Performance and Verifica/on Tes/ng of an Electrical Power System for a CubeSat Seth Folley St. Mary’s University of San Antonio, Texas Mentors: Tom Woods, Chris Sawyer, MaH Carton, Amir Caspi, James Mason 1 Goals •  Develop monitoring soMware for the Electrical Power System for CubeSat mission •  Test/verify the performance of the Electrical Power System 2 CubeSats •  Small satellites •  Standard in Pico satellites –  10cm x 10cm x 10cm which is 1 unit or 1U –  1.33 kg limit per 1U •  Idea developed by Cal Poly and Stanford •  Experience for students 3 MinXSS: Miniature X-­‐ray Solar Spectrometer 4 MinXSS •  3 year Grad Student project •  3U CubeSat •  Low earth orbit 5 MinXSS •  Will measure the intensity of the soM x-­‐ray spectrum, 0.6 keV (20 Å) to 30 keV (0.4 Å) Courtesy of Amir Caspi 6 Mechanical Model +Z +Z +X +Y +Y +X 7 Command and Data Handling •  The brains of MinXSS •  Gathers housekeeping data •  Commands various instruments 8 Solar Cells •  Triple Junc/on •  Triple Junc/on is more efficient, up to 44% efficiency in labs, 30% commercial 9 BaHeries •  Lithium Polymer •  4 baHeries total •  8.4 V max –  2 sets in series at 4.2V each •  4 Ah 10 BaHeries Charging Current Characteris/cs 11 BaHeries 12 Electrical Power System 13 Electrical Power System •  Regulates Power going to the various subsystems •  Solar Panel input •  BaHery Charging 14 SoMware •  Communicate to various devices through Inter-­‐Integrated Circuit or I2C •  Read in raw data numbers and convert to Volts, Amps, and Temperatures 15 16 SoMware: Lessons Learned •
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Talking to the various chips Understanding the raw data Making sure read data was correct data What if the problem wasn’t soMware? Staying organized and commen/ng 17 Tes/ng: Why? •  Comparing modeled vs. actual •  To know and understand the limits of the EPS •  To know the efficiencies of the EPS design 18 Tes/ng: What? •  EPS components –  Solar panel regulators –  3.5 V and 5 V regulators •  BaHeries –  Capacity •  Mission Simula/on: “A Day in the Life” –  Orbi/ng day and night 19 Tes/ng: 3.5 V and 5 V Efficiency Efficiency for 3.5 V Converter 94.00% 92.00% 90.00% 88.00% ? Efficiency 86.00% Efficiency for 5 V Converter 84.00% 95.00% 82.00% 0 0.5 1 1.5 2 Current Load (A) 2.5 3 3.5 94.00% 93.00% 92.00% 91.00% Efficiency 90.00% 89.00% 88.00% 0 0.5 1 1.5 Current Load (A) 2 2.5 3 20 Tes/ng: Panel Efficiency 102.00% 100.00% 98.00% 96.00% 20 V 17 V 94.00% 14 V 92.00% 90.00% 88.00% 0 0.5 1 1.5 Current Load 2 2.5 3 21 Tes/ng: BaHery Discharge Results BaHery Discharge Voltage vs. Time 22 Tes/ng: BaHery Charge Results BaHery Charge Voltage vs. Time Range of Time for Orbit Time (minutes) 23 Tes/ng: Mission Simula/on Reveals Robust Design Solar Array Simulator State of Charge vs. Time 24 Tes/ng: Mission Simula/on Solar Array Simulator Voltage vs. State of Charge Charging Discharging 25 Conclusion •  The EPS board is populated correctly •  EPS design runs correctly and is efficient •  Slight modifica/ons to improve baHery charging 26 Acknowledgements •  Tom Woods •  Grad Students: Chris Sawyer, MaH Carton, James Mason •  Everyone on the MinXSS team •  Marty and Erin •  All the REU students •  Boulder for being awesome 27