Faulty Wiring Puts Shuttle Flights on Hold

NASA has practically grounded its space shuttle fleet because inspections have uncovered a startling number of damaged wires that could endanger a mission.

Technicians discovered that an exposed wire caused a short circuit that knocked out two engine computers during the launch 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.”

Endeavour and Discovery have dozens of wires that must be repaired or reinforced. Endeavour was to have gone up in mid-September with radar equipment to map the 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 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.

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.

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 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.