Dose Predictions for Moon Dose Predictions for Moon AstronautsAstronauts

Image Source: www.astromax.com

Nicholas Bachmann, Ian Rittersdorf

Department of Nuclear Engineering and Radiological Sciences

University of Michigan

AbstractAbstract

NASA has proposed a return to the moon NASA has proposed a return to the moon within the next decadewithin the next decade

New lunar missions will be longer than New lunar missions will be longer than Apollo’s, and may lead to a permanent Apollo’s, and may lead to a permanent moon basemoon base

Effects of radiation on these missions will Effects of radiation on these missions will have to be planned for, but are have to be planned for, but are manageablemanageable

Main Dose SourcesMain 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

Galactic Cosmic RaysGalactic Cosmic Rays

Composition:Composition:85% protons85% protons14% alpha particles14% alpha particles1% heavy nuclei1% heavy nuclei

Heavy nuclei are very dangerous because Heavy nuclei are very dangerous because of the energy they have of the energy they have (proportional to Z(proportional to Z22))

Hard to measure preciselyHard to measure preciselyCurrent Models are believed to be 25% Current Models are believed to be 25%

accurateaccurate

Solar Energetic ParticlesSolar Energetic Particles

SEPs consist primarily of protons and SEPs consist primarily of protons and alpha particlesalpha particles

Formed on active Formed on active surfaces of the sunsurfaces of the sun

Lower energy Lower energy particles than GCRsparticles than GCRs

Higher flux of Higher flux of particles than GCRsparticles than GCRs

Image Source: www.nrl.navy.mil

Solar FlaresSolar Flares

Solar flares emit considerable amounts of Solar flares emit considerable amounts of radiation, up to tens of Gyradiation, up to tens of Gy

Between Apollo 16 and 17 , one of the Between Apollo 16 and 17 , one of the largest solar flares ever recorded largest solar flares ever recorded occurred. If the flare had occurred during a occurred. If the flare had occurred during a mission — even inside their shielded mission — even inside their shielded spacecraft, the astronauts would have spacecraft, the astronauts would have absorbed lethal doses within 10 hoursabsorbed lethal doses within 10 hours

Lunar Thorium HotspotsLunar Thorium Hotspots Because space suits Because space suits

protect well against protect well against αα and low energy and low energy gamma, Th in the soil gamma, Th in the soil is not a major concernis not a major concern

If any kind of space If any kind of space station were station were constructed on the constructed on the moon, radon would be moon, radon would be a major concern if lunar a major concern if lunar soil was used in soil was used in cementcement

Image Source: www.astronomy.com/asy/default.aspx?c=a&id=5357

Apollo Mission DosesApollo Mission Doses

No significant No significant difference between difference between doses of zero/high doses of zero/high time mission time mission implies surface implies surface Th/K is irrelevant Th/K is irrelevant

High Apollo 14 High Apollo 14 dose is due to path dose is due to path directly through directly through Van Allen beltVan Allen belt

Nuclear Radiation from a Planetary Nuclear Radiation from a Planetary SurfaceSurface

http://www.astro.umd.edu/~mcfadden/slides/2001_Mars_Odyssey/11.jpg

Effects on HealthEffects on Health

Worst-case scenario estimates an Worst-case scenario estimates an increase in carcinogenic risk of 45% to increase in carcinogenic risk of 45% to interplanetary astronautsinterplanetary astronautsNASA/NCRP goal is 3%NASA/NCRP goal is 3%

Is difficult to quantify due to the uncertainty Is difficult to quantify due to the uncertainty in the knowledge of the biological in the knowledge of the biological response of to particles of various atomic response of to particles of various atomic numbers and energiesnumbers and energies

ConclusionsConclusions

Elevated or even fatal does to astronauts Elevated or even fatal does to astronauts are possible outside of Low Earth Orbit if are possible outside of Low Earth Orbit if proper planning is not doneproper planning is not done

Radionuclides may be a concern for lunar Radionuclides may be a concern for lunar bases that use soil for building materialsbases that use soil for building materials

Due to longer travel times, manned Due to longer travel times, manned missions beyond the moon would have to missions beyond the moon would have to have increased shielding in case of solar have increased shielding in case of solar flaresflares

Selected ReferencesSelected References

Biomedical Results of ApolloBiomedical Results of Apollo, NASA, 1975, NASA, 1975Radiation Effects and Protection for Moon Radiation Effects and Protection for Moon

and Mars Missionsand Mars Missions, Parnell, Watts, and , Parnell, Watts, and Armstrong, 1998Armstrong, 1998

Seeing Lunar Thorium More ClearlySeeing Lunar Thorium More Clearly, , http://www.astronomy.com/asy/default.asphttp://www.astronomy.com/asy/default.aspx?c=a&id=5357, Available 03/29/2007x?c=a&id=5357, Available 03/29/2007