Home » The fastest manhole cover in human history: legend or truth?

The fastest manhole cover in human history: legend or truth?

Until the 1980s, before the Voyager probes, the fastest object a human had built could be a manhole cover, fired into space, by a nuclear bomb. According to legend, in 1957, the Nevada Test Site saw a series of nuclear explosions that carried this object into orbit.

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On 4 October 1957 the Soviet Union launched Sputnik 1, the first satellite into an elliptical low Earth orbit. It was only 83 kilograms with a diameter of 54 centimetres 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 United States. However, According to legend, America may have accidentally beaten the Soviets in launching something into space: a manhole cover.

Faster Manhole
Nuclear bomb explosion

America and nuclear bombs

The top-secret Manhattan Project that saw the development of the first nuclear bomb at the end of World War II was only the beginning of a long era of nuclear weapons research and development. Between 1945 and 1992, the United States alone detonated more than 1,000 nuclear warheads during testing.

For obvious reasons, these weapons of mass destruction were detonated in highly isolated areas of the country, such as the deserts of New Mexico and Nevada, or the Marshall Islands in the middle of the Pacific Ocean. Even so, scientists were rightly concerned about the nuclear fallout from these tests that could travel through the atmosphere and affect civilians.

So, in the late 1950s, the Pentagon decided that the vast majority of its tests should be performed underground. These were not the first underground nuclear tests, but they would be the first ever projects involving nuclear containment.

Operation Plumbbob

Operation Plumbbob

In the summer of 1957, during Operation Plumbbob, American scientists were testing the capabilities of nuclear explosions at the Los Alamos Scientific Laboratory. They tested different alloys, various yield sizes and, controversially, the way troops react to exposure.

Operation Plumbbob was a series of 29 explosions designed to study various aspects of nuclear bombs, including how to contain the fallout from an underground explosion. To test this, the military set off several explosions at the bottom of deep shafts, covered by metal caps.

During the Pascal-A test on 26 July, scientists tested a nuclear warhead below the surface of the Earth, marking the United States’ first underground nuclear test. The yield of the test was 50,000 times greater than expected and the explosion came out of the 152-metre deep hole. It destroyed 1.5 meters of concrete used to cover the explosion.

A modified W-25 warhead weighing 55 tonnes and measuring 650 centimetres in diameter and 440 centimetres in length was used for the test. But, before scientists could design a fully contained nuclear test, one of them became the stuff of legends.


The fastest manhole cover in the world

On 27 August, instead of the 55-tonne W-25 of the previous test, they used a 300-tonne bomb. So they placed a 2-tonne concrete cap just above the bomb and on top of the hole was the manhole cover that was to become famous.

Scientists expected the concrete cap to vaporize, but as the vapors expanded, the pressure pushed up into the shaft and blew the steel manhole cover into the air.The only high-speed camera, which captured one frame per millisecond, was only able to capture the manhole cover in a single frame.

In those days, it was thought to have reached six times the escape velocity of the Earth (which is 11.2 km/sec). A more modern estimate puts the speed of the steel cap at about 56 km/sec.
Today, the fastest man-made object is the Helios 2, which travels at 70.2 km/sec.

Subsequent tests were designed in such a way that total containment of the nuclear explosion was achieved.

Over time the tests became very sophisticated and expensive, but we were able to achieve complete containment for almost all of the tests. So I would judge that our efforts have been quite successful.


Nowadays we have no way of verifying whether the manhole cover survived the explosion and entry into orbit, but if the calculations were correct, Dr. Brownlee may have been the first to reach space creating the fastest object until the 1980s.


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