Dose Predictions for Moon Dose Predictions for Moon AstronautsAstronauts

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Nicholas Bachmann, Ian RittersdorfDepartment of Nuclear Engineering and Radiological Sciences

University of Michigan

AbstractAbstractNASA has proposed a return to the moon NASA has proposed a return to the moon

within the next decadewithin the next decadeNew 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 SourcesGalactic Cosmic Rays (GCR)Galactic Cosmic Rays (GCR)

Solar Energetic Particles (SEP)Solar Energetic Particles (SEP)

Intrinsic Lunar Radiation (Soil)Intrinsic Lunar Radiation (Soil)

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Galactic Cosmic RaysGalactic Cosmic RaysComposition: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 ParticlesSEPs 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

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Solar FlaresSolar FlaresSolar flares emit considerable amounts of Solar flares emit considerable amounts of

radiation, up to tens of Gyradiation, up to tens of GyBetween 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

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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 HealthWorst-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

ConclusionsConclusionsElevated 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 ReferencesBiomedical 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