Shuttle Discovery cleared for launch, but storm looms

The space shuttle Discovery and its STS-133 crew will deliver the Permanent Multipurpose Module, packed with supplies and critical spare parts, as well as Robonaut 2, the dexterous humanoid astronaut helper, to the International Space Station.
The space shuttle Discovery and its STS-133 crew will deliver the Permanent Multipurpose Module, packed with supplies and critical spare parts, as well as Robonaut 2, the dexterous humanoid astronaut helper, to the International Space Station.
/ Source: Space.com

NASA has decided to press on with plans to launch the space shuttle Discovery on its final mission Thursday after evaluating a last-minute electrical glitch on the spacecraft, but a dismal weather forecast looms ahead.

Teams here at NASA's Kennedy Space Center reviewed the data from the anomaly overnight and concluded that the problem was likely the result of residual contamination on a circuit breaker connection, rather than a problem with the engine controller itself.

Engineers "scrubbed" the connectors by plugging them in and out, which cleans the metallic surfaces of the residue. Mission managers are confident the issue has now been resolved.

"We talked overnight, the team brought us a very nice, cohesive flow through the data," Mike Moses, NASA's shuttle integration manager, said in a news briefing. "We had a unanimous poll out of the [mission management team], and everyone was very comfortable with the story that came together today."

Discovery is slated to blast off from a seaside launch pad here at the Kennedy Space Center at 3:29 p.m. EDT (1929 GMT) tomorrow (Nov. 4). The decision came after an hours-long discussion by top mission managers to clear Discovery of any concerns related to an electrical glitch in a backup main engine computer controller.

Weather, however, still poses a dire threat for Discovery's launch chances. Current forecasts show an 80 percent chance that foul weather could cause yet another delay, though conditions improve for later attempts on Friday.

Managers will reconvene early tomorrow morning before tanking to assess the weather situation.

The glitch was detected yesterday and forced NASA to halt launch preparations for Discovery. The shuttle was initially slated to launch Monday (Nov. 1), but was postponed due to unrelated gas leaks that have since been repaired.[GRAPHIC: NASA's Space Shuttle – From Top to Bottom]

During the orbiter's engine checkouts yesterday (Nov. 2), the backup controller for Discovery's Main Engine No. 3 did not turn on as expected. When it powered on about an hour and a half later, engineering teams subsequently observed an irregular voltage drop.

Discovery is slated to fly an 11-day mission to the International Space Station to deliver a new storage module and a humanoid robot for the orbiting lab's crew. It will be the 39th and last flight for space shuttle Discovery, which is the first of NASA's three shuttles to be retired as the agency winds down its orbiter program next year.

If NASA cannot launch Discovery by Sunday, Nov. 7, it will miss the current window and have to stand down until Dec. 1 to try again.

Follow SPACE.com Staff Writer Denise Chow on Twitter as she covers Discovery's final space voyage from Cape Canaveral, Fla.