The Air Force said Wednesday it was only as "an added precaution" that an armored car was hurriedly parked atop a Minuteman 3 silo after the nuclear missile inside gave off false signals suggesting it was about to launch itself nearly four years ago.
Capt. Bill Kalton, a public information officer at F. E. Warren Air Force Base in Cheyenne, Wyo., said the vehicle "would have fallen on top of the missile and prevented it from going any place" if a launch had occurred.
A spokesman for the Strategic Air Command, Capt. Phillip Delaney, added: "The malfunction was such an unusual occurrence that (missile wing) officials decided to take that step (with the vehicle) as an added precaution."
Occurred in 1984
The incident at a missile site on the Nebraska-Wyoming border occurred on Jan. 10, 1984. Fifteen days later, SAC made a brief announcement. The Casper, Wyo., Star Tribune published further details this week, including the use of the armored car to block a firing missile.
Then and now, SAC stressed that there was no danger to the public and no chance that its ballistic nuclear missiles could accidentally launch themselves.
"There was absolutely no way a Minuteman missile could have been accidentally launched," Delaney said. "There are too many safeguards and too many other procedures that must be carried out in sequence."
According to Delaney, there is a certain amount of guesswork involved in the procedure of blocking a firing missile with a car. The huge door that sits atop a Minuteman is thrown horizontally off the silo by explosive charges during launch.
The theory, according to the spokesman, is that the cover is blown aside so rapidly that a vehicle parked atop it with brakes off will be left hanging in thin air--like yanking a tablecloth out from under dishes--and then drop straight down, in hopes of keeping the launching missile from going anywhere.
The procedure has never been tested, he added.
The spokesman said an Air Force investigation established the troubles began with the failure of the navigation guidance unit inside the missile. That is not unusual, he said, because the guidance units have a finite life and must be replaced periodically.
Normally when a guidance unit fails, sensors that monitor the status of a missile on alert simply inform the underground crew of the failure. The missile is taken off alert and technicians are dispatched to install a new guidance unit.
In the 1984 incident, however, Delaney said the electronic sensors flashed false signals--"some, but not all, of the indications that light during a launch sequence."
The spokesman indicated the two-man missile silo crew was confident that a launch was not under way.
"The key (step-by-step) sequences for a launch were not taking place," he said.
"They were getting certain launch signals out of sequence. And there were other actions that would have been required for a true launch. But they knew something was out of whack."
SAC's "missile potential hazard network" was activated and security and technician teams mobilized, the spokesman said. At that point, the armored car was parked atop the silo until technicians were able to enter the silo and verify nothing was amiss.