Some day soon two British balloonists will take an open-air trip to the very edge of space -- if the weather cooperates. If the mission succeeds, they will secure the world record for the highest crewed balloon flight.

That's the goal of 48-year-old Andy Elson and 51-year-old Colin Prescot. Aboard their craft, the QinetiQ 1, Elson and Prescot plan to ascend to an altitude of 25 miles, with only their modified Russian space suits between them and the harsh environment.

Their plan is to go for a straightforward ascent under a gigantic weather balloon. Fully inflated, the balloon or envelope will dwarf New York's Empire State building. However, the pilots won't have to travel in fear of an enormous "pop" deafening them if the balloon bursts. The balloon's helium gas will not be under any pressure -- in fact the balloon is designed to leak, in a controlled way of course. As it rises from ground level, the envelope will need to vent helium in order to maintain equilibrium with the outside air.

The polyethylene envelope is being built at the QinetiQ 1 headquarters in Glastonbury, England. This material is the same thickness as a household freezer bag, but has been manufactured with special additives aimed at strengthening its performance at high altitudes where temperatures may drop down to -94° Fahrenheit (-70° centigrade).

Assuming all goes well, Prescot and Elson will ride their great translucent elevator upward for about five to six hours. After an hour or two's stay at the 25-mile height, further helium will be vented from the balloon and a leisurely six-hour descent will carry the two men back to ... well, somewhere off the coast of Ireland. As an unguided balloon, QinetiQ 1 will need a wide berth, and should set down somewhere near its rescue ship in the North Atlantic.

"Using the University of Reading's novel trajectory projection model, we've been able to make predictions before we choose the time to fly and select the right time to go where our flight will be made over water," Prescot explained.

"We'll splash down in the Atlantic just south of Ireland. In fact, the envelope will come down like a massive streamer by the time we're approaching the sea. A professional search and rescue team will already be at the point of splashdown to pick us up from where we land."

Unlike most high-altitude balloon flights, QinetiQ 1's crew cabin will not be enclosed. Still, it's several steps up from a simple lawn chair suspended below the balloon.

"Predominantly, our flight platform is open due to the need for it to be very light weight," said Prescot, who along with Elson will be wearing a Russian-model space suit. "The whole craft with us on it cannot be heavier than 1.5 tons."

While at their peak of 25 miles above the surface of the Earth, Prescot and Elson will be privileged to a view few people have ever seen. They will definitely have the feeling of being at the edge of space, even if the formally defined edge itself is still higher at 62 miles.

"Beyond that, it's a far more exciting proposition to travel on an open deck, in our spacesuits with nothing between us and the inky black sky with the curvature of the earth beneath! I can't wait," Prescot enthused.

Which is not to say the gondola, though light, is at all flimsy.

"The QinetiQ 1 flight platform has been designed by my co-pilot Andy Elson to be stable in air and water, sturdy in structure but also incredibly lightweight and amazingly safe," said Prescot.

So, when are they going? It's hard to say exactly. The QinetiQ 1 team has settled on a date some time before the end of September 2002. However, since so much of the mission depends on the cooperation of Mother Nature, they won't be exactly sure until about 72 hours before lift off.

"The weather is important to our mission," said Prescot, "But we're working with the UK [meteorological] Office to pinpoint the right conditions for the flight."

Indeed the weather hasn't been helpful for a while. Their launch window, which opened in mid June, has been slowly shrinking as the summer wanes. Nevertheless, Prescot remains optimistic.

"This year, the UK summer has been a disappointment to everyone," admits Prescot, "And the winds in the stratosphere have been very unstable and unpredictable. However, with a good few weeks left in our weather window, we're still really optimistic that we'll find a good opportunity to launch and fly QinetiQ 1."

Even without a risk of a single puncture collapsing the balloon, the powerful winds at the altitudes the vehicle will cross could tear it apart. In this worst case scenario, the envelope will be cut away and the pair will be in for wild ride at supersonic speeds as the gondola free falls. A series of stabilizing parachutes will be deployed and discarded, before parachutes designed to slow their descent take over. It is hoped this strategy would be enough to provide a reasonably soft landing for the crew.

As Prescot and Elson plan a multitude of ways of broadcasting their adventure to the world, the prospect of someone selling these sorts of excursions has crossed Prescot's mind. After all, his day job is selling regular hot air balloon flights and filming them, notably providing footage for the last eight James Bond films.

"This is possible - but perhaps in the medium rather than short term," says Prescot of the feasibility of high-altitude balloon tourism.

"I bet there's plenty of people out there who couldn't wait to get the sort of view of the earth that we will on QinetiQ 1, as well as plenty who'd rather stay in doors and watch us doing it on TV! As with any tourism, it depends on the demand and then depends on whether it can be made affordable enough for anyone to go!"