KENNEDY SPACE CENTER, Florida (CNN) -- NASA mission managers decided Friday to push the space shuttle Atlantis' scheduled Saturday launch to Sunday afternoon.
The liftoff is now scheduled for 3:21 p.m. Sunday and managers were still meeting to discuss final details of the plan, Kennedy Space Center spokesman Allard Beutel said.
The shuttle originally was to have blasted off Thursday, but the launch was put off until Saturday after two of the four engine cut-off sensors for the spacecraft's external fuel tank failed during preflight testing.
The root cause of the problem continues to elude NASA engineers.
Shuttle Program Manager Wayne Hale compared it to an intermittent electrical problem with a car that presents itself while someone is driving around, but "fixes itself" by the time they get to the mechanic.
"I find this extremely frustrating," Hale said. "We frankly have done everything that we know to do to improve that system." Watch Hale talk about the delay »
The malfunctioning sensors act like a "low fuel" sensor in a car.
As the shuttle rockets toward space, the sensors monitor the amount of fuel in the tank and can automatically shut off the main engines if they determine the tank is empty.
If the sensors were to malfunction, they could shut the engines down before the shuttle reaches orbit, requiring a dangerous emergency landing.
"We don't like to accept risk at the launch site. We don't want to get launch fever... we want to make sure that when we go launch it is safe," Hale said.
NASA rules say three of the four sensors must be working before the shuttle can head toward space, according to The Associated Press.
The focus of the shuttle's upcoming 11-day mission is delivering the long-awaited European addition to the International Space Station -- a 23-foot-long laboratory module named "Columbus," after the 15th-century explorer.
The high-tech lab has been in the works for 25 years and is considered a huge milestone toward the completion of the space station.
Atlantis must launch by the end of next week or wait until the next launch window next month, the AP reported. E-mail to a friend
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