Novel Concepts for Radiation Shielding Materials

The likelihood of safely sending astronauts to Mars is becoming bleaker because of the health risks that would result from exposure to galactic cosmic radiation (GCR). The dilemma of how to best protect those astronauts has continued over the years, with evaluation of both radiation protection materials and vehicle design architectures for possible solutions. Recent studies reveal that polyethylene, a lightweight polymeric material that is a strong candidate for shielding radiation because of its high percentage of hydrogen, is not much better than the much heavier-weight metallic aluminum. Studies also suggest that earlier predictions that older astronauts would be more resistant to radiation than younger astronauts might not be valid. The breakthroughs needed for magnetic or electrostatic shielding to be feasible are likely many years away.

It is critical that safety factors be maximized with respect to long duration, extraterrestrial space flight. Any significant improvement in radiation protection will be critical in ensuring the safety of crew and hardware on such missions. The project goal was to study novel concepts for radiation shielding materials that can be used for long-duration space missions. As part of this project we investigated the use of thin films for the evaluation of a containment system that could retain liquid hydrogen and provide the necessary hydrogen density for effective shielding.

The technical challenge of this project was to identify or design/develop a polymeric/composite material, laminate system that can contain a large quantity of liquid hydrogen in deep space for Galactic Cosmic Radiation (GCR) shielding. This material/system must be strong enough to handle the pressure generated by this cryogenic material, yet maintain some degree of elasticity, even at liquid hydrogen temperatures (typically 20 K). It must be thin enough to minimize secondary particles from GCR, yet not allow the hydrogen to diffuse through it.

Finally, it would be desirable to have high emissivity at long wavelengths so that radiative cooling can occur. Specific architectural designs and thermal controls of hydrogen contaminant system were not addressed in this project.  This project also aligns with joint activities currently being worked with other NASA centers and the integration of technologies that are considered necessary for future exploration.