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Managing Space Radiation Risk in the New Era of Space Exploration
exploration missions until uncertainties in risk prediction and radiobiological methods of risk management have advanced to the point that they can be conducted within the limits of acceptable risk.
Finding 5-1. The NASA Space Radiation Laboratory. The entire Space Radiation Biology Research program is critically dependent on the availability of the NASA Space Radiation Laboratory. This facility is dependent on the DOE heavy-ion physics program and may not be available if the needs of this program change. There are no other facilities available that meet the requirements for high atomic number and energy (HZE) space radiation biology research, worldwide.
Recommendation 5-1. Radiation biology research. NASA’s Space Radiation Biology Research program should be adequately funded. NASA should perform research at the NASA Space Radiation Laboratory aggressively to take advantage of the existing window of opportunity while this facility is still available. The results of the biological research will thus be able to have an impact on the Project Constellation missions in the short term, as well as provide knowledge essential for the management of space radiation risk in the long term.
Finding 5-2. Dose estimation in the Orion crew module. The use of ray-tracing analysis combined with state-of-the-art radiation transport and dose codes is an appropriate method for estimating dose within the Orion crew module, and can be used to guide decisions on the amounts and types of spot or whole-body shielding that should be added to provide protection during solar particle events.
Finding 5-3. Orion Radiation Protection Plan. The Orion Radiation Protection Plan, as presented to the committee, appears to meet the minimum radiation protection requirements as specified in NASA’s radiation protection standards. Any reduction in the Orion Radiation Protection Plan may pose potentially unacceptable health risks.
Finding 5-4. Existing transport data. New measurements do not need to be taken solely for the purposes of code validation. In addition, structure in the energy dependence of relevant fragmentation yields for heavy charged particles is considered to be sufficiently small to have a negligible impact on interpolation schemes. One exception is that additional data on production of light ions (Z = 1, 2) and neutrons may be required.
Recommendation 5-2. Testing transport code predictions. The predictions derived from calculations of radiation transport need to be tested using a common code for laboratory and space measurements that have been validated with accelerator results, existing atmospheric measurements, and lunar and planetary surface measurements as they become available.
Finding 5-5. SPE prediction. At present, the ability to predict an SPE and to project its evolution once underway does not exist. Such a capability will play an important role in managing the SPE radiation hazard.
Recommendation 5-3. Research on solar particle events. NASA should maintain a vigorous basic science program that can clarify the mechanisms that produce SPEs and lead to accurate, quantitative predictions of SPE behavior and identification of observables critical in forecasting SPEs or all-clear periods.
Finding 5-6. Experimental data for designers. NASA has not made an adequate effort to collect, catalog, and categorize existing experimental data obtained by the worldwide heavy-ion research community and to make it available in appropriate form to the shielding engineering community.
Recommendation 5-4. Empirical data for shielding design. NASA should ensure that necessary experimental data in sufficient quantities are collected, analyzed, and managed in a manner appropriate for their use in designing radiation shielding into spacecraft, habitats, surface vehicles, and other components of human space exploration. The data should include information on energy and angular dependence of cross sections for production of nuclear interaction products, and on their multiplicities.