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Providing protection against the hazards of space radiation is a major challenge to the exploration and development of space. The great cost of added radiation shielding is a potential limiting factor in deep space missions. In the present report, we present methods for optimized shield design over multi-segmented missions involving multiple work and living areas in the transport and duty phase of lunar and Mars missions. The total shield mass over all pieces of equipment and habitats is optimized subject to career dose and dose rate constraints.

The projected radiation levels within the International Space Station (ISS) have been criticized by the Aerospace Safety Advisory Panel in their report to the NASA Administrator. Methods for optimal reconfiguration and augmentation of the ISS shielding are now being developed. The initial steps are to develop reconfigurable and realistic radiation shield models of the ISS modules, develop computational procedures for the highly anisotropic radiation environment, and implement parametric and organizational optimization procedures. The targets of the redesign process are the crew quarters where the astronauts sleep and determining the effects of ISS shadow shielding of an astronaut in a spacesuit. The ISS model as developed will be reconfigurable to follow the ISS. Swapping internal equipment rack assemblies via location mapping tables will be one option for shield optimization.

The hazards of ionizing radiation in space continue to be a limiting factor in the design of spacecraft and habitats. Shielding against such hazards adds to the mission costs and is even an enabling technology in human exploration and development of space. We are developing a web accessible system for radiation hazard evaluation in the design process. The framework for analysis and collaborative engineering is used to integrate mission trajectory, environmental models, craft materials and geometry, system radiation response functions, and mission requirements for evaluation and optimization of shielding distribution and materials. Emphasis of the first version of this integrated design system will address low Earth orbit allowing design system validation using STS, Mir, and ISS measurements. The second version will include Mars, lunar, and other deep space mission analysis.

Meeting radiation protection requirements during EVA is predominantly an operational issue with some potential considerations for temporary shelter. The issue of spacesuit shielding is mainly guided by the potential of accidental exposure when operational and temporary shelter considerations fail to maintain exposures within operational limits. In this case, very high exposure levels are possible which could result in observable health effects and even be life threatening. Under these assumptions, potential spacesuit radiation exposures have been studied using known historical solar particle events to gain insight on the usefulness of modification of spacesuit design in which the control of skin exposure is a critical design issue and reduction of blood forming organ exposure is desirable.

Research committed by the Langley Research Center through 1995 resulting in the HZETRN code provides the current basis for shield design methods according to NASA STD-3000 (2005). With this new prominence, the database, basic numerical procedures, and algorithms are being re-examined with new methods of verification and validation being implemented to capture a well defined algorithm for engineering design processes to be used in this early development phase of the Bush initiative. This process provides the methodology to transform the 1995 HZETRN research code into the 2005 HZETRN engineering code to be available for these early design processes. In this paper, we will review the basic derivations including new corrections to the codes to insure improved numerical stability and provide benchmarks for code verification.