The U.S. National Research Council's views of the radiation hazards in space

摘要

The author was the Chairman of a Task Group on the Biological Effects of Space Radiation formed as a result of discussions between NASA and the U.S. National Research Council's Committee on Space Biology and Medicine -- a committee under the U.S. National Research Council's Space Studies Board. The Task Group was asked to review current knowledge on the effects of long-term exposure to radiation in space and to consider NASA radiation shielding requirements for orbital and interplanetary spacecraft. The group was charged with assessing the adequacy of NASA planning for the protection of humans from radiation in space and with making recommendations regarding needed research and/or new shielding requirements. This manuscript is a summary of the findings and recommendations of the Task Group. Beyond the protection of the Earth's atmosphere and its magnetosphere, the exposure to ionizing radiations far exceeds that on Earth. Of all the risks astronauts may face, this one is probably the most straightforward to control -- by providing adequate shielding. However, because shielding adds weight, cost and complexity to space vehicles, it is important for designers to have a good quantitative understanding of the true risk and its degree of uncertainty so as not to under- or overshield spacecrafts. The extrapolations from our knowledge of ionizing radiation effects of low linear energy transfer (LET) to the risks from high-atomic-number high-energy energetic (HZE) cosmic rays are very uncertain because the necessary experiments on the effects of such particles have not been carried out and the extrapolation from low-LET to very high-LET has great uncertainties. These uncertainties were enumerated by the Task Group, and the types of experiments needed to minimize the uncertainties were described. The report found that, because of the small amounts of available time for biological research at HZE accelerators, it would take more than a decade of effort to obtain the answers to a narrow set of key questions that would facilitate reduction in risks and identification of the types of shielding needed.