Wearable Vest Cuts Astronaut Radiation 60% in Moon Test

One of the greatest dangers facing astronauts on long-duration deep-space missions isn't the vacuum of space or the extremes of temperature — it's radiation. Solar storms can unleash torrents of high-energy protons capable of raising cancer risk or, in extreme cases, causing acute radiation sickness. Earth's magnetic field and atmosphere shield us, but astronauts heading to the Moon or Mars have no such protection.

Now, a wearable vest developed by Israeli-American startup StemRad has passed its first major real-world test — and the results are encouraging enough to reshape how future lunar missions are planned.

The AstroRad vest flew aboard NASA's Artemis I uncrewed mission in late 2022, nestled inside the Orion spacecraft on a 25-day journey beyond the Moon and back. To measure its performance, two identical phantom torsos — nicknamed Helga and Zohar — were packed with thousands of radiation dosimeters and placed in the capsule. Zohar wore the AstroRad vest; Helga flew unprotected as a comparison. Both captured precise radiation data across every phase of the flight.

The key insight behind the AstroRad design is that the human body isn't uniformly vulnerable to radiation. "Tissues like the bone marrow are a lot more sensitive to radiation compared to the brain," explained Oren Milstein, co-founder of StemRad. The vest targets the most radiation-sensitive organs — concentrating protection around the hips (which house roughly half the body's bone marrow), breasts, stomach, colon, and reproductive organs — without encasing the entire body.

Critically, the material of choice is high-density polyethylene (HDPE), an ordinary plastic that packs more hydrogen by mass than water. Hydrogen is an exceptionally effective radiation shield because of its atomic properties. To maintain flexibility, StemRad's engineers broke the HDPE into thousands of hexagonal tessellated rods of varying lengths sandwiched between elastic fabric layers. "It almost behaves the same way that water would, while still remaining solid," said Jordan Houri, another member of the research team.

The Artemis I flight didn't encounter a solar storm directly, so the researchers used the spacecraft's passage through Earth's Van Allen radiation belt as a proxy — the belt's proton energies overlap significantly with those generated during solar particle events. Using Monte Carlo simulations validated to within 5% of actual dosimeter measurements, the team then modeled the vest's performance during two historical solar storms: the August 1972 event and the more intense October 1989 storm.

The results were striking. For a 1972-type storm — representative of a typical large solar particle event — the AstroRad vest reduced the effective radiation dose by approximately 60%. For the more energetic 1989 storm, the reduction was around 40%. Both represent meaningful protection.

"We're able to reduce the effective dose by 60 percent without protecting the head, the arms, or even the legs," Milstein said. "Everybody asks, what about the head? But it's still a dramatic reduction in overall risk."

Translated into mission planning, wearing the vest during a major solar storm could potentially extend the safe surface time available to astronauts on the Moon by years — a critical factor for future Artemis missions planning extended lunar stays and, ultimately, for crewed Mars missions where solar events might last for days and the spacecraft is far beyond any protective shelter.

The vest also performed as well as the onboard radiation shelter inside the Orion spacecraft — the heavily shielded compartment astronauts would normally retreat to during a storm. "That was the main test," Milstein said. "Does the vest give you the protection of the shelter? The answer is yes, for a typical event."

For a technology designed to protect the people who will carry humanity's next chapter to the Moon and beyond, the results represent a quiet but significant victory: a piece of smart, lightweight, wearable engineering that could save lives in one of the most hostile environments humans have ever dared to explore.