Will Launch If Only Three ECO Sensors Are Cleared

They've done all they can. That's the underlying tone to NASA's announcement this week shuttle launch operators won't require all four engine cut-off sensors to be operational when Atlantis finally lifts off the pad next month.

On Thursday, NASA's Program Requirements Control Board recommended launching Atlantis on February 7, even if only three of four ECO sensors installed within the shuttle's external fuel tank give the proper readings during fueling.

As ANN reported, NASA has worked for nearly two months to fix a stubborn glitch in the ECO sensor system, which monitors fuel levels and sends shut-off signals to the orbiter's main engines. The sensors detect the level of liquid hydrogen in the fuel tank, to determine when to shut down the shuttle's three main engines.

Failure of the sensors could shut the engines down too early, or, conversely, run them dry -- the latter a catastrophic scenario.

An on-pad test of the fuel system revealed the likely cause of the glitch -- a connector that feeds wiring through the skin of the external tank, and mates up with the orbiter. Engineers have since installed connector.

The decision reverts Launch Commit Criteria  back to original standards; following the initial scrubbed launch December 6, NASA called for all four sensors to be operational before the shuttle could lift off; during each attempt, two sensors failed.

"That wasn't a permanent change," NASA spokesman Candrea Thomas told Florida Today. "That was just for that launch attempt."

The decision to launch Atlantis if only three of four ECO sensors are operational must be approved by NASA management. A Flight Readiness Review, led by shuttle program manager Wayne Hale, was scheduled for Friday.

FMI: www.spaceflight.nasa.gov