How nuclear weapons were tested in front of the public in Mississippi, bypassing the treaty with the USSR

At 10 a.m. on October 22, 1964, a five-kiloton nuclear weapon was detonated in Lamar County, Mississippi.

A year earlier, in response to growing public concern about the potential negative consequences of increasingly large US test explosions, Britain signed the Partial Nuclear Test Ban Treaty, which banned all nuclear weapons testing in the atmosphere, underwater and in space. Underground explosions were not banned because it was still technically unclear how to define them.

After the treaty was signed, US authorities created Project Dribble, a project to study how underground nuclear tests could be detected or hidden.

The first explosion of this project was carried out 45 kilometers southwest of Hattiesburg at the Tatum site, where large Mesozoic salt deposits exist more than 300 meters underground.

According to the plan, it was necessary to carry out two explosions. The first, codenamed Project Salmon, was to occur at a depth of 820 meters directly in solid salt deposits. The second explosion, Project Sterling, would have used a smaller bomb, but would have used a hole made by the first bomb.

According to scientists' hypotheses, shock waves from the second explosion will be suppressed by the cavity from the first explosion, which will effectively mask the tests from seismographs.

The first explosion was scheduled for September 22, but was postponed several times due to inappropriate wind direction.

In the end, on October 22, all the ideal conditions coincided. Four hundred local residents were evacuated from the area around the explosion and downwind. Adults were paid $10 for their trouble, and children $5.

At 10 a.m., the Project Salmon bomb exploded with about one-third the power of the bomb that destroyed Hiroshima. Dust rose into the air and rolled in waves, nuts fell from trees, dogs howled in horror, streams turned black from sediment rising from the bottom, and buildings 50 kilometers away shook for a long time after the explosion.

A week later, hundreds of local residents sued the government for damages, complaining of broken pipes, cracked brickwork and suddenly dry wells.

Nevertheless, the tests were considered successful. The explosion created a cavity with a diameter of 33.5 meters in the salt deposits. When sensors were lowered there three months later, the temperature at the depth of the explosion was still over 200 degrees Celsius.

Two years after Project Salmon, the second part of the tests, Project Sterling, was carried out. A much smaller bomb with a yield of 350 tons of TNT was detonated in the cavity, while the yield of the first bomb was 5,000 tons of TNT. As scientists expected, the cavity absorbed almost the entire seismic force of the explosion. The people on the surface barely felt the impact.

The explosions, which brought a wealth of information to American authorities about how underground nuclear tests can be hidden and detected, were called successful. These are the only nuclear explosions carried out in the eastern United States.