Plastic may shield astronauts from dangerous cosmic radiation

Lighter materials like plastic can effectively shield astronauts from radiation hazards faced during extended space travel, according to new analysis of data gathered by NASA's Lunar Reconnaissance Orbiter (LRO).
The finding could help reduce health risks to humans on future missions into deep space, say space scientists from the University of New Hampshire (UNH) and the Southwest Research Institute (SwRI).
Aluminum has always been the primary material in spacecraft construction, but it provides relatively little protection against high-energy cosmic rays and can add so much mass to spacecraft that they become cost-prohibitive to launch.
The new research is based on observations made by the Cosmic Ray Telescope for the Effects of Radiation (CRaTER) on board the LRO spacecraft.

Lead author of the paper is Cary Zeitlin of the SwRI Earth, Oceans, and Space Department at UNH. Co-author Nathan Schwadron of the UNH Institute for the Study of Earth, Oceans, and Space is the principal investigator for CRaTER.
"This is the first study using observations from space to confirm what has been thought for some time - that plastics and other lightweight materials are pound-for-pound more effective for shielding against cosmic radiation than aluminum," said Zeitlin.

"Shielding can't entirely solve the radiation exposure problem in deep space, but there are clear differences in effectiveness of different materials," Zeitlin said.

The plastic-aluminum comparison was made in earlier ground-based tests using beams of heavy particles to simulate cosmic rays.
"The shielding effectiveness of the plastic in space is very much in line with what we discovered from the beam experiments, so we've gained a lot of confidence in the conclusions we drew from that work," said Zeitlin.
"Anything with high hydrogen content, including water, would work well," he said.
The space-based results were a product of CRaTER's ability to accurately gauge the radiation dose of cosmic rays after passing through a material known as "tissue-equivalent plastic," which simulates human muscle tissue.

The CRaTER observations have validated the models and the ground-based measurements, meaning that lightweight shielding materials could safely be used for long missions, provided their structural properties can be made adequate to withstand the rigours of spaceflight.
The findings were published in the American Geophysical Union journal Space Weather.