Hunt goes on for shuttle parts, cause of crash

Crews combed suburban gardens and remote Texas woodlands for the remains of space shuttle Columbia yesterday as experts focused on a heat surge on the left side of the doomed spacecraft in the early investigation of why it disintegrated.

For a third day, hundreds of police and soldiers fanned out across east Texas and Louisiana in a search for debris and the remains of the seven astronauts who perished on Saturday when Nasa's oldest shuttle broke apart high over Texas.

Body parts, fragments and pieces of the shuttle were strewn across an area more than 160 kilometres long and 16 kilometres wide, much of it in the thick Texas forests known as the Piney Woods.

Nasa scientists pored over reams of data for clues, focusing initially on a sharp heat spike along Columbia's left side and an unusually sharp corrective manoeuvre recorded just before the vehicle disintegrated.

An independent inquiry board appointed by Nasa also was to meet for the first time yesterday, led by retired Navy Admiral Harold Gehman, who co-chaired an independent commission that investigated the attack on the destroyer USS Cole in Yemen.

That review will run parallel to Nasa's internal review. The New York Times reported yesterday that Nasa had removed five of the nine members of a safety panel after it warned that the shuttle would face safety problems if the agency's budget was not raised.

Bill Readdy, Nasa Associate Administrator for Space Flight, a former shuttle commander who flew three times, said Nasa was keenly aware of the need for safety upgrades.

"This is far from something being ignored, it is a constant part of what we do. We have made tremendous upgrades to the shuttle over the past 10 years.

Even though it looks the same on the launch pad, from the tip of the external tank to the hold-down posts of the solid rocket boosters, the entire vehicle has been continually upgraded," he told reporters via a video hookup.

Columbia blew apart just 16 minutes before it was due to land in Florida, ending a 16-day science mission, and almost 17 years to the day after the shuttle Challenger exploded during liftoff.

Data beamed down from Columbia - which first flew 22 years ago - showed the temperature on part of the left fuselage spiked 32 degree celsius in five minutes as the spacecraft was reentering the atmosphere.

Four minutes later, "we had an increase in drag on the left side of the vehicle," Shuttle program manager Ron Dittemore told a news conference on Sunday. "The flight control system was countering that drag by trying to command the vehicle to roll to the right-hand side. ... Soon after, we had loss of signal."

Dittemore said the flight control surfaces moved to a degree "outside our family of experience."

There was no "smoking gun" to focus on, but Dittemore added: "We are gaining some confidence that it was a thermal problem, rather than ... a structural indicator."

A shuttle endures 1,650-C temperatures when it re-enters the Earth's atmosphere, but is protected by tiles that shield it from heat.

Dittemore said Columbia's left wing was banged 80 seconds after launch by insulation from its fuel tanks, but engineers believed it caused no serious damage to the heat shield.