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Space Radiation Health Effects of Astronauts in Explorative Missions

Space Radiation Health Effects of Astronauts in Explorative Missions. Günther Reitz Radiation Biology Department Institute of Aerospace Medicine German Aerospace Center (DLR ). ‘ Fault tree’ of Fatal event. Fluxes of primary space radiation components. inner Van Allen belt protons.

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Space Radiation Health Effects of Astronauts in Explorative Missions

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  1. Space Radiation Health Effects of Astronauts in Explorative Missions Günther Reitz Radiation Biology Department Institute of Aerospace Medicine German Aerospace Center (DLR)

  2. ‘Fault tree’ of Fatal event

  3. Fluxes of primary space radiation components inner Van Allen belt protons

  4. Effective Doses Low Earth Orbit Missions and Missions to the Moon

  5. GCR exposure in interplanetary space BON2011/BON2010≈ 1.35 BON2011/DLR ≈ 1.1 DLR BON2010 BON2011

  6. Worst$ case' SPE radiation exposures in Sv during different mission phases for critical tissues under different mass shielding

  7. Limits for Astronauts in LEO (NASA as example) Career non-cancer and Short term effects Career cancer risk limits For reference: Limits for radiation workers on Earth: 20 mSv annual and 400 mSv career

  8. How Astronauts are Affected by Cosmic Rays?

  9. DNA is the MainTarget of Radiation Action • Cell cycle arrest • Repair • Mis-repair • No repair • Mutations • Cell death, e.g. by • Apoptosis • Misdifferentiation • Senescence • Cellular Survival • Transformation • Clonal Expansion • Carcinogenesis Energy deposition DNA damage

  10. RadiationEffects

  11. Early morbidity/mortality for worst case SPE behind 10 gm/cm2 in interplanetary space early mortality early morbidity

  12. How Real are Radiation Risks for Astronauts from SPEs ?

  13. Uncertainties in Radiation Risk Projection Risk Projections 10% • Maximum Acceptable Risk • Mars • ▲ 1% • ▲ • ISS Mission • SPE?? • Lunar 0.1% • ▲ • “95% Confidence Interval” • 95% Confidence Interval • ShuttleMission • ▲ 0.01% • Individual’s Fatal Risk • Point Estimate

  14. Major sources of uncertainty of risk estimation from space radiation field

  15. Radiation Risk in a 550 day mission to Mars Cucinotta (Space Radiation Risk Calculation) 45 Year old male, US Population, 20g/cm^2 shielding • Aug 72 Solar Particle event, 340 mSv REID 0.98 % (0,23;2.59) • 550 day Mission to Mars GCR ,550 mSv) REID 2.00 % (0.33;5.01) ICRP • 550 day mission Excess Risk/Sv 4x 10^-2 results in 3.6%

  16. Significance of Shielding Material for GCR (20g/cm^2 shielding, 40-yr males) f

  17. Light Light Flash Observations

  18. Observation ofCataracts • RBE ~ 200 !! F. A. Cucinotta et al., 2001

  19. develop proper risk criterion for exploratory LONG term missions • integrate radiation risk assessment into total risk analysis • reduce uncertainties for exposure estimates • reduce uncertainties for dose effect relations (late & early) Improve advance risk assessment Countermeasures against radiation effects • optimise shielding design, include storm shelters (material & thickness ) • optimise mission design • duration • timeline relative to solar activity cycle • guarantied shelter accessibility • advance forecasting capabilities for solar particle events • monitor and document exposure history and health status Minimise radiation exposure • select genetically resistant individuals • modify dose response curve of ‘normal’ crew members • attenuate early effects by prior and post medication • mitigate late effects by prophylactic nutrition Maximise radiation resistance

  20. Radiation Assessment Detector (Cruise Measurements) SPE Exposures mSv 23-29 Jan 4 7-15 March 19.5 17-18 May 1.2 GCR Exposure/day 1.8

  21. GCR Risks • Stochastic effects such as cancer induction and mortality or late deterministic effects, such as cataracts or damage to the central nervous systems are of concern • Doses present no acute health effects in deep space missions • There are no data for human exposures to these radiation to estimate risks of astronauts • Usual methods of estimating risk by calculating dose equivalent or equivalent dose are questionable to be appropriate for these particles • Upper 95% C.I. for excess cancer risks from GCR for an mission to Mars may exceed current limits defined for Low Earth Orbits • During interplanetary cruise shielding is limited and will therefore not significantly reduce GCR risks SPE Risks • Risks are manageable by shielding measures • Shielding should limit excessive exposure to prevent acute effects • Hydrocarbon shields offer a reduction of a factor of two compared to Aluminium • Exploration vehicles shielding should focus on SPE instead on GCR Conclusions

  22. SPARES

  23. Solar corona and sudden release of a huge clouds of particles

  24. Excess Relative Risk as a function of rate of exposure Gregoire O. et.al., Radiat. Biol., 2006

  25. Excess Relative Risk as function of dose rate

  26. Fatal Cancer Risks near Solar Minimum (20 g/cm^2 shielding) • Slide Courtesy of F. A. Cucinotta

  27. Fatal Cancer Risk Near Solar Maximum (PHI=1100MV including 1972 SEP) • Slide Courtesy F. A. Cucinotta

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