NASA Puts Off Space Shuttle Launch To January

Two attempts to launch Atlantis were stymied by erratic fuel sensors, which are part of an emergency engine cutoff system.

NASA on Sunday canceled plans to launch space shuttle Atlantis until January, delaying the arrival of Europe's science laboratory to the International Space Station.

Two attempts to launch Atlantis were stymied by erratic fuel sensors, which are part of an emergency engine cutoff system.

Two of the four sensors in the ship's hydrogen tank failed during NASA's first launch attempt on Thursday. One of them failed again when the tank was being filled for a second launch try on Sunday.

"The Mission Management Team is still meeting, but we are off until no earlier than Jan. 2," said NASA spokesman Allard Beutel.

The sensors, which operate like dipsticks to determine fuel levels, are part of a backup system to cut off the shuttle's three hydrogen-burning main engines if the tank runs dry due to a leak or other problem.

Running the engines without propellant could cause their pumps to break and possibly trigger a catastrophic explosion.

"The ground rules that were laid out before we went into (Sunday's) launch attempt were that we would have to have four sensors that were mandatory for launch," launch commentator George Diller said.

NASA had until Thursday or Friday for launch attempts this year, and any analysis and repair of the problem would take longer than that to complete, officials said.

"It takes a great deal of courage for people to climb on board of that rocket ship and launch into space on any given day," shuttle program manager Wayne Hale said on Saturday.

Disasters in 2003 and 1986, which killed the crews aboard the shuttles Columbia and Challenger, have made NASA especially cautious about launch safety.

After's Thursday's scrubbed launch, managers met for two days and had decided to attempt the Atlantis launch again on Sunday despite the erratic sensors, which have a history of glitches.

Engineers believed they had traced the problem to a subtle manufacturing issue and thought they solved it by replacing all suspect devices.

Hale told reporters late on Saturday that the continued problems show no one knows what is causing the discrepancies.

NASA will start another round of investigations and engine upgrades to try to determine the cause of the problem, he added.

NASA has 10 shuttle flights remaining to complete construction of the $100 billion space station. It also wants to make two resupply flights and a servicing call to the Hubble Space Telescope before the shuttle fleet is retired in 2010.