AAE450 Spring 2009

Lunar Descent Trajectory

February 5th, 2009

[John Aitchison] [Mission Ops]

AAE450 Spring 2009

Descent Trajectory

[John Aitchison] [Mission Ops]

Goal– Determine trajectory, attitude,

burn time, range & altitude

EOM Derivation Assumptions• Moon/spacecraft system,

spherical & does not rotate, point masses

• 2-D problem• T/m varies only with changing

propellant mass (no throttling)

2

AAE450 Spring 2009

Useful Numbers

[John Aitchison] [Mission Ops]

Variability with:– Vehicle Mass– Thrust Capability– Lunar Parking Orbit

Time (s) Action Downrange (km) Altitude (km)0.0 Retro 0.0 15

170.3 27° 170.1 5.7207.5 Vertical 175.4 0.9222.1 Touchdown 175.4 0.0

3

AAE450 Spring 2009

Code (pg. 1)

[John Aitchison] [Mission Ops]4

AAE450 Spring 2009

Code (pg. 2)

[John Aitchison] [Mission Ops]5

AAE450 Spring 2009

Code (pg. 3)

[John Aitchison] [Mission Ops]6

AAE450 Spring 2009

Code (pg. 4)

[John Aitchison] [Mission Ops]7

AAE450 Spring 2009

Coordinate System

[John Aitchison] [Mission Ops]8

AAE450 Spring 2009

Coordinate System Definitions

[John Aitchison] [Mission Ops]9

AAE450 Spring 2009

Assumptions

[John Aitchison] [Mission Ops]10

AAE450 Spring 2009

Calculations (pg. 1)

[John Aitchison] [Mission Ops]11

AAE450 Spring 2009

Calculations (pg. 2)

[John Aitchison] [Mission Ops]12

AAE450 Spring 2009

Calculations (pg. 3)

[John Aitchison] [Mission Ops]13

AAE450 Spring 2009

Calculations (pg. 4)

[John Aitchison] [Mission Ops]14