Image: Shuttle workers
John Raoux  /  AP
NASA workers walk along a platform on the fixed service structure next to the space shuttle Discovery on Launch Pad 39A at the Kennedy Space Center in Florida on Tuesday.
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updated 11/2/2010 11:54:32 PM ET 2010-11-03T03:54:32

The final launch of space shuttle Discovery has been delayed again, this time because of an electrical problem.

NASA decided early Tuesday evening to bump the liftoff until at least Thursday. The decision came less than 24 hours before the scheduled launch on Wednesday.

The space agency has until Sunday — possibly as late as Monday — to send Discovery to the International Space Station. Otherwise, it will have to wait until December because of sun angles.

Gas leaks had already forced a two-day postponement for Discovery's last trip into orbit.

"Discovery is not going out easy," said launch director Mike Leinbach. "She's giving us a little bit of trouble, but that's fine. She'll fly perfectly when she does."

The weather may keep Discovery grounded even longer. Looking ahead to Thursday, forecasters said there is a 70 percent chance that rain and perhaps even thunderstorms will stall what's officially NASA's next-to-last shuttle flight.

The electrical problem cropped up aboard Discovery early Tuesday. A backup controller for one of the shuttle's three main engines was sluggish in turning on. Voltage irregularities then were noted. Mission managers wanted more time to figure out what's wrong, and put the countdown on hold.

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.

Mike Moses, chairman of the prelaunch mission management team, said a bit of dust or other debris may have prevented the circuit breaker for the controller from making a solid contact. Engineers want to make certain that's the reason for the slight voltage irregularities, and that the problem will not worsen and consequently pose an increased risk to launch.

Moses and his team will reconvene Wednesday afternoon to determine whether it's safe to launch Discovery on Thursday, or whether repairs might be needed. The latter likely would push the launch into December.

"We like to say we don't fly with unknown risk, and right now, this risk is a little bit still unknown to us," Moses told reporters. "We're going to take another day to get to know it better."

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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 (320 kilometers) above Earth.

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

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.

One final shuttle mission is officially on the books for next year as NASA looks toward newer and farther-flying craft. An extra flight may be added if money is forthcoming.

© 2013 The Associated Press. All rights reserved. This material may not be published, broadcast, rewritten or redistributed.

Interactive: All about the International Space Station

Photos: Month in Space: January 2014

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  1. Southern stargazing

    Stars, galaxies and nebulas dot the skies over the European Southern Observatory's La Silla Paranal Observatory in Chile, in a picture released on Jan. 7. This image also shows three of the four movable units that feed light into the Very Large Telescope Interferometer, the world's most advanced optical instrument. Combining to form one larger telescope, they are greater than the sum of their parts: They reveal details that would otherwise be visible only through a telescope as large as the distance between them. (Y. Beletsky / ESO) Back to slideshow navigation
  2. A balloon's view

    Cameras captured the Grandville High School RoboDawgs' balloon floating through Earth's upper atmosphere during its ascent on Dec. 28, 2013. The Grandville RoboDawgs’ first winter balloon launch reached an estimated altitude of 130,000 feet, or about 25 miles, according to coaches Mike Evele and Doug Hepfer. It skyrocketed past the team’s previous 100,000-feet record set in June. The RoboDawgs started with just one robotics team in 1998, but they've grown to support more than 30 teams at public schools in Grandville, Mich. (Kyle Moroney / AP) Back to slideshow navigation
  3. Spacemen at work

    Russian cosmonauts Oleg Kotov, right, and Sergey Ryazanskiy perform maintenance on the International Space Station on Jan. 27. During the six-hour, eight-minute spacewalk, Kotov and Ryazanskiy completed the installation of a pair of high-fidelity cameras that experienced connectivity issues during a Dec. 27 spacewalk. The cosmonauts also retrieved scientific gear outside the station's Russian segment. (NASA) Back to slideshow navigation
  4. Special delivery

