Post on 13-Mar-2018
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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
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DragonSat-1 (1U CubeSat)
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PROBLEM STATEMENT
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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
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PAST MICROPROPULSION SYSTEMS
Characteristics Nominal Values
Specific impulse (sec) 220
Thrust (N) 1
Thruster Mass with Valve (g) 290
Propellant Hydrazine (N2H4)
Accumulated Burn Life (hours) 50
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1 N Hydrazine Thruster
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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
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MICRO-CATHODE ARC THRUSTERS
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Micro-cathode Thruster Heads
Characteristics Nominal Values
Specific impulse (sec) 3000
Thrust (N) 1µN
Thruster System Mass (g)
200
Propellant Titanium cathode
Average Power (W) 0.1
Thruster System Volume (cm3)
200
Delta-V (for 4 kg satellite) (m/s)
300
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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
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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
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Thruster Firing and Rotation
Z
X -Y
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MISSION PLAN
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BRICSat-P Mission Flow Chart
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SUCCESS CRITERIA
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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.
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Satellite Overview
Specifications Values
Size 1.5 U
Mass (kg) 1.9
Volume (cm3) 1500
Antenna Lengths (cm) HF-182.88 VHF-48.26 UHF-15.24
Number of Thruster Systems
4
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INTEGRATION AND MISSION ANALYSIS
USNA TEAM
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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
13 Initial Design with Thruster Placement
2 1 4
X Y
Z
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ATTITUDE DYNAMICS AND CONTROL
• MATLAB Simulink model – Simulate effects of
aerodynamic drag, magnetic field, and gravity gradient torque
– Permanent magnet de-tumbling analyzed
– Incapable of de-tumbling spacecraft
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0 0.5 1 1.5 2 2.5 3
x 104
-20
-15
-10
-5
0
5
10
15
20
time(s)
wB
ody
(deg
/sec
)
x-axisy-axisz-axis
Failed Magnetic Stabilization
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FINAL DESIGN CONSIDERATION
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X-Wing Configuration
• 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
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THRUSTER CONFIGURATION
• 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
16 Subsystem Layout
Z
Y X
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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.
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X-WING CONFIGURATION
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0.00E+00
2.00E+00
4.00E+00
6.00E+00
8.00E+00
1.00E+01
1.20E+01
1.40E+01
0 1 2 3 4 5 6
Detu
mbl
ing
Tim
e (o
rbits
)
Thruster Separation (cm)
Composite Stability
0 2 4 6 8 10 12 14
x 104
-25
-20
-15
-10
-5
0
5
10
15
20
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time(s)
wB
ody (
deg/s
ec)
Thruster Detumbling
x-axisy-axisz-axis
Satellite can successfully stabilize from initial tumbling in 7 orbits!
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ALTERING INITIAL CONDITIONS
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0.00E+00
5.00E+00
1.00E+01
1.50E+01
2.00E+01
2.50E+01
3.00E+01
0 1 2 3 4 5 6De
tum
blin
g Ti
me
(orb
its)
Thruster Separation (cm)
50% Duty Cycle
0 0.5 1 1.5 2 2.5 3
x 104
-25
-20
-15
-10
-5
0
5
10
15
20
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X: 1.123e+04Y: 0.9968
time(s)
wB
ody
(deg
/sec
)
Thruster Detumbling
x-axisy-axisz-axis
Altering Inertia Tensor
Mass distribution and duty cycle affect thruster’s performance in rotation control mode.
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FINAL DESIGN PARAMETERS
Configuration X-wing
Placement -Y Face
Separation (cm) 4.5
Duty Cycle (%) 50
Misalignment Tolerance 5 degrees 2 mm
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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
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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
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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
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Triangular Advanced Solar Cells (TASC)
PAYLOAD DESIGN GW TEAM
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PAYLOAD OVERVIEW
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Propulsion System Overview
Thruster Head
Power Processing Unit
Inductors
Thruster Head Thruster Controller
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THRUSTER SPECIFICATIONS
Diameter (cm) 1
Length (cm) 2.29
Backflux None
Operational Life (years) 10
Total Impulse (N-sec) 120,000
Input Voltage (VDC) 5
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Thruster Spark in Live Fire Test
Final Thruster Boards
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FUTURE SCHEDULE
Final Testing
Delivery
Launch
Begin Operations
Collect and Analyze Data
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CONCLUSION
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. ✓
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REFERENCES • Jahn, Robert G. Physics of electric propulsion. McGraw-Hill, New
York, 1968. • 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, 33rd International Electric Propulsion Conference, IEPC-2013-409.
• https://www.mpnl.seas.gwu.edu/index.php?option=com_content&view=article&id=49&catid=16&Itemid=124
• http://heraeuscatalysts.com/en/catalystschemical/catalystsspecial/catalystsspecialforhydrazinedecomposition/catalysts_special_for_hydrazine_decomposition.aspx.
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REFERENCES
• http://cs.astrium.eads.net/sp/spacecraft-propulsion/hydrazine-thrusters/1n-thruster.html
• Sutton, George. Rocket propulsion elements. Hoboken, N.J: Wiley, 2010.
• Goebel, Dan M. and Katz, Ira. Fundamentals of Electric Propulsion. Hoboken, N.J: Wiley, 2008.
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QUESTIONS?
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Christopher K Dinelli kenji.dinelli@gmail.com