Spaceflight Now: Space Station/STS-98

Shuttle Atlantis' booster wiring appears OK

Posted: January 22, 2001
Updated to correct STS-102 mission goal

Checks of wiring in Atlantis' solid rocket boosters did not reveal any major problems. Photo: NASA
No major problems were found with suspect electrical wiring in the shuttle Atlantis' twin solid-fuel boosters during weekend inspections, NASA officials said today. Assuming no other issues crop up during final review and closeout, Atlantis will be hauled back to pad 39A Thursday for launch on a space station assembly mission Feb. 6.

That date could slip another day or so, however, based on the current orbit of the international space station and the shuttle's ability to catch up with its target.

It is not yet clear whether Atlantis can launch on Feb. 6 and complete its rendezvous and docking with the station on flight day three as desired. If a flight day four rendezvous is the only option for a Feb. 6 launch, shuttle mission STS-98 likely would slip at least one more day.

NASA managers continue to assess the overall space station assembly schedule and it now appears the next flight in the sequence, shuttle mission STS-102 - launch of the station's next crew - will slip from March 1 to March 8.

While engineers believe they could launch Discovery March 1 as had been planned, sources say senior program managers want a bit of additional time between the end of Atlantis' voyage and the start of Discovery's.

The goal of Atlantis' mission is to install the $1.38 billion U.S. laboratory module, Destiny, to the space station's multi-hatch Unity node.

Launch originally was scheduled for Jan. 18. But rollout to the pad was delayed from mid December to early January to inspect critical wiring in the shuttle's booster separation system after an explosive circuit failed to fire during a launch in November.

Atlantis returns to the VAB last week for the wiring inspections. Photo: NASA
Atlantis ultimately was given a clean bill of health and moved to pad 39A for work to ready the ship for launch Jan. 19. In the meantime, engineers began inspecting and testing booster wiring across the shuttle inventory.

In all, 194 multi-wire cables were tested and four wires out of 3,098 were found with intermittent electrical continuity. Last week, shuttle program manager Ronal Dittemore ordered Atlantis back to the Vehicle Assembly Building for additional wiring inspections to make sure all the cables in Atlantis' boosters were healthy.

The shuttle's twin solid-fuel boosters provide most of the orbiter's power during the first two minutes of flight. The boosters then are jettisoned, recovered in the Atlantic Ocean and reused.

Each booster is equipped with 105 multi-conductor electrical cables that control a variety of critical functions, including booster separation and, if necessary, self destruction.

Twenty-four cables in each booster are water tight and reusable, 41 are not waterproof but are reusable and 40 are used only once. Of the 24 waterproof cables, five are located in the external tank attachment ring and 19 are located in a long systems tunnel that runs the length of each rocket.

The 10 external tank attachment ring cables in Atlantis' boosters were inspected and cleared in December. The rollback was ordered to inspect 36 of the other 38 watertight, reusable cables in the systems tunnels of each rocket.

Those cables appear to have passed muster during weekend tests, including X-rays of critical cable connectors and the wiring leading to them and so-called "wiggle tests," in which cables are physically moved about while power is applied.

Engineers are still studying the data to resolve a few last-minute questions, but no major problems have been uncovered, sources say, that would block a return to the pad Thursday.

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