In-Water Simulations in Astronaut Training
Underwater environments simulate the conditions of space exploration and allow NASA to test equipment, perform research, and prepare for future missions in extreme settings such as the moon or Mars. Being underwater replicates the isolation, confined spaces, and limited resources astronauts experience in space.
There is a long history of underwater operations to prepare astronauts for space missions. The first use of underwater environments for astronaut training dates to the early 1960s, when preparations were underway for NASA’s Gemini program.
The Neutral Buoyancy Simulator (NBS), a large water-tank facility at NASA’s Marshall Space Flight Center in Huntsville, Alabama, was used to simulate the weightlessness of space. When the Neutral Buoyancy Laboratory (NBL) at the Sonny Carter Training Center in Houston, Texas, became operational in 1997, it superseded the NBS as NASA’s primary facility for astronaut training in spacewalks and extravehicular activities (EVAs).
At 202 feet (62 meters) in length, 102 feet (31 m) wide, and 40 feet (12 m) deep, the NBL is large enough to submerge mockups of large objects, such as the space shuttle’s cargo bay or sections of the International Space Station. Astronauts typically spend an average of 10 hours training here for each hour of planned EVA on their missions.
The NASA Extreme Environment Mission Operations (NEEMO) program began in 2001 to saturate astronauts, engineers, and scientists in an underwater habitat and prepare them for space missions. The program was based at the Aquarius Reef Base off Key Largo, Florida, at a depth of 62 feet (19 m) and offered a unique setting to tackle the challenges of isolation, confined space, and communication delays in conditions similar to long-duration space exploration. There were 23 missions conducted between 2001 and 2019, each focusing on specific training, including testing EVA techniques, developing equipment, and evaluating human performance under pressure.
Current Activities
The Space Environment Analog for Training, Engineering, Science, and Technology (SEATEST) also uses the natural environment to prepare astronauts for EVAs but specifically focuses on refining and testing tools, logistics, and technologies for missions to the moon. The most recent SEATEST project, SEATEST 7, occurred at the University of Southern California Wrigley Marine Science Center on Santa Catalina Island.
The objectives were to optimize transporting cargo from rovers to crewed pressurized living quarters and support long-term lunar missions as part of the Artemis lunar landing missions. A lunar habitat mockup at 30 feet (9 m) let the team evaluate a variety of loading and offloading techniques for moving cargo.
This mission brought together five astronauts from four different space agencies — NASA, the European Space Agency, the Canadian Space Agency, and the United Arab Emirates Space Agency — to work closely with a support team of engineers, communications specialists, flight surgeons, and support divers. The group tested different scenarios to plan for future logistics operations on the moon.
The first Artemis mission to land astronauts on the moon, Artemis III, is planned for September 2026. The mission will mark NASA’s return to the lunar surface for the first time since Apollo 17 in 1972. The goal is to land near the lunar South Pole, where astronauts will engage in scientific research and exploration activities. Many operational aspects of the mission need to be tested and codified to improve safety and efficiency.
Training
SEATEST 7 had two phases in the waters off Catalina Island, California. The engineering structures were assembled and placed underwater in August 2024 to prepare for the simulations. During Phase 2 in September 2024, the flight crew and support team conducted a series of cargo handling tests and simulations.
Eight people — whose dive experience ranged from only four open-water dives to thousands of dives — were involved with the simulation, and everyone participated in orientation and skills review activities. The initial dive training was a refresher on open-water procedures followed by additional training according to American Academy of Underwater Sciences (AAUS) standards. The crew then used commercial diving procedures once the lunar habitat was in place on the seabed.
The astronauts had daily dive briefings and fitness evaluations and practiced using tools, emergency air supplies, and standby diver procedures underwater. Three astronauts and two support staff earned advanced dive certifications during the training.
The astronaut team used full-face masks (FFMs), enabling them to communicate with the topside team and the Mission Control Center (MCC) set up in one of the residential buildings about a third of a mile (500 m) away. Most of the participants had not used FFMs, so they had an introductory fitting and dive preparation session with the masks before entering the water. In addition to the regular emergency procedures, they had additional practice in removing the FFM and changing to a standard mask and changing from the integrated regulator to a standard second
stage, a small independent air supply, and a 40-cubic-foot (5.7-liter) bailout bottle.
The FFMs were fitted with hard-wired communications using a tethered line. The line also incorporated a video feed from a mask-mounted camera, allowing the MCC to observe the team working and moving while completing their tasks. The additional lines required even more practice for the divers and those tending them from the surface.
The Mission
The purpose of SEATEST 7 was to allow astronauts to rehearse complex movements and operational procedures associated with handling cargo on the moon. As problems arose while practicing in the underwater environment, astronauts identified them and developed problem-solving skills in a low-gravity context, which is a vital skill during actual space missions.
The crew worked underwater in teams of two divers, with an additional crew member serving in the MCC and the others off rotation for any given dive. Each astronaut performing mission simulations wore a 1-millimeter white neoprene suit over their wetsuit and had a personal safety diver providing configuration support.
The support diver helped them into their Personal Life Support Systems (PLSS) — a housing that encloses the scuba cylinder and approximates the size of the PLSS they will use on the moon — and also weighted the divers to be negative on the underwater platform, managed communications lines during the simulation, removed the weights at the end of the dive, and helped the astronauts back into their fins for their swim back to the surface.
The program aimed to identify appropriate procedures for moving cargo from the lunar rover into the habitat, from the habitat back to the rover, and from the rover to the habitat platform separate from the living quarters. The crew tested multiple cargo transfer methods, including davit (a small crane), zipline, block and tackle hoist, and hand held.
They also evaluated various types of cargo containers with differing volumes, shapes, and weights, as well as simulated oxygen cylinders that will supply breathing gas in the lunar habitat. Every astronaut practiced with all the methods, noting difficulties and challenges during each iteration and discussing potential solutions and future improvements.
The team also simulated removing dust from the cargo and their spacesuits with brooms and brushes before entering the mock habitat’s airlock. Lunar regolith is very crystalline and abrasive, which can affect both the equipment and the astronauts’ health. Inhaling the fine, sharp dust particles can potentially injure the lungs.
Additional support divers conducted photography and videography for later mission evaluation. Several 360-degree video systems recorded data and operations from static positions underwater.
Conclusion
SEATEST is an unusual and exciting application of scuba diving designed to lead astronauts into the unknowns of space. The significant data that the participants collected regarding cargo-handling procedures will inform the next iteration of testing and ultimately the procedures for the Artemis missions.
Explore More
Learn more about NASA’s Neutral Buoyancy Lab and astronauts training underwater in these videos.
© Alert Diver – Q1 2025