space suit may get torn or punctured. It is also possible that compartments of the space ship may be penetrated by space debris or meteoroids. The psychological stresses of confinement for long periods may present health problems. Literature searches on the effects of confinement should be made. Recreational facilities should be planned. 2.6.3.3 Radiation The amounts and types of radiation to space workers will be a limiting factor in the length of time allowed in the space environment. NASA has in-house radiation research programs and, in addition, is supporting some research in other laboratories. The approximate composition of galactic cosmic radiation is 85% protons, 13% alpha particles, and 2% high-energy heavy ions (Li-Fe). A great deal of research covering many years and many areas where problems may arise has been and is being done on the biological effects of protons and alpha particles. These data need to be reviewed to predict SPS radiation problems and time limits in space that will be imposed by the effects of these particles. Data are very scarce, to date, on the biological effects of high-energy heavy ions (HZE). The unique characteristics (i.e., very high energy deposition at the path core surrounded by a penumbra of lower energy deposition) of this type of radiation make its effects unpredictable on the basis of results from research on other types of radiation. A few studies have been completed, some are in progress, and others have been proposed. It appears, tentatively at this stage, the HZE is more effective than other types of radiation in cell transformation, in inducing at least one type of tumor in mice, blocking nerve transmission, and damaging visual elements. However, some of these experiments have been done with much higher doses than will be encountered in space. Much more information is needed on carcinogenic effects, damage to non-regenerating tissues such as the central nervous system and visual elements, reproductive and genetic effects including teratology (birth defects), life-shortening effects, relative biological effectiveness as compared to other types of radiation, and possible synergistic effects with other types of radiation.
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