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A Change in the Lineup
03.01.04
 
When the Space Shuttle returns to safe flight next year, Discovery, fresh from an extended overhaul, will pinch-hit for Atlantis.

Discovery at the beginning of its overhaul"That was in order to accommodate the additional time for any inspection and refurbishment, if it's required," said William Readdy, associate administrator for Space Flight.

Orbiter Discovery rolls to its processing facility to begin its overhaul in September 2002. NASA believes Discovery will be ready to fly earlier than Atlantis.

NASA also moved the target planning window from September 2004 to March 2005. The date change may be a bit disappointing to space enthusiasts. But as NASA officials pointed out, the extension is crucial to ensuring the safety of the crew and orbiter.

Moving the target date gives the agency the time it needs to prepare for new launch constraints. For example, a new rule states that for at least the next few flights, Shuttles should only launch during daylight hours to allow the best photography of the Shuttle assembly for post-launch review. Another challenge will be having a second Shuttle on standby, ready to launch a rescue mission if necessary.

"We're going through the process of further defining exactly what that rescue capability will be and defining the mission products that are required to be on the shelf, ready to execute," Readdy said.

The extension also allows NASA to work out some technical challenges.

Workers checking a rudder speed brake actuatorDuring Discovery's overhaul period, technicians analyzed the actuators that drive the rudder speed brake, which helps control and slow the orbiter during entry and landing. Because the inspection revealed minor corrosion, wear and installation problems, further work is required to inspect and repair the actuators on all three orbiters. Discovery was the first orbiter to receive this attention, so it was selected as the Return to Flight vehicle.

Workers in the Orbiter Processing Facility measure the alignment of bearings on a rudder speed brake actuator.

NASA also needs more time to design and build the boom that will allow the astronauts to inspect the orbiter for damage while in space. Designing the camera/laser sensor package for the end of the boom has proven challenging, but Readdy is confident that a solution is close.

Finally, further research, analysis and testing are necessary before the Shuttle's massive orange external tank can be deemed safe for flight. NASA is paying special attention to the way debris that comes off the tank reaches the orbiter during launch, and how the tank's foam insulation is applied.

"We've said for months that we'd be driven by milestones, not a calendar," said Readdy. "When we successfully reach those milestones, that's when the Space Shuttle will return to safe flight."

+ View News Release
+ Learn more about Discovery's overhaul
+ View a video about Discovery's maintenance process