Skillz That Killz Critical Design Review Jocelyn Mulkey, Jess Davidoff, Kaitlyn Zimmitti, Taylor Smith, Travis Dowdy, Hunter Hoopes October 8, 2009

Mission Overview To investigate both the benefits and cost s of generating energy with solar at high altitudes Solar cells use photons as light energy to create electricity We would like to determine if encapsulated monocrystalline solar cells generate more electricity at higher altitudes as a result of clearer and more intense light Purpose of Our Experiment: Answer the question: Could solar cells replace batteries in future BalloonSat missions? If this is true, future BalloonSat missions may not be constrained by battery life, weight and volume Our results may also increase knowledge about solar energy Could help answer the question: Is installing solar panels to airplanes to power them a feasible solution to reducing their carbon footprints?

Requirements Flowdown Goal (G1)‏ –Our BalloonSat shall rise to an altitude of roughly 30 kilometers in order to perform a scientific experiment that will measure the energy output of solar cells at altitudes higher than ground level so as to better understand the ability of these cells to generate more electricity at higher altitudes as a result of clearer and more intense light. O1 (comes from G1)‏ –Assemble BalloonSat in order to advance our understanding of solar energy at an altitude of 30 kilometers for under $100 by 11/07/2009. O2 (comes from G1)‏ –Determine altitude by measuring tilt in one axis. O3 (comes from G1)‏ –Establish a function of altitude to find the correlation between altitude and solar energy.

Design Structural Design 17 centimeter cube Double-layer foam core, secured with hot glue, aluminum tape, and Velcro, if necessary We will have a small Plexiglas window on one side to protect the camera's lens during flight. We will have a solar cell on each side of the cube placed into an inset in the foam core The solar cells are monocrystalline and encapsulated (no further protection needed from moisture) ‏ Hardware Design Six solar cells will be connected to an 8-input multiplexer inside the cube, which will direct the analog input from each cell to one input on the AVR Microcontroller board. The multiplexer is necessary because we only have four available inputs on the AVR, but six solar cells from which to collect data. The AVR will record the voltage from each solar cell. Because the AVR records data in volts, and the solar cells output in volts, there will be no need to convert the data after retrieval other than with the Data Parser Utility. When we are retrieving our data, we will use the utility to convert the data from binary to voltages.

Other hardware pieces AVR Microcontroller board (to record data from temperature, altitude, air pressure, and voltage from solar cells)‏ Heater system (temperature control to protect hardware)‏ Digital camera (to record pictures from the flight)‏ Multiplexer (to take the voltage inputs from all 6 solar panels and channel them into one input on the AVR)‏ Four 9V batteries, foam core, Velcro, hot glue, insulation, a non-metal flight string tube, extra wire, MUX, test batteries, and dry ice. (All of these materials are provided or are in the SpaceGrant inventory except for the solar cells and the MUX, which will be purchased from Sundance Solar and West Florida Components, and the test batteries and dry ice, which will be paid for by our team and purchased from Safeway. )‏ Experimental Design The reason for placing a solar cell on the four sides of the cube is to ensure there is always light reaching at least one cell. The bottom cell –May collect photons reflected from the ground (especially if snow is present), and, when high enough, reflected from the clouds – We will draw conclusions from our data if this is true.

Design Sketches

Functional Block Diagram

ItemWhere to get itCostWight AVR Microcontroller and batteries Provided$0150 g Heater system and batteries Provided$0100 g Foam CoreProvided$0108 g InsulationProvided$0TBD SwitchesProvided$020g Flight String TubeProvided$0TBD Canon Digital CameraProvided$0220 g Monocrystalline Solar CellsSundance Solar$ g (6 cells) 8-Input MultiplexerWest Florida Components$26.78TBD Plexiglas (9x7.5 cm)Space Grant Inventory$064 g Resistors (if needed)SGI$0Not required at this time VelcroSGI$0Not required at this time Aluminum TapeSGI$0<1 g Hot GlueSGI$016 g Extra WireSGI$0Not required at this time Test Batteries and Dry IceSafewayApprox $35 (cost covered by team) N/A TOTAL$96.18 (not including cost covered by team) Total of Known: 721 g Weight allowed for unknowns: 129 g

