Tested aboard NASA’s uncrewed Artemis I lunar flight in late 2022, the 57-pound AstroRad vest can reduce deep-space radiation exposure by up to 60 percent during severe solar storms, a new study reveals, offering critical protection for future lunar base crews and Mars missions.
Artemis I Flight Test Puts Radiation Shielding to the Test
Deep-space exploration demands confronting an invisible hazard that no spacecraft hull can entirely block. While Earth’s protective atmosphere and magnetic field shield travelers close to home, astronauts venturing toward the moon face intense, unpredictable outbursts from the sun known as solar particle events. A new study published in the journal Science Advances examines data from a protective garment tested on a manikin during NASA’s first Artemis moonshot in late 2022.
The uncrewed Artemis I mission paved the way for humanity’s return to the moon by a flyby crew of four. Although the debut flight encountered no major solar outbursts, researchers gathered valuable measurements as NASA’s Orion capsule zipped through the inner Van Allen radiation belt. Lead author Jordan Houri, lead scientist for space exploration at the Israeli startup StemRad, called the project the largest experiment ever conducted to determine astronaut radiation exposure beyond low-Earth orbit
.
Why Zohar and Helga Flew Without Spacesuits
Coating an entire spacecraft with a meaningfully thick layer of radiation shielding remains impractical due to severe weight constraints. Instead, researchers experimented with the AstroRad vest, designed by StemRad with support from the Israel Space Agency and aerospace giant Lockheed Martin.
Artemis I carried two life-size female manikins, dubbed Zohar and Helga, which spent nearly a month flying to the moon and back strapped into the passenger seats of the Orion capsule. Each 3-foot dummy contained more than 5,600 radiation sensors. Zohar wore the 57-pound (26-kilogram) vest, while Helga flew vest-less to serve as a baseline comparison. The manikins were intentionally designed as adult females because women are predicted to face a higher risk of radiation-induced cancer
, according to study co-author Oren Milstein, CEO of StemRad.
“Targeted shielding could help narrow that difference in risk between male and female astronauts.”
Oren Milstein, CEO and co-founder of StemRad
The German Aerospace Center contributed Helga, whose name is a traditional German name. The Israel Space Agency contributed Zohar, selected through a public outreach campaign as a traditional Hebrew name meaning radiance
.
Engineering Personal Protection Against Solar Storms
While lead is traditionally used to block X-rays and gamma rays on Earth, it performs poorly against the high-energy particles encountered in space. High-energy electrons can trigger secondary X-ray showers when striking dense lead, and neutrons can knock loose dangerous atomic sprays.
To solve this, the AstroRad vest relies on a high-density plastic rich in hydrogen atoms. Because hydrogen possesses a high density of electrons and lacks neutrons, it blocks incoming particles safely without generating hazardous secondary radiation. The garment is constructed from thousands of hexagonal rods of rigid plastic joined together like scales, creating a flexible shield tailored to protect vulnerable organs.
Different organs and tissues have very different sensitivities to radiation, so shielding every part of the body equally is not the most effective approach,
Houri explained. The vest specifically covers the lungs, stomach, bone marrow, breasts, and ovaries. This targeted strategy provides about a 30 percent greater dose reduction than distributing the same amount of shielding uniformly across a full-body suit.
Simulating Historic Solar Calamities for Future Artemis Crews
Because Artemis I missed major solar storms, researchers used their sensor data to simulate how much protection the vest would provide during extreme solar particle events like those recorded in 1972 and 1989. The 1972 event occurred between Apollo moon landings, while the 1989 storm collapsed a power grid.
- 1972 Solar Storm: The vest reduced an astronaut’s radiation dose by about 60 percent, equivalent to saving 193 days of unnecessary deep space radiation exposure.
- 1989 Solar Storm: The vest cut the exposure dose by nearly 40 percent, equivalent to 131 days of avoided deep space radiation.
Those reductions matter as mission durations expand. While Apollo moonshots lasted under two weeks, planned lunar bases will require stays lasting weeks or months. Expeditions to Mars will stretch across months or years, heightening the risk of encountering dangerous space weather.
Scientists are already working to trim additional weight from the vest without reducing its protective capabilities, while also investigating methods to recycle spacecraft materials into emergency radiation shielding. Zohar and her vest are now on display at Florida’s Kennedy Space Center.