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
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