safety instructions given to us when Team Solkraft starts soldering. Through all of the testing Team Solkraft will use common sense. Also, for all tests at least two team members will be present. For the drop test we make sure the drop zone is clear and give the person dropping the correct signal to proceed. We will make sure the rope/wire is very secure before starting the whip test and we will clear a safe radius from the person ‘whipping.’ The stair well and sides and bottoms of it will be clear of people before we start the stair test just in case the satellite goes over the side. The hot glue gun will be operated very carefully and with finesse. The glue will be given time to cool. The exacto blade will be handled with one hand and with the other a good distance to the side. We will never operate it with rapid motions, just slow careful cuts. 7.0 EXPECTED RESULTS The monocrystalline cells will outperform the polycrystalline cells, while both cells will perform better in a near space environment than on the ground. Monocrystalline cells are more expensive to manufacture than polycrystalline, but monocrystalline cells are known to be more efficient than polycrystalline when used on the ground.3 Team Solkraft expects that the solar cells will perform more efficiently in the near space environment for a multitude of reasons. First, team Solkraft expects that the atmosphere interferes with the light from the sun that hits Earth and causes the intensity of the light to decrease as it goes through the atmosphere. Therefore, at higher altitudes the solar cells will produce a higher voltage output because there is a higher light intensity. This was the case with the control tests on the ground. This can be seen in the graph of voltage readings in section 6.0 under Data Tests. Second, team Solkraft expects that the solar cells will function more efficiently at the colder temperatures of near space because of the increase in the Carnot efficiency of the cell. This 19 Team Solkraft BalloonSat Mission to the Edge of Space Design Document Revision D happens because the temperature difference of the source of light, the sun, and the solar cell are greater as the temperature of the solar cell and its surroundings decrease.3 More control test are needed to determine how much temperature affects the voltage output of the solar cells. Team Solkraft will perform more control tests in the days leading up to launch. Team Solkraft expects that the lower temperatures and higher light intensities of the upper atmosphere will affect the voltage output of the solar cells. If Team Solkraft’s assumptions are correct that the lower temperatures will increase solar cell output the data will show a peak in voltage as the BalloonSat goes through its coldest point, the tropopause. However, light intensity is also a factor and from the data it can be determined whether the light intensity or temperature affect it more based on whether the peak voltage is at the tropopause or at the maximum altitude. 8.0 LAUNCH AND RECOVERY Launch Procedure 1. BalloonSat will be attached to flight string before launch day by Chris Koehler 2. HOBO will start recording automatically for 6:45 AM on November 6 3. Team Member A will flip switches to start the camera, heater and Arduino. (Camera switch will be flipped back to “off” position after the wires have been short circuited to start the camera and will therefore not be a drain on the battery) 4. Team Member B will hold Team Solkraft’s BalloonSat awaiting release of weather balloon 5. As weather balloon is released Team Member B will move forward so a smooth launch will be achieved Recovery 1. Quinn McGehan will drive Team Solkraft to the recovery site 2. After recovering the BalloonSat the heater and Arduino switches will be turned off. Data Retrieval The science data will be recorded to a microSD card connected to the Arduino microcontroller. The data will be in the form of a .txt file. In the data will be the time that has passed since the microcontroller was turned on, the input of the multiplexer that the Arduino is currently taking data, and a voltage reading. This file will then be opened in Excel. The programming of the Arduino allows for tabs between each data value and a return after each line of data so that when the file is imported into Excel it will be in three columns: time, input number, voltage. The data can then be split up into each of the 16 inputs based on the input number in the second column. The voltage will be given on a scale from 0-1023 which corresponds to 0-5V DC. The relative voltage coming through the thermistors will change because the resistance changes based on the temperature. The voltage from the photodiodes corresponds to relative light intensity. The 20 Team Solkraft BalloonSat Mission to the Edge of Space Design Document Revision D voltage output from the solar panels can be used to find their power output based on the resistance of the circuit which we will know based on the resistor we connect. The HOBO data will be stored on the HOBO’s internal memory and can be analyzed by using Boxcar. The pictures from the camera will be stored on the camera’s SD card. LAUNCH DAY Launch and recovery went well. We were able to retrieve most all of our data; one thermistor did not work correctly, but other than that we were able to get data. At the launch site our satellite sustained minimal damage. The structure was intact and there was only one polycrystalline solar cell that a corner broke off. 9.0 RESULTS, ANALYSIS, AND CONCLUSIONS Our hypotheses that the monocrystalline cells will outperform the polycrystalline, and that both cells will perform better in near space than on the ground were both proven true by the data from our experiment. 