    The International Space Station's Canadian-built robotic arm moves toward Orbital Sciences Corp.'s Cygnus autonomous cargo craft as it approaches the station for a Jan. 12 delivery. The mountains below are the southwestern Alps. (NASA) Back to slideshow navigation
  5. Accidental art

    A piece of art? A time-lapse photo? A flickering light show? At first glance, this image looks nothing like the images we're used to seeing from the Hubble Space Telescope. But it's a genuine Hubble frame that was released on Jan. 27. Hubble's team suspects that the telescope's Fine Guidance System locked onto a bad guide star, potentially a double star or binary. This caused an error in the tracking system, resulting in a remarkable picture of brightly colored stellar streaks. The prominent red streaks are from stars in the globular cluster NGC 288. (NASA / ESA) Back to slideshow navigation
  6. Supersonic test flight

    A camera looking back over Virgin Galactic's SpaceShipTwo's fuselage shows the rocket burn with a Mojave Desert vista in the background during a test flight of the rocket plane on Jan. 10. Cameras were mounted on the exterior of SpaceShipTwo as well as its carrier airplane, WhiteKnightTwo, to monitor the rocket engine's performance. The test was aimed at setting the stage for honest-to-goodness flights into outer space later this year, and eventual commercial space tours.

    More about SpaceShipTwo on PhotoBlog (Virgin Galactic) Back to slideshow navigation
  7. Red lagoon

    The VLT Survey Telescope at the European Southern Observatory's Paranal Observatory in Chile captured this richly detailed new image of the Lagoon Nebula, released on Jan. 22. This giant cloud of gas and dust is creating intensely bright young stars, and is home to young stellar clusters. This image is a tiny part of just one of 11 public surveys of the sky now in progress using ESO telescopes. (ESO/VPHAS team) Back to slideshow navigation
  8. Fire on the mountain

    This image provided by NASA shows a satellite view of smoke from the Colby Fire, taken by the Multi-angle Imaging SpectroRadiometer aboard NASA's Terra spacecraft as it passed over Southern California on Jan. 16. The fire burned more than 1,863 acres and forced the evacuation of 3,700 people. (NASA via AP) Back to slideshow navigation
  9. Where stars are born

    An image captured by NASA's Spitzer Space Telescope shows the Orion Nebula, an immense stellar nursery some 1,500 light-years away. This false-color infrared view, released on Jan. 15, spans about 40 light-years across the region. The brightest portion of the nebula is centered on Orion's young, massive, hot stars, known as the Trapezium Cluster. But Spitzer also can detect stars still in the process of formation, seen here in red hues. (NASA / JPL-Caltech) Back to slideshow navigation
  10. Cygnus takes flight

    Orbital Sciences Corp.'s Antares rocket rises from NASA's Wallops Flight Facility on Wallops Island, Va, on Jan. 9. The rocket sent Orbital's Cygnus cargo capsule on its first official resupply mission to the International Space Station. (Chris Perry / NASA) Back to slideshow navigation
  11. A long, long time ago...

    This long-exposure picture from the Hubble Space Telescope, released Jan. 8, is the deepest image ever made of any cluster of galaxies. The cluster known as Abell 2744 appears in the foreground. It contains several hundred galaxies as they looked 3.5 billion years ago. Abell 2744 acts as a gravitational lens to warp space, brightening and magnifying images of nearly 3,000 distant background galaxies. The more distant galaxies appear as they did more than 12 billion years ago, not long after the Big Bang. (NASA / NASA via AFP - Getty Images) Back to slideshow navigation
  12. Frosty halo

    Sun dogs are bright spots that appear in the sky around the sun when light is refracted through ice crystals in the atmosphere. These sun dogs appeared on Jan. 5 amid brutally cold temperatures along Highway 83, north of Bismarck, N.D. The temperature was about 22 degrees below zero Fahrenheit, with a 50-below-zero wind chill.

    Slideshow: The Year in Space (Brian Peterson / The Bismarck Tribune via AP) Back to slideshow navigation
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