Death to the space shuttle Columbia astronauts must have been painless and should have come before they could even say their prayers, missile designer and former defence official R Gopalaswami said.

At the time the shuttle disintegrated, the re-entry temperature should be at least 2,800 degrees centigrade, the retired air commodore of the Indian Air Force said.

"At this temperature the body vaporises so fast there will not be even time for the brain to register the pain," he said in Hyderabad.

Gopalaswami was formerly chief of Bharat Dynamics Limited that builds India's military missiles like Prithvi and Agni and is a key designer of hyperplane, a pet project of President A P J Abdul Kalam. The hyperplane is designed to take off like a rocket and land like an aircraft producing its own fuel from oxygen in the air during its ascent.

He said the video pictures shown on television suggested that engines that had separated from the airframe, created the streaks seen in the sky.

The de-orbiting procedure called for coordinated work of more than one astronaut and human error cannot be ruled out, he said.

Failure of insulation or very small errors [one hundredth of a degree] in the angle of attack while entering the atmosphere, or encounter with chunks of ice by the leading edge of the wing could be some of the possible technical causes for the break-up of the shuttle, Gopalaswami said.

Damage to the insulating tiles caused by the ice chunks would expose the aluminium wing to 2,000 degrees centigrade and simply melt it, he said.  

According to Gopalaswami, finding the exact cause for the mishap would be a challenge without photographic evidence. In the case of the challenger disaster in 1986 there were photographs showing what had happened.

He said, "In my view one of the possible long-range consequences of this disaster --- apart from avoidance of the Iraq war --- would be the emergence of International cooperation in space for a global Reusable Launch Vehicle mission of the type proposed by President Kalam.

"I hope our people and the government of India will see the wisdom of Kalam's recent call for a global space mission in his space summit address for energy, water and minerals".