Radiation Hazards and Radiation Safety Standards in Manned Space Operations

Publisher Website
Google Scholar
Abstract
The natural environment of ionizing radiation in space consists of three components: galactic radiation, trapped particles in the radiation belt and solar particle beams. Whereas the exposure dose rate for the galactic radiation remains well below 100 mrad/24 hr, dose rates in the radiation belt may exceed 200 rad/hr. Still higher values can occur in solar particle beams. The energy spectra of trapped and flare produced particles are quite similar exhibiting steep negative flux/energy gradients. As a consequence, radiation levels and depth-dose distributions in the body depend sensitively on shielding. The fact that flare events occur essentially at random with only very limited prediction possibilities in connection with the further fact that space flight is an endeavor of high risk in general would seem to call for a basically different philosophy of radiation protection in space. Yet even if one is prepared to allow substantially greater Maximum Permissible Doses (MPD''s) or Radiation Protection Guides (RPCs) for manned space operations, the principal difficulty arises that critical dose levels for incipient deterioration of performance cannot be defined for the unique depth-dose distributions encountered in space radiation exposures. The dosage fields in the body as they develop from trapped of flare produced particles vary, depending on shielding and spectral type, over a very wide range with Half Value Layers (HVL''s) from less than 1-mm tissue to several centimeters. The fact that animal or human data on the effects of such total body exposures are missing constitutes a serious gap in present radiobiological knowledge assessing the astronaut''s exposure status in operational emergencies.

This publication has 0 references indexed in Scilit: