Although the balloonists' ascent will keep them well clear of space, the extremely high altitude means spacesuits are vital live-saving equipment.

The pilots' suits, which have a bright orange outer layer and a white inner, have been made by a Russian company that serves their national space program.

Not only do the suits provide oxygen, they will also protect the two men from extreme cold.

Should the suits fail at 35,000 feet (10,668 metres) Andy and Colin would lose consciousness. At 80,000 feet (24,384 metres) the pilots would die within a matter of seconds, as the low pressure would make their blood boil almost immediately.

The two men will not eat during their mission, and they are hoping they will not have to go to the toilet either. A special fibre-free diet will begin three days before the trip in the hope that waste will be kept to a minimum.