2nd International Conference on Recent Advances in Space Technologies, June 09-11,2005, İstanbul,TÜRKİYE
Spacecraft Energy Storage and Attitude
ControlAlkan ALTAY
Assoc. Prof. Dr. Ozan TEKİNALPMiddle East Technical University Aerospace Engineering Dept.
TUSAŞ Aerospace Industries Inc.
2nd International Conference on Recent Advances in Space Technologies, June 09-11,2005, İstanbul,TÜRKİYE
Energy Storage in LEO Spacecrafts
Electrochemical Battery Packs
2nd International Conference on Recent Advances in Space Technologies, June 09-11,2005, İstanbul,TÜRKİYE
Attitude Control in LEO Spacecrafts
Control Moment Gyroscope ( CMG )
2nd International Conference on Recent Advances in Space Technologies, June 09-11,2005, İstanbul,TÜRKİYE
Integrated Power and Attitude Control
IPACS
A Variable Speed CMG ( VSCMG ) That Stores Energy
IPACS - VSCMG
2nd International Conference on Recent Advances in Space Technologies, June 09-11,2005, İstanbul,TÜRKİYE
IPACS - VSCMG
)1(2
1..
2max
2min2
max
min
max
JdIEstored
2nd International Conference on Recent Advances in Space Technologies, June 09-11,2005, İstanbul,TÜRKİYE
Conceptual Design Calculations
Small Spacecraft Requirements
Energy Storage ( Wh ) 100
Number of Charge/Discharge Cycles 30,000
Torque Capacity ( Nm ) 0.025
Angular Momentum Capacity (Nms ) 6
Number of Attitude Actuators 4
ElectroChemical Battery Parameters
Ni-Cd Li-Ion
Energy Density (Wh/kg) 35 110
Depth of Discharge 20 % 20 %
Reaction Wheel Design Parameters
MaxWheel Speed ( RPM ) 5000
Maximum Torque (Nm) 0.015
Angular Momentum Capacity ( Nms ) 3.4
CMG Design Parameters
Operating Speed (RPM) 15000
Max. Gimbal Speed (rad/s) 0.1
Maximum Output Torque (Nm) 0.22
Angular Momentum Capacity (Nms) 1.9
IPACS-VSCMG Design Parameters
FW1 FW2 FW3a
Max Wheel Speed (kRPM) 30 60 240
Angular Momentum Capacity (Nms)
15.3 7.7 1.9
Max Torque (Nm) 1.74 0.87 0.22
DoD 0.9375
Energy Density (Wh/kg) 5.0 8.3 25.0
a fails structurally
2nd International Conference on Recent Advances in Space Technologies, June 09-11,2005, İstanbul,TÜRKİYE
Comparisons
Electric Power System AdvantagesOf IPACS
Uncoupled energy storage and power capacity
More Charge/Discharge Cycles
Long Life
High Charge/Discharge Rates
Deterministic State of Charge
Attitude Control System Advantages of IPACS
Large Control Torques
Large Momentum Storage
Low Vibration (for Magnetic Bearing)
0
5
10
15
20
25
30
Mas
s (k
g)
Battery
Actuator
RW
+ L
i-Io
n
RW
+ N
i-C
d
CM
G +
Li-
Ion
CM
G +
Ni-
Cd
FW
- 3
0
FW
- 6
0
FW
- 2
40
Total Mass Comparison For Energy Storage and Attitude Control System Combinations
2nd International Conference on Recent Advances in Space Technologies, June 09-11,2005, İstanbul,TÜRKİYE
Simulation of a S/C Equipped With IPACS
Spacecraft Inertias (kgm2) [15, 15, 10]
Initial Orientation of S/C (deg) [0, 0, 0]
Skew Angle, β (deg) 54.73
IPACS-VSCMG FW2 (60 kRPM)
Initial Flywheel Spin Rates (kRPM)
[35, 40, 45, 50]
Initial Gimbal Angles (deg)[110, -125, 110, -
125]
60 deg of roll maneuver is
expected from the spacecraft
while energy is being drawn from
the IPACS-VSCMGs
2nd International Conference on Recent Advances in Space Technologies, June 09-11,2005, İstanbul,TÜRKİYE
Simulation Results
- Smooth Maneuvering Capability
- Both Attitude and Power Objectives Satisfied
- Uncoupled Power and Attitude Functions
2nd International Conference on Recent Advances in Space Technologies, June 09-11,2005, İstanbul,TÜRKİYE
Simulation Results
- We are able to follow any desired spin rate profile
- Low gimbal rates due to the high angular momentum content
2nd International Conference on Recent Advances in Space Technologies, June 09-11,2005, İstanbul,TÜRKİYE
Future Work
The Solution To The Kinematic Singularity Problem :
Application of “Blended Inverse”
Building A Prototype ?