It is an exceptional individual who is prepared to gamble their life against the fickle whims of a jet-stream, in the chase for one of the last great unclaimed world records.

Which makes it all the more difficult to establish a suitable crew for such a venture.

Little is know about relations between the two Breitling-Orbiter 3 pilots, Brian Jones and Bertrand Piccard.

Partly this is because the pair have not flown together on such a venture before, and partly it is down to their virtually unbroken silence since bidding farewell to solid ground on 1 March.

Crew members ration teabags and loo rolls

But it is possible to ponder the likely pressures they will have been under.

In many ways the Breitling-Orbiter flight is more like a latter-day manned space mission than a balloon trip.

Its international crew - Jones is British, Piccard is Swiss - must constantly weigh the risk to their lives against the challenge in hand, while coping with the strains of confined living.

According to Russian research, carried out to smooth the way for Mir astronauts who face seemingly interminable spells in orbit, total compatibility is vital when selecting candidates.

Stress on compatibility

It found sensitivity to be as important as aptitude and motivation. A crew that lacks "total compatibility" can lead to "conflicts, neurotic states and undesirable psychosomatic symptoms".

The American astronaut Shannon Lucid gave a more straight-forward interpretation in an article in the Scientific American.

Life at 10,000m: Don't forget the can opener

Even with the latest technology on board, "if crew members do not enjoy working together, the flight will be a miserable experience," she wrote.

There's not much in the way of creature comforts to soften the experience for Jones and Piccard.

Fresh food, including bread, cheese and pre-cooked steaks were due to last for the first six or seven days, after which they were expected to make do with a "dried diet" that included cereals and powdered milk.

Not counting the loo rolls

They had planned to alternate six-hour shifts at the controls, before retiring to a bunk and sleeping bag for some rest. Kitted-out with insulating synthetic fibre clothes, they hoped to keep the cabin at a comfortable 15°C.

There is a toilet on board although, unlike the Cable and Wireless team which went before, the crew did not reveal how man loo rolls they carried. (The C&W team of Andy Elson and Colin Prescot thought eight would be enough).