It’s Always the Connectors 2: TDR Pinpoints Shuttle Connector Failure

NASA now believes it has confirmed the cold-induced failure of the Space Shuttle external tank Engine Cutoff (ECO) sensors is due to the failure of the 3-piece feedthrough connector used to pass the sensor signals from the internal tank sensors to external wiring. (See my previous blog entry on this topic.) The connector system consists of a 37-pin female connector inside the tank, a similar 37-pin female connector outside of the tank, and a male-to-male connector that acts as the actual feedthrough. NASA techs identified the failure mechanism using time-domain reflectometry (TDR), see photo below and big version here.

Unidentified NASA tech uses TDR to spot ECO sensor failure mechanism
(Photo credit: NASA/Kim Shiflett)

The photo shows an interesting instrumentation mashup. That’s clearly an Agilent TDR hooked to a Dell laptop through a well-used IEEE-488 converter box made by National Instruments. There’s a Fluke DMM (I think) hanging around for good measure. Quite an egalitarian mix of T&M products.

And The Fix …

Now that NASA has identified the failure mechanism, the apparent fix (at this point) looks to be direct soldering of the wires to eliminate the connectors. This approach has reportedly been used previously in Centaur rockets.