Final Presentation Draft Slides Description Some draft slides

Final Presentation Draft Slides Description: Some draft slides and ideas 3/26/09 1 AAE 450 Spring 2009 Kris Ezra Attitude

Areas of Analysis (Review) § § § Attitude Determination in Low Earth Orbit – Sun Sensors and Star Sensor are selected Gimbaled Main Engine Alternative – Found that the propellant cost is higher for desaturation using main engines Momentum Transfer Landing Alternative – Discarded since the required accelerations exceeded the limit of communications equipment Spinning Tether Landing Alternative – Discarded due to large tether length and high mass cost Arbitrary Payload Main Engine Selection – Recommended BHT-8000 for having lowest cost per kg • This is not currently in the report 2 AAE 450 Spring 2009 Kris Ezra Attitude

Attitude Determination in LEO Valley Forge Sun Sensors § Performance Accuracy: +1 Degree § Mass: ~0. 35 kg § Power Consumption : 2. 5 Watts Peak § Operating Temperature: ~ -20 to +60 deg. C Valley Forge Star Sensors § Performance Accuracy: 15 arcseconds § Mass: <3. 2 Kg § Dimension: 32 x 16 (cm) § Power Consumption : 10. 2 W § Operating Temperature: -40 to +60 deg. C Total Attitude Determination Mass (Including Star Sensor): ~3. 55 kg Package Cost (including attitude control equipment): $400, 000 These numbers need updated. Specifically total attitude determination mass and dimensions of the sun sensor 3 AAE 450 Spring 2009 Kris Ezra Attitude

Gimbaled Main Engine Alternative Gimbal Mount Specifications: 1. Approximate mass of 6 kg 2. Angular maximum motion of 20º – 3 Axis Gimbal Mission Length (days) Desaturation Maneuvers (#/day) Max Reation Wheel Torque (Nm) H 202 Specific Thrust (N/kg) Attitude Moment Arm (m) Engine Moment Arm (m) Total mass (kg) (Attitude DS) Total mass (kg) (Engine DS) 365 6 0. 03 9. 5 1. 1 0. 3858 m 1. 06 m 20º 6. 287081 17. 92584 Gimbal Alternative Discarded based on Mass Cost 4 AAE 450 Spring 2009 Show Formulation? Kris Ezra Attitude Group Translunar Phase

Rationale for Discarding Momentum Transfer Concept: The momentum transfer concept was analyzed just using work/energy relationships subject to the conditions that the Lander could not experience an accelerati Momentum Transfer Alternative Acceleration sustainable by Communication Equipment: 10 g Most Conservative Reasonable Collision Distance: 1 -2 m Earth g’s Sustained at this Distance: 1 x 105 Collision distance required at 1. 7 km/s = ~150 km Because the sustained acceleration in a reasonable spring collision would be four orders of magnitude higher than the communication equipment can withstand (and maybe higher than the molecular bonds of the structure can withstand) this alternative is entirely infeasible. 5 AAE 450 Spring 2009 Kris Ezra Attitude Group Translunar Phase

Rationale for Discarding Momentum Transfer Concept: The momentum transfer concept was analyzed just using work/energy relationships subject to the conditions that the Lander could not experience an accelerati Spinning Mass Tether Alternative Acceleration sustainable by Communication Equipment: 10 g Required Tether Length to Match Orbital Velocity: ~50 km Additional mass cost at this Length: 325 kg (Total mass of 400 kg) Orbital Height: ~100 km Result: Weight of tether exceeds propellant mass and tether length is nearly half the orbital height. Completely infeasible. 6 AAE 450 Spring 2009 Kris Ezra Attitude Group Translunar Phase

Other Ideas § Calculation Slides which outline methodology alone § Slides which detail the actual setup of alternatives – For example, diagrams: 7 AAE 450 Spring 2009 Kris Ezra Attitude

References Valley Forge Composite technologies. “Sun Sensors, ” Accessed 3 Feb 2009, URL: http: //www. vlyf. com/aerospace/sun-sensors/ 8 AAE 450 Spring 2009 Kris Ezra Attitude