News of the potential schedule slip came Monday during a teleconference with project managers in NASA's Project constellation office.

The Ares I-X test flight is currently targeted to blastoff from Kennedy Space Center's Launch complex 39-B around April 15, 2009. The launch pad hasn't been used since Discovery's STS-116 launch in December, 2006.

No more space shuttle launches are scheduled to take place from the pad, but it can't be modified to accommodate the Ares I-X flight until after space shuttle Atlantis mission to service Hubble later this year.

Before the launch pad can be handed over to Constellation, the shuttle program will require its availability to mount a mission to rescue the crew of Atlantis should that orbiter become disabled or experience serious damage that would prevent a safe re-entry.

Because HST flies in a 28.5 degree inclination orbit compared to the space station 51.6 degree flight path, the astronauts won't have the option to fly from Hubble to the space station and await a rescue mission from its relative safety.

Instead, NASA has put in place the requirement to have space shuttle Endeavour processed alongside Atlantis and to have both shuttle's on the launch pad for STs-125. Endeavour would then be ready to mount a quick-reaction rescue mission if necessary.

The requirement for the pad to be available for the Hubble mission means that Constellation won't be able to take it over and make the major modifications necessary to support Ares I-X until after Atlantis returns to Earth.

Likewise, modifications to the assembly bay in the Vehicle Assembly building that the Ares rocket requires have to wait until after the shuttle program no longer needs it.

As a result, any significant delay in getting Atlantis off the ground could result in a comparable delay in the launch of Ares I-X.

Unfortunately, STS-125 is facing a likely five-week delay, from late August to early October, due to external tank processing difficulties.

Jeff Hanley, NASa's Project Constellation Project Manager, said that, as of now, it appears the impact of the shuttle processing delays "suggest a day-for-day slip."

Following the Columbia accident, the shuttle's external tanks have undergone extensive modifications and redesign. Up until now, all the tanks that have flown post-Columbia have been tanks that were already assembled or partly built before the STS-107 accident.

Those tanks were subsequently retrofitted with the design changes ordered to mitigate the occurrence of foam, ice and other debris shedding during launch.

Beginning with STS-124, the tanks being delivered to Kennedy Space Center are "clean". That is, they were assembled from the ground up with the modifications in place. Due to different procedures that are now in place, and additional inspections and testing, it's taking longer to assemble the tanks than in the past.

The net result of all this is that tanks are getting to KSC later than originally anticipated, and hence the next several shuttle launch dates face delays of several days to weeks.

Next week, NASA managers will likely push back Atlantis launch from August 28 to October 8. This will have a ripple-effect and push back Ares 1-X by a similar amount.

Some processing work on the pad and mobile launch platform can be done concurrent with preparing Endeavour for a rescue mission, but the major work will have to wait until Endeavour is moved over to Pad A for its STS-126 mission to the space station early next year.

This means that the first Ares test flight faces, in a worst-case scenario, a day-for-day slip matching Atlantis' launch delay, although it's possible several days can be made up by then.

"We're doing what we can to look at what could be done to do parallel work or other ideas that might be in play to get the modification work to the Mobile Launch Platform done and still mitigate some of that impact to the (Ares) I-X launch date," Hanley said.

Nonetheless, the launch date for Ares I-X will slip from mid-April until late May 2009.

Among the modifications that Pad B will undergo include extending the Fixed Service Structure by about 100 feet and the addition of a new, taller lightning mast to protect the Ares rocket while it's sitting on the pad. The new mast is necessary given that the 309 foot tall Ares I launch vehicle is over 100 feet taller than the space shuttle and is, in fact, taller than the top of the current lightning mast.

Other modifications include outfitting a shuttle mobile launch platform with necessary umbilicals and connections to support the Ares I-X launch configuration.

Constellation program officials downplayed the significance of the Ares I-X slippage, pointing out that the driving factor is getting the data from the test flight in time to do a thorough analysis before the Ares I critical design review in March 2010.

Engineers need the raw data at least six-months befoe the design review in order to give sufficient time to analyze the results and make any modifications to the Ares I baseline design that might be required before the new launch vehicle will pass the review.

Even with a five-week slip, the Ares I-X test flight still has a several month margin in which to launch the test flight before additional delays impact the March CDR.

Ares I???X is planned to be the first test flight of the Ares I vehicle. The test flight objectives are focused on first-stage flight dynamics, controllability, and separation of the first and upper stages. The Ares I???X flight will consist of a four-segment shuttle solid rocket booster with a dummy fifth segment first stage and an upper stage mass simulator, which has the same mass as the actual upper stage. The test flight will also verify the performance and dynamics of the shuttle???s solid rocket booster in ???single stick??? arrangement as opposed to the two-booster configuration of the space shuttle.

(The Spacearium / SpaceflightNews.net)