WASHINGTON (AP) _ NASA researchers in Virginia are sending wind-tunnel results to Johnson Space Center that experts believe may help determine the amount and location of damage to Columbia's left wing that permitted superheated air into the shuttle during its descent.
The testing, conducted since last week at NASA's Langley research facility in Hampton, Va., heated a ceramic, scale-model of the shuttle orbiter to mimic unusual temperature readings experienced by Columbia just before its breakup on Feb. 1.
Engineers placed the model, about 12 inches long, in a wind tunnel capable of blowing air over its wing surfaces at speeds up to six times the speed of sound, or about 4,450 miles per hour _ still far slower than Columbia was flying when it came apart, and under significantly different atmospheric conditions.
Additional aerodynamic testing will continue into next week. But results from thermal tests have been completed and sent this week to Johnson Space Center in Houston, Langley spokesman Keith Henry said Friday. NASA officials declined to disclose results of the tests or characterize whether they were successful.
The wind tests were ordered by experts at Johnson, not the accident board investigating the Columbia disaster. But NASA was expected to share its findings with the board, Henry and others said.
In addition to the wind tests, Henry said, engineers at Langley used powerful computers to try to simulate the conditions experienced by Columbia in its final moments. Experts were hopeful that changes they made to the surface of the shuttle model resulting in similar temperature readings would help them determine what might have happened to Columbia's left wing.
The accident board has said previously that Columbia almost certainly suffered a devastating breach along its wing and possibly its wheel compartment that allowed searing air to seep inside the shuttle during its fiery descent at nearly 12,500 miles per hour. Unusual temperature readings inside the wing began to occur within minutes of its re-entry, far off the coast of California.
NASA acknowledged that it will need to make important assumptions from its testing because the wind tunnel at Langley was unable to simulate the speed at which Columbia was flying when it disintegrated.
``It's not an exact simulation of the heating seen at higher speeds,'' Keith said. ``But it's good enough to give us a good indication of what was happening at higher speeds.''
The wind tests were just part of the bigger investigative picture. The accident board was focused intently on how foam insulation was applied to NASA's space shuttles _ territory with a troubled track record.
One leading theory is the insulation or the heavier material beneath may have damaged Columbia during liftoff, enough to trigger a deadly breach as the spaceship hurtled toward its Florida landing.
The foam insulation is applied at a Lockheed Martin plant in New Orleans. More of the foam is applied about a month before liftoff in several small areas of the tank needing touchup at NASA's Kennedy Space Center in Florida.
The investigation board has visited both sites and is going back for a second, harder look at the techniques _ and safeguards _ used.
``That is getting a good bit of attention by more than one of the groups,'' said NASA's Steve Nesbitt, referring to the board's three working groups. ``A couple of the groups are looking at the thermal protection on the tank in this area, and some of them will be going back to see the manufacturing facilities, to talk to the people involved. So it is getting some special attention.''
Nesbitt said Thursday the theories that focus on the left side of Columbia _ where all the overheating and other problems developed _ ``will be getting the earliest attention.'' The board suspects a breach in the left wing led to the shuttle's breakup. 1. All seven astronauts were killed.
Searchers gathered early Friday in Caliente, Nev., to search the desert hills for what is believed to be a piece of Columbia debris that was tracked falling to Earth by air traffic control radar.
Imagery, trajectory and ballistics experts have been analyzing video images of the shuttle as it flew across California and the Southwest. National Transportation Safety Board officials are using those findings to hunt for any unusual radar trackings in an attempt to pinpoint wreckage.
About 25,000 pounds of Columbia debris is now at Kennedy.
Air Force Maj. Gen. John Barry said earlier this week he and other board members are reviewing NASA's troubled history of foam coming off the so-called bipod area, where a pair of struts holds the tank to the upper belly of the shuttle.
That is the spot where a chunk of foam came off 81 seconds into Columbia's flight Jan. 16; the debris slammed into the left wing during launch. An engineering analysis days later concluded any damage was minimal and posed no safety threat.
NASA officials said that finding was based, in part, on the fact that previous foam impacts had not caused severe damage.