You must not only be an experienced researcher or trained pilot, you must also be technical and able to handle extreme stress.

Maybe you shouldn't be the kind of person who gets weak in the knees when you queue for a free fall or a roller coaster.

Because during the journey out and back into the atmosphere you will be exposed to g-forces.

SVT visited one of Sweden's two centrifuge facilities, where future fighter pilots and astronauts can train on g-forces.

- What the astronauts have to train for is to become familiar with this type of force, says Roger Kölegård, researcher in environmental physiology at KTH.