WHAT IS A CUBESAT? DragonSat-1 (1U CubeSat)

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2 WHAT IS A CUBESAT? Miniaturized satellites classified according to height (10-30 cm) Purpose is to perform small spacecraft experiments. Use has increased due to relatively low cost DragonSat-1 (1U CubeSat) 2

3 PROBLEM STATEMENT CubeSat missions are becoming more important Missions are reliant on launch vehicle locations Limited control on the CubeSat s orbital altitude Need better attitude control systems Feasible propulsion system is needed to increase mission capability 3

4 PAST MICROPROPULSION SYSTEMS Characteristics Nominal Values Specific impulse (sec) 220 Thrust (N) 1 Thruster Mass with Valve (g) 290 Propellant Hydrazine (N 2 H 4 ) Accumulated Burn Life (hours) 50 1 N Hydrazine Thruster 4

5 ALTERNATIVE OPTION Electric Propulsion (EP) provides an option Specific impulse values up to 5,000 seconds Thrust duration lasts from weeks to years Xenon and Teflon are common propellants Problems: Require large amounts of power (>~300 W) Take up about half of payload volume and mass of 1U to 3U CubeSats 5

6 MICRO-CATHODE ARC THRUSTERS Characteristics Nominal Values Specific impulse (sec) 3000 Thrust (N) 1µN Thruster System Mass (g) Propellant 200 Titanium cathode Average Power (W) 0.1 Thruster System Volume (cm 3 ) Delta-V (for 4 kg satellite) (m/s) Micro-cathode Thruster Heads 6

7 MISSION AND OBJECTIVES Mission: Collaborate with The George Washington University to successfully demonstrate an electric propulsion system in orbit for application to CubeSat missions Primary objectives: Integrate a miniature size propulsion system into a 1.5U CubeSat Perform three maneuvers in space: de-tumbling, pointing control, and delta-v Secondary objective is to expand APRS network 7

8 CONCEPT OF OPERATIONS Will fire up to four thrusters Perform three key maneuvers: Initial De-tumbling Controlled spin about two axes Delta-V Operation Gyro and magnetometer used for measurements Z -Y X Thruster Firing and Rotation 8

9 MISSION PLAN BRICSat-P Mission Flow Chart 9

10 SUCCESS CRITERIA Criteria Attainable The thrusters can successfully fire. BRICSat-P can de-tumble successfully BRICSat-P can spin and de-spin in a stable manner. Enough power is available to perform successful Delta-V maneuver. The process can be repeated. 10

11 Satellite Overview Specifications Values Size 1.5 U Mass (kg) 1.9 Volume (cm 3 ) 1500 Antenna Lengths (cm) HF VHF UHF Number of Thruster Systems 4 11

12 INTEGRATION AND MISSION ANALYSIS USNA TEAM 12

13 BRICSAT-P DESIGN PROGRESSION Place four thruster heads around center of mass Permanent magnet to stabilize CubeSat Intermediate Design: Integrate four full thruster systems into BRICSat-P Power unit changed from 1.5U to 1U Thruster systems placed on y-axis plane X 1 4 Z 2 3 Y Initial Design with Thruster Placement 13

14 ATTITUDE DYNAMICS MATLAB Simulink model Simulate effects of aerodynamic drag, magnetic field, and gravity gradient torque Permanent magnet de-tumbling analyzed Incapable of detumbling spacecraft AND CONTROL wbody (deg/sec) x-axis y-axis z-axis time(s) x 10 4 Failed Magnetic Stabilization 14

15 FINAL DESIGN CONSIDERATION Use thrusters for attitude and rate control Meets all of mission objectives Fully characterize thruster system Two possible thruster configurations: Staggered (2 thrusters on opposite face) X-wing (all thrusters on same face) Staggered Configuration X-Wing Configuration 15

16 THRUSTER CONFIGURATION Y Z X Staggered configuration is only one orbit faster. X-wing configuration was chosen: Less complicated mechanically Makes delta-v scenario more feasible Can de-tumble within 7 orbits Subsystem Layout 16

