Space shuttle repairs to delay Hubble mission

File photo of Discovery on the launchpad

November 3, 1999
Web posted at: 5:14 p.m. EST (2214 GMT)

From Space Correspondent Miles O'Brien

HOUSTON (CNN) -- Space shuttle mission managers at the Johnson and Kennedy Space centers said Wednesday they will be forced to change an engine on Discovery, prompting yet another delay in the launch of the high-profile Hubble Space Telescope repair mission.

The launch was scheduled for Thursday, December 2, and now will be delayed by at least three or four days to allow technicians to install a new right main engine.

A half-inch long fragment of a drill bit was discovered inside the coolant system for the engine currently installed on Discovery.

NASA said the drill bit broke off while the engine was being worked on in April. It was as yet unclear when and how the fragment was discovered.

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Apparently it is not uncommon for drill bits to break off during engine processing. In the past, shuttle engines have flown with such fragments after it was determined the chances of them dislodging and damaging the engine were slight, NASA said. But after a stray part caused a leak in an engine during the last shuttle flight, mission managers are taking fewer chances.

During Columbia's launch in July, a pin designed to block a propellant line dislodged, striking the engine bell. Some cooling tubes were dented and ultimately sprang leaks.

If more fuel had leaked, the shuttle crew might have been forced to make an emergency landing.

Discovery is in its hangar -- the Orbital Processing Facility -- at Kennedy Space Center. NASA said it will move the shuttle into the Vehicle Assembly Building, attach it to its fuel tank and solid rocket boosters and roll the vehicle to the launch pad before changing the engine.

Shuttle engines have been changed on the launchpad several times in the past and generally it means a three- or four-day delay. NASA says changing them while the orbiter is in the vertical position is, in some ways, easier than performing the task while the shuttle is horizontal.

There are two other areas of concern. NASA technicians discovered defective, heat-resistant tiles near the nose wheel on Discovery's sister ship, Atlantis. Concerned about a possible manufacturing defect, technicians will check to see if any of Discovery's tiles share the same pedigree.

Technicians will also be repairing a defective valve spring in one of Discovery's auxiliary power units.

Discovery is slated for a 10-day mission to rendezvous with, grapple and then repair the Hubble Space Telescope during four spacewalks.