A forgotten torque wrench on September 18, 1980, led to a blast that nearly set off a nuclear warhead.

An airman at a missile silo in the US state of Arkansas was doing a check on a Titan II missile with a ratchet spanner instead of a torque wrench.

As a result, a 3.6kg socket fell 24m down the silo before piercing the side of the missile's fuel tank.

A cloud of rocket fuel then started leaking into the enclosed space, filling the confined space with explosive gas.

When an exhaust fan was switched on hours later, it created a spark that set off an explosion.

The initial blast was so powerful it sent a 750-tonne silo door flying.

"It was the loudest explosion I'd ever heard in my life—before or since," airman Greg Devlin told Popular Mechanics .

"A concussion of wind hit me lik

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