The shuttle Discovery is on track for launch May 31 on a high-priority flight to deliver Japan's huge Kibo lab module to the international space station. But subsequent flights are slipping four to five weeks each because of external tank production issues, and a flight that had been targeted for late this year will slip into early 2009, a senior NASA manager said today.

Firm launch dates are not yet available, but the long-awaited Hubble Space Telescope servicing mission, STS-125, is expected to slip to around Oct. 8 or a bit later. A space station logistics delivery mission, STS-126, is expected to slip from mid October to around Nov. 15 and the flight after that, STS-119, likely will be delayed from December to early February 2009. Similar delays are expected for subsequent flights.

It has been clear for several weeks that tank delivery issues would affect the manifest, but shuttle Program Manager John Shannon's comments today during a pre-flight briefing for Discovery's upcoming mission were the first official word that one of six flights originally planned for 2008 will slip into 2009. Even so, Shannon said NASA still has margin built into the schedule to complete the space station and retire the shuttle fleet by the end of fiscal 2010 as planned.

"I would stress that the manifest we had laid out for the remaining 11 flights had us ending in about May of 2010," Shannon said. "I don't see (additional tank issues) beyond this one-time delay that we're going to have for the new processing. So I would say we're still on track to complete the program in the June or summer time frame of 2010, with some margin."

The tank that will be used by Discovery for its launching May 31 is the first to be built from scratch with post-Columbia safety upgrades and it has taken engineers at Lockheed Martin's Michoud Assembly Facility in New Orleans additional time to perfect and implement required manufacturing techniques.

The Hubble mission remains officially targeted for launch on Aug. 28, but "we really cannot make that date with the external tank processing schedule," Shannon said. "And this all kind of falls from the processing changes that were made to assemble the tanks with the post-Columbia mods in line. This was the first time through, we learned a little bit this time. I was just out at the Michoud Assembly Facility. I saw the Hubble tank, it looks good, I saw the rescue flight tank, it looks really good as well."

Shuttle crews bound for the space station have the option of "safe haven" aboard the lab complex if any Columbia-class problems occur that might make a safe re-entry problematic. That is not possible for the Hubble repair crew because the telescope is in a different orbit and the shuttle cannot reach the station from there.

As a result, NASA plans to have a second shuttle ready for launch on a rescue mission in case of any major problems and that, in turn, means two tanks will be needed.

"The changes that we made, it's added about four to five weeks of processing time on those two tanks," Shannon said. "So what we're looking at is a four- to five-week slip in the Hubble date. So sometime late September, early October, we're working through that. The tank team has done a really nice job of taking the lessons learned processing the tank that's about to fly, and the Hubble tank. So I don't expect that to (expand the time needed) on each of the downstream tanks. They have a mitigation plan in place so that the 2009 tanks come in more on a normal template. So we're going to take a one-time hit of this four to five weeks, it will move pretty much all of the tanks in series, the next 10 tanks that will come out, about that four to five weeks."

NASA originally hoped to launch six missions in 2008, but Shannon said the external tank production issues, along with unavoidable temperature constraints based on the station's orbit, will force the agency to move the STS-119 flight into 2009.

"The problem I have is that this year, from an orbital mechanics standpoint, is only 11 months long," Shannon said. "There's what's called a beta constraint, where the sun angle with respect to the orbital plane is such that I can't fly from Nov. 29 through the middle of December. So really, I can only fly up to Nov. 29. And what that means, with a four- to five-week slip, is that we would fly Hubble this year, we would fly ULF-2 (STS-126) this year and then we would move the STS-119 flight over to the early part of 2009."

Shannon said the launch delays are "a small price to pay ... for all the improvements we're getting on this tank."

"Really, everything immediately post Columbia that we thought of that would be a good modification has been implemented on the tank," he said. "It's a much, much better tank than we were flying pre Columbia, but it's a more laborious process. Now that the team has that figured out, we're going to get back on our normal production schedule. It just took a little extra time."

In the near term, NASA's sights are set on launching shuttle Discovery on May 31. On board will be commander Mark Kelly, pilot Kenneth Ham, flight engineer Ronald Garan, Karen Nyberg, Michael Fossum, Japanese astronaut Akihiko Hoshide and Gregory Chamitoff, who will remain behind aboard the space station to replace flight engineer Garrett Reisman. Reisman, launched to the station in March, will return to Earth aboard Discovery.

"We've got an exciting mission ahead of us," Kelly told reporters today. "I think we're pretty fortunate, well just fortunate, period, to be part of the space shuttle program, but to carry one of the major elements to the space station, install it and check it out is really a great privilege for all of us. We've got a complicated, busy mission ahead of us."

Discovery is scheduled to be hauled to launch pad 39A Saturday. The astronauts will fly to the Kennedy Space Center on Tuesday to review emergency procedures and participate in a dress-rehearsal countdown Friday. Shuttle program managers will hold a two-day flight readiness review May 13 and 14, followed by an executive-level review May 19. If all goes well, the countdown will begin May 28, setting up a launch attempt at 5:02:05 p.m. on May 31.

The flight plan calls for Kelly to guide Discovery to a docking with the space station around 1:51 p.m. on June 2. The next day, Fossum and Garan will stage the first of three spacewalks and the Kibo lab module will be attached to the left-side of the Harmony connecting module. Undocking is scheduled for June 10, with landing expected around 12:08 p.m. on June 13.

Additional coverage for subscribers:
VIDEO: KIBO LABORATORY TRAVELS TO THE LAUNCH PAD PLAY
VIDEO: TRANSPORT CANISTER WITH KIBO ROTATED UPRIGHT PLAY
VIDEO: CRANE PLACES KIBO MODULE INTO TRANSPORT CANISTER PLAY
VIDEO: DISCOVERY HOISTED FOR ATTACHMENT TO FUEL TANK PLAY
VIDEO: THE SHUTTLE MOVES TO THE VEHICLE ASSEMBLY BUILDING PLAY
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