AstroRad Vest Could Cut Astronaut Dose Nearly 60% in Modeled Solar Storm
Nearly 60 percent is the headline result from a radiation-protection vest flown around the Moon, but it is a modeled result not a dose reduction observed during an actual solar storm. Measurements from NASA’s uncrewed Artemis I mission indicate that the AstroRad vest could reduce an astronaut’s effective radiation dose by about 60 percent during a strong storm resembling the August 1972 event.
The findings published in Science Advances on August 12, 2026, put a second boundary around that figure. For a storm modeled on the more energetic October 1989 event, the estimated reduction was just under 40 percent. The difference reflects the greater penetration of the higher-energy proton spectrum, showing that the vest’s benefit depends on the character of the storm rather than one universal protection percentage.
Two instrumented bodies made the comparison possible
The Matroshka AstroRad Radiation Experiment flew aboard Orion during the 25.5-day Artemis I lunar mission in late 2022. Instead of astronauts, two female-body radiation phantoms named Zohar and Helga occupied passenger seats. Zohar wore AstroRad, while Helga flew without wearable shielding.
Each phantom contained 38 tissue-equivalent sections representing different densities of bone, soft tissue and organs. Several thousand passive dosimeters and multiple active detector systems measured radiation inside and around the structures, allowing researchers to estimate exposure in specific organs and tissues rather than relying only on a detector mounted somewhere in the cabin.
The arrangement provided an unusually direct in-flight comparison, although it was not a perfect laboratory control. The two Orion seats had slightly different surrounding shielding. Researchers accounted for that difference when modeling the solar-storm cases, giving the vested and unvested digital bodies the same simulated distribution of spacecraft shielding.
Artemis I did not encounter the storm behind the estimate
Solar activity did not increase significantly during Artemis I, so neither phantom experienced a major solar particle event. Instead, the active detectors recorded proton exposure as Orion crossed Earth’s inner Van Allen radiation belt. The team built a radiation-transport model around those measurements, checked its output against the detector readings and then substituted proton spectra from the August 1972 and October 1989 storms.
That distinction explains what Artemis I proved directly and what remains an extrapolation. During the Van Allen belt passage itself, modeling of the measured environment found an effective-dose reduction of about 25.8 percent for the vested phantom, from 1.61 to 1.19 millisieverts. The much larger storm figures came from simulations validated against those flight measurements.
For the August 1972-type spectrum, the torso model estimated that AstroRad would lower effective dose from 222.3 to 87.5 millisieverts, a 60.7 percent reduction. A more realistic whole-body female model produced a similar 58.2 percent reduction, from 204.2 to 85.3 millisieverts. For the October 1989-type spectrum, the estimated reductions were 38.5 percent for the torso model and 36.9 percent for the whole-body model.
Targeted shielding buys protection without shielding everything
AstroRad, developed by Israeli company StemRad, uses hydrogen-rich polyethylene to attenuate proton radiation. Its thickness varies across the body, concentrating material around radiation-sensitive tissues including bone marrow, lungs, stomach, breasts and ovaries. The Artemis I vest weighed approximately 26 kilograms on Earth.
That mass is substantial for flight hardware, but it is lower than the penalty of distributing an equivalent shielding thickness across an entire spacecraft. Simulations comparing AstroRad with a uniform full-body suit of the same mass found that the targeted vest improved effective-dose reduction by about 30 percent. The trade is incomplete coverage: organs and tissues judged more important to effective dose receive more material, while the head and extremities receive little or no direct protection.
The experiment used female body models because accepted risk models predict a higher radiation-induced cancer risk for women, though the shielding principle also applies to men. It was also the first experiment to measure wearable shielding’s effect on dose deposited inside a human phantom in space and to map that deposition beyond low Earth orbit.
AstroRad is therefore best viewed as an additional emergency layer, not proof that wearable shielding solves deep-space radiation exposure. It targets proton-heavy solar storms more effectively than the more penetrating chronic background from galactic cosmic rays, and it could complement an Orion storm shelter while allowing some cabin mobility. The next practical question is whether that protection justifies 26 kilograms of dedicated mission mass and whether future crewed testing can confirm that astronauts can work in the vest for the hours or days a solar storm may last.
By David Whitaker — Associate editor for AMI’s aerospace and drone systems desk, translating flight systems, aircraft programs, spaceflight, and UAV developments into accessible technical stories.