9.1 FLIGHT DATA Below are graphs of the BalloonSat flight. They show voltage data from the two different types of solar panels recorded by the Arduino. The voltage from all four sides of the BalloonSat were averaged and plotted. The temperature data is an average from the three working thermistors on the BalloonSat. The altitude data was obtained from the EOSS GPS. From the graphs we can see that temperature corresponds very closely to voltage output. The values on the axis for temperature are reversed to better show the correlation between a decrease in temperature and an increase in voltage. 21 Team Solkraft BalloonSat Mission to the Edge of Space Design Document Revision D 22 Team Solkraft BalloonSat Mission to the Edge of Space Design Document Revision D From the first two graphs we see that the temperature data and the voltage data points follow a similar curve. As the temperature decreases, the voltage output from both the monocrystalline and the polycrystalline solar cells increases. This correlation is best seen as the BalloonSat travels through the tropopause on assent and descent. On ascent the BalloonSat travels through the tropopause during the time 50-90 minutes and on descent passes through it again during time 160-170 minutes. This is the coldest point of the flight with the temperature reading -69.16 degrees Celsius. During these two time intervals the solar cells experienced the highest voltages with the monocrystalline having a maximum of .675 V and the polycrystalline having a maximum of .646 V. We concluded that temperature has a greater effect on the solar cells than altitude because both types of cells follow the plot of the temperature data rather than the altitude data. After plotting the voltage data from both the monocrystalline and polycrystalline we can see that while both data plots follow similar curves, the monocrystalline solar cells had a higher voltage output throughout the entire flight. This confirmed our hypothesis that the monocrystalline solar cells would have a higher voltage output than the polycrystalline cells. This is caused by monocrystalline cells, although more expensive, being made from a single homogenous silicon crystal while polycrystalline cells are made from many smaller silicon crystals. Because the single silicon crystal has no grain boundaries it becomes a more efficient cell. 23 Team Solkraft BalloonSat Mission to the Edge of Space Design Document Revision D Temperature Data of The Balloonsat 40 20 0 Temperature (°C) -100.00 0.00 100.00 200.00 300.00 400.00 500.00 HOBO Internal -20 HOBO External Thermistor -40 -60 -80 Time (in minutes, time 0 is when thermistors were turned on) Above is the temperature data from the flight. It shows the data from the HOBO’s internal (blue) and external sensors (red). It also shows the average temperature data from our three working thermistors (green). The thermistors were attached to the outer side of the BalloonSat so the temperature stays generally between the temperature of the outer and internal temperature. In general the internal temperature lags behind the thermistor temperature which lags behind the external temp. This makes sense because it takes time to equilibrate from the outside temperature to the internal. 24 Team Solkraft BalloonSat Mission to the Edge of Space Design Document Revision D Photodiode Voltage Output 10 per. Mov. Avg. (Series1) 0.8 0.7 Voltage Reading 0.6 0.5 0.4 0.3 0.2 0.1 0 0 50 100 150 200 250 Time (Minutes) The photodiode voltage output was to be used to determine light intensity. However, it was found that the photodiodes used on the balloonsat were too affected by temperature to get accurate light intensity data. 25 Team Solkraft BalloonSat Mission to the Edge of Space Design Document Revision D 9.2 GROUND TESTING Monocrystalline Ground Moved Solar Cells out of direct sunlight Monocrystalline Temperature 0.6 0 Output (V) 10 0.4 15 0.3 20 25 0.2 30 0.1 Temperature (celsius) 5 0.5 35 0 40 0 20 40 60 80 100 120 140 160 180 200 Time (min) Polycrystalline Ground Moved Solar Cells out of direct sunlight Temperature Monocrystalline Polycrystalline 0.6 0 Output (V) 10 0.4 15 0.3 20 25 0.2 30 0.1 Temperature (celsius) 5 0.5 35 0 40 0 20 40 60 80 100 120 140 160 180 200 Time (min) 26 Team Solkraft BalloonSat Mission to the Edge of Space Moved Solar Cells out of direct sunlight Design Document