NASA studies shuttle solid rocket booster problem
Posted: August 3, 2001

Update for 5:45 p.m. Saturday: NASA officials have again delayed making a decision on replacing one of Discovery's SRB hydraulic power units. Another meeting is planned for late Sunday afternoon. For now, pre-launch preparations will continue on schedule including the astronauts' trip from Houston to KSC on Sunday.

  Pad 39A
Discovery sits atop pad 39A for liftoff on mission STS-105. Photo: NASA-KSC
Space shuttle engineers are investigating cracks found inside a solid rocket booster hydraulic steering unit that could force NASA to delay next week's planned blastoff of Discovery.

Discovery is slated to launch at 5:38 p.m. EDT Thursday to ferry the three-man Expedition Three crew to the international space station and return the Expedition Two crew back to Earth after five months in orbit.

But the mission is in jeopardy of being delayed at least a few days after post-flight inspections from a recent shuttle launch revealed cracks and corrosion on a part called an injector within a hydraulic power unit inside a solid rocket booster.

Each booster has two independent hydraulic power units that gimbal the rocket's nozzle to provide the primary means of steering the shuttle during launch. A hydraulic system failure could have catastrophic consequences.

The injector in question comes from a specific manufacturing batch that also includes an injector inside a hydraulic power unit on Discovery's left-hand solid rocket booster. About 20 percent of injectors in the shuttle fleet come from this same lot.

Shuttle program chief Ron Dittemore held a meeting late Friday to review the situation. Engineers made a recommendation to replace Discovery's suspect hydraulic power unit. That job would take eight to 10 days from the point a replacement decision was made, resulting in a launch delay of three to four days.

However, officials deferred making a decision until a follow up teleconference on Saturday.

The injectors can't be inspected on the launch pad, so Dittemore must decide to either launch Discovery "as is" or else replace the hydraulic power unit.

Engineers believe the "stress corrosion" is being caused by the multiple splashdowns in the Atlantic Ocean where the boosters are retrieved for reuse.

Although the cracked injector did not hamper the recent launch in question, NASA wants to resolve this problem before it does cause a serious problem for a shuttle in flight.

If Discovery's liftoff is delayed, the Boeing Delta 2 rocket with NASA's Genesis spacecraft would be poised to move up its next launch attempt to take the shuttle's Thursday reservation on the Eastern Range. At present, Genesis is booked for Sunday, August 12 on the Range.