The contestants have been chosen for their suggestibility

Space Cadets involves the group being told they are to visit space thanks to a Russian tourism agency.

The group, aged between 19 and 28, include a student, a call centre worker and an electrician. Contestants have been picked for their suggestibility.

Channel 4 admitted the joke could be on them if the participants cotton on.

Unbeknown to the contestants, the shuttle will be a Hollywood creation, made originally for the Clint Eastwood film Space Cowboys.

Special effects

The producers must also persuade the participants that the disused UK base where they are being "trained" for space, is actually Russia's Space Tourism Agency.

A custom-built screen just outside the shuttle will attempt to provide the illusion of a view of Earth and sounds will be created by special effects experts.

However, producers will not have to recreate weightlessness because the contestants are to be told their orbit will take them to Near Space, not Deep Space, where they could experience the sensation.

The 10-day series, which is on at 2100 GMT, is presented by Johnny Vaughan and has been created by Endemol, the firm behind Big Brother.

'Big risk'

Some of the contestants are self-confessed pranksters, and TV executives will be hoping that they will see the funny side when the show concludes.

Three of the space cadets are actors pretending to be thrill-seeking contestants.

At the end of the training period, one of the actors will be chosen, along with three genuine contestants, to "blast off" in the shuttle.

Channel 4's factual entertainment commissioning editor Angela Jain has admitted that "a big risk" had been taken with the show, adding: "We don't know who will have the last laugh".