- Associated Press - Tuesday, November 2, 2010

CAPE CANAVERAL, Fla. | The final launch of space shuttle Discovery has been delayed again.

NASA decided Tuesday evening to hold the liftoff until at least Thursday. The decision came less than 24 hours before the scheduled launch time.

An electrical problem cropped up aboard Discovery early Tuesday. A controller for one of the shuttle’s main engines was sluggish, but engineers got it working. Voltage irregularities then were detected. Mission managers said they needed more time to figure out what’s wrong.

NASA has until Sunday — possibly Monday — to launch Discovery to the International Space Station. Otherwise, it will have to wait until December because of unacceptable sun angles.

Gas leaks had already forced a two-day postponement.

It’s the next-to-last shuttle flight on NASA’s official schedule, and Discovery’s final one, as the agency looks toward newer and farther-flying craft. An extra mission may be added next year.

Each of the main shuttle engines has both a primary and backup computerized controller that serve as electronic brains. They are critical parts that must work perfectly before going ahead with a launch.

Earlier, NASA test director Steve Payne said the controller trouble appeared to be caused by debris in the circuit breaker.

As the shuttle team scrambled at the launch site, the rest of NASA celebrated 10 years of continuous human presence at the space station. The six U.S. astronauts and Russian cosmonauts there now fielded calls of congratulations.

“You all are incredible ambassadors,” NASA Administrator Charles Bolden Jr. said in a broadcast hookup from Kennedy Space Center. “What you do is actually a modern-day ‘Star Trek.’”

On Nov. 2, 2000, three men moved into the young space station. People from around the world have been there ever since, living and working more than 200 miles above Earth.

On its 39th and final flight, Discovery will take six visitors as well as thousands of pounds of supplies, including a humanoid robot.

Mr. Payne said there was a lot of excitement as the countdown entered its final stages before postponement.

Shuttle workers “put their heart and soul into this one,” with the intent of making this last voyage of Discovery as good as the 38 that have come before, he said.

Discovery has carried 180 individuals into orbit over its 26-year career, and logged nearly 150 million miles and more than 5,600 orbits of Earth. It is NASA’s oldest surviving shuttle and fleet leader, and will be the first to be prepared for museum retirement.