Nasa rejects launch damage theory

The search for debris has been extended

Nasa is moving away from the theory that insulation foam seen to peel away from Columbia's external tank and hit the vehicle's left wing was responsible for the disaster.

Ron Dittemore, Nasa's shuttle programme manager, has consistently doubted the theory that the foam caused the accident.

We apparently will never know if they suffered

Gadi Ramon, brother of Israeli astronaut Ilan Ramon

And at a news conference at the Johnson Space Center, Houston, on Wednesday, he again stated his view that the reason for the disaster lay elsewhere.

"It doesn't make sense to us that a piece of debris could be the root cause of the loss of Columbia and its crew," Mr Dittemore said. "There's got to be another reason."

Earlier relatives of Israeli astronaut Ilan Ramon, said that the doomed crew of Columbia would have known something was wrong with the spacecraft for more than a minute before it began to break apart.

Nasa's investigation has focused on the insulating foam

"It's very difficult, as if I'm with them and I try to imagine what they went through," Eliezer Wolferman, father of Colonel Ramon said.

"One second is like 20 years," he added.

Extensive testing

In his briefing Mr Dittemore said investigators had studied video of the launch and the moment the foam hit the wing and were now trying to improve the quality of the pictures.

But he said from what they could see already, there were "no gross, large areas of damage" to the wing.

When Nasa officials found out that the wing had been hit on launch, the event was modelled by engineers to work out what might have happened.

SHUTTLE BREAK-UP

Re-entered atmosphere at 12,500 mph (20,000 km/h)

Disintegrated 40 miles (65 kilometres) above the Earth

Debris scattered over Texas and Louisiana - reports now being checked of sightings in California and Arizona

Click here for a step-by-step guide to the disaster

The engineers estimated the foam block weighed about 1.2 kilograms (2.6 pounds) and measured 50 centimetres by 40 by 15 (20 inches by 16 by 6).

Even when these values were altered and the angle of strike varied, the engineers could find no scenario in which significant damage would be done to the vehicle.

"We doubled the local air velocity, we were conservative on the weight and we were using a tool that we knew over estimated damage. We could find no safety of flight concerns"

Nasa, which has expanded its search for debris, said it hopes to review footage taken by a US military helicopter above Texas. This may include pictures of the shuttle's re-entry into the Earth's atmosphere.

Nasa officials also want to examine amateur video footage taken of the shuttle over California which is said to show the craft breaking up.

Remains returned

Nasa teams are now in California and Arizona to investigate reports of debris landing there.

Authorities said that material found in the two western states could be from the wings. This could lend weight to the possibility that the shuttle was experiencing problems sooner than originally thought.

SHUTTLE CREW

Commander Rick Husband, US

Pilot William McCool, US

Michael Anderson, US

David Brown, US

Kalpana Chawla, US

Laurel Clark, US

Ilan Ramon, Israel

Click here for profiles

"Early debris early in the flight path would be critical because that material would obviously be near the start of the events," said a senior Nasa official, Michael Kostelnik.

"It would clearly be very important to see the material earliest in the sequence."

Ilan Ramon's brother, Gadi, said he had been told by Nasa officials that the astronauts most likely perished as soon as the shuttle began to disintegrate.

"We apparently will never know if they suffered," he told an Israeli newspaper.

His brother's remains have now been identified using DNA and dental records, Israeli reports say.

His body will be flown to Israel in the coming days after a service in Texas.

"This is a relief to all of us, especially the family," Brigadier General Rani Falk, an Israeli air force attache in Washington, told the Associated Press.

Nasa has reportedly recovered some remains of at least three other crew members but has not yet released their names.