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

2. Abstract NASA has proposed a return to the moon within the next decade 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 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 Effects of radiation on these missions will have to be planned for, but are manageable

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

4. Galactic Cosmic Rays Composition: Composition: 85% protons 85% protons 14% alpha particles 14% alpha particles 1% heavy nuclei 1% heavy nuclei Heavy nuclei are very dangerous because of the energy they have (proportional to Z 2 ) Heavy nuclei are very dangerous because of the energy they have (proportional to Z 2 ) Hard to measure precisely Hard to measure precisely Current Models are believed to be 25% accurate Current Models are believed to be 25% accurate

5. Solar Energetic Particles SEPs consist primarily of protons and alpha particles SEPs consist primarily of protons and alpha particles Formed on active surfaces of the sun Formed on active surfaces of the sun Lower energy particles than GCRs Lower energy particles than GCRs Higher flux of 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 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 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 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 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 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 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 Worst-case scenario estimates an increase in carcinogenic risk of 45% to interplanetary astronauts NASA/NCRP goal is 3% 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 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 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 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 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 Biomedical Results of Apollo, NASA, 1975 Radiation Effects and Protection for Moon and Mars Missions, Parnell, Watts, and Armstrong, 1998 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.asp x?c=a&id=5357, Available 03/29/2007 Seeing Lunar Thorium More Clearly, http://www.astronomy.com/asy/default.asp x?c=a&id=5357, Available 03/29/2007