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Brian Erson Attitude Control Systems

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  1. Brian ErsonAttitude Control Systems Trans Lunar Phase Alternative Design Analysis Cold Xe Gas Thrusters 1 [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 2 [Brian Erson] [Attitude]

  3. Cold XeGas 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 (4 @ 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 (4@ $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 3 [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. 4 [Brian Erson] [Attitude]

  5. Backup Slide 2 Xe DS propellant calculation Total DS force needed: Max torque of Rxn Wheel: 0.03 Nm DS per day: 6 Mission length: 365 days Moment arm 1.0 m Total:65.7 N Total number of thrusts @ .015 N 4380 thrusts Marotta Cold Xe gas thruster Specs: Mass: 0.075 kg Isp: 68 sec Thrust: 0.015 N Time per thrust: 0.04 sec Mass Flow Calculation: Isp = Force/massflow * gravity Mass flow: 0.0022 kg/sec Total Mass: 0.0022 kg/sec * 0.04 sec/thrust * 4380 thrusts = 0.385 kg 5 [Brian Erson] [Attitude]