Space Radiation Shielding

Assessment of Radiation Shielding Materials for Protection of Space Crews

Joel DeWitt

 

A significant obstacle to long-duration human space exploration is the risk posed by prolonged exposure to space radiation. This is particularly relevant to the establishment of a permanent base on the surface of the Moon or a manned mission to Mars. In order to keep mission costs at acceptable levels while simultaneously minimizing the risk from radiation to space crew health and safety, a judicious use of optimized shielding materials will be required. We are currently carrying out a comprehensive study to characterize the radiation shielding properties of a variety of baseline and advanced shielding materials at heavy ion accelerators using CR-39 plastic nuclear track detector (PNTD). Baseline materials include aluminum, copper, and polyethylene, while advanced materials include carbon, Kevlar, and polyethylene composites and simulated Martian and Lunar regolith. The study consists of analyzing CR-39 PNTDs exposed in front of and behind shielding targets of varying composition and depth relevant to the development and testing of materials for space radiation shielding. The targets are 10 × 10 cm slabs of solid materials ranging in thickness of 5-30 g/cm2. Exposures were made with heavy ion beams of Si and Fe at energies of 1 GeV/n at the Brookhaven National Laboratory’s NASA Space Radiation Laboratory (NSRL). Analysis of the exposed detectors yields LET spectrum, dose, dose equivalent, and percent fragmented as functions of target depth and composition for a given heavy ion exposure. We are compare the results from these experiments with results from computer simulations made using the FLUKA radiation transport code.