Part of Fuel Tank Believed Found

KENNEDY SPACE CENTER, Fla. —  A small manned submarine operating in waters 100 feet deep off the Florida coast Sunday retrieved a 15-foot-long hunk of metal from the ocean floor believed to be part of the space shuttle Challenger’s external fuel tank.

The recovery, if confirmed by National Aeronautics and Space Administration officials, could provide an important piece of evidence in the search for the cause of the disaster.

It was the tank, filled with half a million gallons of volatile liquid hydrogen and liquid oxygen, that exploded 73 seconds after launch, destroying the shuttle and killing its seven crew members.

Although a leak in the shuttle’s right solid rocket booster is widely thought to have triggered the explosion, there has been new evidence that a cold spot on or near the external tank could have chilled the seals on the nearby rocket, causing them to become too rigid to seat properly.

The debris thought to be part of the 154-foot fuel tank is 15 feet long and 8 to 14 feet wide, Navy Lt. Cmdr. Deborah Burnette said.

Meanwhile, an unmanned Navy submarine five miles closer to shore photographed what appears to be pieces of a motor that may be part of the shuttle’s main engines.

The presidential commission investigating the disaster said it has virtually ruled out any malfunction in those engines or the orbiter itself, however.