Revision D Ground Comparison Monocrystalline Polycrystalline 0.6 0.5 Output (V) 0.4 0.3 0.2 0.1 0 0 20 40 60 80 100 120 140 160 180 200 Time (min) Control Experiment-Ground Voltage Output (One Solar Panel) 0.6 0.5 Voltage 0.4 0.3 0.2 Upper line is when side was directly in the sun. Lower line is when this side was away from the sun. 0.1 0 10 15 20 25 30 35 40 Temperature (Degrees C) From the ground tests it can be seen that temperature is directly relatable to voltage output. The slope of the points in the graph directly above shows a very linear relationship between 27 Team Solkraft BalloonSat Mission to the Edge of Space Design Document Revision D temperature and voltage. The ground testing also shows that the monocrystalline cells outperformed the polycrystalline during the ground tests as well as during flight. 9.3 SUMMARY Our hypothesis that the solar cells would perform better in a near space environment than on the ground was confirmed. The maximum voltages reached during ground testing were .567 and .537 for the monocrystalline and polycrystalline cells respectively. These maximums are lower than the maximums reached during flight which were discussed previously. While the conclusion can be drawn that the cells are more effective at lower temperatures, it can not necessarily be said that they are more effective at higher altitudes. The extremely low temperature experienced in the tropopause is what led to the cells producing more voltage in near space than on the ground. It is possible that the same voltages reached in near space could be reproduced on the ground at similar temperatures. 10.0 READY FOR FLIGHT Our main problems during the flight consisted of an internal temperature dropping below minus ten degrees Celsius and one of our thermistors on the outside panel did not record proper temperature readings. The internal temperature failure that the HOBO recorded was due to the camera hole letting cold air inside the satellite. Although we put insulation surrounding the camera lens to partition that inside section separate, this insulation did not prevent the inside temperature reading from dropping below minus ten degrees Celsius. To correct this problem for next flight we added additional insulation around the camera lens to keep the interior of the satellite separated and protected from the camera hole that lets in cold air. To verify that this corrected the problem, Team Solkraft conducted another cold test by placing the satellite in a cooler filled with dry ice. When the HOBO internal temperature reading was recorded again the internal temperature did not fall below minus ten degrees Celsius. The other failure in our satellite was a faulty thermistor that did not record the external temperature during the flight. We tested the thermistor with the multimeter and the sensor worked under different temperatures by giving out different voltages. When then tested the connections of the thermistor to the multiplexor that fed into our Arduino microcontroller and found there wasn’t a closed circuit. After taking off the electrical tape that covered each junction of the wires we found that one junction had come loose which caused our thermistor to not report any temperature data to Arduino. Once this joint was fixed by re-soldering it we found the thermistor was working. Team Solkraft’s BalloonSat should be stored in a dry, room temperature environment, in a case that prevents the satellite from moving around. Any movement or collision to the sides of the satellite could damage the sensors, especially the polycrystalline solar panel. In order to activate the BalloonSat first both the micro SD and the SD card for the Arduino and camera need to be wiped of all pre-launch data and pictures. Second, the HOBO 28 Team Solkraft BalloonSat Mission to the Edge of Space Design Document Revision D needs to be set and turned on to start recording at a specific time. Once all the components are in, the satellite needs to be sealed by taping up the seams with aluminum tape. Right before launch the switches for the camera, heater, and Arduino need to be turned to the on position and then the satellite is ready for flight. Our payload will last if it is not launched within 6 months; the only parts that might need to be changed would be the batteries for the camera, heater, and microcontroller. 