Shuttle prepared to ‘go’ with a glitch

Preparations on track
Preparations for launch continued on track for launch at 10:39 a.m. ET Tuesday, with no significant issues standing in the way, test director Jeff Spaulding said earlier in the day. Weather officer Kathy Winters put the chances for acceptable weather at 60 percent.

Meanwhile, Discovery's crew of astronauts — headed by the only woman ever to command a shuttle mission, Eileen Collins — continued their own preparations. Because Discovery's landing is now due to take place before sunrise, Collins and shuttle pilot Jim Kelly are practicing night landings, using planes outfitted to duplicate the shuttle's aerodynamics.

Spaulding said the mood among members of the launch team has brightened, after days of focusing so intensely on the glitch that they couldn't look ahead to the launch. "I think now it's finally come to that point where people can realize that we are close, and we really are going to get a shot this time," he said.

However, the key test will come in the wee hours of Tuesday morning, when the launch team starts filling up Discovery's fuel tank with superchilled liquid hydrogen and oxygen. When the low-level sensors are covered with fuel — about a half-hour after fueling begins — managers will begin testing the sensors to make sure they can switch between a "wet" and a "dry" reading.

That "wet/dry" testing would be interrupted for two series of normal automated checkouts — one about an hour before Discovery's crew boards the shuttle, and the other during a T-minus-9-minute hold. The glitch that stopped the first countdown on July 13 could arise at any time during the continuous testing, and that would trigger another series of checks to determine whether the glitch had to do with the tank's sensor or the shuttle's circuitry.

"Some of us are kind of hoping that it recurs," Hale said, so that engineers could definitively track down the source of the problem.

He said one other concern was raised in advance of Sunday's management team meeting: the buildup of ice on the exterior of Discovery's supercold fuel tank during the previous countdown. Mike Wetmore, director of shuttle processing, said the launch team would keep a close eye on the potential icing problem during the current countdown.

If the launch has to be postponed again, mission managers can schedule as many as three more attempts later this month or perhaps even in early August. Then they'd have to wait until September.

12-day mission
Discovery's 12-day mission is aimed at resupplying the space station as well as testing all the safety enhancements that have been made since the shuttle Columbia broke up, killing all seven astronauts aboard. More than 100 cameras will be recording the launch, and so NASA wants to make sure liftoff occurs during daylight. Mission managers also want to get a good look at the fuel tank as it comes off the orbiter, and that's why they're debating exactly when the current launch window will close.

The fuel tank is a key concern, because foam insulation that flew off Columbia's tank just after launch is thought to have knocked a hole in that shuttle's left wing — setting the stage for Columbia's destruction 16 days later when hot atmospheric gases entered through the hole.

During Discovery's mission, astronauts will use cameras and a newly designed extension boom to make a close inspection of the orbiter's protective skin after launch. If serious damage is found, Discovery's crew would take refuge aboard the space station and wait for another shuttle crew to come to the rescue next month.

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