SPACE.com -- Potential Booster Problem Could Prompt Shuttle Launch Delay

The STS-105 Discovery crew, as well as the Expedition Two and Expedition Three crews.
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Shuttle Discovery arrives at launch pad 39A on July 2, 2001 for a planned launch of STS-105 in August.
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Space Shuttle Discovery sits on Launch Pad 39A after an early morning rollout from the Vehicle Assembly Building. Discovery is scheduled to launch Aug. 3 on mission STS-105.

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	Potential Booster Problem Could Prompt Shuttle Launch Delay By Todd Halvorson Cape Canaveral posted: 08:00 pm ET 03 August 2001

CAPE CANAVERAL, Fla. -- A potentially serious problem with one of shuttle Discovery's twin solid rocket boosters could conspire to delay the planned launch next week of a crew rotation mission to the International Space Station, officials said Friday.

As its stands, Discovery remains scheduled to blast off from Kennedy Space Center Thursday on a mission to ferry a new crew to the station and then return to Earth with the current outpost tenants Yuri Usachev, Susan Helms and Jim Voss.

The launch, however, could be delayed three or four days if NASA engineers decide to replace a suspect hydraulic power unit on the shuttle's left-hand booster rocket.

Still unclear, however, is whether the repair job will be necessary.

"We don't know that we're going to have to go off and do this yet," said Rob Navias, a spokesman for NASA's Johnson Space Center in Houston, Texas. "Right now, we're still planning to send the crew down to the Cape on Sunday and pick up the launch countdown Monday."

Here's the situation:

During the course of a routine examination of previously flown parts, engineers this week detected cracks within a shuttle solid rocket booster hydraulic power unit.

The device provides the hydraulic power needed to steer a booster nozzle in flight, and the cracks were discovered within an injector stem that regulates the flow of fuel needed to drive a turbine within the unit.

The turbine, in turn, drives an actuator that enables a booster nozzle to swivel.

Engineers still are trying to determine the root cause of the injector stem cracks. The leading suspects: Metallurgical age or the corrosive stress of repeated booster splashdowns.

The shuttle's reusable boosters are jettisoned two minutes into flight and then fall into the Atlantic Ocean where they are recovered and refurbished for future flights.

NASA managers, meanwhile, are concerned that a cracked injector stem could trigger booster steering problems in flight. The hydraulic units on one of Discovery's two boosters is equipped with an injector stem from the same manufacturing lot as the one which cracked.

Senior shuttle managers will hold a teleconference Saturday to determine whether to replace the hydraulic unit with the suspect injector stem. Such a repair job likely would take 8 to 10 days, prompting about a three or four day delay in the Discovery launch.

In that case, the postponed launch of a Delta rocket and NASA's Genesis solar science satellite - now slated for Aug. 12 - might be moved up to Aug. 9.