Engineers Continue Work On ECO Sensor Glitch

Will NASA launch the shuttle Atlantis "as is," with two out of four sensors in the external fuel tank malfunctioning? That's one option NASA is reportedly considering, in its desire to launch the orbiter towards the International Space Station before an eight-day launch window expires.

As ANN reported, NASA scrubbed Thursday's launch attempt due to malfunctions in two engine cut-off (ECO) fuel level sensors within the enormous fuel tank. The sensors are meant to safeguard the orbiter's three main engines, by cutting power if lower-than-expected fuel levels are detected during the launch phase.

The agency also opted to forego a Friday launch, so it could continue work on the issue. Late Friday night, NASA announced it would move the launch off yet another day, to Sunday.

NASA's standard protocols require at least three ECO sensors be functioning for launch... but the agency adds it's possible to launch the shuttle with only two operational sensors, although that's not the preferred option.

CBS News reports if a third sensor were to fail during launch, the last remaining sensor would trigger a premature engine shutdown. In fact, that's what it is designed to do -- so the engines remain protected in case the fourth sensor were to fail.

In that scenario, depending on what phase of the ascent such a failure occurred, the shuttle would abort directly to a landing site, or abort to orbit and then return to Earth following a subsequent trip around the planet.

A catastrophic failure could occur if the shuttle's main engines remained powered up as the tank ran dry, according to NASA.

Due to the tight eight-day launch window for STS-122, NASA doesn't have enough time to replace the errant sensors... meaning engineers must either develop a work-around solution, or sign off on launching with only two functional ECO sensors.

NASA engineers and mission personnel met Friday to discuss possible options. At the end of the six-hour meeting, mission managers determined it was too late to push for a Saturday launch.

Stay tuned...

FMI: www.spaceflight.nasa.gov