Shuttle Probe Shifts Back to Intensive Sea-Floor Search

A major focus of the probe into the explosion of the space shuttle Challenger has returned to the Atlantic Ocean, where investigators suspect the definitive answer to what caused the accident rests.

Five hundred people and 15 vessels now work on the Challenger salvage operation, searching 400 square miles of ocean floor in one of the most ambitious deep-sea fishing expeditions ever.

Fitting Pieces Together

At a block-long warehouse four miles across the Florida scrub from the silent space shuttle launching pad, engineers piece together the recovered remains of Challenger like paleontologists fitting together dinosaur bones.

So far, the Navy-led search has not found the joint on the right solid rocket booster that is suspected of failing after liftoff, leading to the explosion. But the salvage team has hope; it has photographed parts that fit eight feet away on the booster.

National Aeronautics and Space Administration officials say they hope also to discover new truths about all their shuttles--things they like to call “fracture mechanisms and failure modes.”

Hearing at Space Center

The underwater search has regained the spotlight now that members of the presidential commission investigating the accident have concluded that NASA’s decision-making process leading to the ill-fated launching was “clearly flawed.” On Friday, the commission will hold its first hearing at the Kennedy Space Center “on results to date of the accident analysis.”

So far, the operation has recovered 8% of the shuttle’s orbiter, 9% of its giant fuel tank and 5% of its boosters. There has been no trace of the cabin that held the seven crew members. Nevertheless, NASA believes that, within two to three months, it could find everything relevant to the investigation. Edward O’Connor, the Air Force colonel leading the search effort for NASA, believes 90% of the shuttle could be recovered within six months.

On Wednesday, much of the operation had ground to a halt because of broken sonar devices, winch problems and persistent rough seas. A nuclear submarine equipped with wheels to traverse the ocean floor--crowded with twice its normal complement to accommodate a 24-hour schedule--had returned to port to let crew members stretch their legs.

The facts of the search alone are daunting: a complex machine blasted to smithereens, dropped into the sea from 10 miles up, scattered over an area the size of a small county and buried under as much as 1,200 feet of water.

One-Foot Visibility

Visibility at those depths can shrink to a foot. Surface currents move at a swift four knots. An estimated 400,000 pounds of solid rocket fuel, unexploded, lies on the bottom.

Ships towing sonar sensitive enough to detect a conch on the ocean floor have been plying the search area like lawn mowers. As of Wednesday, they had scanned about 200 square miles in what officials described as a time-consuming, boring and often frustrating process.

“It’s like taking a quarter of a toothpick and tying it to three feet of string, then dragging it through a bathtub and trying to cover every square inch,” said Navy Lt. Cmdr. Deborah Burnette.

Divers or one of several submarines and smaller “submersibles” inspect the objects the sonar has mapped. Pieces of the shuttle are videotaped and photographed and then they are hauled up by basket, manipulator arm or 100-ton crane.

Cost of Search a Secret

The cost of the search and salvage has remained one of NASA’s secrets. Nevertheless, Burnette said that published figures of $50,000 a day are gross underestimates.

Meanwhile, in the giant warehouse at Kennedy, aircraft accident analysts for the National Transportation Safety Board on Wednesday were scrutinizing soot patterns, tear directions and metallurgical data on the retrieved wreckage to see where flames first flared and what exploded against what.

Eventually, their conclusions are to be compared with findings from the shuttle’s telemetry--the electronic readings of its vital functions in the 73 seconds before it blew up.

“By combining that information with information from the debris, we should get a hard story that hangs together,” O’Connor confidently predicted. “ . . . It’s one big detective story. And we’re certainly not at the last page of that story.”

Fishermen Perturbed

The scallop fishermen along central Florida’s space region seemed particularly perturbed by the salvage delays. The are being battered by a bad season and could do without this unexpected invasion of their turf.

But, on Tuesday, they sensed a glimmer of hope, based on rumors emanating from the Holiday Inn bar: Was it true, fishermen asked O’Connor at a briefing, that the salvage teams had happened on shrimp of near-mythic proportions?

O’Connor said he would keep his eyes peeled.