CAPE CANAVERAL, Fla. -- A rash of recent technical concerns have drained all the extra time from shuttle Columbia's ongoing launch campaign, leaving NASA one significant problem away from delaying a planned Hubble Space Telescope servicing mission.
As it stands, Columbia and seven astronauts remain scheduled to blast off Feb. 28 on a mission to outfit Hubble with new solar arrays, a spare pointing control device and an advanced planetary camera.
"But there is no time to lose," Kennedy Space Center spokesman George Diller said Wednesday.
Here's the situation:
A recent review of ground test data on a spare Hubble pointing control device has prompted NASA engineers to lay plans to rush a new back-up unit to NASA's coastal Florida spaceport from Goddard Space Flight Center in Greenbelt, Md.
A pair of problems encountered during a recent shuttle propellant load, meanwhile, left little to no extra time in the schedule of work that still needs to be completed on Columbia prior to flight.
Consequently, any additional problems that crop up between now and Feb. 28 could prompt a day-for-day slip in the already-delayed launch.
Once set for Feb. 14, the flight was pushed back two weeks to give engineers time to ready a spare Hubble pointing control device. An identical Reaction Wheel Assembly on the telescope suffered a momentary glitch in orbit last summer and managers in December decided it would be prudent to replace it.
One of four such devices on the telescope, the reaction wheels enable the spacecraft to precisely point at celestial targets, and at least three need to be operating properly to carry out normal scientific observations.
A spare unit sent down to the launch site earlier this month had exhibited some erratic behavior during tests at Goddard, but those problems initially were attributed to faults in associated ground test equipment.
Engineers, however, since have had second thoughts about the spare. Consequently, they decided to ship another replacement unit to Florida on Saturday. All of the gear and equipment being launched to Hubble must be installed in Columbia's cargo bay by Sunday to maintain the schedule for a Feb. 28 launch.
Shuttle launch preparations, meanwhile, hit a snag late last week when a pair of quick disconnect valves failed while toxic rocket fuels were being loaded into onboard storage tanks aboard Columbia.
The tanks feed propellant into the shuttle's twin orbital maneuvering engines and 44 nose-and-tail steering jets. The separate valve failures stalled the propellant load, exhausting extra time within an otherwise routine launch-processing schedule.
Jack King, a spokesman for United Space Alliance, NASA's prime shuttle contractor, characterized the remaining schedule of work as "tight."
Engineers, meanwhile, also are investigating another technical issue.
A recent review showed that the hydraulic pumps on each of the shuttle's three Auxiliary Power Units were mounted with lubricated bolts, but design specifications call for the pumps to be attached with bolts that have not been lubricated.
The units provide the hydraulic power needed to steer the shuttle's main engines in flight. They also are key to operating the ship's wing flaps, rudder speedbrake, landing gear and brakes during landing.
King said the hydraulic pumps in question have inadvertently flown with lubricated bolts in the past. But, he added, an analysis nevertheless is under way to determine whether the pumps could develop fluid leaks during flight.
A move to replace the bolts almost certainly would delay the planned launch.
"It would be quite a bit of work as I understand," King said.
Senior NASA and shuttle contractor managers will be briefed on the various issues during a traditional flight readiness review to be held here at KSC Thursday. A firm launch date is to be set at the conclusion of the all-day meeting.
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