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 ?