the NSBRI and NSCORT programs and in their competitive, peer-reviewed research projects, which are reported at annual space radiation health investigators’ workshops.

SUMMARY

At the present rate of progress it would take 20 or more years to complete the high-priority experiments recommended in the Strategy report, because of the limited accelerator times available to carry out HZE particle and energetic proton irradiations at 1 GeV per nucleon. NASA understands this problem and, to address it, has allocated initial funds to begin construction of a dedicated accelerator facility (the Booster Application Facility (BAF)) that, when completed, will supply the necessary energetic particles for the following decade and longer. Arrangements have been made to use other lower-energy facilities (Loma Linda: 250-MeV protons; HIMAC in Japan: 0.4 GeV per nucleon of HZE nuclei). The high costs of building and operating facilities could seriously deplete the funds for fundamental research in the many relevant and important biological, biomedical, physiological, and behavioral areas associated with long-term spaceflight.

The projects in high-priority radiation research areas—carcinogenesis and CNS—are at present poorly represented in the area of biological end points as determined in animals. The majority of projects are related to determinations of changes in cells, following exposure to HZE nuclei, in parameters such as turning genes on or off, cell cycle alterations, production of chromosome aberrations, mutation, and transformation. These experiments are state of the art, but it is not clear how the results will translate into helping estimate the radiation risks to astronauts.

Radiation dosimetry and computations and measurements of the radiation fluxes behind various types and thicknesses of shielding are well carried out, but they have to be validated by ground-based experiments on simple in vitro systems. The risk to astronauts of exposure to galactic cosmic radiation, estimated from ground-based experiments on molecules, cells, and animals, cannot be validated experimentally but could be approached by using several independent methods to calculate risks as proposed in the Strategy report.

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National Research Council (NRC), Space Studies Board. 1998. A Strategy for Research in Space Biology and Medicine in the New Century. Washington, D.C.: National Academy Press.

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