Nasa’s reduced gravity education programme holds a special place in space history. Since 1959 a series of specially modified jetliners have taken to the skies, climbing and then rapidly descending so that astronauts can simulate the feeling of weightlessness that they will experience in space.
Officially the planes are known as Weightless Wonders, but after the ill effects that some people feel during the flight, the name Vomit Comet has stuck. Nowadays there are two Vomit Comets in use: a modified C-9B and a modified Boeing 727.
To find out what the experience is like, BBC Stargazing Live’s Dara O Briain went on board, and explains how the flight creates the sensation of floating.
To see more from Stargazing Live, click here.