Project Schedule Team Meetings: All Tuesdays at 2:00 p.m. Design complete 9/20/09 Complete Proposal 9/15/09 Proposal Due9/17/09 6 p.m. Conceptual design review 9/ 22/09 8 a.m. Program AVR 9/27/09 Order all hardware 9/29/09 Foam Core Structure Built 0/05/09 Critical design review 10/06/09 8 a.m. DD Rev A/B due 10/06/09 Structure Testing – Drop/Whip Tests 10/06/09 2 p.m. Prototyping design complete 10/13/09 Experiment Testing 10/14/09 Subsystem Testing (Heater/Solar Cells) 10/14/09 Testing final design complete 10/20/09 Cold Test 10/20/09 Functional Test – Heater, Camera 10/20/09 Camera/Imaging Test 10/20/09 Subsystem Test 10/20/09 Pre-Launch Inspection (Bring hardware) 10/27/09 Mission simulation tests (bring B.Sat) 10/29/09 Launch Readiness Review 11/03/09 8 a.m. DD Rev C due 11/03/09 8 a.m. BalloonSat Weigh-in and Turn in 11/06/09 2 p.m. DLC 270 A and FRR Cards Due 11/06/09 Launch Day!!! 11/07/09 4:45 a.m.

Test Plans TestPlans Experimental Testing Place BalloonSat in sun for same amount of time as flight Rotate B.Sat to simulate spin during flight Record voltage input from solar cells and temperature (to test temp effects on cells) Retrieve and analyze data from cells and temp sensor Make sure input from solar cells does not exceed 5V limit and install resistors if needed Structural Testing Whip test (determine force of flight will not destroy or weaken structure) Drop test (determine burst/landing will not destroy structure) 4-story drop + kick down stairs Cold Test (placed in a cooler of dry ice for ~2 hours to simulate temperatures during flight) Functional/Subsystem Testing Test correctness of software codes Test camera’s ability to turn on Test heater’s ability to keep B.Sat above (-10°c) for ~2 hours Test all subsystems work together and that power input/output does not exceed 5V Mission Simulation TestingIn class mission simulation Camera/Imaging TestingTest camera to ensure Images/videos are being recorded Images/videos are clear Determine if Plexiglas obstructs images

TestCompletion Date Experiment Testing10/14/2009 Structural Testing10/6/2009 Functional/Subsystem Testing10/20/2009 Mission Simulation Testing10/29/2009 Camera/Imaging Testing10/20/2009

Expected Results The purpose of our mission is to determine the advantages of generating energy with solar cells at altitudes other than ground level. We hope to discover if solar cells are more beneficial when at higher altitudes. Expected Results: To either show increased energy as altitude increases or show negligible difference in energy input. To retrieve data: Connect AVR board with data to computer and use Data Retrieval Utility to retrieve data from board. To read data: Use Data Parser Uttility to transform data from binary to voltages which we can use to analyze data To organize data: Use Excel where we can then interpret and draw conclusions.

These graphs indicate what our data for the four side cells should look like, whether the payload is spinning, if it is stationary, or a combination of the two circumstances. The data from the top and bottom cells will not be affected by spin so they are not included in the graphs. If the payload rotates, each reading should provide about the same average voltage reading over the course of the flight: If the payload starts rotating and ends in a static condition, we should see several of the cell's data drop-off and only one or two cells producing current: If there is no or minimal rotation we should only see in the data two cells providing current: The data of the voltages of each solar cell will allow us to determine which solar cell was facing the sun (or snow, for the bottom cell) at what time. The voltage data of the cell facing the sun will be higher than the others. This will help us to visualize the attitude of the satellite throughout the flight. In order to determine altitude from the air pressure data, we will use the equation p = ( h) where p = air pressure (Pa) and h = height above sea level (m).

Team Organization Team MemberTitleSecondary TitleAdditional Responsibilities Jocelyn MulkeyProgramming/ Schedule ScienceFunctional Testing Mission Simulation Testing Schedule Jess DavidoffPower/ Team Leader Budget/ReportingCamera Testing Presentations Reporting Kaitlyn ZimmittiBudgetSoftwareMission Simulation Testing Hardware Ordering/Budget Experiment Testing Taylor SmithStructure Design/ Testing Leader PowerFunctional Testing Satellite Recovery Design Documents Travis DowdyScienceProgrammingExperiment Testing Camera Testing Data Analysis Hunter HoopesSoftwareStructure DesignFunctional Testing Data Recovery Block Diagram

Biggest Worries Flight weather conditions Voltage input from cells over 5V Effects of temperature on solar cells