Minuteman ICBM launcher closure door - photos

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My Dad took a job working for the Core of Engineers at the Grand Forks Air Force Base in 1955. I grew up there because of the cold war. It was a farm field when he started there. They built 150 Minuteman silos, around that base.
That concrete cover is quickly removed on the rails with explosives. I was told it ends up in the field. The ground around this area of North Dakota, is clay with high levels of alkali. Very corrosive, as well high water table. The missile silos have all been abandoned, because of frequent flooding.
They did a silo upgrade program in 1975 to thicken that concrete cover, as someone tested that a near miss would disable the missile launch. They also put the missile on a turn table, as it had a pre determined flight, and target. The missiles were also upgraded to carry 5 Nuclear bombs, that could be dropped along the flight path.
Crazy cold war stuff. There still is 5 other airbases with 800 total missiles in ready.
So the one thing I learned from my dad, you don't want a nuclear bomb going off near yours, as it reduces the yield, so first strike is the intent of warfare with these toys.