Image: Shuttle move
John Raoux  /  AP
The space shuttle Discovery makes its way to Launch Pad 39B at NASA's Kennedy Space Center in Florida on Friday.
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updated 5/19/2006 10:14:08 PM ET 2006-05-20T02:14:08

The space shuttle Discovery is back at the launch pad as workers prepare the spaceplane for NASA’s second orbiter mission since the 2003 Columbia accident.

A massive crawler carrier hauled Discovery and its mobile launch platform up to Launch Complex 39B at the Kennedy Space Center here on Friday evening, more than seven hours after leaving the shelter of NASA’s Vehicle Assembly Building at about 12:45 p.m. ET.

“It’s a fabulous feeling to see that we’re rolling Discovery back to the launch pad for our next launch attempt,” said NASA shuttle program manager Wayne Hale, who rode out from the Vehicle Assembly Building with the orbiter. “I think we’re on a really good path to make that July 1 window opening day.”

The orbiter's move marked a major milestone for NASA's STS-121 mission — the agency's second shuttle test flight since the 2003 Columbia accident. Discovery is currently slated to launch its astronaut crew, commanded by shuttle veteran Steven Lindsey, on a mission to test shuttle fuel tank modifications, orbiter repair techniques and resupply the international space station.

Hale said that preliminary results of wind tunnel tests to check changes to Discovery’s external fuel tank — primarily the removal of a foam ramp to reduce debris hazards at launch — are positive, but won’t be final for about three weeks. While wind tunnel tests have concluded, a detailed analysis of the resulting data is still under way, he added.

“We have to wait until we get to the bottom line,” Hale said. “We could be smarter tomorrow, and somebody could find out something we need to deal with.”

Friday’s rollout allowed Discovery to meet up with its payload — a cargo pod dubbed Leonardo, spare space station parts and other items. The Leonardo module and equipment palettes will be loaded into Discovery’s cargo bay after engineers shroud the spacecraft with its protective service structure, an activity currently slated to occur Sunday, NASA officials said.

Meanwhile, Hale said is confident that Discovery’s planned July launch will be the first of three shuttle flights this year. Additional launch opportunities open up on Aug. 28 and Dec. 14, he noted.

“Now it will be tight … it depends a lot on the tank,” Hale said, referring to the external tank for the third shuttle flight. Engineers are trying to finish work on External Tank 123 early, in time to support a possible rescue flight should anything go awry during August's planned space shot.  “Given that, we have a good shot at making three shuttle flights this year.”

Preparing Discovery
Engineers at Kennedy Space Center spent the last week mating Discovery to the external tank and solid rocket boosters that will push the 100-ton spaceplane into orbit. During that time, shuttle workers also took detailed photographs of the orbiter's heat shield to be compared with images from in-orbit inspections during the STS-121 mission, integration engineers told Space.com. They said they took similar photos while preparing Discovery for NASA's first post-Columbia mission, STS-114.

"Everyone was excited for STS-114, and they're doubly so for STS-121, because it's our opportunity to get into regular launch mode again," Tim Riley, the shuttle integrated operations chief for NASA contractor United Space Alliance, said in a recent interview. "Hopefully, we'll get a couple more [shuttle flights] in this year."

Discovery's STS-121 mission is the last of two post-Columbia accident test flights to shake down new shuttle safety and repair methods, in preparation for the resumption of space station construction later this year. While NASA is currently targeting July 1 for STS-121's launch, the orbiter has a flight window that extends through July 19. If Discovery misses the July window, launch would be rescheduled for the next opportunity in late August.

NASA's 5.5 million-pound (2.5 million-kilogram) crawler vehicles have transported NASA spacecraft to and from launch pads since 1966, during the Apollo program. The entire assembly — including the shuttle, its fuel tank and boosters, mobile launch platform and crawler vehicle — weighs about 17.5 million pounds (7.9 million kilograms) and can move at a top speed of about one mile per hour (1.6 kilometers per hour).

“It was great,” Hale said after his ride on the crawler. “It’s better than going on a cruise ship.”

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