Solar storms emit intense streams of protons. On Earth, humanity is reliably protected by the atmosphere and magnetic field. However, crews traveling to the Moon or Mars remain defenseless against an invisible threat that can cause acute radiation sickness and a high risk of developing cancer.
Attempts to build solid aluminum hulls, water barriers, or superconducting magnetic shields run into the main limitation of spaceflight — mass. Every additional gram of weight aboard costs enormous resources. A team from the Israeli-American startup StemRad, led by Jordan Khoury and Oren Milstein, proposed an alternative approach: shield not the entire spacecraft, but the astronaut’s body directly.
The Principle of Selective Protection
The idea of an anti-radiation suit was long considered unrealistic because heavy lead armor would make a person immobile. However, StemRad engineers took into account that tissues of the human body have different sensitivities to radiation. For example, bone marrow, which is responsible for blood formation, is significantly more vulnerable than the brain or muscles.
Preserving even part of the bone marrow allows the body to recover after exposure to a high radiation dose. Together with Lockheed Martin, the company developed the special AstroRad protective vest. It protects the hip area, where about half of the body’s bone marrow is located, as well as the chest, abdomen, large intestine, and reproductive organs. This targeted concept makes it possible to reduce the effective radiation dose by almost 60% without protecting the head and limbs.
A Mosaic of Flexible Polymers
The effectiveness of a protective material depends on the ratio of its atomic number to its atomic mass. Hydrogen performs best in this respect, making high-density polyethylene (HDPE) — a solid plastic with a high hydrogen content — an ideal choice.
To prevent a thick layer of plastic from restricting movement, it was divided into thousands of hexagonal rods ranging from 9 to 60 mm in length and placed between layers of elastic fabric. The design was calculated using the Bethe-Bloch formula, which describes the energy loss of charged particles. The resulting vest remains solid while also being flexible and does not restrict the wearer’s movements.
Testing on Mannequins
To test AstroRad, it was sent on a circumlunar flight aboard the Orion spacecraft as part of the Artemis I mission. Two mannequins were aboard: “Zohar” wearing the vest and “Helga” without protection. Thousands of internal sensors recorded radiation levels.
Because no solar storm occurred during the flight, scientists used data from the spacecraft’s passage through the Van Allen radiation belt and Monte Carlo computer modeling. By comparing these data with the parameters of the solar storms of 1972 and 1989, researchers found that the vest reduces the radiation dose by approximately 60% during typical storms and by approximately 40% during extremely powerful ones. This could extend an astronaut’s safe time in space to 193 days, compared with 40 days under NASA’s established limit of 600 mSv.
Freedom of Movement and Further Optimization
AstroRad provides protection comparable to Orion’s heavy shelter, but does not confine astronauts to a restricted space, allowing them to continue performing operations during solar eruptions. However, the vest provides almost no protection against galactic cosmic rays, which have excessively high energies.
The initial mass of the vest was 26 kg, roughly equivalent to the weight of medieval armor. Using data from the Artemis I mission, StemRad specialists have already reduced its weight to 16 kg without significant loss of protective performance. The developers are now working on an even lighter version for comfortable long-term wear during solar storms.
According to arstechnica.com
