WASHINGTON - Investigators have found a new threat to future space shuttles - a 40-pound bolt fragment that could fly off during launch and smash into the spacecraft with catastrophic results as it races toward orbit.
Members of the board searching for the cause of Columbia's destruction said Thursday they found radar evidence that a piece of a 2-foot-long bolt that joins the solid-rocket boosters to the shuttle's external fuel tank may have flown loose during the launch.
There is no evidence that the bolt fragment hit Columbia, but board member Air Force Maj. Gen. John Barry said, "It has the potential to be catastrophic."
Barry said the discovery does not change the board's working scenario that Columbia was damaged by a chunk of foam insulation that peeled off the fuel tank and smashed into the craft's left wing during launch, damaging the heat shield. It's thought that superheated gases entered the hollow wing and melted it from the inside during re-entry Feb. 1. Columbia broke apart, killing seven astronauts and scattering debris over Texas and Louisiana.
Barry said that while investigating the role that the external tank may have played in Columbia's destruction, engineers looked at launch radar records of the craft and spotted an image of an object near the shuttle just moments after the solid rocket boosters were ejected from the external tank.
Investigators determined the image could be a fragment of the bolt that somehow was thrown free during booster separation. The bolts are normally exploded to free the solid rockets. Fragments of the bolts are supposed to be captured by a cylinder called a bolt catcher.
Tests show that "the bolt catcher is not as robust as it should be," said retired Navy Adm. Hal Gehman, the board chairman.
Barry said the top of the bolt catcher came apart in the tests. If this happened during launch, a 40-pound chunk of the bolt would have been ejected and could have slammed into the space shuttle.
The bolts attach the 150-foot-tall solid rocket boosters to either side of the shuttle's external fuel tank. When the solid rockets are burned out, explosives sever the bolts, separating the boosters, which then fall back into the ocean for later recovery.
Barry's news conference followed a public hearing during which some of the nation's top space experts discussed NASA struggles to fly the space shuttle and build the international space station with budgets that were cut to the bone.
The experts said NASA moved money from the space shuttle program to pay for other programs. The board is investigating whether this compromised safety on the shuttle.