CubeSat Design for Solar Sail Testing Applications Phillip HempelPaul Mears Daniel ParcherTaffy Tingley October 11, 2001The University of Texas at Austin

Presentation Outline Project Goal Satellite Systems Future Work Management Structure Budget Conclusion

Project Goal  Design a Test Platform for Solar Sail Propulsion Technology –Measure Thrust –Measure Solar Sail Efficiency

Management Structure  Daniel Parcher –Project Manager –Tracking Systems Department Head –Electronics Department Head  Phillip Hempel –Mechanical Systems Department Head  Taffy Tingley –Propulsion Systems Department Head  Paul Mears –Orbital Trajectory Department Head

CubeSat Project Background  Sponsored by Stanford University  Utilizes picosatellite satellite Designs that perform some scientific task  Different CubeSat launches provide different initial conditions

Constraints  CubeSat Prescribed Constraints –10cm Sided Cube –1 Kg Weight –Timing System to Delay Power-On –Space-Flown Materials  Adopted Constraints (for Simplicity and Reliability) –No Attitude Control –No Powered Systems (except required Timer) –No Communications Systems

Presentation Outline Project Overview Satellite Systems Future Work Management Structure Budget Conclusion

CubeSat Required Systems  Timer –RDAS accelerometer/timer –Voltage outputs to trigger system events  Casing –Aluminum –Kill Switch –Attached CC reflectors

Tracking / Communcations  No Satellite Communication  Tracking performed with corner cube reflectors –determine position, rotation, acceleration  Corner cube reflectors to be supplied by Banner Engineering Corp.

Mechanical Systems Phillip Hempel

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

Frame  10 cm Sided Cube  Corner Cubes Panels to be Placed on Sides

Corner Cube Reflectors  Flat-Plate Reflectors  Attached to Frame  Released Prior to Inflation  In the Plane of the Solar Sail

Kill Switch/Timer  Kill Switch Triggered by Release  Begins Timer Sequence  Controls All Timing Sequences

Solar Sail Properties  Aluminized Mylar  Circular Shape  Area of 100 m^2 Example of Aluminized Mylar Structure

Capillaries  Tubes attached to the surface of the solar sail  Capillaries will be placed placed strategically for structural rigidity  Tubes are inflated by nitrogen from capsule Total Length= 272 ft. Diameter= 0.5 in

Inflation Capsule  7.6 cm Long  3.8 cm Diameter  86 cm^3 Volume  60.5 psi  Placed in the Center of the CubeSat

Hardening Strips  Thin tape-like strips  Strips will be placed strategically in a spider web pattern on the sail  Strips harden with solar radiation exposure Total Strip Length = 308 ft.

Cut-Away CubeSat

Sequence of Events  P-Pod Release/ Deactivate Kill Switch  Waiting Period  Side Panels Unlock  Inflation Begins  Inflation Ends/ Rigidization Occurs  Solar sail reaches final shape

Propulsion Taffy Tingley

Solar Sail Material Selection Encounter Satellite Solar Blade Solar Sail

Solar Sail Material Selection Star of Tolerance Satellite Cosmos I

Aluminized Mylar  High Strength to Weight Ratio  Tested  Cheap!  Double Reflective

ABAQUS

Finite Element Design  Monitor regions where high stress occurs - Add tear strip or tension line to sail  Monitor rigidity  Model several perturbations and situations  Perform thermal analysis  Monitor effects of additional components  All in 3-D

Future Propulsion Work  Integrate deployment apparatus into FE model  Install Tear Strips into FE model  Perform Thermal Analysis

Orbit Simulation Paul Mears

Solar Radiation Pressure  Electromagnetic radiation flux  Photon energy  Momentum exchange produces force per unit area ΔV

Sail Thrust Function of: T = f (A, S,  ) where A = sail area S = Power (scaled Watt)  = reflectivity  = angle of incidence

Sail Thrust Vector  Thrust Acts in the direction Normal to the Sail  Sail Normal makes an angle  with the Sun Position Vector  Thrust is generated by Incidental and Reflected Light θ -F r FrFr FTFT FiFi ŜNŜN

4-Body Problem (1)Earth (2) Sun (3) Moon (4) Satellite (T) Thrust ECEF Coordinate System (x, y, z)

Forces on the Satellite The gravitational forces of all the planets effect the satellite, as well as thrust FBD: Satellite i = 1, 2, 3

Initial Conditions of Orbit  Injection will occur at perigee  Orbit will be highly elliptic with apogee at 42000km Resulting Orbital Elements R a = km R p = km V p = km/s 2 V a = 3.04 km/s 2 e = a = km

Earth, Sun, Moon Forces Orbit Propagation: Perturbing Forces Earth Forces Only

Orbit Propagation with Thrust Earth, Sun, Moon Forces All Gravitational Forces plus Thrust

Future Work in Orbit Simulation Rotating Thrust Vector

Presentation Outline Project Overview Satellite Systems Future Work Management Structure Budget Conclusion

Budget Personnel- $15,633 Testing - $ 2,000 Materials - $ 5,000 Launch - $50,000 Total - $72,653

Future Work  Hardware integration –Part size and weight definition and orientation within the satellite  Deployment system timing  Finite element analysis  Orbital simulation –Rotating thrust vector definition –Orbital trajectories simulation

Conclusion  PaperSat is developing a picosatellite design for CubeSat  Design will test solar sail propulsion technology  Design will not incorporate attitude control  Deployment system uses compressed gas  Solar sail will be reflective on both sides  Position, acceleration, and orientation will be measured from ground stations

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

Questions?