U.S. investigators begin tests Thursday to determine if a piece of hard foam that hit the space shuttle Columbia during launch could have caused the damage that doomed its return. The probe is winding down as investigators prepare to write their report for the government and Congress.
Technicians at a San Antonio, Texas, research laboratory have designed tests to shoot hard insulating foam at high speeds at a full scale model of space shuttle wing.
They want to reproduce what happened after pieces of foam ripped away from the shuttle Columbia's external fuel tank during launch and smashed into the left wing at speeds of up to 250 meters per second. Investigators have estimated that the foam hit the wing with a force close to one ton.
Columbia disintegrated upon re-entry 16 days later from what the investigators call a breach in the leading edge of the wing that let hot atmospheric gases penetrate the orbiter. The chief theory is that the foam strike cracked the wing.
But the board chairman, retired Admiral Harold Gehman, says they may never be able to prove that foam was the culprit or whether micrometeorite or orbital debris caused the problem. He says that is why the probe has focused broadly on shuttle management and operations practices that might have led to lax attitudes regarding foam shedding and wing durability.
"It has caused us to look much more broadly at the material condition and the operation of the shuttle program probably more broadly than any review in the past," he said. "This probably is a blessing in disguise, particularly if NASA's thinking about operating the shuttle for another 20 years. It probably is a good thing that we're doing such a broad review."
Whether or not shedding foam can be linked to Columbia's demise, investigators have found that shuttle external fuel tanks have lost foam since the first shuttle flight in 1981. They say that the frequency of the shedding without disaster caused the U.S. space agency NASA to see foam loss as a maintenance problem rather than a safety issue.
In fact, Admiral Gehman says NASA workers and contractors have described a relaxation of NASA safety precautions and inspections in recent years after a period of rigor following the Challenger explosion in 1986.
"They've characterized it as a change in posture from one in which you had to prove that it was safe to fly to one in which you had to prove that it was unsafe to fly," he said. "Of course, there are a lot of reasons for this. You have 112 successful flights. You've got to assume you're doing something right."
The shuttle investigating panel will move next week from Houston, where it has operated since February, to Washington, where it will write its report on the shuttle accident and make recommendations for operating the space fleet more safely. Among those the board is considering is a demonstration flight before shuttles return to full-time service.