1. Gravity Gradient Boom Sponsor: John Hines In Collaboration with:
Design Team: Arthur Inglot, Jack Rafalowski, Gene Rossov, Steve Souza, Jason Stricker
Advisor: Gregory Kowalski

2. What is a Gravity Gradient Boom
Boom Arm
Tip Mass
Satellite
Retracted
Deployed

3. Boom Stowed

4. Attitude Control Satellite stabilization and control Purpose:
Maintain communication link to satellites antennas
Maintain a desired view for imaging
Heat dissipation and distribution
Three Axes
Location
Direction

5. Boom Deployed

6. Problem Statement
Design and develop a Gravity Gradient Boom as a stand alone Passive Attitude Control for a small satellite, conforming to the requirements put forth by NASA.

7. ONYX Project developed by Santa Clara U (Ca)
Collaboration with NASA, AFOSR and DARPA and part of the University Nanosatellite Program
Onboard autonomy experiment
Purpose:
To monitor anomalies in orbital motion and resolve them using two independent processing systems autonomously while observing Earth.
Image capturing in multiple spectrums
Research tool and educational service for K-12 and college students.

8. ONYX 30kg 21cm/hexagonal sides x 42cm tall
Center of gravity location [X, Y, Z]: [-0.326, 15.5, ] cm
Moment of inertia about CG: XX: 5.3E6g*cm2
YY: 4.6E6g*cm2
ZZ: 5.0E6g*cm2

9. Requirements and Constraints
Orientation requirements: +/- 5 degrees
Constraints:
Mass: <10 kg
Volume/Dimensions: 12 x 12 x 15 cm (.00216m3 )
Power: < 30 watts
Opening on top: 10 cm x 10 cm
Preliminary Damping: Provided
Shock Resistance: ±20 Gs
Min. Resonance Freq.: 500 Hz

10. Newton’s Law of Universal Gravitation
Low Earth Orbit is 200km-2000km
Mass of Earth is x 1024 kg
Radius of Earth is 6380 km
G is the universal constant, 6.67 x 10-11Nm2/kg2

12. The Whole Picture

13. Offset Initial Angle and Dampening

14. Deployment Options Tethers Telescoping Booms Coilable Boom
Complicated and costly
Motor unwinds long lengths of tether material (2 Km)
Oscillation and reliability concerns
Prone to space collisions
Telescoping Booms
High torsion and bending strength
Intended for many cycles
Extreme deployment and retraction force
Coilable Boom
Very light weight (< 50g/m)
Stowage size is very small
Low cost
High Reliability

15. Wire Drum Deployer Copper-Beryllium Wire wound on a drum
Proven Technology with industry backing
Copper-Beryllium provides sufficient tension
Can be deployed using an electric motor or a passive spring assembly
Low weight, low cost, and space saving packaging
Due to low weight of overall wire deployer a heavier tip mass may be used to provide more stabilization
Have to account for physical and thermal oscillations, additional hardware such as dampers may have to be implemented

16. Design Matrix
Weight Factor Multiplier : 3X 2X 1X 4X
Deployment Type/Boom
Size/Volume
Weight
Mechanical Complexity
Retractability
Thermal Characteristics
Possible Length
Adaptability to other missions
Structural Predictability
Damping/Dynamic Response
Power
Cost
Wire/Drum
3.8
3.2
3.4 3 4
2.6
Telescoping Tubular
1.6
1.4
2.4
2.8 2
3.6
1.8
Tether
2.2
Coilable
Deployment Type/Boom
Totals
Wire/Drum
88.6
Telescoping Tubular
63.6
Tether
47.6
Coilable 60

17. Wire Deployment System
Tungsten Alloy Tip Mass
Deployment Spider
Delrin Mounting Ring
Frangibolt ® system
Copper Beryllium Wire Spool
Aluminum 6061 Machined Components
Release Solenoid
Stowed Configuration
Deployed Configuration

18. The Frangibolt ® System
Non-Explosive Actuator
High Factor of safety
Consumes 25 Watts
Yield strength 2200 N
Compact size
Flight certified with space heritage

20. Wire Deployer
Mounted Deployed

21. Cosmos Deformation Analysis
6.295E6 N/m2
6.295E6 N/m2

22. Final Optimized Decisions for MATLAB Input
Length of wire: m
Tip Mass: kg
Orbit: Circular
Altitude: km
Inputing the parameters into the MATLAB program created from ONYX’s data show resulted for stabilization.

23. Settling Time:9.25 days from 30o +/- 5o tolerance
Stabilization Graph
Settling Time:9.25 days from 30o +/- 5o tolerance

24. Proper Stabilization 3.2 x 10-3 N-m Aero Dynamic Torque 1.1 x 10-8 N-m
Gravity Gradient Boom must overcome all disturbance torques in space
Aero Dynamic Torque
1.1 x N-m
Solar Radiation Torque
2.6 x 10-6 N-m
Magnetic Field Torque
8.6 x 10-4 N-m
Torque Developed by GGB
3.2 x 10-3 N-m

25. Final Optimized Constraints
System Mass of 3.76kg, (6.24kg Under Max)
Center of Mass and Moment of Inertia do not hinder physical properties of the ONYX
High degree of accuracy with initial accuracy of 5 degrees stabilizing to as low as 2 degrees
Low Estimated cost of $4,000
Highly adaptable to other satellites of similar size

26. Improvements Improve modeling for FEA Vibration analysis
Improve metal on metal contact
Integrate the use of a DC motor for more control

27. Any questions?