Solar Sail

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

2. Solar Sailing:

3. Project Overview • Motivation • Scope • Organization (tasks [%complete], groups, [who?]) • Present the scope of your design work. What are you setting out to do? • Explain how you have organized the work. What are the major tasks? What groups have you organized your team into, and who is in each group?

4. Team Members Orbit: Eric Blake, Daniel Kaseforth, Lucas Veverka Structure: Jon Braam, Kory Jenkins ADC: Brian Miller, Alex Ordway Power, Thermal and Communication: Raymond Haremza, Michael Hiti, Casey Shockman System Integration: Megan Williams

5. Design Strategy Not yet complete. Needs: • Describe all of the trade studies you are considering in this project • Describe the trade study conclusions and any other design decisions that you have already made • Discuss the unfinished trade studies and what effect they will have on your design • Summarize the key properties of the mission (orbit, anticipated lifetime, candidate launch vehicles) • Summarize the key properties of the spacecraft (mass, dimensions, peak and average power requirements, ADCS configuration, type of propulsion system, list of any moving parts, other important info as you see fit) • Show a 3D diagram of the spacecraft (use a CAD package, ie Solid Works or Pro-E)

6. Trade Study Results

7. Cost Estimate

8. Orbit Eric Blake Daniel Kaseforth Lucas Veverka

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

10. 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.

11. Orbital Elements

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

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

14. 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.

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

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

17. 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

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

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

21. 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.

22. 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.

23. Lucas Veverka Temperature Orbit Implementation

24. Optimal Trajectory of a Solar Sail: Orbit determination and Material properties. Lucas Veverka

25. Reflectivity Approximation • Reflectivity constant, r, negatively affects the solar radiation pressure force. • P is the solar pressure as a function of distance. • A is the sail area being struck by the solar radiation. • ui is the incident vector. • n is the vector normal to the sail. • Emissivity and specular reflection neglected. • Assumed a Lambertian surface.

26. Sail Surface Temperature • Fsolar is the solar flux. • αis the absorptance. • εis the emittance. • σ is the Stefan-Boltzman constant. • dsunis the distance from the sun.

27. Transfer Orbits • Objective: • Reach an orbit with semi-major axis of 0.48 AU • and inclination of 60 degrees as quickly as possible. • Investigated four possible orbits • Cold transfer orbit • Hot transfer orbit • Inclination first transfer orbit • Simultaneous orbit

28. Cold Transfer Orbit • Advantages: • Very simple two-stage transfer. • Goes no closer to sun than necessary to avoid radiation damage. • Disadvantages: • Is not the quickest orbit available. • Order of operations: • Changes semi-major axis to 0.48 AU. • Cranks inclination to 60 degrees. • Time taken: • 10.1 years.

29. Cold Transfer Orbit

30. Hot Transfer Orbit • Advantages: • Still simple with three-stages. • Is a much quicker transfer. • Disadvantages: • Radiation is very intense at 0.3 AU. • Order of operations: • Changes semi-major axis to 0.3 AU. • Cranks inclination to 60 degrees. • Changes semi-major axis to 0.48 AU. • Time taken: • 7.45 years.

31. Hot Transfer Orbit

32. Inclination First Transfer Orbit • Advantages: • Very simple two-stage transfer. • Avoids as much radiation damage as possible. • Disadvantages: • Takes an extremely long time. • Order of operations: • Cranks inclination to 60 degrees. • Changes semi-major axis to 0.48 AU. • Time taken: • 20.15 years.

33. Inclination First Transfer Orbit

34. Conclusion • Simultaneous transfer is too complicated with little or no real benefit. • Inclination first transfer takes too long. • Hot transfer orbit is much quicker but submits materials to too much radiation. • Cold transfer orbit is slower than the hot but gets the equipment to the desired location safely. • Choice: Cold transfer orbit!

35. Daniel Kaseforth Control Law Inputs and Navigation System

37. Structure Jon T Braam Kory Jenkins

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

39. 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

40. 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

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

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

43. 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

44. Design Layout • Large Picture of expanded module

45. 3-D Model • Large picture

46. 3-D Model

47. Graphics

48. Graphics

49. The blanks will be filled in soon

50. Trade Studies