CubeSat Design for Solar Sail Testing Platform

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CubeSat Design for Solar Sail Testing Platform

• Phillip Hempel Paul Mears
• Daniel Parcher Taffy Tingley

December 5, 2001
The University of Texas at Austin
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Presentation Outline
Introduction
Tracking
Electronics
Structure Deployment
Propulsion
Orbital Simulation
Budget
Conclusion
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Project Goal

• Design a Test Platform for Solar Sail Propulsion
  Technology
• Measure thrust
• Measure solar sail efficiency
• Model satellite orbit

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Constraints

• CubeSat Prescribed Constraints
• 10cm sided cube
• 1 Kg weight
• Timing system to delay power-on
• Space-flown or approved materials
• Adopted Constraints (for simplicity and
  reliability)
• No attitude control
• No powered systems (except required timer)
• No communications systems

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Laser Ranging

• Information needed for thrust analysis
• Orbital position for a significant portion of the
  satellites orbit
• Rotation rates and angles over that time

- A corner cube reflector (CCR) consists of
three orthogonal mirrors that reflect light back
to source
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Laser Ranging

• McDonald Observatory Laser Ranging (MLRS)
• Satellite visibility sufficient
• Can provide position to within 1 centimeter

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Laser Ranging Specifics

• Four CCRs will define sail plane
• Defines position and attitude
• Double sided glass arrays with 3mm corner cubes
  (custom design)
• Design impact
• Volume and weight
• Laser pulse force 9.5e-26 N

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Electronics

• Rocket Data Acquisition System
• Input - 10.7 V at 9-10 mA
• Output- time coordinated voltages
• Three UltraLife Lithium Ion Polymer Batteries
• Output- 3.8V for 530 mAh
• Thermal Analysis

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Presentation Outline
Introduction
Tracking
Electronics
Structure Deployment
Propulsion
Orbital Simulation
Budget
Conclusion
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Mechanical SystemsPhillip Hempel
Structural Design and Solar Sail Deployment
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Satellite Components

• Frame/ Corner Cube Reflectors
• Satellite Components
• Kill Switch
• Timer
• Sail
• Capillaries
• Inflation Capsule
• Hardening Strips

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Mechanical Overview

• Satellite Components
• Weight and Volume Budgets
• Component Placement
• Solar Sail Deployment / Model

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Satellite Assembly
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Sequence of Events

• CubeSat Released / Deactivate Kill Switch
• Timer Waiting Period
• Unlock Side Panels
• Begin Inflation
• Inflation Ends / Rigidization Occurs
• Final shape

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PropulsionTaffy Tingley
Solar Sail Design and Finite Element Simulation
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Solar Sail Description
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Solar Sail Material

• Aluminized Mylar

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Solar Sail Configuration
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Finite Element Model Configuration
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FE Test 1Direct Exposure Neglect Coupled
Thermal Stresses
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Test 2Direct Exposure Include Thermal
Stresses
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Test 3Asymmetric Thrust
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Test 4Unevenly Distributed Load
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Test 5Unevenly Distributed Load
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FE Conclusions

• Thermal Loading Not Worth Cost
• Hardening Strip Corrections
• All Deflections are Reasonable
• FE Model Can Be Used for Future Analysis
• Recommendation Crack Propagation

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Orbital Trajectory SimulationPaul Mears
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Simulation Topics

• Review Four Body Problem with Thrust
• Review Initial Conditions
• Rotating Thrust Vector
• Umbra and Penumbra
• Results Orbits
• Measuring Thrust with Observations
  and Simulations

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Four Body Problem with Thrust

• Physics Models
• Newtons Law of Gravitation
• Earth orbit perturbed by the Sun and the Moon
• Solar Radiation Pressure
• Generates thrust based on distance from Sun and
  sail attitude
• Other Orbital Mechanics
• Initial Conditions, Sun and Moon Position Vectors

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Initial Conditions

• CubeSat requires low altitudes due to cost
• Perigee
• LEO altitude
• Highest velocity
• Apogee
• GEO altitude
• Lowest velocity
• Result Highly eccentric orbit (e0.74)

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Rotating Thrust Vector

• Thrust acts along the sail normal vector.
• Sail normal is rotated in three dimensions.

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Umbra and Penumbra

• When the sail enters the Umbra, thrust is zero
• Penumbra effects are ignored

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Results Thrust

• Thrust Generated by Solar Radiation Pressure is

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Results - Orbit1 No Rotation
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Orbit 3 Rotating Thrust Vector
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Orbit 4 Rotating Thrust Vector
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Orbit 5 Rotating Thrust Vector
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Measuring Thrust

• Purpose of simulation is to compare simulated
  orbit to observed orbit
• Two possible situations
• Thrust accurately predicted by sail manufacturer.
• Observed orbit equals simulated orbit
• Thrust generated is different from prediction.
• Comparison of simulated and observed orbits to
  determine thrust

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Comparison Technique

• Make several observations of position and
  attitude
• Calculate orbit and sail rotation rate
• Simulate orbit for known orbital elements and
  rotating sail normal
• Extract thrust vector from equations of motion
• Calculate the magnitude of the thrust vector

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Presentation Outline
Introduction
Tracking
Electronics
Structure Deployment
Propulsion
Orbital Simulation
Budget
Conclusion
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Budget Summary

• Personnel Costs 15,000
• Materials Electronics 06,500
• Testing (CalPoly) 02,000
• Launch 50,000
• Total 73,500

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Conclusion

• PaperSat has developed a picosatellite design for
  the CubeSat program
• Design will test solar sail propulsion technology
• Design will not incorporate attitude control
• Position, acceleration, and orientation will be
  measured from ground stations
• Solar sail will be reflective on both sides with
  tear strips, hardening strips and inflation
  capillaries
• Orbital simulation provides prediction of
  satellite orbit for thrust determination
• http//www.ae.utexas.edu/design/papersat/

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Acknowledgements

• Dr. Wallace Fowler
• Dr. Cesar Ocampo
• Dr. Eric Becker
• Meredith Fitzpatrick
• Previous CubeSat Design Groups

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Questions