1. AAE450 Senior Spacecraft Design Anderson (1) Brandon Anderson Week 7: March 1st, 2007 Structures Group EP Vehicle, TC Landing Gear

2. AAE450 Senior Spacecraft Design Anderson (2) EP System Vehicle Structure Primary Structure –Supports major loading –Al-Li 2090 –Stringers & Stiffeners Monocoque Structure will offer better micrometeorite protection, but more massive –EP systems 3 & 4 require more than 1 vehicle by mass –Radiator Vol. is limiting factor Assuming that reactor will be able to fit in 1 Ares V payload Code is flexible, can easily alter to final configurations Skin mass is 2.082 mt in all cases Reactor Image Courtesy: Courtney Rogge System Total Structural Mass (mt) Stringer Mass (mt) Stiffener Mass (mt) Fastener Mass (mt) 14.8421.5710.1541.035 26.0382.5110.2361.209 35.5132.1160.2111.104 44.4211.3290.1250.885 54.6861.5220.1430.939 63.9070.9450.0970.783 75.1251.8340.1831.026 84.0421.0510.10.81 94.151.1260.1120.83

3. AAE450 Senior Spacecraft Design Anderson (3) TC Landing Gear Al-Li 2090 4 equally spaced struts Shock/Strut –More massive –Proven –Reusable Crushable Honeycomb –Lightweight –Proven –One and done Both Struts and landing pads have honeycomb 6.7 m/s nominal landing Assume 10m/s max Mass (kg) Pad Comb Mass (kg) Strut Comb Mass (kg) Leg Mass (kg) 26518.4 175 Connecting Structure (kg)Volume (m^3) 53.20.07

4. AAE450 Senior Spacecraft Design Anderson (4) Backup Slides Source Data Courtesy Jummie Garba Vm0mhardmpTPtb (km/s)(mt) (N)(MW)(yrs) EP 110233.6428.6443.1123.40.572.87 EP 210377.746.369.6837.80.932.87 EP 35.9563.6769.128.3514.10.351.76 EP 410490.6560.1590.5249.11.22.87 EP 55.9563.6769.163.956.41.381.76 EP 610137.0216.825.2813.70.342.87 EP 710260.4331.9252.34260.642.87 EP 810153.4518.8128.3115.30.382.87 EP 910153.4518.8131.7515.30.382.87

5. AAE450 Senior Spacecraft Design Anderson (5) More EP System Data # StringersStringer Width (m)Stringer thickness (m)# Stiffnersskin thickness (m) 1670.0980.0011220.001 2700.0970.0017220.001 3690.0940.0015230.001 4700.0970.0009220.001 5700.10.001220.001 6640.0970.0007220.001 7690.0940.0013230.001 8690.10.0007220.001 9660.0980.0008220.001

6. AAE450 Senior Spacecraft Design Anderson (6) Failure Modes of Stringers Critical Buckling Force, Where k=1 for stringers, can model as simply pinned Loads Must Not Exceed Material Yield Stress

7. AAE450 Senior Spacecraft Design Anderson (7) Stress on Stiffeners Hoop Stresses Transverse Loads taken on by the ring stiffeners in this case. Loads not adequate to fail stiffeners of size needed to support stringers.

8. AAE450 Senior Spacecraft Design Anderson (8) Failure Mode of Skin Stringers and stiffeners split into enough sections that stresses are of small magnitudes for each section. 1mm assumed to be the minimum realistic thickness for the skin

9. AAE450 Senior Spacecraft Design Anderson (9) Honeycomb Calculations Mass of honeycomb to absorb Energy of impact Specific energy of honeycomb. Fc is the ultimate compressive stress of the material. Dh is the crushable length (Assumed to be 2/3 of the initial honeycomb length), he is the initial length of honeycomb, wc is the weight density of the material. Total Energy that needs to be dissipated. Mtc is the mass of the capsule at touchdown, vland is the touchdown velocity, and hcg is the distance from the ground to the center of gravity.

10. AAE450 Senior Spacecraft Design Anderson (10) Landing Gear Specs Pad diameter (m)Pad Height (m)Strut Comb Length (m)Leg Total Length (m) 0.11 0.63.5 Usable pad StrokeUsable Strut Stroke (m)Min Ground Clearance (m) 0.0733333330.41 Each Pad is assumed to be able to absorb ¾ of kinetic energy (per NASA research, see references). Honeycomb in struts meets same requirements, basically an added safety feature. Assumption made that honeycomb absorbs energy until 2/3 of initial length is compacted. Legs designed to give 1m clearance if system is fully crushed Each leg can fully support mass of TC on the Martian surface for safety Same buckling failure mode as stringers in EP

11. AAE450 Senior Spacecraft Design Anderson (11) Material Properties Al-Li 2090 Material Properties and Loading Parameters Elastic Modulus7.60E+10Pa Poissons Ratio0.34 Density2590kg/m^3 Yield Strength5.20E+08Pa Safety Factor for Loads1.5 Safety Factor for Internal P2 Axial Load Factor nx10g Lateral Load Factor nz2.5g Lateral Load Factor ny2.5g

12. AAE450 Senior Spacecraft Design Anderson (12) References This is for each side. Annarella, Cyril. Spacecraft Structures. Black, Raymond J (1964).Quadrupedal Landing Gear Systems for Spacecraft. Journal of Spacecraft. 1, 196-203. Duncan, John (2005). The Lunar Module Descent Stage. Retrieved February 21,2007, from Lunar Module News Reference Web site: http://apollosaturn.com/Lmnr/descent.htm Fischer, Mark. Aerobraking and Impact Attenuation. 1995 Grandt, A.F. AAE 454 Course Notes. 2006. Landau, Dr. Damon F. “Strategies for the Sustained Human Exploration of Mars” Thesis Submitted to the Faculty of Purdue University, Dec. 2006.