Shuttle Carried No Booster Sensors : Reliability of Rockets Made Detectors Seem Unnecessary, NASA Chief Says

Neither Challenger’s crew nor NASA’s mission controllers in Houston received any warning of the impending explosion of the shuttle because the two booster rockets were considered so reliable that they carried no sensors that might have detected a rupture in their casings, William R. Graham, NASA’s acting administrator, said Sunday.

There was no “credible” belief that the boosters could fail, he said, even though the boosters are such an essential part of the vehicle that any failure would be considered catastrophic.

Graham likened putting such sensors on a booster to having sensors on an airplane to signal that the wings had fallen off.

Earlier shuttle flights did in fact have sensors to verify booster performance; but they were removed to save weight after it was felt that the solid rocket boosters were performing well.

‘Never Compromised’

In interviews Sunday on all three major television networks, Graham asserted that the shuttle system is fundamentally sound and added: “We never compromised on safety.”

Challenger exploded 73 seconds after launch Tuesday morning. National Aeronautics and Space Administration officials Saturday night released film that showed “an unusual plume” emanating from Challenger’s right solid rocket booster 13 seconds before the explosion.

The rupture of the booster--which eventually caused the external fuel tank to explode--is now believed to be the most likely cause of the conflagration, which destroyed Challenger and killed its seven crew members.

In Los Angeles, two Rockwell officials familiar with the disaster inquiry said still-unreleased NASA data shows that the three main engines of the Challenger spacecraft experienced a power loss just milliseconds before the shuttle ex ploded, possibly as a result of damage to the external tank or to the fuel supply line from a leaking solid rocket booster.

The power loss was noted between one-tenth and one-one hundredth of a second before the explosion, they said.

According to the Rockwell sources, who did not want to be identified, the right solid rocket booster had seconds earlier suffered a 3% loss of power, or a loss of about 100,000 pounds of thrust.

Although Graham and other NASA officials have refused to draw a definite link between the fiery plume and the subsequent explosion pending a more complete investigation, Graham said the phenomenon was one never before seen and was “very surprising” to engineers watching new footage of the launch taken from a different angle than that seen initially by television viewers.

Shuttle crew members most likely never had a hint of any structural failure in the booster. The sophisticated instrumentation that monitored pressure, vibration and temperature changes within the rocket boosters during the first shuttle missions was reduced by about half after the rockets proved themselves, a NASA spokesman said. The remaining sensors were not the type that would detect the rupture in the booster casing that occurred Tuesday.

NASA’s confidence in the boosters was based largely on the virtually problem-free performance during the 24 previous shuttle flights, leading NASA engineers to believe there was little likelihood the boosters would fail.

Little Benefit

In any case, because the boosters cannot be controlled once they are ignited, the crew would receive little benefit from such sensors. Graham noted that there is little that can be done to save a shuttle crew in the event of catastrophe in the initial, critical 2 minutes of any launch.

And even if the crew had the benefit of sensors, its options would have been limited, according to NASA.

The crew might have been able to jettison the rocket boosters, but it would have been difficult for the orbiter to stay clear of them and the huge external fuel tank, Graham suggested.

But a NASA spokesman said later that shuttle crews have never trained for such a maneuver. And NASA documents state that such an escape is possible only after the boosters have completed firing. That would have been nearly a minute after Challenger blew up.

But even if the orbiter had been able to get out of the way of the boosters and the external tank, it still would have faced the near impossible task of “ditching” at sea.

NASA has recovered a nose cone from one of the solid rocket boosters with its separation engines unfired--which supports the belief that Challenger commander Francis R. Scobee did not realize the imminent danger, agency spokesman Jim Mizell said.

Second Nose Cone

NASA officials believe that they may also have located the nose cone of the second rocket booster, giving them hope that additional sections of the rocket boosters may be recovered to provide further clues as to what caused the shuttle disaster.

Seconds after the external tank and the shuttle exploded Tuesday, an Air Force safety officer deliberately detonated both boosters because one of them began veering toward a populated area.

Meanwhile, NASA investigators are looking at data sent by both boosters to Mission Control in Houston before the explosion. Much of that data was not immediately available to controllers, Mizell said.

Graham appeared on NBC’s “Meet the Press,” ABC’s “This Week With David Brinkley” and CBS’ “Face the Nation.”

He said he is confident that NASA will be able to make a quick determination of the cause of the Challenger explosion and resume the shuttle program.

“This is a fundamentally sound system,” he said. “It’s gone through 24 successful flights. There was obviously an accident. There’s a problem there. But the overall configuration and design we believe to be fundamentally sound and we believe it won’t take a very long time to get the problem corrected.”

Graham refused to comment directly on reports that many NASA officials expect to have the program back on track in time for the scheduled June 24 launch of the Columbia shuttle. “Nothing ends here. Our flights and our journeys continue,” he said.

NASA, Navy and Coast Guard officials worked throughout Sunday gathering shuttle debris in the Atlantic, expanding the surface search area to 6,300 square miles of the ocean. NASA officials said they still have not identified a large submersed object that may be a part of the Challenger.

About 10 tons of debris have been recovered, according to Coast Guard Cmdr. James Simpson. “They’re finding less and less. They’re finding a lot of empty ocean today,” he said.