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Solar Sail Project AEM 4332W – Spacecraft Design

Solar Sail Project AEM 4332W – Spacecraft Design. Preliminary Design Review March 28, 2007. Eric Blake Jon Braam Raymond Haremza Michael Hiti Kory Jenkins Daniel Kaseforth Brian Miller Alex Ordway Casey Shockman Lucas Veverka Megan Williams (Team Lead). Team Organization.

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Solar Sail Project AEM 4332W – Spacecraft Design

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  1. Solar Sail Project AEM 4332W – Spacecraft Design Preliminary Design Review March 28, 2007 Eric Blake Jon Braam Raymond Haremza Michael Hiti Kory Jenkins Daniel Kaseforth Brian Miller Alex Ordway Casey Shockman Lucas Veverka Megan Williams (Team Lead)

  2. Team Organization • Systems Integration & Management: Megan Williams • Orbit Control: Eric Blake, Daniel Kaseforth, Lucas Veverka • Structures: Jon Braam, Kory Jenkins • Attitude Control: Brian Miller, Alex Ordway • Communications: Casey Shockman • Thermal: Raymond Haremza • Power: Michael Hiti AEM 4332W - Solar Sail

  3. Presentation Outline • Project Overview • Design Strategy • Subgroup work • Orbit • Structure • Attitude and Control • Communication • Thermal Analysis • Power • Demonstration • Acknowledgements AEM 4332W - Solar Sail

  4. Project Overview Top Level Requirements • The payload mass is 34 kg • The payload average power draw is 24.5 Watts • The final orbit should have a semi-major axis of 0.48 AU and an inclination of 60 deg • The launch vehicle will provide a hyperbolic escape velocity of 0.5 km/s. A Delta II 7425 will be used for launch. • The structure will fit inside the selected launch vehicle. AEM 4332W - Solar Sail

  5. Project Overview MAJOR TASKS 1) Develop control law for semi-major axis change and inclination change to determine solar sail orientation. 2) Analyze transfer time for different sail sizes to determined optimum sail size. 3) Conduct a trade study between sliding mass and tip thruster attitude control systems. 4) Determine the data transfer rate and power requirements for data downlinks to Earth. Assume 2 downlinks per week to the DSN. 5) Conduct a trade study between conformal solar array and normal-pointing solar array. 6) Size the solar array to meet total power requirements. 7) Analyze the thermal properties of the solar sail spacecraft. 8) Choose a configuration and compute the total mass and moment of inertia. 9) Design a payload module. 10) Design for the satellite actuation. 11) Calculation and testing of attitude control law. AEM 4332W - Solar Sail

  6. Project Overview Orbit • Non-Keplarian orbit • Inclination 60° • Semi-major axis 0.48AU Structure • Target mass: 500 kg • Sail size: 100m x 100m • Inflatable boom structure, heated curing Attitude Control • Sliding mass configuration with secondary tip thruster control • Interstellar compass – primary ADS Communications • Ka-Band (32 GHz) Horn antennae Thermal • Carbon mesh sail material • Multifunctional Structure (MFS) configuration Power • Power Requirements approximately 878 W • Normal Pointing Solar Array area: 2.39 meters • Silver-Cadmium (Ad-Cd) battery mass: 13.92 kg AEM 4332W - Solar Sail

  7. Design Strategy Orbit • Trade Studies • Sail area versus transfer time • Varied sail size and ran simulation • Larger sail results in a faster transfer • Transfer maneuver variations • Comparison between “hot”, “cold” and simultaneous transfer trajectories • “Hot” transfer is quickest but may not be feasible due to thermal restrictions Structure • Zero level sizing based on existing designs • Trade Studies • Deployable space structure types • Method of rigidizing inflatable structure • Stress analysis • Determine power/time for boom deployment • Coordinate with Attitude Control and Power subgroups • Solid Modeling AEM 4332W - Solar Sail

  8. Design Strategy Attitude Control • Trade Study • Sliding mass vs Tip thruster ACS • Simulink modeling Communication • Researched communication devices Thermal • Trade Study • Solar Sail material: Mylar vs Carbon fiber mesh • Research into thermal management of spacecraft Power • Zero level sizing for power requirements • Trade Study • Normal vs. Conformal Solar Array • Solar Array sizing • Battery sizing AEM 4332W - Solar Sail

  9. Eric Blake (Simulation) Daniel Kaseforth (Control Law –Simulation ) Lucas Veverka (Control Law – Orbits) Orbit Control AEM 4332W - Solar Sail

  10. Orbit Control • Problem • How to get from Earth’s orbit to an orbit about the sun with inclination of 60° and semi-major axis of 0.48 AU using solar pressure? • Assumptions • Gravity and solar pressure are only forces • Sail is rigid flat plate and does not degrade • Sail material is perfectly reflecting • Instantaneous change in sail orientation AEM 4332W - Solar Sail

  11. Orbit Control • Technical flow of work • Simulation • Two-body force interaction (Sun, spacecraft) • Force of gravity • Force of Solar pressure AEM 4332W - Solar Sail

