Astronaut Boot Test in JPL's CITADEL

A boot that's part of a NASA lunar surface spacesuit prototype is readied for testing inside a thermal vacuum chamber called CITADEL at the agency's Jet Propulsion Laboratory in Southern California on Nov. 8, 2024. The thick aluminum plate at right stands in for the frigid surface of the lunar South Pole, where Artemis III astronauts will confront conditions more extreme than any previously experienced by humans.

Built to prepare potential future robotic spacecraft for the frosty, low-pressure conditions on ocean worlds like Jupiter's frozen moon Europa, CITADEL (Cryogenic Ice Testing, Acquisition Development, and Excavation Laboratory) has also proven key to evaluating how astronaut gloves and boots hold up in extraordinary cold. It can reach temperatures as low as low as minus 370 degrees Fahrenheit (minus 223 degrees Celsius), approximating conditions in permanently shadowed regions that astronauts will explore.

Figure A, showing the outer boot sole, was taken from inside CITADEL on Nov. 13, 2024. The boot is positioned in a load lock, one of four small drawer-like chambers through which test materials are inserted into the larger chamber.

Initiated by the Extravehicular Activity and Human Surface Mobility Program at NASA's Johnson Space Center, the boot testing took place from October 2024 to January 2025. The boot is part of a NASA spacesuit called the Exploration Extravehicular Mobility Unit, or xEMU.

Results haven't yet been fully analyzed. In addition to spotting vulnerabilities with existing suits, the experiments are intended to help NASA develop this unique test capability and prepare criteria for standardized, repeatable, and inexpensive test methods for the next-generation lunar suit being built by Axiom Space.