StemRad

StemRad is a Tel Aviv, Israel-based radiation protection technology company founded in 2011, developing personal radiation shielding products for emergency responders and astronauts. StemRad's core technology uses hydrogen-rich polymer materials optimized to shield the body's most radiation-sensitive tissues — particularly hematopoietic stem cells in the bone marrow of the pelvis — from high-energy proton and heavy ion radiation encountered in deep space.

StemRad's flagship space product is the AstroRad radiation protection vest, co-developed with Lockheed Martin as part of their collaboration on deep space crew safety for the Artemis lunar program. AstroRad is designed to protect astronauts during solar particle events (SPEs) — intense bursts of energetic protons ejected by the Sun during solar flares and coronal mass ejections that can deliver radiation doses exceeding 1 Sv within hours to unshielded crew members en route to the Moon or Mars. The spacecraft hull provides partial shielding but is insufficient alone during extreme SPE events.

AstroRad's shielding design is anatomically targeted: rather than surrounding the entire body uniformly (which would require prohibitively heavy shielding mass), AstroRad concentrates polymer material over the pelvis and torso where bone marrow contains the highest concentration of radiation-sensitive hematopoietic stem cells. Preserving stem cell viability is critical because radiation injury to marrow produces radiation sickness and immune suppression — the primary life-threatening mechanism of acute radiation syndrome — even when other organs survive the dose.

The AstroRad vest flew on NASA's Artemis I mission in November 2022 aboard the uncrewed Orion spacecraft as part of the MARE (Matroshka AstroRad Radiation Experiment), a collaboration between StemRad, Lockheed Martin, DLR, and the Israel Space Agency. Phantom torso mannequins instrumented with radiation dosimeters inside and outside the vest measured the shielding effectiveness of AstroRad during the Artemis I lunar flyby — providing the first comprehensive dose attenuation data for hydrogen-rich polymer body armor in deep space. StemRad competes with passive shelter concepts (water wall storm shelters) and pharmaceutical radioprotectants (amifostine) as complementary radiation mitigation strategies.