NASA tackles prelaunch problems

NASA wrestled with two late-breaking technical concerns that showed up Tuesday, two days before the scheduled launch of space shuttle Discovery, but managers weren’t sure whether they would delay the start of the mission.

The launch still was scheduled for Thursday night.

The first problem dealt with a power surge in one of the shuttle’s power systems during preparations overnight, although key elements such as the external tank, the solid rocket boosters and the main engines probably weren’t affected, said LeRoy Cain, launch integration manager.

The second concern was with an adhesive on the reusable solid rocket motor, which may have failed a test.

“We’re probably not going to have any issues, but we want the teams to go off and assess that everything is OK,” Cain said. “If there is anything we need to retest or check out more so than what we otherwise would do ... we want to talk about that.”

The weather forecast for the planned liftoff was downgraded slightly Tuesday but still remained favorable for the first nighttime shuttle launch in more than four years.

Concerns about clouds over Kennedy Space Center during the 9:35 p.m. Thursday launch caused forecasters to reduce the chances of favorable weather to 60% from 80%. Strong winds were expected Friday and Saturday, diminishing the chances of good launch weather for those days to 40%.

“The first day is the best day weatherwise,” said Kathy Winters, shuttle weather officer.

NASA probably won’t attempt to launch past Dec. 17 because flight controllers want Discovery on the ground before the new year. Shuttle computers aren’t designed to make the change from the 365th day of the old year to the first day of the new year while in flight. A potential solution to the problem hasn’t been thoroughly tested.

In Houston, engineers tested a fix to a software problem that had caused a breaker to open on a circuit to the motor that rotates the International Space Station’s giant solar arrays toward the sun. The solar arrays will generate power for the space station after Discovery’s mission.

During their 12-day mission, Discovery’s seven astronauts plan to rewire the space station, deliver a 2-ton addition and replace one of the space station’s three crew members.

NASA required daytime liftoffs for the three flights after the 2003 Columbia accident to make sure the agency could get good photos of the external fuel tank. Foam breaking off the tank at liftoff damaged that shuttle, which caused it to break up upon reentry, killing the crew of seven astronauts.