Another Delay For Discovery

NASA managers Wednesday ordered engineers to replace one of the shuttle Discovery's three main engines because of concern about a broken drill bit lodged inside the Rocketdyne power plant. The engine will be removed and replaced at pad 39B, work likely to delay blastoff on a Hubble Space Telescope repair mission from December 2 to around December 5.

"We're not going to make Dec. 2, that's for sure,'' NASA spokesman Rob Navias said. "But where we wind up is under review.''

The drill bit in question broke off during routine engine maintenance several months ago. Because of its location, engine managers do not believe the half-inch-long bit of debris posed any credible safety threat during engine operation. But shuttle program manager Ron Dittemore Wednesday ordered Discovery's lower right engine, No. 2045-2A, replaced at the launch pad. A reliable source said the work would delay liftoff to at least December 5 and possibly a day or two later. But as of this writing, NASA has not officially given up the December 2 target.

There is another issue under discussion that could cause additional problems. Some of Discovery's heat-shield tiles are from a batch that has exhibited bonding problems in ground tests. Engineers are expected to conduct pull tests on selected tiles aboard Discovery as soon as possible to ease concerns about possible de-bonding in flight. No other details are available as of this writing.

CBS News Space Consultant Bill Harwood

An official "drop-dead" date for getting Discovery off the ground this year has not been announced. Dittemore says flying over the Christmas holidays is not an issue, if it comes to that. But NASA will not operate a shuttle mission over the New Year's holiday because of Y2K concerns. Given the possibility of landing weather delays, a diversion to Edwards Air Force Base, Calif., and other factors, Discovery must get off the ground by December 14 or the flight will be delayed to next year.

Assuming a launch on December 5, Discovery would blast off at 3:07 a.m., two days after NASA's Mars Polar Lander touches down a few hundred miles from the red planet's south pole. French astronaut Jean-Francois Clervoy, operating Discovery's robot arm, would pluck Hubble out of open space at 4:14 a.m. on December 7, setting the stage for the first of four back-to-back spacewalks starting at 9:57 that evening. On this schedule, Hubble would be re-deployed around 12:52 a.m. on December 12 and Discovery would land back at the Kennedy Space Center at 1:14 a.m. on December 15.

But all of that assumes a lanch on December 5 and a firm target date has not yet been established. A detailed mission preview is posted on the CBS News Current Mission page.