Why do astronauts train underwater?

One of NASA’s many projects running concurrently to its space missions is NEEMO. It stands for NASA Extreme Environment Mission Operations and it prepares a crew for the conditions of space by putting them through ‘analog’ test missions: in other words, terrestrial missions which are analogous, or comparable, to those they will encounter on leaving this world.

An analog mission might require an astronaut to sit in a giant centrifuge and be spun at dizzying g-forces and various pressures in a specialised chamber or, in the case of NEEMO, it might focus on underwater activities that simulate low gravity. NASA uses the Aquarius Reef Base situated off Key Largo in the Florida Keys for its NEEMO missions, which is owned by another US government department – NOAA (National Oceanic and Atmospheric Administration).

The base is a habitat located 19 metres (62 feet) underwater that weighs around 85 tons. The astronauts-in-training can stay in the habitat for several weeks, with training simulations like moving from one workstation to the next, using tools and working in an asteroid space environment.