You can be psychologically normal but claustrophobic or think ..something will happen....

"It's a real probability that a flight to Mars would fail if the very serious problem of isolation is not investigated first," says Oliver Knickel, an army engineer from Germany who is one of the volunteer "astronauts" for the experiment.

"The impact of the isolation would almost certainly kill the crew on board."

Whether the six volunteers taking part in the current experiment will come to blows is a moot point.