That time US scientists launched a manhole cap towards space

On Oct. 4, 1957, the Soviet Union launched Sputnik 1, the first satellite into an elliptical, low-Earth orbit. It was only 184lbs with a 23" diameter and managed to stay in orbit for 21 days before the battery powering the transmitter ran out. It burned up in the atmosphere three months later. This marked the beginning of what would be known as the "Space Race" between the Soviets and the U.S. However, according to legend, America may have accidentally beaten the Soviets at launching something into space — a manhole cover.

In the summer of 1957, during Operation Plumbob, American scientists were testing the capabilities of nuclear explosions in all fashions at the Los Alamos Scientific Laboratory. They tested different alloys, various yield sizes, and, controversially, how troops react to exposure, but this story's all about using a nuclear explosion as a propellant.

During the Pascal-A test on July 26, scientists tested a nuclear warhead underneath the surface of the Earth, marking the first U.S. underground nuclear test. The test yield was 50,000 times greater than expected and the blast spewed out of the 500-foot, deep-cased hole. It destroyed the five feet of concrete that was used to cap the explosion.

Like every good scientist, they tried it again on Aug. 27 to test "safety." Instead of the 55-ton yield of the previous test, they used 300 tons and placed a 2-ton concrete cap just above the bomb. Sitting atop the hole was the destined-for-greatness manhole cover. Scientists expected the concrete plug to vaporize, but when the vapors expanded, the pressure was forced up the shaft and blew the 4-in thick, 500lb, steel manhole into the air. The only high-speed camera, capturing one frame per millisecond, was only able to capture the manhole cover in a single frame.

When asked about the manhole cover, Dr. Robert Brownlee, the designer of the experiment, said that there was no way to account for all the variables at play and determine the fate of the steel cover. When pressed by a supervisor, he said that it must have reached six times the escape velocity of Earth (which is 11.2km/sec). A more modern estimate puts the speed of the steel cap at around 56 km/sec. For comparison, the speed of sound in air is 0.33 km/sec — or if you need a more veteran-friendly comparison, the muzzle velocity of an M4 is 0.9km/sec. The fastest man-made thing is the Helios 2, which travels 70.2km/sec.

There was no way to verify any of this, as the manhole cover was never found, but if the math was right and the manhole cover survived the extreme pressure and heat, Dr. Brownlee may have made it to space first, created the fastest object while in Earth's atmosphere, and the third-fastest object known to man.