Up, up and away —into the ‘impossible’

Press, 18 March 1987, Page 21

Up, up and away —into the ‘impossible’

By

LAURENCE MARKS

Somewhere outside New York this summer, the British industrialist Richard Branson will climb into the pressurised aluminium capsule of a hot-air balloon the height of Nelson’s Column, float up to 9000 metres and attempt to cross the Atlantic.

The feat is said, for technical reasons, to be impossible. Nowadays, hot-air ballooning is primarily a week-end sport, but it traces its ancestry back to the origins of manned flight. It was invented by the Montgolfier brothers in France just before the Revolution. The first flight albeit short by Jean Francis de Rozier a ad the Marquess Francois d’AYlandes was

from the Bois de Boulogne outside Paris in 1783, burning straw and wool to supply the hot air.

Not long afterwards, de Rozier was killed when a balloon in which he and his passenger were trying to cross the English Channel caught fire. This, the world’s first aviation disaster, quickly killed interest in the hot-air balloon, though the gasfilled variety was used in warfare, and eventually (in the form of the airship) as transport, for the next century and a half.

In the late 19505, hot-air ballooning was revived in the United Stated Two Americans, Ed Yost and Bon Picard, in 1963

became the first exponents to cross the English Channel, but travel over long distances has remained difficult.

The reason is that, in order to fly at all, a hot-air balloon needs to maintain a temperature differential of about 38 degrees Celsius between the envelope and the outside air. It is thought impossible to carry enough fuel to sustain that temperature for a flight across the Atlantic.

A helium-filled balloon, manned by the Americans Ben Abruzzo, Maxie Janderson and Larry Newman, crossed the

ocean from Maine to Brittany (5000 km in 1978 after 137 hours aloft. But the longest flight by a hot-air balloon so far was by the American Harold Warner from Calgary to Nebraska (1500 km It lasted 27 hours and 23 minutes.

Branson and his fellow crewman, Per Lindstrand, are now hoping to crack the record by harnessing solar energy. The four liquid propane fuel-burners will be used only during takeoff and to top up the hot air during the hours of darkness. The main source of heat will be the sun. This should makepos-

sible a flight of 100 hours — long enough to cross the Atlantic.

The balloon will take off at dawn, when the wind is still and the sun is about to rise. It

The balloon will be the largest ever built, with an envelope capacity of 2.3 million cubic feet, 59 metres tall and 52m across, capable of lifting a payload of 12,500 kilograms. It will have a double skin. The inner skin will contain the hot air. The outer skin will act as a sort of greenhouse, allowing maximum infra-red radiation absorption and minimum heat loss. The burners have been designed to operate most efficiently at altitudes between 8000 m and 10,000 m, where oxy-

should climb at 32m a minute to reach its cruising height around noon. Throughout the climb, the sun will heat the air contained within the envelope. This solarheating effect should continue throughout the afternoon. Nearly 10 tonnes of propane will be carried in cylinders fixed outside the capsule in order to act as floats in case the crew are forced to ditch. If their mathematics are correct, they should be over southern England some time on the fourth or fifth day.

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