17 DE-TUMBLING GOALS Determine appropriate thruster configuration based on: Initial Tumbling: 15 deg/sec Target stability: +/- 1 deg/sec Determine the exact placement of thrusters Fewest number of orbits to stabilize Determine duty cycle for thruster firing. 17

18 X-WING CONFIGURATION Thruster Detumbling x-axis y-axis z-axis 1.40E E+01 Composite Stability wbody (deg/sec) Detumbling Time (orbits) 1.00E E E E E time(s) x E Thruster Separation (cm) Satellite can successfully stabilize from initial tumbling in 7 orbits! 18

19 ALTERING INITIAL CONDITIONS Thruster Detumbling x-axis y-axis z-axis 3.00E E+01 50% Duty Cycle 10 wbody (deg/sec) X: 1.123e+04 Y: Detumbling Time (orbits) 2.00E E E E time(s) x 10 4 Altering Inertia Tensor 0.00E+00 Mass distribution and duty cycle affect thruster s performance in rotation control mode Thruster Separation (cm) 19

20 FINAL DESIGN PARAMETERS Configuration X-wing Placement -Y Face Separation (cm) 4.5 Duty Cycle (%) 50 Misalignment Tolerance 5 degrees 2 mm 20

21 ROTATIONAL EXPERIMENT Target rotation rate of 6 rpm 22% duty cycle 10 minutes to spin 70 minutes of rest 10 minutes to de-spin Camera will take pictures of thrusters Communications sent to USNA ground station 21

22 DELTA-V SCENARIO Magnetometer for CubeSat orientation Based on magnetic field orientation Can identify orientation in two axes planes Fire 4 thrusters along Earth s magnetic field line Send pictures of thruster firing Modeled in MATLAB Simulink and STK 22

23 SOLAR POWER ESTIMATES Power Predictions: Worst case scenario: 2.04W Best Case: 4.34W Orbit Average Power: 3.25W Thruster power requirements: 1 Watt Power required is based on continuous firing Triangular Advanced Solar Cells (TASC) 23

24 PAYLOAD DESIGN GW TEAM 24

25 PAYLOAD OVERVIEW Thruster Head Thruster Controller Power Processing Unit Inductors Propulsion System Overview Thruster Head 25

26 THRUSTER SPECIFICATIONS Diameter (cm) 1 Length (cm) 2.29 Backflux None Operational Life (years) 10 Total Impulse (N-sec) 120,000 Thruster Spark in Live Fire Test Input Voltage (VDC) 5 Final Thruster Boards 26

27 FUTURE SCHEDULE Final Testing Delivery Launch Begin Operations Collect and Analyze Data 27

28 CONCLUSION Criteria The thrusters can successfully fire. BRICSat-P can de-tumble successfully Attainable BRICSat-P can spin and de-spin in a stable manner. Enough power is available to perform successful Delta-V maneuver. The process can be repeated. 28

29 REFERENCES Jahn, Robert G. Physics of electric propulsion. McGraw-Hill, New York, M. Keidar, S. Haque, T. Zhuang, A. Shashurin, D. Chiu, G. Teel, E. Agasid, O. Tintore, E. Uribe, Micro-Cathode Arc Thruster for PhoneSat Propulsion, 27th Annual AIAA/USU Conference on Small Satellites, Logan, UT. Paper # SSC13-VII-9. M. Keidar, S. Haque, G. Teel, E. Agasid, O. Gazulla, A. Perez, G. Trinh, E. Uribe, Micro Cathode Arc Thruster PhoneSat Experiment for Small Satellites, 33 rd International Electric Propulsion Conference, IEPC w=article&id=49&catid=16&itemid=124 talystsspecialforhydrazinedecomposition/catalysts_special_for_hydr azine_decomposition.aspx. 29

30 REFERENCES Sutton, George. Rocket propulsion elements. Hoboken, N.J: Wiley, Goebel, Dan M. and Katz, Ira. Fundamentals of Electric Propulsion. Hoboken, N.J: Wiley,

31 QUESTIONS? Christopher K Dinelli 31