I mentioned in this item about measurements of radiation exposure for trips to Mars, the best shielding for your spaceship is with materials that contain lots of hydrogen. A new study of rad measurements on NASA’s Lunar Reconnaissance Orbiter (LRO) bears this out: Moon Radiation Findings May Reduce Health Risks to Astronauts – Univ. of New Hampshire

Says Zeitlin, “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. Shielding can’t entirely solve the radiation exposure problem in deep space, but there are clear differences in effectiveness of different materials.”

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,” says Zeitlin. “Anything with high hydrogen content, including water, would work well.”