ON BOARD THE VOMIT COMET

You’d better have a strong stomach: in space, everyone can hear you spew

- Ian Evenden

Earth has a problem, at least if you want to train astronauts. It’s called gravity, and while useful for things like attaching your feet to the ground, it’s an inconvenience when you need to acclimatise people to weightlessness. So what do you do? If you’re a national space agency, you set up a special flight that takes advantage of free fall to simulate the weightless experience.

In order to simulate a feeling of weightlessness like astronauts experience once free of Earth’s gravity, the aircraft flies a particular flight path. It climbs at an angle of 45 degrees to altitude before nosing over and descending at 30 degrees in a parabolic path relative to the centre of the Earth, using just enough engine thrust to cancel out the drag of the aircraft moving through the air. During certain parts of the flight, the aircraft and all aboard it are in free fall and experience weightlessness. This begins while the craft is still ascending, continuing while it passes the peak of its climb and begins to descend, until the pilot is forced to pull up on the stick to climb again and avoid hitting the ground. For each parabola, passengers and crew experience around 25 seconds of weightlessness, and a flight is likely to carry out 40 to 60 such manoeuvres.

The idea goes back to 1950, when it was proposed by German brothers Heinz and Fritz Haber, a physicist and aerospace engineer respectively. They had been taken to the US as part of Operation Paperclip at the end of World War II, where they undertook pioneering research in space medicine and worked with Wernher von Braun. Heinz would also collaborate with Shih-Chun Wang, a Chinese-American doctor studying nausea in astronauts for NASA, on the creation of the Vomit Comet.