AAE450 Spring 2009 Brian Erson Attitude Control Systems Trans Lunar Phase Alternative Design Analysis Cold Xe Gas Thrusters [Brian Erson] [Attitude] 1

AAE450 Spring 2009 [Brian Erson] [Attitude] 2 Current H2O2 system Advantages System is useful for an arbitrary payload mass No increased inert mass System has dual role in OTV and Lunar descent Disadvantages Current H202 system is too large (13N thrust) to use for in flight attitude control with 100g and 10kg payloads De-saturation (DS) maneuvers alone cost > 6kg Small attitude adjustments more complex with large system

AAE450 Spring 2009 [Brian Erson] [Attitude] 3 Cold Xe Gas Thruster Advantages Xe DS propellant use is negligible (< 400g) Easy to integrate Small thrust is suitable for OTV attitude control and DS maneuvers Thruster mass is very small 75g each) Total system mass is 5.4kg (at least 1 kg less than H2O2) Disadvantages Both systems would need to be used Dollar cost is significant $25K each) Power usage increases (1 Watt Peak ) System would not be as useful for arbitrary payload mass Recommendation Cost tradeoff favors H2O2 thrusters for Earth to LEO cost estimates Need to integrate smaller H2O2 thrusters within current system

AAE450 Spring 2009 [Brian Erson] [Attitude] 4 Backup Slide 1 Cost tradeoff: Xe thruster system cost:$100,000 Current Earth to LEO cost/kg:$4400 Economical mass savings 22.7 kg Xe system mass savings < 5.0 kg Xe system Earth to LEO cost:~$20,000/kg Note: Unless Xe system saves upward of 22.7 kg,or the cost decreases, it is not economically feasible to install the system. Further analysis will be done to improve mass and dollar cost numbers of both systems.

AAE450 Spring 2009 [Brian Erson] [Attitude] 5 Backup Slide 2 Xe DS propellant calculation Total DS force needed: Max torque of Rxn Wheel:0.03Nm DS per day:6 Mission length:365 days Moment arm1.0m Total:65.7 N Total number of N4380thrusts Marotta Cold Xe gas thruster Specs: Mass:0.075kg Isp:68sec Thrust:0.015N Time per thrust:0.04sec Mass Flow Calculation: Isp = Force/massflow * gravity Mass flow:0.0022kg/sec Total Mass: kg/sec * 0.04 sec/thrust * 4380 thrusts = kg