Spaceflight Now: Space Station/STS-98

Booster repairs threaten to delay next shuttle launch
BY WILLIAM HARWOOD
SPACEFLIGHT NOW

Posted: December 18, 2000

Launch of the shuttle Atlantis next month on the next space station assembly mission faces a potentially significant delay because of work required to fix a crumbling electrical cable in the shuttle's booster separation system.

Shuttle mission STS-98 currently is targeted for launch at 2:44 a.m. EST on Jan. 18. The goal of the 102nd shuttle flight is to attach the U.S. laboratory module, Destiny, to the space station.

Inspection
A Kennedy Space Center worker inspects the reusable cables and connectors located inside the external tank attachment ring on Atlantis' left-hand solid rocket booster. Photo: NASA
 
But repairs to the shuttle's booster separation system could, in a worst-case scenario, require engineers to first remove Atlantis and its external tank from its two solid-fuel boosters to gain access to a damaged electrical cable.

If "destacking" is, in fact, required, launch of mission STS-98 likely would be delayed at least a week and probably longer. But as of late Sunday evening, no such decisions had been made and launch remained officially targeted for Jan. 18.

But a NASA spokesman said in a recorded status report that work to repair the cable in question "significantly threatens the STS-98 launch date of Jan. 18."

Atlantis originally was scheduled to be hauled to launch pad 39A on Dec. 11, but the move was held up when engineers discovered a booster separation problem that occurred during launch of the shuttle Endeavour on Nov. 30.

During Endeavour's launching, one of two explosive cartridges used to separate a strut holding the base of the orbiter's left-side solid-fuel booster to the ship's external fuel tank failed to fire.

A redundant "NASA standard initiator," or detonator, inside the strut in question did fire, however, and the booster separated cleanly. As it turned out, a wiring problem prevented the detonation signal from reaching the initiator.

But a shuttle could be lost if both detonators in a given booster attach strut failed to fire and NASA managers wanted to make sure the booster separation system used by Atlantis was healthy before moving the shuttle to the launch pad. As a result, Atlantis's rollout was delayed to give engineers time to X-ray wiring in the separation system and to review ground processing.

"On Friday, a cable located in the lower strut of (Atlantis') left-hand booster failed a standard (electrical) resistance check," NASA spokesman Joel Wells said in a recorded status report Sunday. "On Saturday, managers decided to replace a faulty connector on that cable.

"Meanwhile, workers performing final X-rays on cables located in the SRB forward skirt identified a damaged outer shield on one ordnance cable. While replacing that cable connector, workers had to peel back an outer layer of shielding. During that process, technicians noticed a loss of integrity on an inner layer of cable shielding.

"Further inspection revealed a crumbling effect on most of that shielding layer throughout that single cable," Wells said. "Engineers are now evaluating the cause of this cable issue and work planners are discussing plans to replace this entire cable."

The spokesman said gaining access to the cable "may require the external tank to be demated in a worst-case scenario before the work can be done."

To demate, or remove, the external tank, the shuttle itself first would have to be disconnected and lowered to the transfer aisle of the Vehicle Assembly Building. The tank then could be removed to give repair crews access to the booster separation system.

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