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Controls Analysis of the McConnell- Tolley Refuelable Spacecraft

Controls Analysis of the McConnell- Tolley Refuelable Spacecraft. Presented By Eliot Hariton AE245 – San Jose State University Professor Datta-Barua. http://ehariton.weebly.com/ae245.html. Highlights. Diagram of Spacecraft Mission Design Benefits of Refuelable Design

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Controls Analysis of the McConnell- Tolley Refuelable Spacecraft

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  1. Controls Analysis of the McConnell-Tolley Refuelable Spacecraft Presented By Eliot Hariton AE245 – San Jose State University Professor Datta-Barua http://ehariton.weebly.com/ae245.html

  2. Highlights • Diagram of Spacecraft • Mission Design • Benefits of Refuelable Design • Subsystems Specifications • Center of Gravity • Moment of Inertia • Equations of Motion and Transfer Functions • Control Analysis with Bode and Impulse • Artificial Gravity with Momentum Wheels

  3. The Spacecraft

  4. Dimensions

  5. Section View

  6. Mission Design • Round trip to Phobos • Largest Martian Moon • Mean Diameter 22.2 km • Orbital Period ~8 hours • Low Spectra Intensity 0.071 • DeltaV = 11.4 km/s • Hohmann Transfer *http://photojournal.jpl.nasa.gov/target/phobos

  7. Refuelable Design • The main engines on the craft are Electrothermal • capable of vaporizing water for 800 ISP++ • burning waste products • Fabric / Pykrete hull structure • strong as concrete • insulation, radiation protection, • water, fuel, • energy storage as hydrogen peroxide

  8. Systems Specifications • Payload 24,000 kg • Spacecraft Dry Mass 46,514 kg • Wet Mass 203,954 kg ~77% Fuel Water • Solar Array Capacity 480kW / 40kW per Hab • Main Engines RF Electrothermal ISP=800 • Hydrogen Peroxide attitude control Isp =150 • Thermal Regulation adjustable albedo

  9. Evaluating Center of Gravity • Changes based on which Hab water is drawn from. Simplify with water drawn equally from all Habs. • CG with Full Fuel 0.16 (m) • CG with Half Fuel 0.26 (m) • CG with 5% Fuel 0.61 (m)

  10. Moment of Inertia • Assumptions • Hab Module – Hollow Cylinder w/ End Caps, Uniform Mass Distribution, Variable Mass • Coupling – Hollow Cylinder, Static Uniform Mass • Engines – Cylinder, Static Uniform Mass • Solar Arrays – Flat Plate, Static Uniform Mass • Payload – Cylinder, Static Uniform Mass • Moment arm to CG changes with fuel level

  11. Moment of Inertia • Full Fuel • Half Fuel • 5% Fuel • Governing Equation

  12. Equations of Motion

  13. Open Loop Transfer Function

  14. Open Loop Transfer Function

  15. OL TF- Bode Plot, Full Fuel p(s)/My(s) Primary factor in long thrust intervals p(s)/Mx(s) Primary factor, thrust times < 0.1 s

  16. OL - Impulse Response – p(s)/Mx(s) Full Fuel – Start of Mission Half Fuel – During mission

  17. OL - Impulse Response – p(s)/Mx(s) Full Fuel – Start of Mission 5% Fuel – End of Mission

  18. Artificial Gravity - Momentum Wheel • Assume Momentum wheel located on the Z axis in the front of the craft • Despin wheel at start of mission to max (-175 rad/sec) • Spin wheel up as desired to rotate s/c and start artificial gravity • Assume inner (5m) and outer (7.5m) radius of wheel and density of ice • Wheel Height = 0.3m • Wheel Mass =27,161kg

  19. Sources • Main source information for this text is drawn from • Reference Design for a Simple, Durable and Refuelable Interplanetary Spacecraft, Brian McConnell (bsmcconnell@gmail.com) and Alexander Tolley (alexandertolley@gmail.com ) • Dimensional Drawings created with Solidworks • Phobos Picture by the Mars Reconnaissance Orbiter • Calculations performed in Mathematica and Matlab • All Calculations, 3D models and dimensional drawings are online at: http://ehariton.weebly.com/ae245.html

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