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Orbital Transfer Vehicle (OTV) Masses and Costs

Orbital Transfer Vehicle (OTV) Masses and Costs. Ian Meginnis March 12, 2009 Group Leader - Power Systems Phase Leader - Translunar Injection OTV Power Systems OTV Thermal Control. OTV Power and Thermal Control (For Arbitrary Payload). OTV Total Masses.

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Orbital Transfer Vehicle (OTV) Masses and Costs

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  1. Orbital Transfer Vehicle (OTV) Masses and Costs Ian Meginnis March 12, 2009 Group Leader - Power Systems Phase Leader - Translunar Injection OTV Power Systems OTV Thermal Control Ian Meginnis Power Systems

  2. OTV Power and Thermal Control (For Arbitrary Payload) Ian Meginnis Power Systems

  3. OTV Total Masses Ian Meginnis Power Systems Note: Total masses include only wet OTV masses (not Lunar Lander or Payload)

  4. OTV Costs and Masses(For Arbitrary Payload) Ian Meginnis Power Systems • Thermal control configuration used for 100g and 10kg payloads will be used for arbitrary payload case • 4116W needs to be removed from electronics board • Ammonia + Heat Pipes + 2 Radiators = 38.3kg • Area of each radiator = 8.5m2 • Two valves used to ensure electronics are not cooled too much • Xenon needs to be stored at gaseous state • 79W tank heater: 3.1kg (this mass is included in propulsion mass) • Total Thermal Control System Mass: 38.3g

  5. Calculation of Electronics Board Thermal Control (For Arbitrary Payload) Ian Meginnis Power Systems • Sizing of heat pipes • Mass of ammonia: • Latent heat of vaporization of ammonia: 4000kJ/kg • Mass = 4kW * 10sec / (4000kJ/kg) = 0.0102kg • Assumes ammonia boils in 10 sec • Mass of titanium pipes: • Diameter of pipes: 3.78cm (OD); 3.38cm (ID) • Length of pipes: 15m • Mass = π[(3.78cm)2 – (3.38cm)2] * 1500cm * 0.00454kg/cm3 = 15.3kg • Mass of radiators • Area of radiators: A = q / (εσT4) = 8.4m2 • For aluminum with white paint (Z93): Emissivity (ε) = 0.92 • σ = 5.67E-8 J/(K4*m2*s) • q = 4kW • T = boiling point of ammonia @ 4 atm = 271K • Mass of radiators = 2700kg/m3 * 8.5m2* 0.0005m = 11.5kg (each) • Total cost to implement design: < $100

  6. Calculation of Hall Thruster Thermal Control (For Arbitrary Payload) Ian Meginnis Power Systems • Find q radiated to space from EP structure • Need to radiate 16.2kW • For aluminum with white (Z93) paint: Emissivity (ε) = 0.92;Absorptivity (α) = 0.20 • Max. operating temperature of Hall thruster = 473K • Hall thruster surface area: A = 0.4625m2 • 9 sides available to radiate power from Hall thruster • Without radiators, the hall thruster radiate 1.2kW • q = AεσT4 = 1.2kW • Sun contributes 120W of heat to thrusters • q = Aα(1300W/m2)= 120W • Net heat to dissipate = 16.2kW – 1.2kW + 0.12kW = 15.12kW

  7. Calculation of Hall Thruster Thermal Control(For Arbitrary Payload) Ian Meginnis Power Systems • Need to dissipate 15.12kW • Conduction transports heat from thruster to radiators attached to thrusters • OTV back cover will serve as a radiator • Minimum area of cover: A = q / (εσT4 – α*1300W/m2) = 6.45m2 • q = 15.12kW • T = 473K • α*1300W/m2 = power input from sun

  8. Single, Simplified Orbit of OTV (Arbitrary Payload) Moon • At least 1 of the OTV’s set of radiators will not be exposed to sun’s rays at any point during the trajectory • Each radiator, alone, can provide thermal control for OTV electronics Sun Earth Note: Not to scale Ian Meginnis Power Systems

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