11.0 CONCLUSIONS AND LESSONS LEARNED From the flight and resulting data, team Solkraft observed that the voltage output of solar cells depends more on the temperature of the cell than the altitude that the cell is at. This information points to the conclusion that solar cells would produce maximum voltage if placed in low temperature environments such as the tropopause. An object (such as a stratospheric platform) placed in the tropopause would be able to produce the maximum amount of power from its solar cells. This means it could use more instruments simultaneously because of the added power from the low temperature, allowing it to be more useful when placed at that altitude. Team Solkraft also learned the importance of organization. Due to the number of sensors we had, wiring became a problem. Instead of taking our time to come up with an organized method of wiring our instruments, we tried to get it down as fast as possible. The end result was a mass of wire that made a lot of the space in our BalloonSat useless, and would have made any repairs very difficult because of the difficulty following the wires. We have also learned a lesson about teamwork. Working in a team is a very important skill to have, if the team cannot function well then the whole project is put in jeopardy. The lesson that we learned about team work was that not all team members are as dedicated as others, this left uneven amounts of work to be done by each member, and a lack of trust between the members who were always at the meetings and the ones who were not. 12.0 MESSAGE TO NEXT SEMESTER This class will be one of the most rewarding and unique experiences of your education. Gateway will give you an inside look into the life of an engineer through hands on experience. That being said, this class is very difficult and very time consuming. Be prepared to learn entire new concepts with little guidance in a very short amount of time. If you have the dedication then you will get through it, but it will be challenging. Start early, work hard, and you will have the time of your life. REFERENCES 1. NREL http://www.nrel.gov/news/press/2008/625.html 2. Solar Server http://www.solarserver.com/knowledge/basic-knowledge/photovoltaics.html 29 Team Solkraft BalloonSat Mission to the Edge of Space Design Document Revision D 3. Projects at the Solar Energy Group http://www.physics.usyd.edu.au/app/solar/about/projects.html BIOS Scott Taylor Scott is a freshman in Aerospace Engineering at University of Colorado at Boulder. He was born August 29, 1992 in Boulder, CO. He likes to kayak and mountain bike in his free time. In the future Scott hopes to work for NASA or a private space company with human spaceflight and spacecraft propulsion. Phone: 303-945-1488 Address: 9016 Crosman Hall. Boulder, CO 80310-0010 Email: scott.f.taylor@colorado.edu Kyle Garner Kyle is a freshman in Aerospace Engineering at the University of Colorado at Boulder. Born in Longmont, CO, he enjoys the outdoors and playing video games when he has some extra time. Kyle was actively involved in debate in high school, and enjoys judging at meets and helping out the team however he can. In the future, Kyle dreams of working with NASA on human spaceflight projects. Phone: 720-210-8615 Address: 9012 Aden Hall. Boulder, CO 80310-0002 Email: kyle.garner@colorado.edu Mark Sakaguchi Mark was born on July 23, 1992 in Denver Colorado. He is a freshman at the University of Colorado at Boulder and is studying Aerospace Engineering. Mark likes to play golf and is an active member in the Japanese drumming group, Denver Taiko. In the future Mark wants to be working for Lockheed Martin or working for NASA as an aerospace engineer. Phone: 720-281-3545 Address: 9008 Andrews Hall. Boulder, CO 80310 Email: mark.sakaguchi@colorado.edu Quinn McGehan Quinn is a jovial fellow, who was born in Fairfield, California on April 25th 1992. He has been raised almost completely in Boulder and attended Fairview High School. He currently attends CU- Boulder, majoring in Aerospace engineering. He greatly enjoys ping-pong, sports, and movies. Quinn wants to one day go to space himself, and in the future hopes to work for NASA. 30 Team Solkraft BalloonSat Mission to the Edge of Space Design Document Revision D Phone: 303-877-7962 Address: 9057 Aden Hall. Boulder, CO 80310 Email: Quinn.mcgehan@colorado.edu Anna Alexandra Jung Alexandra is an international student from Copenhagen, Denmark from where she also has a B.Sc. in astrophysics. She plans on doing her masters in aerospace engineering, which is why she came to Boulder to get as much experience as possible within this field. Born in Dragør just outside of Copenhagen on December 6th 1986, she has always aimed for the stars and wanted to become an astronaut. The dream is still alive, but all she knows for sure is that she wants to work with human spaceflight in one way or another. Being a former elite athlete she enjoys swimming, skiing and athletics in general. Besides that, music and socializing takes up a lot of her time. And she loves to travel, meeting new people and learn about different cultures. Address: 1024 Adams Cir Apt. F-224.Boulder, CO 80303 Phone: 720-278-4973 Email: anna.jung@colorado.edu Thomas Buck Thomas was born in San Antonio, Texas, but moved to Colorado when he was three. Thomas went to Thomas Jefferson High School and decided to go to CU Boulder, because of the Aerospace program, the campus and the people. He is a fun guy to hang around with and has a good sense of humor. In his free time Thomas enjoys snowboarding, playing the guitar, shooting some hoops and adventuring through Colorado’s vast and beautiful landscape. Phone: 303-517-7760 Address: 9055 Aden Hall. Boulder, CO 80310. Email: Thomas.buck@colorado.edu 31 Team Solkraft