Cape Canaveral, Fla. ? For the fourth time in two weeks, NASA nixed the launch of the space shuttle Atlantis, this time for a faulty fuel tank sensor – the same glitch that has thwarted two other missions.

A fifth attempt will be made at 10:15 a.m. CDT today to get the spacecraft headed on a mission to resume construction of the international space station.

On Friday, the six astronauts were already strapped in with the hatch closed when the space agency called off the launch with just 45 minutes to go. Although the fuel sensor had malfunctioned hours earlier, NASA wanted to keep discussing the problem before scrubbing the flight.

But they knew the odds for a liftoff weren’t good. The agency has a new rule requiring a stand-down of 24 hours when one of the hydrogen tank’s four engine cutoff sensors doesn’t work properly; such a delay would allow engineers to gather more data on the problem.

“We had a lot of discussion. … We follow the rules,” launch director Mike Leinbach radioed Atlantis’ crew, notifying them about the scrub.

A large number of managers favored flying, but opposition to launching was led by NASA’s flight crew operations director.

The fuel gauges are designed to prevent the main engines from running too long or not long enough during the climb to space. An engine shutdown at the wrong time could prove catastrophic, forcing the astronauts to attempt a risky emergency landing overseas, or leading to a ruptured engine. NASA managers are confident the shuttle can launch successfully with only three of the four sensors working properly.