Hoping To Avoid Trip Back To VAB
Technicians and engineers in NASA's space shuttle program plan
to test the engine cutoff (ECO) sensor system onboard space shuttle
Atlantis by pumping super-cold liquid hydrogen into the external
fuel tank. The test is tentatively planned for December 18, and
will be conducted on the launch pad at Kennedy Space Center where
Atlantis remains poised for launch.
As ANN reported, NASA was
forced to postpone last Thursday's scheduled launch of Atlantis,
due to the problematic sensors located within the shuttle's
external fuel tank. After a second launch attempt Sunday was
scrubbed, NASA rescheduled the launch for no earlier than January
Space Shuttle Program Manager Wayne Hale said additional
instruments will be used during the test to pinpoint the problem
that led to false readings during two previous countdown attempts
The companies that built the pieces of the space shuttle are
conducting tests at other facilities to help determine a cause,
"This is part of broad-ranging effort," Hale said.
NASA hopes the on-pad test will pinpoint the cause of the
recurring malfunction of the four ECO sensors within the tank, and
determine a fix is possible without sending Atlantis back to the
Vehicle Assembly Building for a more thorough teardown. Such a move
would likely delay launch for months... throwing NASA's tight
shuttle launch schedule into total disarray.
"We have a high degree of confidence of pinpointing the location
of where we are having problems," Hale told The Houston Chronicle.
"Once we know the location — and there is about 100 feet of
wiring with several connectors and sensors at the end -- we will be
able to concentrate on our go-forward efforts, presumably put
together a fix, and go fly."
The ECO sensors detect when levels of hydrogen within the
external tank run low, and send a signal to shut off the orbiter's
three main engines before fuel runs out. Continuing to operate the
engines without fuel would lead to a catastrophic failure;
likewise, cutting off the flow of fuel too soon would lead to a
Two sensors malfunctioned during last Thursday's countdown;
NASA's launch standards require three of the four sensors to be
operational at time of launch. A third sensor mysteriously failed
as NASA began loading hydrogen into the tank Sunday morning.