1. AAE450 Spring 2009 Brian Erson Attitude Control Systems Trans Lunar Phase Alternative Design Comparison [Brian Erson] [Attitude] 1

2. AAE450 Spring 2009 [Brian Erson] [Attitude] 2 Orbit Transfer Vehicle Stabilization 3-AxisSpin Attitude Sun Sensors, Star Sensors, Reaction Wheel Doppler Data, Conical Scanner Power Large Solar ArraysSmall Efficient Solar Cells, Battery Power Propulsion(Attitude) H202 impulse Communication Unidirectional AntennaDe-spin pointing, high-gain antenna Structure/Thermal Increased thermal protection needed “Barbecue Roll” decreases reliance on thermal protection Sources of Instability Thrust Misalignment, 3-6 de-saturation maneuvers/day, environmental perturbation Fuel Slosh Torque

3. AAE450 Spring 2009 [Brian Erson] [Attitude] 3 Mass Layout 3-AxisSpin Attitude Control 40.1 kg27.1 kg Power < 40 kg> 100 kg Communication 3 kg Thermal 17.1 kg< 5 kg Structure/Prop 500* kg Total 600.1 kg634.7 kg Conclusion: Mass difference represents a savings of >34.6 kg with 3-axis stabilized spacecraft * Conservative estimate minimally affected by stabilization method

4. AAE450 Spring 2009 [Brian Erson] [Attitude] 4 Backup Slide 1 Attitude Control Mass Calculations: 3-axis Sun Sensors0.7 Star Sensors6.4 Reaction Wheels6 H2O2 Thrusters1 Propellant(H2O2)*26 Total:40.1 kg Spin Conical Scanner6 Doppler Device1 H2O2 Thrusters1 Propellant(H202)**19.1 Total:27.1 *Prop Mass Includes Lunar Descent

5. AAE450 Spring 2009 [Brian Erson] [Attitude] 5 Backup Slide 2 **H2O2 De-Saturation(DS) Mass Calculation: DS of reaction wheels: Estimate of DS maneuvers/day:6 Reaction wheel max torque:0.03 N-m H2O2 Thrust:9.5 N/kg Max Mission Length:365 days Total Mission DS H2O2 mass: (365)(6)(1/9.5)(0.03) = 6.9 kg

6. AAE450 Spring 2009 [Brian Erson] [Attitude] 6 Backup Slide 3 Other Mass Calculations: Power: Masses based on posted Power Group Data Mass of battery without solar cells based on assumption of >1.2 kW needed to power OTV Communication: 3 kg mass based on posted Com Group Data Thermal: 3 axis mass based on posted data Spin stabilized Thermal Protection: Assume 15 rpm Mass = [(1/15(17.1))+4*] =~ 5 kg *Estimated mass of standard thermal protection

7. AAE450 Spring 2009 [Brian Erson] [Attitude] 7 References http://sciencelinks.jp/j-east/article/200313/000020031303A0423712.php http://cat.inist.fr/?aModele=afficheN&cpsidt=4572226 http://cs.astrium.eads.net/sp/SpacecraftPropulsion/Propellant%20Tanks/Spi n_Stabilised%20Tanks.html http://www.peroxidepropulsion.com/article/5 http://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/20050243594_2005246 327.pdf http://www.sandia.gov/ess/Publications/Conferences/2002/ESKRA%20- %20NiMetalHydride.pdf