Preliminary Findings Point To Bad Connector, Not Faulty Sensors

Here's a case where failure is actually a good thing. Engineers at NASA think they know why engine cut-off sensors installed within the external fuel tank connected to the shuttle Atlantis are malfunctioning, after two of the problem sensors failed during an on-pad test Tuesday.

NASA traced the problem to a bad connector between the tank and the shuttle, reports The Associated Press. But the agency isn't sure how long it will take to fix the problem, or when the shuttle will fly again.

"We're going to follow this trail where it leads us and we're going to solve this problem, and then we'll go fly ... whether it's January 10 or February 10 or March 10," said shuttle program manager Wayne Hale, adding the results of the test "sets us on the right path to correct this problem so we can return this important safety system to operational capability so we can fly again."

The good news stems from the likelihood the sensors themselves aren't to blame for the problem. Replacement of problem sensors would require Atlantis to head back to the Vehicle Assembly Building, and a teardown of the tank.

Preliminary information from Tuesday's test points to a section of wiring known as a "feed-through" connector. The data collected Tuesday will continue to be analyzed and presented to program managers Wednesday with recommendations on how to proceed.

To test the sensors, engineers pumped super-cold liquid hydrogen into the external fuel tank, and monitored for signs of failure.

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 launch abort.

As ANN reported, two sensors malfunctioned during the original December 6 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 December 9, halting the countdown once again.

So far, NASA has only said the shuttle won't launch before January 10.

FMI: www.nasa.gov/shuttle