  12. Orbit Control • Control Law • Cone and clock angle equations AEM 4332W - Solar Sail

  13. Orbit Control “Cold” orbit transfer AEM 4332W - Solar Sail

  14. Orbit Control Orbital elements AEM 4332W - Solar Sail

  15. Orbit Control • Conclusions • Simulation works • Control law functions as desired • Recommendations for further work • Sail shape analysis • Optimize transfer trajectory • Simulate sail degradation effects AEM 4332W - Solar Sail

  16. Orbit Control • FDR Presentation • Discuss control law and simulation assumptions. • Discuss possible transfer orbits. • Show simulation results. • Justify selected transfer orbit. • Discuss further work. AEM 4332W - Solar Sail

  17. Structural Design Jon Braam Kory Jenkins AEM 4332W - Solar Sail

  18. Solar Sail Structure and Deployment Challenge: Design a deployable structure to support the sail and deliver a scientific payload. Solution: The sail support structure consists of four inflatable, rigidizable booms attached to a payload module. Based on L’Garde solar sail demonstrator design. AEM 4332W - Solar Sail

  19. Aluminum Module • Aluminum Unistrut • Ti Weld • Unistrut Washer • Titanium Hardware • Rubber Washer • Vibration Damping AEM 4332W - Solar Sail

  20. Hexagonal Shape • Maximize area inside capsule • Maximize packing area inside module • Allowable surface area for features • Antenna • Camera • Solar Panel Attachment AEM 4332W - Solar Sail

  21. Sail Mount • Hexagonal Shape • Mounting • Strength • FEA • Add Gussets • Starburst Mount • Add connections • Center Hole • Routing • Wiring • Propellant AEM 4332W - Solar Sail

  22. Boom Geometry • Packing constraints require tapered geometry. • Laminate thickness t = 0.25 mm. • r = 10 cm. • R = 16 cm. • l = 30 cm. • n = number of folds. • L = 72 m. • Mass ≈ 20 Kg/boom R = r + t ( l/L) AEM 4332W - Solar Sail

  23. Estimate Worst Case Loading Assumptions: • Solar Pressure at 0.48 AU = 19.8 µN/m^2. • Tip thruster forces of 150 µN. • Worst case force = 0.05 N. • Deployment load of 20 N in compression. • Thin wall tubes. • Sail quadrant loading is evenly distributed between 3 attachment points. • Quadrant area 2500 m^2. • Homogeneous material properties. • Safety factor of 3. AEM 4332W - Solar Sail

  24. Boom Material • [0/90] carbon fiber laminate. • Polymer film inflation gas barrier. • IM7 carbon fiber, E = 276 GPa. • Low CTE. • TP407 polyurethane matrix, E = 1.3 GPa. • Tg = 55 degrees C. AEM 4332W - Solar Sail

  25. Expected deployment loads of 20 N in compression dictate boom sizing. • Conclusion: Booms sized to meet this requirement easily meet other criteria. AEM 4332W - Solar Sail

  26. Deployment • Booms heated to 75 degrees C. • Inflation gas pressurizes booms for deployment. • Booms rigidize as they cool to Sub-Tg (glass transition) temperatures. • Deployment speed is controlled by a single motor which pays out the tensioning cables at 1 cm/sec. • Motor retracts tension cables after booms are rigidized to pull out the sail. AEM 4332W - Solar Sail

  27. Deployed Boom with Micro PPT Tip Thrusters AEM 4332W - Solar Sail

  28. Future Work: Sliding mass Size Placement Effects of structural deformation on attitude control. Investigate low frequency vibration modes. Volume of inflation gas needed. Proper laminate analysis. FDR Deliverables: Configuration: Solid Model stowed and deployed Total Mass/Moment of inertia Deployment Methodology Structural Analysis Future Work and FDR Deliverables AEM 4332W - Solar Sail

  29. Attitude Control Alex Ordway Brian Miller AEM 4332W - Solar Sail

  30. Attitude Control • Detailed description of trade study • Sliding Mass characteristics • Power consumption • 10 W • Approximate control torques • Being calculated; will be sufficient • Mass required • 10 kg, open for refinement • Tip thruster characteristics • Power Consumption • 100 W • Mass required • 10 kg AEM 4332W - Solar Sail

  31. Attitude Control • Detailed description of ACS • Primary use of sliding mass • Tip thrusters utilized as secondary ACS • Configuration chosen for a number of reasons • Thrusters require more power to operate (~1kw) • Ion ejection from ions could interfere with solar arrays • Operational life of thrusters limited to 3000 hours • Sliding mass offers comparable transfer times without aforementioned drawbacks • Tip thrusters chosen offer smaller force at lower power usage, no significant life restrictions, lower probability of system interference AEM 4332W - Solar Sail

