Mars Mission Radiation Dose/Shielding Summary Note: Dr. Cary Zeitlin generously contributed these...
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Transcript of Mars Mission Radiation Dose/Shielding Summary Note: Dr. Cary Zeitlin generously contributed these...
![Page 1: Mars Mission Radiation Dose/Shielding Summary Note: Dr. Cary Zeitlin generously contributed these slides from two full-length presentations. For brevity’s.](https://reader035.fdocuments.in/reader035/viewer/2022070415/5697bf9e1a28abf838c94372/html5/thumbnails/1.jpg)
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:
– wR = 1 for sparsely-ionizing types, e.g., g– wR = 5 for protons, 20 for a and heavier
nuclei.• In “mixed field” wR 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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15th Humans in Space, Graz, Austria
1.0E-06
1.0E-05
1.0E-04
1.0E-03
1.0E-02
1.0E-01
1.0E+00
1 3 5 7 9 11 13 15 17 19 21 23 25 27
Nuclear Charge
Re
lati
ve
Co
ntr
ibu
tio
n
FluxDoseDose equivalent
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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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15th 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 CH2.
0 0.01 0.02 0.03 0.04 0.05 0.06 0.07
Lead
Tin
Copper
Aluminum
PETI -5
Al(5 g cm-2) + CH2 (2 g cm-2)
CH2/ Li6
Al(5 g cm-2) + CH2 (5 g cm-2)
LiF
CH2/ LiC
CH2 (17 g cm-2)
CH2 + Boron
Graphite Epoxy (10 g cm-2)
Carbon
Graphite Epoxy (5 g cm-2)
Martian Regolith + CH2
CH2 (5 g cm-2)
Boron-Epoxy
Epoxy
Be
H (estimated)
Dose reduction per g cm-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.