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Published byCora Thornton Modified over 9 years ago
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Mars Mission Radiation Dose/Shielding Summary Note: Dr. Cary Zeitlin generously contributed these slides from two full-length presentations. For brevity’s sake, supporting details have been removed. Use at your own risk… Contributor Credits: Cary Zeitlin (SwRI), NASA, Lawrence Berkeley National Lab Collator: Brian Enke (SwRI)
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Dose Dose is physical: energy deposited per unit mass. 1 gray = 1 Gy = 1 J / kg = 100 rads
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Dose equivalent 1 sievert = 1 Sv = 100 rem. Sv dffers from Gy by weighting factor: – w R = 1 for sparsely-ionizing types, e.g., – w R = 5 for protons, 20 for and heavier nuclei. In “mixed field” w R replaced by Q(L).
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Shielding against GCR is impractical. Some exposure to heavy ions is inevitable in space. DNA repair works for simple damage, but heavy ions cause complex damage.
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15 th Humans in Space, Graz, Austria
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1% 0.1%.01% Maximum Acceptable Risk = 3% Shuttle Mission ISS Mission Mars Mission Increase in Individual’s Risk of Fatal Cancer ▲ ▲ ▲ “95% Confidence Interval” 10 % Lunar ▲ SPE??
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15 th Humans in Space, Graz, Austria Dose Reduction Chart Revisited Hydrogen clearly superior as predicted by Wilson et al. Best-performing composites give results similar to CH 2.
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Conclusions from ODY GCR ~ as expected from models & near-Earth data. Radial gradient for solar particles is large SPE weaken as they propagate out to Mars. Need ground truth – surface environment more complex.
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GCR transport model calculation from NASA-JSC. Unshielded doses ~ 1000 times greater on Mars than Earth but lower than free space by factor of 2. Surface well-shielded from most SPEs. Annual dose-equivalent (Sv/yr)
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Mars Science Laboratory Next Mars rover Launches Nov. 2011. Includes RAD, a small (1.5 kg) but capable detector with neutron capability.
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