While the Expedition Three astronauts aboard the orbiting international space station were entertaining house guests on Wednesday, technicians at Kennedy Space Center moved shuttle Endeavour a step closer to launching a replacement resident crew next month.

Endeavour is backed out of its hangar atop the orbiter transporter. Photo: NASA

Riding atop a special transporter, Endeavour was hauled the quarter-mile from its Orbiter Processing Facility hangar to the 52-story Vehicle Assembly Building where it will be attached to an awaiting external fuel tank and twin solid rocket boosters atop a mobile launcher platform.

The combined shuttle stack is scheduled to roll to launch pad 39B next week, but NASA isn't disclosing a specific date, citing the heightened level of security at the space center.

"With safety and security as our No. 1 priorities, the prudent thing to do is to continue with the normal processing but not to divulge that many details," Kennedy Space Center spokesman Joel Wells said.

"The vehicle is in good health and processing continues to go well," Wells added.

Expedition Three commander Frank Culbertson, pilot Vladimir Dezhurov and flight engineer Mikhail Tyurin are mid-way through their four-month tour-of-duty on Alpha. They are currently sharing the station with their first visitors in space.

The Russian-French "taxi crew" who flew a fresh Soyuz lifeboat capsule to Alpha on Tuesday are spending the week running experiments and conducting Earth observation studies. Commander Victor Afanasyev, flight engineer Konstantin Kozeev and French researcher Claudie Haignere will ride the station's old Soyuz back to Earth next Tuesday night after 7 1/2 days aboard Alpha.

Endeavour heads to the VAB for mating with the external tank and booster rockets. Photo: NASA

Endeavour remains slated for blastoff at 7:44 p.m. EDT on November 29 (0044 GMT the 30th) for an 11-day mission to ferry the Expedition Four crew to the station. The Expedition Three crew, who arrived at the outpost in August, will ride home aboard Endeavour on December 10.

Endeavour's crew is led by commander Dom Gorie, with pilot Mark Kelly and mission specialists Linda Godwin and Dan Tani. The Expedition Four crew is commanded by Yuri Onufrienko with American flight engineers Carl Walz and Dan Bursch.

The shuttle will also carry an Italian-made cargo module packed with equipment and supplies for the station. The Raffaello module will be temporarily mounted to the station so its payload can be unloaded by the astronauts. The reusable module then will be returned to Endeavour's cargo bay for the trip back to Earth.