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Connector Woes - October 8, 2009

It was in the early 1970s. I was fresh out of college and found myself working for a major aerospace company in their power systems group.  Our group handled most of the power supplies and power converters for company’s space craft and missiles.  For many months I had been assigned the task of supporting the company with their various “squib fire circuits.” 
These were small black boxes that were used to provide power to various stage separation and self destruct explosive devices on the company’s ICBMs and satellite launch vehicles.  The circuit was pretty simple.  It was a fully isolated DC to DC converter, which routed high current to the explosive squibs, when DC was applied to the converter input, together with some redundant control lines. 

On this fateful Saturday, I had gone into work to try and catch up on some paperwork.  I was the only one in the lab.  My phone rang.  It startled me since my phone seldom rang, even on normal business hours.  The caller introduced himself as General “so and so” at Cap Kennedy.  He said they were T-xyz and holding for a launch of a classified satellite. 

Their countdown was put on hold after finding out that a technician had mixed up one of the connectors during prelaunch and had managed to connect one of the squibs backwards for a few minutes, then corrected the error. Their protocol called that when such mistakes occurred that a knowledgeable engineer be called in.  I was in a panic.  I said to the General that I thought that the connector was keyed so it could only be connected to its mate one way.  But the General didn’t care.  He wanted to know if the act of connecting the thing backwards could damage the circuit or the squib. 
I quickly dug out the circuit schematic and pulled out my slide rule (before electronic calculators).  I calculated the leakage currents that could occur if the polarity was switched and also imagined any other combination.  The only way I could see that current would flow was when the connector was in the right position.  So, I said they were good to go.  The General thank me and clicked off.  I watched the TV news that day, expecting that if the thing blew up that there would have been some mention of it.  Nothing was said. 
Then, around mid morning on Monday, my supervisor summoned me to the main conference room.  He told me to bring my slide rule and the squib fire schematics.  When I came into the room I was shocked.  There were a dozen or so military top brass and a lot of high-level company “suits” waiting for me.  After I was introduced to everyone, I was grilled for hours about the circuit and my decision.  Toward the end of the meeting there were some suggestions about making some squib fire connector design changes and then I was asked to sign some documents.  In the end, everything worked out but having a missile launch put on hold until someone like me could say it was OK to blast off was more pressure than I wanted at that time in my career.

November 2009     Issue 3

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