  32. Attitude Control Detailed description ACS cont… • Tip Thruster Selection • Micro Plasma Pulsed Thruster (Micro PPT) • Solid polymer fuel bar • Eliminates need for auxiliary fuel transport infrastructure • Can be utilized in off-nominal attitude situations in addition to being an available ACS when the solar sail is not deployed AEM 4332W - Solar Sail

  33. Attitude Control ADS • Primary • Interstellar Compass (ISC) • Low power • 3.5 W • Exceptional Accuracy • 0.1 deg (1σ) • Low mass • 2.5 kg • Technology has not flown • Developed by Draper Laboratory AEM 4332W - Solar Sail

  34. Attitude Control ADS • Secondary • Sun Sensors • Located on all solar oriented exterior planes • Reorient space craft in off-nominal attitude situations • Provide data to orient solar arrays for optimal solar collection AEM 4332W - Solar Sail

  35. Future Work • Finish attitude control simulation • Calculate final required mass for ACS • Refine simulation using information from structures group • Consider sail ejection once orbit is achieved • Independent module ACS • Reaction wheels most likely candidate AEM 4332W - Solar Sail

  36. Communications Casey Shockman

  37. Frequency • X-Band: 8.4 GHz • This is the typical frequency used, so DSN is becoming overloaded at this frequency. • Ka-Band: 32 GHz • Due to overloaded X-Band frequency, the DSN is migrating to Ka-Band frequency. • Can transfer data much more quickly than X-Band. AEM 4332W - Solar Sail

  38. Antenna • Horn • High data transfer rate with low power required. • Works directly with recently developed Small Deep Space Transponder. • New design works with X-Band and Ka-Band transmit as well as X-Band receive. • Lighter and smaller than parabolic reflector or array. • High gain. AEM 4332W - Solar Sail

  39. AEM 4332W - Solar Sail

  40. AEM 4332W - Solar Sail

  41. Current/Future Work • Currently, I am working on a design space to optimize values for power required, antenna sizing, pointing accuracy, and signal to noise ratio. • Problems include finding accurate equations for horn antenna systems. AEM 4332W - Solar Sail

  42. Thermal Analysis Raymond Haremza AEM 4332W - Solar Sail

  43. Carbon Fiber Mesh • Carbon Fiber Mesh developed by ESLI • Mesh is composed of a network of carbon fibers crisscross linked into a matrix that is mostly empty space. • 200 times thicker than the thinnest solar sail material, but so porous that it weighs the same AEM 4332W - Solar Sail

  44. Common Problems • Traditional materials • tear easily • require heavy support structure to maintain tension • can build up static electricity • UV degrades and melt at high temperatures AEM 4332W - Solar Sail

  45. Carbon Fiber Mesh • Can tolerate temps as high as 4,500 deg F • Small areal mass density: 30μm thickness compared to 2μm with same area density (~5g/m^2) • Immune to UV degradation • Ability to self-deploy, the carbon scrub-pad material could be packed so it pops out flat once released. This can eliminate the need for any complicated mechanical deployment mechanism, which decrease mass of the craft. • Easier to deploy because it doesn’t cling or wrinkle • Higher Melting Point AEM 4332W - Solar Sail

  46. Carbon Fiber vs. Traditional Material Carbon Fiber Aluminum Coated Mylar Using sample microtruss which is formed from perfectly electrical conducting (PEC) wires. The time-average force on the sail can be found using physical optics assuming microtruss is illuminated by a uniform plane wave (UPW) and Force at 0.48AU = 0.348N AEM 4332W - Solar Sail

  47. CP1 Solar Sail Material • Developed by SRS Technologies created a 5 micro meter thick film constructed of CP1 with an aluminized front surface and a black emissive black surface. • CP1 is a unique polymer which has favorable structural characteristics. AEM 4332W - Solar Sail Source: Scalable Solar Sail Subsystem Design Considerations

  48. Thermal Analysis of Payload Module • Found an innovative way to configure spacecraft parts which eliminate chassis, cables and connectors. • MFS (Multifunctional Structures) achieves this by using MCM (multichip modules) and dissipating its heat through a thermal core fill, and utilizing aluminum honeycomb sandwiched between 2 fiber reinforced cyanate ester composite faceplates. • This high density configuration increases payload-mass fraction and provides major weight volume and cost savings. AEM 4332W - Solar Sail

  49. MFS Configuration Thermal copper strap used to transfer heat to radiator surface. Hi-K facesheets (K13C2U) Multichip Module - Specialized electronic package where multiple integrated circuits are packaged to do many jobs with one module. High Conductivity Filler Kz = 700 W/mK Aluminum Honeycomb High K Isotropic Carbon- Carbon Doubler Edge corefill AEM 4332W - Solar Sail Kz

  50. Thermal Control of MFS • In order to dissipate waste heat from the MCM along with solar energy loads on the outer skin. Rate of heat flow Effective rad environment Radiation Equation Emissivity of radiator Temp of base plate Lateral Conductance Heat flow path length Setting equal and solving for temp of baseplate yields Average radiator temp Cross sectional area Material thermal conductivity AEM 4332W - Solar Sail

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