1. AAE450 Spring 2009 Slide 1 of 8 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. AAE450 Spring 2009 Slide 2 of 8 OTV Power and Thermal Control (For Arbitrary Payload) Ian Meginnis Power Systems SystemComponent Mass (kg) Cost (millions USD) Power Solar Arrays28142.1 Power Conditioning and Distribution Unit 2875 Direct Current/Direct Current Converter 10.24 Battery2660.48 Solar Array Motor34-- TOTALS86947.82 Thermal Control Radiators23<$40E-6 Heat Pipes & Ammonia15.3<$50E-6 TOTALS38.3<$100E-6

3. AAE450 Spring 2009 Slide 3 of 8 OTV Total Masses Ian Meginnis Power Systems Group Mass (kg) for 100g Payload Mass (kg) for 10kg Payload Mass (kg) for Arbitrary Payload Attitude 10.610.830 Communication 000 Propulsion 1501543840 Power 46.5 835 Thermal Control 5.5 38.3 Structures 49.456.61668 TOTALS 262273.46411 Expected Cost (Millions USD) 6.0 TBD Note: Total masses include only wet OTV masses (not Lunar Lander or Payload)

4. AAE450 Spring 2009 Slide 4 of 8 OTV Costs and Masses (For Arbitrary Payload)  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 = 8.5m 2 –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 Ian Meginnis Power Systems

5. AAE450 Spring 2009 Slide 5 of 8 Calculation of Electronics Board Thermal Control (For Arbitrary Payload)  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/cm 3 = 15.3kg  Mass of radiators –Area of radiators: A = q / (εσT 4 ) = 8.4m 2 For aluminum with white paint (Z93): Emissivity (ε) = 0.92 σ = 5.67E-8 J/(K 4 *m 2 *s) q = 4kW T = boiling point of ammonia @ 4 atm = 271K –Mass of radiators = 2700kg/m 3 * 8.5m 2 * 0.0005m = 11.5kg (each)  Total cost to implement design: < $100 Ian Meginnis Power Systems

6. AAE450 Spring 2009 Slide 6 of 8 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 = 0.4625m 2 –9 sides available to radiate power from Hall thruster –Without radiators, the hall thruster radiate 1.2kW »q = AεσT 4 = 1.2kW Sun contributes 120W of heat to thrusters –q = Aα(1300W/m 2 ) = 120W Net heat to dissipate = 16.2kW – 1.2kW + 0.12kW = 15.12kW

7. AAE450 Spring 2009 Slide 7 of 8 Calculation of Hall Thruster Thermal Control (For Arbitrary Payload)  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 / (εσT 4 – α*1300W/m 2 ) = 6.45m 2 –q = 15.12kW –T = 473K –α*1300W/m 2 = power input from sun Ian Meginnis Power Systems

8. AAE450 Spring 2009 Slide 8 of 8 Ian Meginnis Power Systems Note: Not to scale 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 Earth Sun Moon Single, Simplified Orbit of OTV (Arbitrary Payload)