Shuttle: Outdated model led to 'no danger' judgement

A computer model that convinced Nasa the Columbia astronauts were in no danger from damage done to the shuttle by a piece of falling debris was outdated and lacked the right information, accident investigators said.

The analysis by Boeing engineers concluded little harm was done to Columbia’s left wing by a chunk of hardened foam that came off the fuel tank during lift-off. It was a crucial element in the belief by Nasa that the seven astronauts would return safely.

But the analytical model had never been used before to predict damage from falling debris during an actual shuttle flight, former astronaut Sally Ride, one of the board’s newest members, said in Houston, Texas.

A team of engineers involved in the study also realised they needed more data. They asked Nasa officials to seek pictures of the orbiting shuttle, but no pictures were ever taken, Ride said.

In the two months since the disaster on February 1, attention has focused on flyaway foam insulation as a major suspect in causing the breach in Columbia’s left wing. Superheated gases entered the wing, causing the shuttle to break apart over Texas on its way to a Florida landing.

Nasa’s video of the launch debris striking the wing was not clear enough. The engineers needed to know more about the speed and location of where the falling foam hit on the wing and the size of the foam itself, in order to properly assess the potential damage.

“If you had given them good information to start with, they could have given you an answer,” she told reporters, referring to the analytical programme used by engineers to assess damage. “But there wasn’t enough information. So you’re asking them to predict where something’s going to hit but you can’t tell them how it started.”

All the unknowns “led this whole group to say, ‘Get us more data, get us some photos’.”

Speaking after yesterday’s hearing into the cause of the accident, Ride said the request for photos came out of a meeting that occurred on January 21 – just five days after Columbia was struck by foam.

“It looks as though it was literally a miscommunication,” Ride said, “where one group was saying, ‘Let’s wait until the analysis is complete to see whether we need photos’ and then that was interpreted as, ‘There will be no photos.’ In other cases, it was for different reasons. It’s a pretty complex story. It’s a real web of interpersonal communications.”

Ride said this web apparently stretched even up to the astronauts aboard Columbia, who accepted the engineers’ conclusion that they would be in no danger during their descent through the atmosphere on February 1.

That conclusion by Boeing engineers, after just a week or so of analysis, was accepted by virtually everyone. But other company engineers testified earlier that the space shuttle’s outer thermal protection layers were never meant to be struck by anything stronger than perhaps bugs or rain – certainly not a 2lb piece of foam.

Nasa became accustomed to the 140-plus debris strikes that occurred on every flight. Such damage was viewed as a nuisance that called for more maintenance, these engineers told the board. The damage wasn’t always caused by flyaway foam, however.

Recalling her own tenure as an astronaut unaware of the many life-threatening problems affecting a space shuttle, Ride said, “I’m not sure that it’s an appropriate analogy, but I’d never heard about O-rings before the Challenger accident.”

Ride, a member of the presidential commission that looked into the Challenger disaster, added that Nasa’s same acceptance of routine hazards was evident then as well: ”You survived it the first time, so suddenly it becomes more normal.”

The chairman of the Columbia Accident Investigation Board, Harold Gehman Jr, a retired US Navy admiral, said neither his panel nor Nasa was satisfied with the model that was used in the Boeing analysis during the flight. He described it as a spreadsheet, not a computational model, and noted that it was based on testing of much smaller debris – not anything nearly as large as what hit Columbia 81 seconds after lift-off.

Investigators believe the debris caused a breach somewhere along the leading edge of the left wing.

So far, about 32% of Columbia has been recovered.

Gehman plans to release in the next few days a set of interim recommendations to Nasa. These will include adopting non-destructive measures for gauging spacecraft age and photographing shuttles in orbit every time they fly.