Shuttle Discovery On Track for Wednesday Launch

CAPE CANAVERAL, Fla. - NASA's space shuttle Discovery is on track to launch Wednesday evening to deliver new solar arrays to the International Space Station, mission managers said.

Even the weather appears to be cooperating so far for the planned launch from NASA's Kennedy Space Center at Cape Canaveral, Fla. on March 11 at 9:20 p.m. EDT (0120 March 12 GMT).

"The weather looks good for launch, I'm very happy to say," NASA weather officer Kathy Winters said at a briefing here. "We have these nice, mild conditions, warm temperatures? so a 90 percent chance of 'go' weather."

The only possible threat to launch from weather could be from a ceiling of clouds that may come in to block launch, Winters said. If that happens, mission managers said they can attempt to launch every day up until March 16, after which they would have to stand down to allow a Russian Soyuz craft to make its scheduled flight to the space station.

Discovery's seven-man crew, led by commander Lee Archambault, arrived in Florida yesterday on T-38 jets. They will spend today undergoing medical exams, checking out their launch suits and reviewing launch plans. This evening Archambault and shuttle pilot Tony Antonelli are scheduled to practice landing the space shuttle by flying shuttle training aircraft, which are modified Gulfstream planes.

Mission managers said Monday that no technical problems currently pose a threat to Discovery's planned launch. They did investigate one minor worry associated with a controller on the shuttle's Orbital Maneuvering System (OMS) engines, which had had a "hiccup" during last year's May launch of the shuttle Discovery's STS-124 flight. Ultimately, they decided it posed a very low risk.

"If this part fails, it's one of two controllers on a single OMS engine," said Mike Moses, chair of Discovery?s mission management team, adding that the controller was part of a tiered system full of backups. ?So redundancy-wise, we're in really great shape there."

After weeks of delays to Discovery's launch date over fears that fuel control valves in the shuttle's main engines might be faulty, NASA mission managers said they are confident the shuttle is in good shape to fly.

"The team is anxious to go," said NASA shuttle launch director Mike Leinbach. "We?re fully trained, ready to execute this mission."

Engineers ended up replacing the three valves on Discovery with a set that had been scanned to be sure they had no damage. Last year, a valve on NASA's shuttle Endeavour cracked during its November 2008 launch. Though the problem didn't affect the shuttle's flight, and Endeavour completed its mission successfully, mission managers wanted to be sure a similar occurrence wouldn't endanger Discovery.

The valves monitor the pressure of liquid hydrogen fuel in the shuttle's main engines during launch, and leak off excess gaseous hydrogen if needed. After extensive tests, engineers found that even if a valve were to crack during a future shuttle launch, the chances of it causing serious damage are extremely low. Nonetheless, managers decided to replace Discovery's set of valves with a new complement that were free of cracks even a fraction of a hair wide.

Discovery is set for a 14-day mission featuring four spacewalks to install the new solar array wings on the International Space Station (ISS). It will also ferry up Koichi Wakata, a Japanese Space Exploration Agency (JAXA) astronaut who is to become his country's first long-duration ISS crewmember. He is scheduled to join the station's expedition 18 for about six months as a flight engineer.

"I am expecting that this week will become a historic event for the Japanese human space program," said Kuniaki Shiraki, JAXA ISS program manager.

SPACE.com is providing continuous coverage of STS-119 with reporter Clara Moskowitz at Cape Canaveral and senior editor Tariq Malik in New York. Click here for mission updates and SPACE.com's live NASA TV video feed.

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