Was a manhole cover in the 1950’s the first manmade object in space?

At a minimum it could have been the fastest ‘large’ object ever in Earth’s atmosphere.

A high speed camera at the detonation could only capture the cover in a single frame.

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In 1956, astrophysicist Dr Robert Brownlee was asked by his boss at the Los Alamos National Laboratory in New Mexico to figure out a way to test nuclear weapons underground. The scientists working on Operation Plumbbob were concerned about the amount of radiation spewed out by the nukes during tests above the surface, so Dr Brownlee started experimenting with the idea of blowing up small a-bombs below the surface.

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In a 500 feet long and 4 feet wide vertical cylindrical tunnel, they put a nuclear bomb. The top of this tunnel was sealed using a 4 inch thick man hole cover (on steroids). The lid weighed about 2 tons! They were sure that even the 2 ton lid would blow off like feather due to the nuclear explosion. However, they weren’t sure on exactly how fast it’d travel up. To measure the speed, high-speed cameras were placed near the opening.

The bomb was detonated. Some say that the high speed cameras were only able to capture the image of the lid in a single frame. Which by the way could also contribute to an enormous error margin in the speed calculation. Nevertheless, the speed was of the lid at which it flew up in the air was calculated to be 41 miles per second – approximately 6 times the escape velocity! Never before had any man made objects moved at that speed inside the earth’s atmosphere. The lid went. It was never seen again. No one knows where it is now.

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