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WASHINGTON (AP) - The margin for error in operating ICBMs can be excruciatingly small — an eighth of an inch, in one case.
That tiny gap led to a disturbing incident in October 2010 in which the Air Force lost communication for nearly an hour with an entire squadron of Minuteman 3 missiles. Their 50 missiles represented one-ninth of the entire Minuteman 3 missile fleet.
Investigators determined that a single replacement circuit card in a Minuteman 3 computer system's slot connector was one-eighth of an inch from being fully seated. That effectively jammed communications between the missiles and the five launch control centers to which they are connected by buried cables.
"This scenario sounded very familiar," the investigators wrote in a report from Nov. 15, 2010. The same problem occurred in 1998, they said, and some recommendations from that incident were never put in place.
One recommendation was remarkably low-tech: place a straightedge across the top of the circuit cards after replacing any of them, to verify they are properly seated.
"Use of this technique may have prevented the situation completely," it said, referring to the 2010 event at F.E. Warren Air Force Base in Wyoming.