Fuel Tank Sensors Will Be Replaced
ANN REALTIME REPORTING 03.14.06 1610 EST: NASA today
announced the launch of the space shuttle Discovery -- the second
since the program's return to flight after the 2003 Columbia
disaster -- has been delayed until at least July. Shuttle Program
Manager Wayne Hale said he told his shuttle prep team today that
the delay was brought about by the discovery of faulty sensors in
the shuttle's external tank.
"We wish it had worked out differently, but it's of course,
first and foremost that we fly safely," Hale said during a briefing
from the Johnson Space Center in Houston.
Discovery will now launch no earlier than July 1st.
In his televised briefing, Hale detailed the ongoing saga of
external fuel tank problems -- including the delamination of foam
from the tank, which caused the Columbia disaster and threatened
Discovery during its latest launch last July. Ironically, however,
it wasn't the foam issue that forced today's delay of the May
Instead, it was the
discovery of faults in the four low-level fuel sensors inside the
external tank itself.
The fuel sensors -- known as ECO, or engine cut-off sensors --
are important to the mission, because they monitor propellant
levels and are responsible for ensuring the shuttle's main engines
shut down at the proper speed needed to reach orbit, and stay on
its assigned course.
As Aero-News reported last
week, one of those sensors had been reading slightly
low -- which could have shut off fuel flow to the engines sooner
than needed, potentially compromising the shuttle's ability to
reach orbit. There is also the chance an abnormal reading could
cause the engines to run at an excessively high rate, when they
should actually shut down -- a scenario that arose during the
earliest days of shuttle testing.
Almost the exact same type of problem also cropped up during
last year's return-to-flight mission on Discovery. After a glitch
was detected in one of the fuel tank sensors for that flight, NASA
ultimately decided to launch in spite of the risk. All four sensors
performed flawlessly for that launch... but NASA doesn't want to
take any chances this time around.
Despite the delay, NASA still hopes to launch three shuttle
missions before the end of 2006 -- although the timeframe, already
compressed, has now been narrowed even further.
"We should still be able to get three missions in this year,"
Hale said, "but we don't have the details on that yet."