May 25, 1953: US Conducts its Only Nuclear Artillery Test Shot

A Brief History

On May 25, 1953, the United States Army conducted a live nuclear artillery test shot, the only time the US ever conducted such a test.

Digging Deeper

Conducted in the Nevada desert (Nevada Test Site, later renamed the Nevada National Security Site) the test firing and detonation of a live nuclear (fission type) bomb fired from a cannon was called by the code-word Upshot-Knothole Grable. One of only 4 “gun” type atom bombs ever detonated by the US, the warhead was constructed similar to the “Little Boy” bomb that obliterated Hiroshima in 1945. It used 2 chunks of uranium at separate ends of a pipe like “gun” that were forced together at high speed and pressure by an explosive charge, creating a critical mass and resulting in the nuclear explosion. Yield of the artillery fired shell was 15 kilotons, about the same as the Hiroshima bomb.

Considering that the 11 inch bore cannon (280 mm) could only lob the shell 11,000 yards (6.25 miles) this made the blast a bit close for comfort for the gun crew. Since presumably the M65 Atomic Cannon, nicknamed “Atomic Annie,” would not be the forward-most US troops and equipment, this means friendly troops would be even closer to the blast if the weapon was used in battle. The test shot was detonated about 524 feet above ground level, lower than nukes were usually detonated at that time. The nearness to the ground resulted in a sort of double wave pressure effect that caused a rethinking of employment of nuclear warheads. (Note: The other type of nuclear fission atom bombs are the “implosion” type that use a hollow sphere of plutonium that is collapsed on itself by surrounding high explosives.)

The Atomic Cannon was not a particularly good idea, as the 83.3 ton weight of the cannon and carriage was not very mobile and could crush most bridges. Only 20 of the big guns were built, and were fielded in 1953 in Europe and South Korea. Obviously, the enemy would keep track of wherever these guns were on the battle field and they would become a primary target. The US Army kept shuffling the guns around in an effort to keep the enemy guessing where they were, but it is likely the enemy knew where the giant guns were, anyway. Despite the lack of realistic usefulness, the guns stayed in service until 1963 when they were superseded by 155 mm and 203 mm (8 inch) artillery nuclear shells that could be fired from any cannons of those calibers, making it impossible for the enemy to know which gun tube might be launching a nuke.

Other artillery (we are not counting battlefield rockets here) gun fired nuclear capable weapons for which nuclear warheads were made included the 16 inch battleship guns, and the aforementioned 155 mm and 203 mm artillery pieces that came in both towed and self-propelled forms.

The United States military had a peak number of 31,255 nuclear warheads during the Cold War, a stupendous number that we could never come close to needing! As of 2017, it is estimated that the United States maintains a stockpile of about 6800 nuclear warheads, and the Russians have a stockpile of about 7000 nuclear warheads. The next country with the most nukes is France, with 300. A total of 9 countries are believed to have nuclear weapons ready to use.

Question for students (and subscribers): Does the U.S. need to maintain such a large number of nukes? How many do we need to keep the Russians or anyone else afraid of our retaliation, so as to keep other countries from using theirs? Should nuclear weapons be banished from the Earth? Is such a ban even possible? Please share your opinions on these subjects in the comments section below this article.

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