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Fingers crossed, NASA set for launch

Amid nagging worries and talk of bending its own safety rules, NASA plans to return the shuttle Discovery to space today.

By CURTIS KRUEGER
Published July 26, 2005

CAPE CANAVERAL - The Kennedy Space Center gift shop is selling T-shirts that bear the famous motto of a legendary NASA flight director: "Failure is not an option."

Failure still is not an option, but the question NASA is grappling with this morning is whether it's a possibility.

More than two years after the accident that destroyed the space shuttle Columbia and its seven-member crew, NASA is counting down the launch of the Discovery today, weather permitting.

It is possible the launch could be scrubbed early this morning; NASA engineers are still scrutinizing a fuel sensor that gave a faulty reading inside the shuttle's giant external fuel tank. The glitch prompted NASA to cancel a previously scheduled launch on July 13.

After 13 days of intense testing, engineers say they think they have pinpointed the fuel sensor problem - insufficient grounding in an electrical system. They admit, though, that they aren't sure.

That puts NASA in the position of making what could amount to life-or-death judgment calls: whether Discovery blasts off today or later.

NASA already has decided that it's okay to prepare for launch, despite lingering uncertainty about the cause of the original glitch. It also is poised to make another call that could prove controversial: to approve the launch even if the same sensor system fails again, though normal rules would prohibit it.

NASA has successfully flown space shuttles 111 times and engineers say they have learned from each of the missions. Sometimes NASA has made the wrong decision, such as believing that lightweight falling foam would not doom a crew.

That's why deputy shuttle program manager Wayne Hale said this weekend that "we are all still struggling a little bit with the ghosts of Columbia. "

"There's very little in life that is 100 percent guaranteed, and there's probably less in rocket science that's 100 percent guaranteed," he said. "That is part of the risk we take."

NASA's rules say the space shuttle should have four working sensors in the hydrogen fuel portion of its large, orange, torpedo-shaped external tank. The sensors work much like a gas gauge in a car, except that if fuel runs low, they are designed to automatically shut off Discovery's main engines. This is important because the engines could break apart if they continue firing until the tank runs empty.

Discovery vehicle manager Stephanie Stilson said that in the years since the four-sensor rule was first adopted, all sensors have been given separate power sources, which makes them less likely to fail together. That's why officials now say they think they could launch with only three working sensors without compromising safety.

While that decision may be based on solid engineering, it also would put NASA in the awkward position of changing a safety standard for a flight that resonates with memories of the Columbia tragedy.

Howard McCurdy, a space policy expert and chairman of public administration at American University, said changing the standard is not necessarily a bad idea, as long as NASA understands the glitch it has been monitoring.

"If you're just saying it's okay to fly with three but we don't have a clue why the fourth is malfunctioning, that's an invitation to disaster," McCurdy said.

However, if one sensor malfunctions again and NASA understands why, launching with three would not necessarily be a bad idea, he said.

Stilson said some glitches in the sensor system during countdown would be easy to understand, and would likely lead NASA to give the launch a green light. "If we see anything different than what we expect, we'll scrub," she said. She said engineers are optimistic that all four sensors will work correctly.

NASA spokesman Kyle Herring said three of the four sensors would have to fail for the engines to not shut down properly. Even that probably wouldn't happen, because the shuttle's on-board computers normally shut down the engines before the sensors ever kick in.

In addition to the sensor issue, NASA said there is a 40 percent chance that bad weather will delay today's flight. And as always with the launch of a complex spacecraft, there is the chance of other problems cropping up.

"I would like everything to go perfectly the first time," Stilson said, "but that's not the business we're in."

Curtis Krueger can be reached at 727 893-8232 or at krueger@sptimes.com Information from the Associated Press was used in this report.

[Last modified July 26, 2005, 04:42:41]