Underwater training: Astronauts use swimming pools to simulate low gravity

Throughout the Apollo missions, one of the astronauts’ many training regimes took them poolside. Training underwater was one of the best ways to simulate a low-gravity environment, and it was much more pleasant than the zero-G training they did on an airplane (which they referred to as the “Vomit Comet”). Instead, they suited up and practiced maneuvers underwater at facilities like this, the Water Immersion Facility at NASA's Johnson Space Center. 

Astronauts not only needed to practice being weightless, they also needed to practice for when they’d encounter real water after splashing down on their return to Earth. Here, Apollo 1 astronauts Gus Grissom (exiting craft), Roger Chafee (center) and Ed White (foreground) participate in egress training in June 1966 at Ellington Air Force Base. Less than a year later, this crew would meet a tragic end when they were killed after a  fire broke out during a launch rehearsal.

Egress training was important throughout the Apollo missions. Here, Apollo 10 astronaut Eugene Cernan joins fellow crew member John Young in a life raft. Thomas Stafford is still inside the Command Module, waiting his turn to practice his egress at the Manned Spacecraft Center in August 1968.

Underwater training continued throughout the Apollo program and is still in use at NASA today. Here’s Apollo 17 command module pilot Ronald Evans in September 1972, practicing on the Scientific Instrument Module bay of the Apollo 17 Service Module. This prepped him for the hour-long solo spacewalk he’d complete three months later, as Apollo 17 returned to Earth in December.

Here, Apollo astronaut Thomas “Ken” Mattingly takes his turn underwater back at the Manned Spacecraft Center.