1. Lunar Descent Trajectory
February 19th, 2009
[John Aitchison] [Mission Ops]

2. [John Aitchison] [Mission Ops]
Descent Trajectory
Steering Program
Descent times >1000s, working on better model
Gimbaled Engine
No savings until arbitrary payload case
[John Aitchison] [Mission Ops]

3. Useful Numbers/Recommendations
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 Sensor
System Updates
[John Aitchison] [Mission Ops]

4. 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
[John Aitchison] [Mission Ops]

5. Updated Lunar Descent Masses
System
Subsystem
Mass (kg)
Power
Batteries 20
Solar Panels 2
Communications
CPU
0.57
Camcorder
0.38
Receiver
0.2
Transmitter
Antenna
0.1
Propulsion
Structure
34.1
Propellant
157.7
Attitude
Thrusters 7
2.5
Star Sensor
3.2
Rover
31.5
Frame
30.45
Thermal Control
24.7
Total Dry
156.9
Total Wet
314.6
[John Aitchison] [Mission Ops] 4

6. Landed Mass vs. Prop Mass -Also basis of EOM code
[John Aitchison] [Mission Ops]

7. Landed Mass vs. Prop Mass (cont.)
[John Aitchison] [Mission Ops]

8. [John Aitchison] [Mission Ops]
Landed Mass vs. Prop Mass (cont.)
[John Aitchison] [Mission Ops]

9. [John Aitchison] [Mission Ops]
Landed Mass vs. Prop Mass (cont.)
[John Aitchison] [Mission Ops]

10. Effects of Non 110km Circ Orbit
[John Aitchison] [Mission Ops]

11. Effects of Non 110km Circ Orbit (cont.)
[John Aitchison] [Mission Ops]

12. Effects of Non 110km Circ Orbit (cont.)
[John Aitchison] [Mission Ops]

13. [John Aitchison] [Mission Ops]
Descent EOM’s
[John Aitchison] [Mission Ops]