During NASA’s uncrewed Artemis I moon mission, a specialized radiation-shielding vest called AstroRad successfully protected a female test dummy named Zohar from high-energy solar radiation. Researchers reported that the gear could cut radiation doses by up to 60 percent during severe solar storms, paving the way for safer long-duration lunar and Mars expeditions.
While space agencies look ahead to permanent lunar bases and crewed missions to Mars, radiation remains one of the most formidable hurdles for human spaceflight. When violent solar particle events erupt, they unleash unpredictable waves of radiation that can drastically elevate an astronaut’s lifetime risk of cancer. Coating an entire spacecraft in thick shielding is impractical due to weight constraints, forcing engineers to explore personal garments worn directly by travelers.
During NASA’s uncrewed Artemis I moon mission in late 2022, a protective garment underwent its most rigorous trial yet beyond low-Earth orbit. The uncrewed debut flight paved the way for humanity’s return to the lunar vicinity, while carrying a unique payload designed to measure deep-space hazards.
Inside the AstroRad Vest Design and the Artemis I Phantom Test
The protective garment, known as the AstroRad vest, was developed by the U.S.-Israeli startup StemRad in collaboration with aerospace giant Lockheed Martin, with support from the Israel Space Agency. Rather than utilizing heavy lead—which can trigger secondary showers of hazardous X-rays and neutrons when struck by fast-moving space particles—the vest relies on a high-density plastic rich in hydrogen.
Hydrogen possesses the highest density of electrons per atom, creating an effective shield against incoming particles without generating dangerous secondary neutron sprays. The designers assembled thousands of hexagonal plastic rods like scales to form a flexible 57-pound (26-kilogram) garment that targets the most vulnerable organs, including the lungs, stomach, bone marrow, breasts, and ovaries.
“different organs and tissues have very different sensitivities to radiation, so shielding every part of the body equally is not the most effective approach,”
Jordan Houri, lead scientist for space exploration at StemRad
Houri further noted that a full-body suit would be more difficult to put on and move around in.
To test the garment, Artemis I carried two life-size, three-foot-tall female phantoms named Zohar and Helga into the passenger seats of the Orion capsule, where they spent nearly a month traveling to the moon and back. Zohar wore the AstroRad vest, while Helga flew unprotected. Both dummies were equipped with more than 5,600 internal and external radiation sensors.
Simulating Extreme Solar Storms from 1972 and 1989
Although Artemis I encountered no major solar outbursts during its flight, the mission successfully zipped through the inner Van Allen radiation belt. Using those measurements alongside historical data from extreme solar particle events, researchers simulated how much protection the vest would have provided during past solar catastrophes.
The historical benchmark solar storms of 1972 and 1989 served as the primary test cases. The 1972 event notably occurred between the Apollo 16 and Apollo 17 moon landings, narrowly averting a dangerous exposure for lunar crews.
- 1972 Storm: The AstroRad vest reduced an astronaut’s radiation dose by about 60 percent, equivalent to saving 193 days of unnecessary deep-space radiation exposure.
- 1989 Storm: The garment cut exposure by nearly 40 percent, saving the equivalent of 131 days of deep-space radiation exposure.
By significantly reducing the radiation dose during a severe solar storm, the vest aims to protect astronauts who might otherwise have to retreat to heavily shielded storm shelters or risk severe health consequences during lunar extravehicular activities.
Targeting Higher Radiation Risks for Female Astronauts
The decision to utilize female-shaped phantoms for the experiment addresses a critical disparity in space medicine. Previous research established that female astronauts face a statistically higher risk of radiation-induced cancer due to the higher sensitivity of organs like breasts and ovaries.
“Radiation in space is unavoidable, and a single major solar particle event can make a substantial contribution to an astronaut’s lifetime risk of radiation-induced cancer,”
Oren Milstein, CEO and co-founder of StemRad
Milstein added that by significantly reducing that contribution, personal shielding could be particularly important for future lunar and Mars missions.
Targeted shielding over vulnerable tissues helps narrow the biological risk gap between male and female space travelers. StemRad’s Jordan Houri characterized the endeavor as the largest experiment ever conducted to determine astronaut radiation exposure beyond low-Earth orbit,
according to Apnews.
Future Moon Bases, Mars Expeditions, and Next Steps
While Apollo moon missions lasted less than two weeks, NASA’s envisioned lunar outpost will require stays lasting weeks or months, vastly increasing the statistical probability that an Artemis crew will endure a dangerous solar particle event. Mars expeditions will extend that exposure across months or years.
The vest did not travel on the subsequent Artemis II flyby mission because of its short 10-day duration and limited cabin space, but it remains a strong candidate for carry-on luggage on later crewed lunar visits. Meanwhile, scientists are analyzing the high-fidelity dataset provided by Zohar and Helga to trim additional weight from future iterations of the vest without compromising safety.
Researchers are also investigating whether similar radiation shielding can be manufactured directly from materials already present inside a spacecraft, opening the door to recycling initiatives that could safeguard deep-space crews. For now, Zohar and her historic vest are on public display at Florida’s Kennedy Space Center.
Related reading
