NEW YORK: The crew of the doomed shuttle Columbia were violently spun around in the cabin as the spacecraft disintegrated on re-entry, the National Aeronautics and Space Administration (Nasa) said in its final report on the 2003 tragedy that included safety recommendations.

The 400-page report took four years to complete and its conclusions will be used in configuring the future Orion spacecraft that will eventually replace the current fleet of three shuttles due to be retired next year.

CREW MADE RIGHT MOVES 'The crew were doing everything they were trained to do, and they were doing everything right.' Astronaut Pam Melroy, deputy project manager for the investigative team, on the Columbia crew ... more Final moments of Columbia THE Columbia's crew likely knew for as long as 41 seconds that they did not have control of the orbiter before they were knocked unconscious. Nasa's reconstruction of their final moments: On the Columbia's re-entry into the atmosphere 20km over Texas, hot atmospheric gases blast inside through a hole punched by a piece of insulating foam. ... more

A chunk of insulation that had broken off from Columbia's external fuel tank during takeoff gouged the shuttle's left wing heat shield, causing the craft to disintegrate as it re-entered the Earth's atmosphere over Texas on Feb 1, 2003.

The seven astronauts onboard slipped into unconsciousness within seconds and their bodies were whipped around in their seats as the space shuttle spun out of control, investigators said in the new report. While the astronauts' upper bodies flailed, the helmets that were supposed to protect them ended up battering their skulls.

But better equipment would not have saved the astronauts, the report said.

'The break-up of the crew module and the crew's subsequent exposure to hypersonic entry conditions were not survivable by any currently existing capability,' the investigators wrote.

The report is the most extensive study ever performed on how the astronauts died and what could be done to improve the chances of survival in a future accident. Nasa deputy associate administrator Wayne Hale told reporters on Tuesday that the document was 'the final report on Columbia'.

A 2003 report had presented a scathing indictment of a 'broken safety culture' at Nasa. It criticised managers as complacent and too tightly focused on scheduling and budgetary pressures.

Columbia's fate had been all but sealed during its ascent when a piece of insulating foam, which weighed about 0.75kg, struck the craft's left wing. The foam punched a hole that would later allow superheated gases to cut through the wing's interior like a blowtorch.

Mission managers, however, did not order inspections because the prevailing belief was that foam strikes were relatively harmless.

The new report found that the crew knew for as long as 41 seconds that they did not have control of the orbiter before they were knocked unconscious.

Warning signs that things were going badly wrong included alerts about tyre pressure, landing gear problems and efforts by the computerised flight system to compensate for the growing damage.

The craft went into a nauseating flat spin and the pilot, Commander William McCool of the US Navy, flipped switches in a futile effort to deal with the problems.

The troubles came on so quickly that some of the crew members did not have time to finish putting on their gloves and helmets. None had the visor down. But the report blamed it on design deficiencies.

'The crew were doing everything they were trained to do, and they were doing everything right,' astronaut Pam Melroy, deputy project manager for the investigative team, said at the news conference.

The sudden loss of cabin pressure asphyxiated the astronauts within seconds, the investigators said.

'On behalf of their colleagues and families, I can say that we are relieved that we discovered this,' Ms Melroy said.

Even if the safety gear had worked, the astronauts would have died due to the winds, shock waves and other extreme conditions in the upper atmosphere, the report said.

Killed in the disaster along with pilot McCool were commander Rick Husband, crew Michael Anderson, David Brown, Kalpana Chawla, Laurel Clark and Israel's first astronaut Ilan Ramon.

The Columbia tragedy was the second shuttle accident since the programme was launched in 1981. The Challenger shuttle blew up 73 seconds after lift-off, killing seven astronauts on board on Jan 28, 1986.

Nasa said it has already incorporated many lessons from the Columbia accident in the design of the Orion spacecraft.

The capsule design is hardier than the delicate, airplane-like shuttle and rides on top of the rocket, out of the range of launching debris.

Within the capsule, Nasa has called for upgraded seat hardware that will provide more restraint. New pressure suits will have helmets that provide better head protection.

NEW YORK TIMES, LOS ANGELES TIMES, ASSOCIATED PRESS, AGENCE FRANCE-PRESSE