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  sci-tech > space > story pagecorner  

64 cases of wiring problems found on shuttle fleet

wires
Inspectors are searching for wiring defects like this one that caused a short on the shuttle Columbia

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Next launch no earlier than mid-October

September 3, 1999
Web posted at: 11:37 a.m. EDT (1537 GMT)

By Robin Lloyd
CNN Interactive Senior Writer

(CNN) -- NASA technicians inspecting two orbiters in the space shuttle fleet have found more than two dozen wiring problems like one that caused a potentially life-threatening short circuit on a July shuttle flight.

Inspectors found wiring defects in 38 locations on Endeavour and 26 locations on Columbia. It was the latter vehicle that carried John Glenn on his landmark return to space last fall.

Less than half of the sites showed nicks and other inadvertent damage like the exposed wire that caused a short circuit five seconds after Columbia's launch on July 23.

NASA managers decided Thursday to expand their inspection to cover all 100 miles of electrical wiring in each of the four shuttle orbiters, said Space Shuttle Program Manager Ron Dittemore. Previously, the inspection was to cover only wiring in the four shuttles' payload bays.

As a result of the extra time for further inspections and repairs, neither of the shuttle missions originally planned for launch in the next several weeks will go up before mid-October.

"We're looking at all the wiring on the entire vehicle from the nose to the tail," said George Diller, a spokesman at NASA's Kennedy Space Center. "We're trying to do work to fix this problem so we don't have to spend time on it again in the future."

liftoff
Columbia  

Endeavour had been set for a September 16 launch for a mission to use a huge radar antenna to map Earth. Discovery was set for an early October launch for a mission to repair gyroscopes on the Earth-orbiting Hubble Space Telescope.

Shuttle managers especially want reliability for upcoming missions to assemble the International Space Station, Diller said.

The short circuit on Columbia was the result of a one-time incident, NASA said, when a technician inadvertently pressed a packet of wires against the stripped screw, rubbing off a wire's insulation. The wire and its insulation are about as thick as a paper clip.

Launch vibrations on July 23 shook the wire to the point that it made contact with the screw, causing the arc, engineers believe. The short knocked out power to two of the three engines on the shuttle, but back-up systems took over. A second short circuit would have meant a permanent loss of power to at least one engine, forcing an emergency landing in Florida or Africa and putting astronauts' lives at risk.

Astronauts protected by redundancy, NASA says

There is no way to know how far back the newly discovered damage to wires dates, but astronauts' lives were not at risk despite the new-found prevalence of damage with the potential to cause short circuits, Diller said.

Most of the damaged wires found in the past few weeks went to "non-critical" systems other than engines and life support systems on the shuttles, he said.

"All those systems where the wiring goes, each thing that is what we call mission critical, has either doubly or triply redundant systems," he said.

"You never fly them knowing that you don't have that redundancy. That's what we could not answer at this point. Do we have all the redundancy there?"

Damage to wiring has been repaired in Discovery and Endeavour. Technicians also are taking measures to prevent future damage to wires by installing flexible plastic tubing over wires, smoothing and coating rough edges near wires and installing other protective shielding.

Columbia currently is being readied for long-term maintenance in California, where inspectors will start a full wiring inspection. Atlantis inspections will begin later this month.

Managers also are reviewing ground procedures to make sure technicians' methods for making repairs in the future don't result in damage in the future, Dittemore said.

It is unclear how long it will take to complete the extensive inspections and new launch dates for the upcoming three shuttle missions will not be announced until that progresses further, Diller said. Shuttle managers will meet in two weeks to look again at future launch dates.

The order of the Endeavour and Discovery liftoffs will depend upon which is ready first for launch. At this point, inspections and repairs are further along on the latter orbiter, he said, which would put the Hubble repair mission ahead of the mapping mission.



RELATED STORIES:
NASA delays shuttle launch to inspect wiring
August 13, 1999
Stripped screw caused shuttle malfunction
August 10, 1999
NASA: Loose pin caused space shuttle hydrogen leak
July 30, 1999
NASA confirms fuel leak after shuttle landing
July 28, 1999

RELATED SITES:
NASA Human Spaceflight - mission STS-99
Kennedy Space Center
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