The entire three-man crew of the Apollo One spacecraft was killed in a rehearsal today when fire swept the Saturn rocket on its launching pad.

The three - Virgil Grissom, Edward White and Roger Chaffee - were due to blast off into space on February 21. Technicians and astronauts had begun today the first of a series of tests leading up to the first Apollo mission.

Navy Lieutenant-Commander Chaffee, aged 31, had never flown in space before. Lieutenant-Colonel Grissom, 39, was the first American to make two flights. Air Force Lieutenant-Colonel White, 35, made America's first space walk. The men were all in the capsule on top of the rocket when the fire and explosion occurred.

The capsule is 218 feet above the ground. Workmen who tried to reach the astronauts were driven away by the dense smoke.

The rocket was in a hazardous condition when the fire broke out because there was some fuel aboard, but a spokesman said the fire was out. He said there were several hundred people in the vicinity, most of them in a blockhouse on the site.

It was the first death of an astronaut while actively engaged in the American space programme, although two astronauts were killed in an air crash on the McDonnell aircraft factory in St Louis, Missouri, shortly before they were due to make a flight in the Gemini programme.

Today's disaster, and the probable severe damage to the spacecraft, sets back the US programme to put a man on the moon by many months, informed sources said.

The Apollo programme is already delayed by more than six months by accidents during testing programmes of its second stage. The tragedy means that late 1969 is now the earliest an American can set foot on the moon.

Most Experienced

Virgil Grissom, with two space trips behind him, was one of the senior and most experienced men in the space team, awarded the Distinguished Service Medal for his suborbital flight in 1961, and again for his trip with John Young when they became America's first space "twins" in March 1965.

In spite of the rigours of the training the astronauts undergo, and the scientific expertise demanded of them, Grissom demonstrated a characteristically pioneering nonchalance on the occasion of the Gemini shot, when he smuggled a bologna sandwich into the capsule and ate part of it during the flight.

On June 3, the same year, Major Edward White stepped out of Gemini-4, 150 miles above the Pacific, and walked in space. He was the second man to do so: Russian Colonel Leonov had already been out.

He, too, found the space experience too enthralling to let himself be totally bound by scientists regimen. Twelve minutes outside, they had told him, was the limit - but at the end of 20, White was still out there, posing for his pilot's cine-camera until, with some reluctance, he obeyed the orders beaming up at him from Houston.