CAPE CANAVERAL, Fla. -- Shuttle Discovery's astronauts and a new International Space Station crew will fly to Kennedy Space Center Sunday despite a booster rocket problem that could delay this week's planned launch to the outpost.
As it stands, Discovery remains scheduled to blast off from Kennedy Space Center at 5:38 p.m. EDT (2138 GMT) Thursday on a mission to taxi the new crew to the station and then return to Earth with current outpost tenants Yuri Usachev, Susan Helms and Jim Voss.
The launch, however, could be delayed three or four days if NASA decides to replace the hydraulic power unit on one of the shuttle's twin solid rocket boosters.
Designed to provide the hydraulic power need to steer a booster nozzle in flight, the unit is equipped with a suspect fuel injector. Senior NASA managers on Saturday deferred a decision on any potential replacement work, opting instead to order inspections of all available fuel injectors from the same manufacturing lot.
Those inspections will be carried out at an Illinois manufacturing plant, and while a decision on repair work could be delayed until Tuesday or later, NASA managers now are expected to make a call during a 5 p.m. EDT (2100 GMT) teleconference Sunday.
"There is a desire to wrap up this discussion one way or another," said Rob Navias, a spokesman for NASA's Johnson Space Center in Houston, Texas.Engineers earlier this week discovered cracks within the fuel injector of a hydraulic power unit that had flown on a previous shuttle flight.
A boroscope tool -- which enables engineers to image the interior of small tube-like parts -- was used to spot tiny cracks within the injector, which regulates the flow of fuel needed to drive a turbine within a hydraulic power unit.
The hydraulic power unit on Discovery's left-hand solid rocket booster is outfitted with a fuel injector that was built during the same manufacturing run as the part that cracked.
NASA managers, consequently, are concerned that a cracked fuel injector might trigger booster steering problems during Discovery's launch.
Engineers, however, now think the faulty injector likely was bent during repeated booster splashdowns in the Atlantic Ocean, likely causing the cracks.
Manufacturing, launch processing and inspection records, however, show that the fuel injector within the suspect hydraulic power unit on the Discovery booster is not bent.
The special inspections at a Hamilton-Sundstrand factory in Illinois are expected to determine whether cracks exist within used fuel injectors that have not been bent over the course of time.
The replacement of a booster hydraulic power unit, meanwhile, 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 2 rocket and NASA's Genesis solar science satellite -- now slated for Aug. 12 -- might be moved up to Thursday.
Discovery's astronauts and the new station crew -- Frank Culbertson, Vladimir Dezhurov and Mikhail Turin -- are scheduled to arrive at NASA's coastal Florida spaceport at 12:30 p.m. EDT (1630 GMT) Sunday.
A three-day launch countdown remains scheduled to pick up Monday.
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