AAE450 Spring 2009

Lunar Descent Trajectory

February 19th, 2009

[John Aitchison] [Mission Ops]

AAE450 Spring 2009

Descent Trajectory

[John Aitchison] [Mission Ops]

Steering Program– Descent times >1000s, working on better model

Gimbaled Engine– No savings until arbitrary payload case

2

AAE450 Spring 2009

Useful Numbers/Recommendations

[John Aitchison] [Mission Ops]3

1 additional kg on lunar surface ≈ 2.1 kg additional kg in lunar orbit

2000 km circular lunar parking = add 55kg descent prop mass!!– Use EP as long as possible

Stay above 20 km until final descent

Also: Altitude SensorSystem Updates

AAE450 Spring 2009 [John Aitchison] [Mission Ops]

Assumptions on First Slide Graph 1

– 110km, 15km orbit; vertical to horizontal burn; constant 2000 N thrust; constant mdot=.67 kg/s

Graph 2– Graph 1 assumptions; 315kg wet mass; worst case

mountain scenario Graph 3

– Added prop to get to 110km circular; instantaneous deltaV; Hohmann transfers

<#>

AAE450 Spring 2009

Updated Lunar Descent Masses

[John Aitchison] [Mission Ops]

System Subsystem Mass (kg)Power      Batteries 20  Solar Panels 2     Communications      CPU 0.57  Camcorder 0.38  Receiver 0.2  Transmitter 0.2  Antenna 0.1          Propulsion      Structure 34.1  Propellant 157.7     Attitude     Thrusters 7 System 2.5 Star Sensor 3.2     Rover   31.5     Structure      Frame 30.45  Thermal Control 24.7

Total Dry 156.9Total Wet 314.6

4

AAE450 Spring 2009

Landed Mass vs. Prop Mass-Also basis of EOM code

[John Aitchison] [Mission Ops]5

AAE450 Spring 2009

Landed Mass vs. Prop Mass (cont.)

[John Aitchison] [Mission Ops]6

AAE450 Spring 2009 [John Aitchison] [Mission Ops]7

Landed Mass vs. Prop Mass (cont.)

AAE450 Spring 2009 [John Aitchison] [Mission Ops]8

Landed Mass vs. Prop Mass (cont.)

AAE450 Spring 2009 [John Aitchison] [Mission Ops]9

Effects of Non 110km Circ Orbit

AAE450 Spring 2009 [John Aitchison] [Mission Ops]10

Effects of Non 110km Circ Orbit (cont.)

AAE450 Spring 2009 [John Aitchison] [Mission Ops]11

Effects of Non 110km Circ Orbit (cont.)

AAE450 Spring 2009

Descent EOM’s

[John Aitchison] [Mission Ops]