Shuttle set for Sunday launch amid space plan shift

The Space Shuttle Endeavour sits on Pad 39-A during roll back in preparation for Sunday's launch at the Kennedy Space Center in Cape Canaveral, Florida, February 6, 2010.

CAPE CANAVERAL, Florida (Reuters) - NASA's space shuttle Endeavour will blast off on Sunday on one of the last remaining shuttle missions, and the U.S. agency's chief said on Saturday the days of big American solo initiatives in space were over.

Endeavour is set to launch at 4:39 a.m. EST from the Kennedy Space Center in Florida on a 13-day construction mission carrying final parts for the International Space Station.

The shuttle will deliver two modules for the station -- a connecting node named Tranquility, and a seven-sided viewing cupola for the crew to oversee robotics and gaze at Earth.

Endeavour's crew of five men and one woman plan to conduct three spacewalks to hook up the new gear.

Forecasters say there is an 80 percent chance that weather conditions in Florida will be good for launch on Sunday.

Including Sunday's mission, five shuttle flights remain to complete assembly of the $100 billion International Space Station, a project involving 16 nations, before the U.S. fleet is retired later this year.

U.S. President Barack Obama has announced plans to cancel the station's follow-on program called Constellation, which was aimed at returning U.S. astronauts to the moon in the 2020s.

Instead, Obama wants NASA to seed development of commercial space taxis to ferry crewmembers to and from the station and to develop technologies to prepare for eventual human missions to other destinations in the solar system.

"The president has instructed me that this is going to be an international effort," NASA chief Charlie Bolden told reporters at the Kennedy Space Center.

"It's going to be different than the way we used to do it. We're going to put international partners in the critical path," Bolden said. Prominent among these is former space rival Russia, which has already taken over the job, previously shared with NASA, of ferrying crew to and from the orbital station.

The decision to cancel the Constellation program stunned NASA and its contractors, which already have spent $9 billion on the initiative.

"Constellation was going to be putting all our eggs in one basket again," said Bolden. He added that the new "flexible" space exploration initiative would focus on developing a heavy-lift transporter that could carry people and cargo beyond the space station's 225-mile (360-km) -high orbit.

"GAME-CHANGING" TECHNOLOGIES

Bolden, for one, would like the United States and international partners to aim for Mars, but the means to do this do not exist today.

The new U.S. space plan supports funding for what he calls "game-changing" technologies, such as non-chemical engines that can shave time off the nine-month journey to Mars and reduce astronauts' radiation exposure.

"The flexible path says we're going multiple destination and we're going to go there as we develop the capability to do it," Bolden said.

Many NASA workers had been counting on the Constellation program to fill the void left by the shuttle's retirement and the completion of the space station.

"There're a few folks that are kind of reeling from the shock," Mike Moses, a shuttle program manager, told reporters.

Bolden said he did not prepare the NASA workforce for the news of the plan change. "I've apologized," he said.

The budget unveiled by the Obama administration on Monday also extended the life of the space station to 2020.

(Editing by Pascal Fletcher and Mohammad Zargham)