In at the deep space end: NASA astronauts train for their next mission in world's largest swimming pool Neutral Buoyancy Laboratory in Texas is the size of 10 Olympic swimming pools reaching depth of 40ft Trains astronauts to prepare for effects of weightlessness while carrying out tasks at the International Space Station By Hugo Gye These amazing photographs show NASA astronauts hard at work training for missions in space - in the world's largest pool. The U.S. space agency has built a swimming pool 10 times as large as an Olympic pool in an attempt to prepare astronauts for the experience of weightlessness. The Neutral Buoyancy Laboratory contains 6.2million gallons of water, used by astronauts in full space suits to carry out the tasks they will be expected to perform in space. Training: NASA astronauts practice carrying out their duties while weightless in the Neutral Buoyancy Laboratory in Texas Rehearsal: The pool replicates the unfamiliar condition of weightlessness on board the International Space Station The pool stretches for more than 200ft and in places reaches a depth of 40ft - roughly the same as four double-decker buses stacked on top of one another. Hundreds of astronauts have used the state-of-the-art training device ahead of missions aboard the International Space Station. Among those who have trained at the lab is Chris Hadfield, who shot to fame over the past few months with a series of popular YouTube videos chronicling his experiences in space. The NBL is located at the Sonny Carter Training Facility, near NASA's Johnson Space Center in Houston, Texas. Simulation: Neutral buoyancy, where objects neither float nor sink, is close to the lack of gravity experienced in space Hard at work: An astronaut in a full space suit trains at the NBL, which is 40ft deep and the size of 10 Olympic swimming pools Familiar sight: Astronauts work on a capsule similar to those fitted to a rocket which transport operatives to the ISS It consists of a large indoor pool of water in which astronauts perform simulated tasks in preparation for upcoming missions, such as spacewalks. Neutral buoyancy is the term used to describe something that has an equal tendency to float as it does sink - providing practically the same situation as being truly weightless. The walls surrounding the pool are six foot thick and support nearly 26,000 tons of water which has been filtered and heated to 86F. Since the mid-1960s, neutral buoyancy has been an invaluable tool for testing procedures, developing hardware and training astronauts. VIDEO NASA are testing in the depths of the Neutral Buoyancy Laboratory Going in: An astronaut stands on a platform prior to being lowered into the NBL for training Taking a breather: An astronaut surfaces after spending time in the lab preparing for a future mission to outer space Monitoring: NASA staff watch the progress of a simulated space walk in the NBL using a bank of video screens Astronauts require preparation for weightlessness because of the difficulty of operating equipment and moving around in such an unfamiliar environment. Many people who travel outside the Earth's atmosphere suffer from 'space sickness', which leads to nausea and vertigo. When astronauts spend extended periods in space, they can suffer more serious conditions such as muscle atrophy due to the difficulty of exercising properly.