Those of us with an interest in the early days of the space race — won by Sputnik 1 in October 1957 — might need to broaden our disciplines a bit to get the whole story. It turns out that the race might have actually been won two months earlier, by the United States, with an entrant from outside the space program. Its name was Operation Plumbbob.

For six months in 1957, Operation Plumbbob put 29 thermonuclear devices to the test in the Nevada Test Range. They were the most varied in the program’s history; all sorts of devices, fired in the air, on the surface, underground, at pigs, near soldiers, and at all kinds of structures. Two of them were particularly interesting. Pascal-A and Pascal-B, on July 26 and August 27, were detonated at the bottom of 500-foot vertical shafts. Both shafts were covered with great heavy steel lids, some four inches thick and weighing some 900 kg.

Pascal-A was supposed to have a yield of 1-2 pounds, but somebody got his slide rule wrong: the true yield turned out to be 55 tons, about 50,000 times greater than expected. For Pascal-B, they added a concrete collimator about halfway down the hole. Once again, the yield was far more than expected, moreover by about six times as much: 300 tons. The concrete collimator was (obviously) instantly vaporized by the explosion, and the massive gas expansion from the concrete turned the shaft into a compressed-gas cannon. That giant metal lid was launched straight up, at what was estimated to be six times escape velocity.

From the March 1992 issue of Air & Space magazine:

Every kid who has put a firecracker under a tin can understands the principle of using high explosives to loft an object into space. What was novel to scientists at Los Alamos was the idea of using an atomic bomb as propellant. That strategy was the serendipitous result of an experiment that had gone somewhat awry. Project Thunderwell was the inspiration of astrophysicist Bob Brownlee, who in the summer of 1957 was faced with the problem of containing underground an explosion, expected to be equivalent to a few hundred tons of dynamite. Brownlee put the bomb at the bottom of a 500-foot vertical tunnel in the Nevada desert, sealing the opening with a four-inch thick steel plate weighing several hundred pounds. He knew the lid would be blown off; he didn’t know exactly how fast. High-speed cameras caught the giant manhole cover as it began its unscheduled flight into history. Based upon his calculations and the evidence from the cameras, Brownlee estimated that the steel plate was traveling at a velocity six times that needed to escape Earth’s gravity when it soared into the flawless blue Nevada sky. ‘We never found it. It was gone,’ Brownlee says, a touch of awe in his voice almost 35 years later. The following October the Soviet Union launched Sputnik, billed as the first man-made object in Earth orbit. Brownlee has never publicly challenged the Soviet’s claim. But he has his doubts.

I first heard about this from reader Simon Spooner, who emailed me about it. He offered his own thoughts on the likelihood of this happening:

I agree that the although steel plate cap may have initially been accelerated past escape velocity (> 11.2 Km/s), given its unaerodynamic shape and the fact that it was travelling through the dense part of our atmosphere (rockets don’t approach escape velocity until very high altitude where the atmosphere is much thinner) it would have acted like a meteor in reverse (i.e. from the ground upwards rather than from the sky downwards) and it would have burned up like a meteor that never reaches the ground (meteors are often largely made of iron, just like the steel plate cap). If it didn’t completely burn up and gravity returned some of it to earth, it would have travelled quite some distance, necessitating a large search area, and the fast falling remains would have probably just buried on impact deep into the desert soil anyway. This might explain why nothing of it was found.

My guess is that the steel plate would fare even worse than Simon supposed: that a blast of such speed would cut a donut hole in the plate before it would lift it off the ground. But I really don’t know. I’d be shocked if it could survive the physical and aerodynamic stresses enough for any significant sized piece of it to make it into orbit.

Here are a few links if you’d like to read more about this. Note that there seems to be some confusion between Pascal-A and Pascal-B; some sources seem to have details between the two transposed, and it’s not always clear which articles are sourced from interviews with guys remembering stuff, and which are based on documentation. Consequently some of my details above may well be inconsistent with what you find on your own.

http://nuclearweaponarchive.org/Usa/Tests/Plumbob.html#PascalB

http://www.youtube.com/watch?v=qEvxSqrtQt4

http://www.dtra.mil/documents/ntpr/factsheets/Plumbbob.pdf