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Solar Sail

Solar Sail. Department of Aerospace Engineering and Mechanics AEM 4332W – Spacecraft Design Spring 2007. Team Members. Solar Sailing:. Project Overview. Design Strategy. Trade Study Results. Orbit. Eric Blake Daniel Kaseforth Lucas Veverka. Eric Blake.

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Solar Sail

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  1. Solar Sail Department of Aerospace Engineering and Mechanics AEM 4332W – Spacecraft Design Spring 2007

  2. Team Members

  3. Solar Sailing:

  4. Project Overview

  5. Design Strategy

  6. Trade Study Results

  7. Orbit Eric Blake Daniel Kaseforth Lucas Veverka

  8. Eric Blake Optimal Trajectory of a Solar Sail: Derivation of Feedback Control Laws

  9. Recall Orbital Mechanics • The state of a spacecraft can be described by a vector of 6 orbital elements. • Semi-major axis, a • Eccentricity, e • Inclination, i • Right ascension of the ascending node, Ω • Argument of perihelion, ω • True anomaly, f • Equivalent to 6 Cartesian position and velocity components.

  10. Orbital Elements

  11. Equations of Motion = Sail Lightness Number = Gravitational Parameter

  12. Problem: Minimize Transfer Time By Inspection: Transversality:

  13. Solution • Iterative methods are needed to calculate co-state boundary conditions. • Initial guess of the co-states must be close to the true value, otherwise the solution will not converge. • Difficult • Alternative: Parameter Optimization. • For given state boundary conditions, maximize each element of the orbital state by an appropriate feedback law.

  14. Orbital Equations of Motion = Sail Lightness Number = Gravitational Parameter

  15. Maximizing solar force in an arbitrary direction Maximize: Sail pointing for maximum acceleration in the q direction:

  16. Locally Optimal Trajectories • Example: Use parameter optimization method to derive feedback controller for semi-major axis reduction. • Equations of motion for a: Feedback Law: Use this procedure for all orbital elements

  17. Method of patched local steering laws (LSL’s) • Initial Conditions: Earth Orbit • Final Conditions: semi-major axis: 0.48 AU inclination of 60 degrees

  18. Trajectory of SPI using LSL’s Time (years)

  19. Global Optimal Solution • Although the method of patched LSL’s is not ideal, it is a solution that is close to the optimal solution. • Example: SPI Comparison of LSL’s and Optimal control.

  20. Conclusion • Continuous thrust problems are common in spacecraft trajectory planning. • True global optimal solutions are difficult to calculate. • Local steering laws can be used effectively to provide a transfer time near that of the global solution.

  21. Lucas Veverka Temperature Orbit Implementation

  22. Daniel Kaseforth Control Law Inputs and Navigation System

  23. Structure Jon T Braam Kory Jenkins

  24. Jon T. Braam Structures Group: Primary Structural Materials Design Layout 3-D Model Graphics

  25. Primary Structural Material Weight and Volume Constraints • Delta II : 7400 Series • Launch into GEO • 3.0 m Ferring • Maximum payload mass: 1073 kg • Maximum payload volume: 22.65 m3 • 2.9 m Ferring • Maximum payload mass: 1110 kg • Maximum payload volume: 16.14 m3

  26. Primary Structural Material Aluminum Alloy Unistrut • 7075 T6 Aluminum Alloy • Density • 2700 kg/m3 • 168.55 lb/ft^3 • Melting Point • ? Kelvin Picture of Unistrut

  27. Primary Structural Material • Density • Mechanical Properties • Allowing unistrut design • Decreased volume • Thermal Properties • Capible of taking thermal loads

  28. Design Layout • Constraints • Volume • Service task • Thermal consideration • Magnetic consideration • Vibration • G loading

  29. Design Layout • Unistrut Design • Allowing all inside surfaces to be bonded to • Titanium hardware • Organization • Allowing all the pointing requirements to be met with minimal attitude adjustment

  30. Design Layout • Large Picture of expanded module

  31. 3-D Model • Large picture

  32. 3-D Model • Blah blah blah (make something up)

  33. Graphics • Kick ass picture

  34. Graphics • Kick ass picture

  35. The blanks will be filled in soon

  36. Trade Studies • Blah blah blah

  37. Why I deserve an “A” • Not really any reason but when has that stopped anyone!

  38. Kory Jenkins Sail Support Structure Anticipated Loading Stress Analysis Materials Sail Deployment

  39. Attitude Determination and Control Brian Miller Alex Ordway

  40. Alex Ordway Sliding Mass vs. Tip Thrusters Component Selection

  41. Brian Miller Tip Thrusters vs. Slidnig Mass Attitude Control Simulation

  42. Attitude Control • Conducted trade between tip thrusters and sliding mass as primary ACS • Considerations • Power required • Torque produced • Weight • Misc. Factors

  43. Attitude Control • Tip Thrusters (spt-50) • Pros • High Torque Produced ~ 1.83 N-m • Low weight ~ 0.8 kg/thruster • Cons • Large Power Requirement ~ 310 Watts • Lifetime of 2000 hrs • Requires a fuel, either a solid or gas

  44. Attitude Control • Attitude Control System Characteristics • Rotational Rate • Transfer Time • Required Torque • Accuracy • Disturbance compensation

  45. Attitude Control • Requirements • Orbit • Make rotation rate as fast as possible • Roll spacecraft as inclination changes • Communications • Within Maximum Torque • Pitch and Yaw Axis ~ 0.34 N-m • Roll Axis ~ 0.2 N-m m – sliding mass F – solar force z – distance from cg M – spacecraft mass

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