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Brandon Anderson Week 7: March 1st, 2007

Brandon Anderson Week 7: March 1st, 2007. Structures Group EP Vehicle, TC Landing Gear. EP System Vehicle Structure. Primary Structure Supports major loading Al-Li 2090 Stringers & Stiffeners Monocoque Structure will offer better micrometeorite protection, but more massive

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Brandon Anderson Week 7: March 1st, 2007

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  1. Brandon AndersonWeek 7: March 1st, 2007 Structures GroupEP Vehicle, TC Landing Gear Anderson (1)

  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 Anderson (2) Reactor Image Courtesy: Courtney Rogge

  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 Anderson (3)

  4. Backup SlidesSource Data Anderson (4) Courtesy Jummie Garba

  5. More EP System Data Anderson (5)

  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 Anderson (6)

  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. Anderson (7)

  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 Anderson (8)

  9. Honeycomb Calculations 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. Mass of honeycomb to absorb Energy of impact Anderson (9)

  10. Landing Gear Specs • 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 Anderson (10)

  11. Material Properties • Al-Li 2090 Material Properties and Loading Parameters Anderson (11)

  12. References • 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. This is for each side. Anderson (12)

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