CubeSat Design for Solar Sail Testing Platform Phillip HempelPaul Mears Daniel ParcherTaffy Tingley December 5, 2001The University of Texas at Austin

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

3 Project Goal  Design a Test Platform for Solar Sail Propulsion Technology Measure thrustMeasure thrust Measure solar sail efficiencyMeasure solar sail efficiency Model satellite orbitModel satellite orbit

4 Constraints  CubeSat Prescribed Constraints 10cm sided cube10cm sided cube 1 Kg weight1 Kg weight Timing system to delay power-onTiming system to delay power-on Space-flown or approved materialsSpace-flown or approved materials  Adopted Constraints (for simplicity and reliability) No attitude controlNo attitude control No powered systems (except required timer)No powered systems (except required timer) No communications systemsNo communications systems

5 Laser Ranging  Information needed for thrust analysis Orbital position for a significant portion of the satellite’s orbitOrbital position for a significant portion of the satellite’s orbit Rotation rates and angles over that timeRotation rates and angles over that time - A corner cube reflector (CCR) consists of three orthogonal mirrors that reflect light back to source - A corner cube reflector (CCR) consists of three orthogonal mirrors that reflect light back to source

6 Laser Ranging  McDonald Observatory Laser Ranging (MLRS) Satellite visibility sufficientSatellite visibility sufficient Can provide position to within 1 centimeterCan provide position to within 1 centimeter

7 Laser Ranging Specifics  Four CCR’s will define sail plane Defines position and attitudeDefines position and attitude Double sided glass arrays with 3mm corner cubes (custom design)Double sided glass arrays with 3mm corner cubes (custom design)  Design impact Volume and weightVolume and weight Laser pulse force = 9.5e-26 NLaser pulse force = 9.5e-26 N

8 Electronics  Rocket Data Acquisition System Input V at 9-10 mAInput V at 9-10 mA Output- time coordinated voltagesOutput- time coordinated voltages  Three UltraLife Lithium Ion Polymer Batteries Output- 3.8V for 530 mAhOutput- 3.8V for 530 mAh  Thermal Analysis

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

10 Mechanical Systems Phillip Hempel Structural Design and Solar Sail Deployment

11 Satellite Components  Frame/ Corner Cube Reflectors  Satellite Components Kill SwitchKill Switch TimerTimer SailSail CapillariesCapillaries Inflation CapsuleInflation Capsule Hardening StripsHardening Strips

12 Mechanical Overview  Satellite Components  Weight and Volume Budgets  Component Placement  Solar Sail Deployment / Model

13

14

15 Satellite Assembly

16 Sequence of Events  CubeSat Released / Deactivate Kill Switch  Timer Waiting Period  Unlock Side Panels  Begin Inflation  Inflation Ends / Rigidization Occurs  Final shape

17 Propulsion Taffy Tingley Solar Sail Design and Finite Element Simulation

18 Solar Sail Description

19 Solar Sail Material Aluminized Mylar

20 Solar Sail Configuration

21 Finite Element Model Configuration

22 FE Test #1 Direct Exposure – Neglect Coupled Thermal Stresses

23 Test #2: Direct Exposure – Include Thermal Stresses

24 Test #3 Asymmetric Thrust

25 Test #4 Unevenly Distributed Load

26 Test #5 Unevenly Distributed Load

27 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

28 Orbital Trajectory Simulation Paul Mears

29 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

30 Four Body Problem with Thrust  Physics Models: Newton’s Law of GravitationNewton’s Law of Gravitation Earth orbit perturbed by the Sun and the MoonEarth orbit perturbed by the Sun and the Moon Solar Radiation PressureSolar Radiation Pressure Generates thrust based on distance from Sun and sail attitudeGenerates thrust based on distance from Sun and sail attitude Other Orbital MechanicsOther Orbital Mechanics Initial Conditions, Sun and Moon Position VectorsInitial Conditions, Sun and Moon Position Vectors

31 Initial Conditions  CubeSat requires low altitudes due to cost  Perigee  LEO altitude  Highest velocity  Apogee  GEO altitude  Lowest velocity  Result: Highly eccentric orbit (e=0.74)

32 Rotating Thrust Vector  Thrust acts along the sail normal vector.  Sail normal is rotated in three dimensions.

33 Umbra and Penumbra  When the sail enters the Umbra, thrust is zero  Penumbra effects are ignored

34 Results: Thrust  Thrust Generated by Solar Radiation Pressure is:

35 Results - Orbit1: No Rotation

36 Orbit 3: Rotating Thrust Vector

37 Orbit 4: Rotating Thrust Vector

38 Orbit 5: Rotating Thrust Vector

39 Measuring Thrust  Purpose of simulation is to compare simulated orbit to observed orbit  Two possible situations: 1.Thrust accurately predicted by sail manufacturer.  Observed orbit equals simulated orbit 2.Thrust generated is different from prediction.  Comparison of simulated and observed orbits to determine thrust

40 Comparison Technique 1. Make several observations of position and attitude  Calculate orbit and sail rotation rate 2. Simulate orbit for known orbital elements and rotating sail normal 3. Extract thrust vector from equations of motion 4. Calculate the magnitude of the thrust vector

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

42 Budget Summary  Personnel Costs15,000  Materials & Electronics06,500  Testing (CalPoly)02,000  Launch50,000  Total73,500

43 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

44 Acknowledgements  Dr. Wallace Fowler  Dr. Cesar Ocampo  Dr. Eric Becker  Meredith Fitzpatrick  Previous CubeSat Design Groups

45 Questions