There appear to be some uncertainties about the composition of HZE in LEO and GEO, i.e., percentage of different ions, energies and fluxes. Firmer data on this may come from current research and information gathered on space shuttle flights. Data on the Relative Biological Effectiveness (RBE) or Quality (Q) factor are being collected and proposals for research to measure these have been made. From the few preliminary data it appears that the RBE ranges from 1 up to at least 10 (i.e., they may be 10 times more effective than X-rays in producing some types of damage). Physical methods of measuring HZE dose appear to have much uncertainty, be excessively time-consuming for read-out, are passive and may not accurately reflect ’’true” dose in terms that can be related to biological effects. More research is needed for real time read-out of dosage. Current methods of shielding against radiation appear to be ineffective for stopping HZE. Furthermore, it is possible that the secondary particles from interaction of HZE with shielding material may be as hazardous as unshielded HZE. The flux of electrons and protons in trapped radiation apparently remains fairly constant and is reasonably well-defined with regard to location, i e., geography and altitude. Revelance to space worker radiation and consequences to their health will depend on the orbit selected and the amount of time spent in any specific orbit. Solar flare particle events consist mostly of high-energy protons. Forecast of these is not possible but onset of buildup can be detected. When buildup is detected, it appears that EVA should be discontinued and that probably all space workers should retreat to a heavily shielded area. NASA Systems Definition is planning such an area in the personnel vehicles. There may be radioactive materials flown on space vehicles in instrumentation, as small power sources, and for diagnostic medical procedures. The extent of these materials is not yet known. Preliminary assessment of thermal radiation is not possible until more information is obtained regarding expected termperatures in space vehicles and space suits. Some other potential problem areas, in which assessment has not been done yet, are effects of magnetic fields, electrical fields, plasma arcing, space debris, and meteoroid collisions. NASA has information and/or research in some of these areas, but time has not permitted the obtaining of this information nor an evaluation of the extent of potential hazards to the space worker.
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