J. W. Wilson1, J. J. Korte1, J. H. Heinbockel2,
M. S. Clowdsley3, and F. F. Badavi4
1NASA Langley Research Center, Hampton, VA; 2Old
Dominion University, Norfolk, VA; 3NRC/NASA Langley Research
Center, Hampton, VA; 4Christopher Newport University, Newport
News, VA
Providing adequate radiation protection has always been a difficult issue in the exploration and development of space (a critical enabling technology). With the discovery that radiation induced cancer risks are much higher than previously believed due to the disproportionate number of solid tumor deaths following radiation exposures in WW-II, the NCRP has recommended a substantial lowering of allowable limits of exposure for space operations [1] and this lowering will add new emphasis to the development of this critical enabling technology. Indeed, a new approach to provision of radiation shielding in space operations will be required [2].
In the past, spacecraft design was approached as a linear design process in which a progression of engineering decisions resulted in a preliminary design and the impact on various subsystems treated in the end as an attempt to overcome limitations imposed by the overall design. Such late decisions resulted in loss of mission performance or redesign with high costs to solve the most immediate design problems. The result was off-optimum solutions to many design issues. From a radiation protection point of view, most of the protection provided on spacecraft results from the onboard structures and equipment. Many design choices can have a negative impact on radiation protection requiring added shielding specific materials to fill out the design (this process is only now being worked on ISS). If we are to develop missions with maximum performance with minimum costs, we must seek design methods which allow a system approach tooptimization as shown in fig. 1.
Such an approach requires a multidiscplinary design team able to collaborate with discipline specific design tools and a framework for integration of the tools and team in a common environment allowing optimization of the spacecraft system model. One challenge is that the tools and associated discipline teams are often located on different platforms at distinct locations around the country. Bringing the teams and tools together efficiently requires a virtual environment which integrates these tools and teams into a single collaborative engineering framework. For this purpose, high-performance communication and computing are required with audio/visual immersive technologies to allow the integration process. One limitation of the past has been the lack of high-speed computational procedures for evaluation of the induced ionizing radiation environment within the craft living space for the evaluation of exposure constraints within the design process. The inherently fast deterministic methods developed at the Langley Research Center are being prepared for the design of the 2nd Generation RLV with the integration chart shown in fig. 2.
1. NCRP, Radiation protection guidance for activities in low-earth orbit. NCRP Report 132, 2001.
2. J.W.Wilson et al. Physica Medica Vol. XVII, Suppl. 1: 67-71; 2001.
Figure 1. Neutron dose conversion factors for ocular lens and BFO.
Figure 2. RLV 2nd Generation MDO integration chart.