NASA clears space shuttle for launch on Wednesday

CAPE CANAVERAL, Florida (Reuters) - NASA managers on Monday cleared space shuttle Endeavour and seven astronauts, including a former school teacher who trained with the ill-fated Challenger crew, for launch on Wednesday.

Endeavour's blastoff from the Kennedy Space Center in Florida on a construction mission to the International Space Station is scheduled for 6:36 p.m. EDT (2236 GMT).

Forecasters predicted a 70 percent chance of good weather for launch.

"We feel very good about where we are," said LeRoy Cain, the top shuttle manager at the space center. "We're in really great shape for launch on Wednesday."

The crew plans to spend seven to 10 days at the orbital complex, which is a little more than half finished.

Up to four spacewalks are planned to install a new piece of the station's structural backbone, replace a faulty gyroscope needed to keep the outpost properly positioned in orbit and tackle a variety of tasks to prepare the station for the arrival of laboratories built by Europe and Japan.

The five-man, two-woman crew includes former Idaho elementary school teacher Barbara Morgan, who trained as the backup for "teacher-in-space" Christa McAuliffe, a member of the final Challenger crew.

McAuliffe and six astronauts were killed 73 seconds after liftoff on January 28, 1986, when one of the shuttle's booster rockets leaked fuel, triggering a catastrophic explosion.

NASA asked Morgan to stay with the program, promising a flight in the future. More than 21 years later, the agency is about to make good on its pledge, though her role as a teacher is far different than what was planned for McAuliffe.

To uphold a post-Challenger ban on civilians flying on the shuttle, NASA opened a spot in the astronaut corps for Morgan, who is now a fully trained mission specialist.

Her role during Endeavour's flight is to operate the shuttle's robotic arm and oversee the transfer of 5,000 pounds (2,268 kg) of cargo to and from the station.

"It is great to see Barbara up there ready to fly," shuttle program manager Wayne Hale said at a news briefing on Monday. "She's been working a long time to have her day in orbit."

Because of the amount of work planned during the mission, Morgan is expected to have only about six hours for in-flight educational activities. She plans to help develop curriculum and student activities after her landing.

Endeavour has not flown in nearly five years. The orbiter underwent a series of inspections and equipment upgrades, most of which had been scheduled before the 2003 Columbia accident.

The modifications include a new power system that will enable the shuttle to tap into the station's electrical grid and extend its stay at the outpost.