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Dose Predictions for Moon Astronauts

Dose Predictions for Moon Astronauts. Nicholas Bachmann, Ian Rittersdorf Department of Nuclear Engineering and Radiological Sciences University of Michigan. Image Source: www.astromax.com. Abstract. NASA has proposed a return to the moon within the next decade

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Dose Predictions for Moon Astronauts

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  1. Dose Predictions for Moon Astronauts Nicholas Bachmann, Ian Rittersdorf Department of Nuclear Engineering and Radiological Sciences University of Michigan Image Source: www.astromax.com

  2. Abstract • NASA has proposed a return to the moon within the next decade • New lunar missions will be longer than Apollo’s, and may lead to a permanent moon base • Effects of radiation on these missions will have to be planned for, but are manageable

  3. Main Dose Sources • Galactic Cosmic Rays (GCR) • Solar Energetic Particles (SEP) • Intrinsic Lunar Radiation (Soil) Image Source : www.archives.gov

  4. Galactic Cosmic Rays • Composition: • 85% protons • 14% alpha particles • 1% heavy nuclei • Heavy nuclei are very dangerous because of the energy they have (proportional to Z2) • Hard to measure precisely • Current Models are believed to be 25% accurate

  5. Solar Energetic Particles • SEPs consist primarily of protons and alpha particles • Formed on active surfaces of the sun • Lower energy particles than GCRs • Higher flux of particles than GCRs Image Source: www.nrl.navy.mil

  6. Solar Flares • Solar flares emit considerable amounts of radiation, up to tens of Gy • Between Apollo 16 and 17 , one of the largest solar flares ever recorded occurred. If the flare had occurred during a mission — even inside their shielded spacecraft, the astronauts would have absorbed lethal doses within 10 hours

  7. Lunar Thorium Hotspots • Because space suits protect well against α and low energy gamma, Th in the soil is not a major concern • If any kind of space station were constructed on the moon, radon would be a major concern if lunar soil was used in cement Image Source: www.astronomy.com/asy/default.aspx?c=a&id=5357

  8. Apollo Mission Doses • No significant difference between doses of zero/high time mission implies surface Th/K is irrelevant • High Apollo 14 dose is due to path directly through Van Allen belt

  9. Nuclear Radiation from a Planetary Surface http://www.astro.umd.edu/~mcfadden/slides/2001_Mars_Odyssey/11.jpg

  10. Effects on Health • Worst-case scenario estimates an increase in carcinogenic risk of 45% to interplanetary astronauts • NASA/NCRP goal is 3% • Is difficult to quantify due to the uncertainty in the knowledge of the biological response of to particles of various atomic numbers and energies

  11. Conclusions • Elevated or even fatal does to astronauts are possible outside of Low Earth Orbit if proper planning is not done • Radionuclides may be a concern for lunar bases that use soil for building materials • Due to longer travel times, manned missions beyond the moon would have to have increased shielding in case of solar flares

  12. Selected References • Biomedical Results of Apollo, NASA, 1975 • Radiation Effects and Protection for Moon and Mars Missions, Parnell, Watts, and Armstrong, 1998 • Seeing Lunar Thorium More Clearly, http://www.astronomy.com/asy/default.aspx?c=a&id=5357, Available 03/29/2007

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