Fuel Sensor Glitch Forces Launch Scrub

Published: Jul 13, 2005
Source: spaceflightnow.com



Launch director Mike Leinbach scrubbed today's planned launch of the shuttle Discovery two-and-a-half hours before takeoff time because of data indicating two of four hydrogen fuel flow sensors in the ship's external tank were not operating properly.

NASA's flight rules require all four to be operating properly for a countdown to proceed because the sensors control how the ship's main engines shut down when the shuttle reaches space. In certain failure scenarios, the engines could run the tank dry, leading to potential catastrophic failures.

It was not clear what caused today's problem, but the sensor system has encountered unusual trouble in recent weeks, possibly due to suspect transisters in an electronics "black box" in Discovery's aft compartment. The so-called "point sensor box" aboard Discovery included eight transisters from a suspect lot, sources said.

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A new launch target was not immediately announced.continue..