Sensor Woes Won't Stall Shuttle

NASA said it will allow Discovery to lift off Tuesday on the first post-Columbia shuttle flight even if a baffling fuel-tank sensor problem resurfaces.

Chances for favorable weather for liftoff were 60 percent Monday morning, reports CBS News Correspondent Peter King.

"The teams are ready. We're certainly very eager. We are anticipating and really look forward to a launch," said NASA Test Director Pete Nickelencko.

NASA workers rewired some of the sensors and made other electrical repairs after the failure forced the space agency to postpone the shuttle's launch while astronauts were boarding Discovery on July 13.

The space agency's own launch rule — in place since the 1986 Challenger disaster — requires that all four hydrogen fuel gauges in the external tank be working properly, though only two are actually needed.

Engineers still do not fully understand the reason for the failure. But NASA will go ahead with the rescheduled launch at 10:39 a.m. Tuesday if the problem doesn't recur or if it is found only in the two sensors that have been rewired, Wayne Hale, deputy manager of the shuttle program, said Sunday.

"If the problem recurs ... we're going to do some more tests just to make sure we understand what is causing this to happen and if we're comfortable that we have a good understanding, then we can go fly," Hale said.

It will be the first shuttle flight since the Columbia disaster 2½ years ago.

NASA Administrator Michael Griffin said he is comfortable with the decision and even hopes the problem recurs to help pinpoint the source of the trouble. He acknowledged that the public might perceive that the space agency is rushing to launch, but insisted it was the right technical judgment.

"It's not a safety-of-flight issue," Griffin said.

Although the focus of NASA's attention has been on the sensor, rain and clouds may end up causing more concern on launch day. Additionally, the weather at the overseas emergency landing sites is not looking good.

First lady Laura Bush, already in Florida on a previously scheduled trip, planned to watch the shuttle launch Tuesday, reports CBS News Correspondent Mark Knoller.
"My observation is that when the weather is good, you have vehicle problems. If the vehicle works, you have weather problems," Hale said jokingly. "Since we have some weather concerns, I'm confident the vehicle is going to be OK."

NASA has just one week to launch Discovery and its crew of seven to the international space station before putting off the mission until September. The space agency is insisting on a daylight liftoff in order to photograph any signs of the type of launch damage that crippled Columbia.

Columbia and its seven astronauts were brought down by a broken section of fuel-tank foam insulation that struck just over a minute after liftoff and proved lethal during descent two weeks later, on Feb. 1, 2003.

Workers last week repaired faulty electrical grounding inside Discovery in hopes that would solve the fuel gauge problem that cropped up during the previous launch attempt. The same type of problem occurred back in April during a fueling test and was written off then as an "unexplained anomaly."

NASA had 14 teams around the country studying the problem. They have eliminated possible explanations one by one, but they have been unable to arrive at a definitive answer.

The fuel gauges are needed to prevent the main engines from shutting down too soon or too late during liftoff. The first scenario could result in a risky, never-attempted emergency landing; the second could cause the engine turbines to rupture and destroy the spacecraft.

Going with three out of four gauges would be a "deviation" in the rule, Hale told reporters, but he said NASA engineers' understanding of the problem is vastly improved than it was 10 days ago.

"I wake up every day and I ask myself, 'Are we pushing too hard? Are we doing this thoroughly? Have we done the right technical things?"' Hale said. "I think we're all still struggling a little bit with the ghost of Columbia and therefore we want to make sure we do it right."