A JPL Facility built to support robotic spacecraft missions to frozen worlds of oceans helps engineers develop safety testing for next-generation suits.
When NASA’s astronauts return to Moon under the Artemis Campaign and eventually venture further into the solar system they will experience conditions that are harsher than anything humans have ever experienced. CITADEL, NASA’s Jet Propulsion Laboratory, Southern California, is a unique chamber that helps test spacesuits for the next generation.
Designed to prepare robotic explorers who may explore ocean worlds such as Jupiter’s frozen Moon for the frosty conditions of low-pressure.
CITADEL can also evaluate how well spacesuit boots and gloves perform in extreme cold. NASA Engineering and Safety Center spearheaded a CITADEL glove testing campaign that ran from October 20, 2023 to March 20, 2024. The Extravehicular Activities and Human Surface Mobilities Program at NASA Johnson Space Center, Houston, began boot testing in October 2024. It continued until January 2025.
The team will adapt CITADEL in the coming months to test spacesuit elbows to evaluate suit fabric for longevity on the Moon. They will introduce abrasion tests and a simulant of lunar regolith (the loose material that covers the Moon’s surface) into the chamber. Danny Green, the mechanical engineer who headed the boot testing at JPL, said that JPL has built space robots that have traveled across the solar system. “It is pretty special to use our facilities to support returning astronauts to Moon.”
The Artemis III mission will explore Moon’s South Pole. This region has much greater extremes compared to the equatorial landsites visited by Apollo-era missions. They will spend up to 2 hours in craters which may contain ice deposits that could be important for sustaining a long-term human presence. These fascinating features, which are called permanently shadowed areasare among the coldest places in the solar system. They can reach as low as minus 248 degrees Celsius (minus 414 degrees F). The CITADEL Chamber gets close to these temperatures.
“We are trying to determine the risks astronauts face when they enter permanently shadowed areas. Gloves and boots will be crucial because they come into prolonged contact with cold surfaces or tools,” said Zach Fester. Zach Fester is an engineer at NASA Johnson’s Advanced Suit Team and the technical leader for the boot tests.
Keep Cool
The CITADEL chamber is housed in the same JPL building as the historic 10-Foot space simulator . It uses compressed helium, which can reach temperatures as low as minus 223 C (minus 370 F). This is lower than most cryogenic equipment, which relies primarily on liquid nitrogen. The chamber is large enough for a human to climb into. It measures 4 feet (1.2 metres) high and 5 feet (1,5 meters) in diameter.
It is also equipped with four load locks – drawer-like chambers that allow test materials to be inserted into the main compartment while maintaining a chilled vacuum. It can take days for the chamber to reach the test conditions. Opening it to insert new materials will start the process again. The load locks enabled engineers to quickly adjust during boot and gloves tests.
Cryocoolers cool the chamber and aluminum blocks can simulate tools astronauts would grab or the cold surface of the moon on which they would walk. The chamber is equipped with a robotic arm that interacts with test materials and multiple visible-light cameras as well as infrared ones to record operations.
NASA has been using the Extravehicular Mobilization Unit spacesuit since the 1980s. The gloves being tested in the chamber is the sixth version of the glove that was first used in the 1980s. The suit, which is optimized for spacewalks on the International Space Station (ISS), is so complex that it’s like a personal spacecraft. The legacy glove failed to meet thermal requirements at the lunar South Pole. The results of boot testing using a lunar surface suit called the Exploration Extravehicular Mobilization Unit have not yet been fully analyzed. This spacesuit is NASA’s reference for an advanced suit architecture. It features enhanced fit and mobility. The CITADEL experiments, in addition to identifying vulnerabilities with existing suits will help NASA develop criteria for standardized and repeatable test methods that will be used for the next generation lunar suit, being built by Axiom Space – the Axiom Extravehicular Mobilty Unit, which NASA astronauts are expected to wear during the Artemis III Mission. This test will identify the limits of the glove or boot in the lunar environment. Shane McFarland is the technology development lead at NASA Johnson for the Advanced Suit Team. We want to quantify our capability gap for the current hardware, so we can provide that information to the Artemis suits vendor. We also want to develop this test capability to assess the future hardware designs. For gloves, astronauts placed their gloved hands in a chilled “glovebox”, grabbed an ice-cold object and held it there until the skin temperature dropped to 50 F (10 C). McFarland said that human-in-the loop testing is essential for future spacesuit safety, but it doesn’t provide the consistent data the CITADEL team is looking to obtain.
The CITADEL team used a manikin foot and hand to obtain objective feedback. A system of fluid-loops simulated the flow of warm, blood through the appendages. Meanwhile, dozens of temperature sensors and heat flux sensors were used to collect data from the inside of gloves and boots.
Morgan Abney, NASA Technical Fellow for Environmental Control and Life Support and the person who conceptualized the glove testing, said: “By using CITADEL and manikin technology we can test design iterations much faster and at a lower cost than traditional Human-in-the Loop testing.” “Now we can push the envelope with next-generation suits and be confident that we understand the risks,” said Morgan Abney, NASA technical fellow for Environmental Control and Life Support. We’re one-step closer to landing astronauts on the Moon.
NASA will send astronauts through Artemis to explore the Moon to discover scientific discoveries, create economic benefits, and lay the foundation for the first crewed mission to Mars.
Melissa Pamer
Jet Propulsion Laboratory, Pasadena, Calif.
626-314-4928
melissa.pamer@jpl.nasa.gov
2025-060
