Hit the Pool, Then Head to the Moon: Preparing Artemis Crews for Lunar Exploration

The summer heat has many of us wishing for a relaxing day at the local pool.

For astronauts preparing to go to the International Space Station or the Moon, a pool day looks quite different. So does their pool, located at the Neutral Buoyancy Laboratory (NBL).

Housed in NASA’s Sonny Carter Training Facility near the Johnson Space Center, the NBL’s most prominent feature is its 202-foot-long, 102-foot-wide, 40-foot-deep pool where astronauts don pressurized suits and train for spacewalks and other mission components while hovering in 6.2 million gallons of water. The pool’s tremendous size allows for the submersion of full-size mockups of space station modules – and, during the Space Shuttle Program, a mockup of the shuttle’s payload bay.

Scott Wray, Artemis Extravehicular Activity (EVA) training lead, joined NASA when astronauts were still training to conduct spacewalks, also known as EVAs, for both programs. Wray participated in NASA’s Contractor Co-op Program with United Space Alliance while completing his studies in aerospace engineering at Embry-Riddle Aeronautical University. During one co-op experience, with the shuttle’s In-Flight Maintenance Team (IFM), Wray observed the IFM and EVA teams collaborating with the STS-117 crew to fix the peeled-back thermal blanket on space shuttle Atlantis’s Orbital Maneuvering System pod. That inspired him to work with the EVA team on his next co-op rotation. “I love to be hands on, to take things apart and come up with creative solutions – that’s what really attracted me to EVA,” Wray said.

Wray became a full-time EVA team member at Johnson after graduation, working under various contracts until he transitioned to a civil servant position in 2021. He started out as an EVA instructor focused on tools and hardware and teaching astronauts how to perform their maintenance and repair duties. “That’s what brought me to the NBL,” he said. “The NBL has been our flagship EVA training facility since it opened in 1997.”

Wray has nearly 15 years of experience as an instructor and flight controller for shuttle and space station EVAs, but in the last two years, his responsibilities have shifted to preparing Artemis crew members who will land on the Moon. While many astronauts have completed the space station training or participated in a spacewalk at the orbiting laboratory, the skills required for lunar exploration will be different. “It’s going to be a completely new spacesuit, new vehicles, new environment,” Wray said. “And now they’re going to be walking instead of translating with their hands like we do with the International Space Station.”

One of the biggest advantages of training in the NBL also presents a significant challenge for Artemis preparations. The facility’s name comes from the team’s use of the neutral buoyancy method to simulate weightlessness for astronauts. In this method, a combination of weights and flotation devices are attached to an astronaut’s spacesuit so they neither sink nor float. If done correctly, this process of “weighing out” allows an astronaut to hover underwater.

“We’ve gotten really good at weighing out crew members for microgravity EVAs, like we’ve done for the space station, and the astronauts can move in the water column as if they are in space,” said Wray. “The challenge now is that we need to simulate one-sixth gravity for the Moon, where you’re heavy enough to keep your feet on the ground.”

Wray said the NBL team is working on a new weigh out technique that accommodates different body types and NASA’s new Exploration Extravehicular Mobility Unit (xEMU) spacesuits, which provide much greater mobility than the current EMUs but also have more mass. (Artemis crews will train in xEMUs until vendor-produced suits are available.) "The trick is to match an astronaut’s center of gravity with their center of buoyancy,” said Wray. “Otherwise, the stability of the suit may not match reality and could be overly stable or unstable. In an extreme case the suit could just flip over and be upside down.”

Another challenge is simulating the lunar environment, including the Moon’s uneven surface. The NBL team worked with a vendor that typically builds large aquarium displays to create terrain panels for the pool floor. “Think of it almost like a stage that we can tilt at different angles and have a ramp that would be like climbing up the side of a hill or maybe down into a shallow crater,” Wray said. The NBL’s moonscape also uses sand to simulate lunar regolith. Choosing the right sand involved various tests to ensure the final selection did not cloud or create issues in the pool water. “We’ve washed a lot of sand to make sure it has the right feeling.”

Lighting will also be different at potential landing sites near the Moon’s South Pole. Low-angle sunlight creates intense differences between lit and unlit areas, and shadows that are much darker than those seen on Earth. The NBL team has installed blackout curtains on portions of the light-colored pool walls and a 4,000-watt lamp to simulate these conditions because lighting has important implications for how crew members take photos and conduct scientific observations. “It’s not easy recreating this inhospitable environment that we’re going to explore, but it’s important that we get at least some of it right,” Wray said. “As an instructor, I want my crew to be prepared. They need to be able to practice different scenarios over and over.”

Although the NBL is unique, it is not the only NASA training facility that Artemis crews will use to prepare for the spacewalks and scientific research they will conduct on the lunar surface. The Active Response Gravity Offload System – a robotic system that uses gimbals and cables to move astronauts like a marionette – will help crew members test suit mobility and practice tasks that can be completed in small areas. Certain geology and navigation trainings will be conducted at field sites in Canada and Iceland, as well as locations around the United States.

For now, the NBL remains the only training facility that allows two crew members to work together, in pressurized suits, to simulate a spacewalk from start to finish. “We can have the crew members practice exiting the vehicle, conducting science, and entering the vehicle,” Wray said. “That’s really important, because if you never do a full dress rehearsal, there’s more room for error.”

Crew members regularly report that their NBL training sessions were tremendously helpful in preparing for their missions. That value is provided by an extensive and diverse team that includes safety and medical staff, suit technicians, engineers, fabricators, and the NBL’s highly trained divers who assist crew members in the pool. The NBL has also begun involving geologists and other scientists from around the world in Artemis trainings to ensure crews are prepared to do excellent science.

“We’re not just going there to plant a flag and say we did it again, we’re back,” Wray said. “Artemis is about exploration and discovery. We want to get the most out of going back to the Moon, to better understand our solar system and the Earth.”