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NASA Technical Reports Server (NTRS) 20110011340: Orion Spacecraft MMOD Protection Design and Assessment PDF

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Orion Spacecraft MMOD Protection Design and Assessment APS Shock Physics Conference, Chicago, IL June 29, 2011 Joshua E. Miller Lockheed Martin SSC Denver, Colorado 0000 4/16/2011 1 Contributing authors • William E. Bohl – LM Space Systems Co., Denver, CO • Cory D. Foreman – LM Exploration & Sciences Co., Houston, TX • Eric Christiansen – NASA Johnson Space Center, Houston, TX • B. Alan Davis – NASA Johnson Space Center, Houston, TX 2 A first-principals, semi-empirical ballistic performance model has been developed for porous ceramics • Lightweight thermal protection systems protect the crew and vehicle of orbital and exo-orbital missions from the intense heat of atmospheric reentry • To maintain low launch weights these materials are their own protection from space hazards like orbital debris and meteoroids • A ballistic performance model is described here that models the performance under a variety of impact conditions 3 Atmospheric braking creates high surface temperatures that must be mitigated • The Orion thermal protection • The small dimensions of high system surfaces can be probability impacts afford heated by the reentry plasma some damage tolerance due to temperatures above 1000 to limited thermal convection °K creating thermal gradients in the small cavities leaving of several 100 °K over their the residual insulation as the thickness key performance parameter 4 Tests of Orion thermal protection tiles are used to establish the thresholds of failure • AETB8 impacts have performed by Orion program at: • UDRI with maximum velocities of ~10 km/s • WSTF with maximum velocities of ~8.5 km/s • 50 internal tile damage impacts have been performed • Impactors include Nylon, Aluminum and Steel • Impact obliquities from normal to 75° to normal • Impact velocities from 3 to 10 km/s • 2 different areal densities of hard outer layer 5 Impacts on tiles involves a sequence of densities that distribute impact energy • The density profile: • Projectile slows to • Projectile impacts the higher density • High density equilibrium in the TUFI/RCG layer TUFI/RCG layer TUFI/RCG layer and then releases and creates a • Low density tile to an initial velocity, cavity as it goes • Higher density U , and a lateral through the lower silica layer and 0 release velocity, U, density tile bonding layer r in the tile 6 A modified logistics function reproduces the ratio of cavity depth to half-width • Empirical relation • Fit parameters: • δωis 0.3 • ω is 0.2 0 • U is 5.5 km/s m • Represents fraction of dispersed projectile and TUFI to large fragments • First term numerator is the product of required pressure and time in projectile for break up • Second term numerator is the product of induced • Points are shot data color pressure of the impact coded to the corresponding and time to rarefaction velocity bin (km/s): 4 (red), generation 7 (orange), 8 (green), 9 • Denominator is the (blue), 9.5 (magenta) dispersion of pressure and time about the required 7 EOS studies show approximately isochoric behavior in jump states of porous silica SESAME7360 • N. C. Holmes and E. F. See in • T. R. Boehly, et al. in Shock Shock Waves of Condensed Waves of Condensed Matter Matter of 1991 with a of 2007 extended silica SESAME 7360 P-α observations for 0.2 g/cc compaction of 2.5 GPa for P aerogels to much higher s overlaid pressures indicating continual significant energy sinks 8 Mass, EOS and momentum equations combine to a 1st order differential • The disrupted • The non- • The normalized projectile dimensional equation for expands as it Lagrangian projectile traverses the form of the velocity tile scattering mass, EOS and decreases increasing momentum rapidly under mass to slow equations (see expansion until faster than a Appendix of the strength of fully intact accompanying the tile finally projectile does paper for full arrests the derivation) projectile 9 Model reproduces the tests performed and shows evidence of a double wall behavior • Simplified solution of the model • Model shows the double wall effect reproduces of fragmentation/melt of impactors • Nylon, aluminum and steel projectiles • Shows the dependence of the onset of fragmentation/melt of impactors on • Impact obliquities to 75° to normal weight of TUFI/RCG layer • Impact velocities to 10 km/s • Light and Heavy TUFI/RCG 10

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