aae450 spring 2009 final slides lunar lander structure april 9, 2009 lunar descent phase group [ryan...

AAE450 Spring 2009

Final SlidesLunar Lander Structure

April 9, 2009

Lunar Descent Phase Group

[Ryan Nelson] [STRC]1

AAE450 Spring 2009

Basic Frame Design Drivers in frame mass

– Total Lunar Lander (LL) mass at lunar touchdown

– Volume of LL

Shape: Conic Frustum– Stores all Lunar Lander subsystems

while minimizing volume

All frame components hollow– Small leg diameter allows for storage

within side supports prior to lunar touchdown

Schematic of frame listing components

2

AAE450 Spring 2009

Backup Slides (Mass/Volume)

Lunar Lander Volume Height Top Diameter Bottom Diameter Mass

100g 1.05 m3 1.0 m 1.0 m 1.3 m 11.44 kg

10kg  1.15 m3  1.1 m 1.0 m 1.3 m 19.97 kg 

Large  14.33 m3  2.0 m 2.4 m  3.6 m  104.86 kg

3

AAE450 Spring 2009

Backup Slides (Frame Design) Thickness of all frame components varies

– First mode of failure (factor of safety = 1.5)– Payload case

Cross sectional shape is circular or rectangular for all components

0.5 mm magnesium skin place around Lunar Lander frame– Micrometeorite protection– Thermal protection

4

AAE450 Spring 2009

Backup Slides (Floor Supports) Support a majority of landing loads

Thickness altered until load is supported Hollow Rectangular Cross section

– Moment of Inertia

– Bending Stress acting on beam

I

My

I

My

12

)2)(2( 33 thtbbhI

5

AAE450 Spring 2009

Backup Slides (Side Supports/Legs)

First mode of failure is buckling

– K=0.5 for side supports (both ends fixed)– K=2.0 for legs (one end is free to move)– Hollowing the rod decreases moment of

Inertia and critical load

2(kl)

EI

2(kl)

EIFcr =

)( 21

22 rrI

6

AAE450 Spring 2009

Backup Slides (Side Supports/Legs)

Compression failure occurs after buckling for both side supports and legs– Despite small cross sectional area– Compression failure

Top, Bottom, and Engine Support rings all designed to have same cross sectional dimensions

A

F

7

AAE450 Spring 2009

Backup Slides (Cross Sectional Dimensions)

100g Payload CaseStructural Component Cross sectional shape Outer Dimensions Thickness

Outer Ring Circular 10 cm Diameter 4mm

Engine Support Ring Circular 10 cm Diameter 4mm

Rectangular Floor Supports Rectangular 10 cm Height, 6 cm Width 6mm

Side Supports Circular 10 cm Diameter 2mm

Top Ring Circular 10 cm Diameter 4mm

Legs Circular 6 cm Diameter 3mm

10kg Payload CaseStructural Component Cross sectional shape Outer Dimensions Thickness

Outer Ring Circular 10 cm Diameter 5mm

Engine support Ring Circular 10 cm Diameter 5mm

Rectangular Floor supports Rectangular 10 cm Height, 6 cm Width 7mm

Side supports Circular 10 cm Diameter 2mm

Top Ring Circular 10 cm Diameter 5mm

Legs Circular 5 cm Diameter 3mm

8