September 03, 1999, 05:00 p.m.

Space shuttle fleet grounded as NASA finds more wiring defects

By MARCIA DUNN, AP Aerospace Writer

CAPE CANAVERAL, Fla. (AP) -- NASA has practically grounded its space shuttle fleet because inspections have uncovered a startling number of damaged wires that could endanger a mission.

damaged wiring
NASA
Technicians discovered that an exposed wire caused a short circuit that knocked out two engine computers during the most recent shuttle launch, that of Columbia in July. Similar flaws later were found elsewhere on Columbia and in the wiring on Endeavour and Discovery.

Now all flights are off until at least mid-October.

"It is a serious situation," shuttle program manager Ron Dittemore said Thursday. "We are not going to fly again until we understand what we have and get it fixed."

Both Endeavour and Discovery have dozens of wires that must be repaired or reinforced. Endeavour should have gone up in mid-September with radar equipment to map Earth's surface, Discovery in mid-October with crucial replacement parts for the Hubble Space Telescope.

The trouble began July 23, when a short circuit five seconds into Columbia's launch knocked out computers for two of the shuttle's three main engines. Because each engine has two computers and only one is needed, Columbia made it to orbit with five astronauts and the powerful Chandra X-ray Observatory.

It was believed to be the first time in 95 shuttle missions that a short circuit occurred during liftoff, by far the most dangerous part of the flight. If an engine had shut down, the shuttle would have had to attempt an unprecedented emergency landing in Florida or in Africa.

Because Columbia was still in the atmosphere -- and not in the vacuum of space -- when the short happened in the cargo bay, sparks could have ignited.

But shuttle circuit breakers are much more sensitive than those in a home or even on a plane; they immediately pop when a short occurs, halting the flow of electricity. That's what happened aboard Columbia.

The half-second short was caused by an exposed wire that had lost its insulation in one spot, allowing the wire to come in contact with a rough screw.

Workers evidently had stepped on the wire or brushed a tool or work platform against it. The damage was done at least four years ago, the last time Columbia underwent an extensive overhaul. It's possible the damage was there since Columbia's first flight in 1981; the wiring is original.

At first, NASA thought the exposed wire in its oldest shuttle was unique and perhaps the result of age. But technicians found another flawed wire on the opposite side of the cargo bay.

As a precaution, NASA ordered inspections of the wiring in its three other shuttles.

As of late this week, technicians had discovered 38 spots with exposed wiring in Endeavour and 26 in Discovery, and even more places where the wires need to be reinforced with tubes and Teflon wrapping "to bulletproof it the best we can," Dittemore said.

Atlantis has yet to be inspected thoroughly, but a quick check turned up one suspect wire.

The inspections will take at least another few weeks. Each shuttle has 200 miles of wiring; half of it is being checked, the half where workers are most likely to have damaged it.

The delays are making this the leanest year for shuttle launches since 1988, when flights resumed following the Challenger disaster. With only two more launches scheduled by year's end, there could be just four in 1999.

NASA has yet to decide which mission will go first once flights resume.

"I've told the folks that I don't want you worrying about launch dates," Dittemore said. "I want your heads down in the foxhole fixing these wires."

from this link

EVENTUALLY the number of serious wiring flaws detected in the fleet of FOUR SHUTTLES numbered 64

Any one of these could have caused a catastrophic fire. NASA Safety Officers were appalled. They thought that their catharsis had been the post-Challenger Safety Programs.  They are now following a "better safe than sorry" philosophy that has just seen them ground the Shuttle fleet in the last week of June 2002 after an instance of fuel pipe cracking was detected.


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