The Trinity Nuclear Test

The first nuclear test ever conducted by humans was code named 'Trinity' and occurred on July 16, 1945 about 60 km (35 miles) southeast of Socorro, New Mexico.

The bomb was an implosion-design plutonium device and was a pure fission weapon.

The fissile material was Pu-239 that was explosively compressed into a chain-reacting critical mass.

A fission nuclear reaction runs on neutrons. It is a balance between neutrons being born, neutrons being absorbed for more fissions, neutrons being absorbed into parasitic material and basically lost to the reaction and neutrons simply escaping altogether.

In a nuclear reactor the balance is maintained safely and in a well controlled and constant state. If more neutrons are born than are lost then the reaction grows. The intention of an atomic bomb ("A-bomb") is to make this happen as fast as possible before the device rapidly self-disassembles (i.e. explodes).

The other type of A-bomb type available at that time was the gun-type where a slug of fissile material is shot into a mating shape of fissile material.

Plutonium was unsuited for this style of bomb because the available Pu-239 was contaminated with Pu-240 which will spontaneously fission. This means that it gives off a low-level of neutrons even when not in a critical mass configuration.

A gun-type of plutonium bomb would have worked but because of the Pu-240 spontaneous fission neutrons it would have started reacting too soon and then self-disassembled before enough of the bomb material could partake in the fissions. It would have been what is called a 'fizzle'.

The Explosion

The detonation occurred at 5:29 am on the morning of July 16 1945 and exploded with an energy equivalent to 20 kilotons of TNT. Eye witnesses said that the surrounding mountains were lit up "brighter than daytime" for a few seconds and it was reported as being as hot as an oven" at the base camp.

The shock wave was felt over 160 km (100 miles) away and the resulting mushroom cloud attained a height of about 12 km (7.5 miles).

A pilot flying a Navy transport about 50 km (30 miles) east of Albuquerque New Mexico, about 160 km (100 miles) from the Trinity test site, reported:

"My first impression was, like, the sun was coming up in the south. What a ball of fire! It was so bright it lit up the cockpit of the plane." Quote sourced from Wikipedia article

Closing Words

The test marked the beginning of the atomic era and was the culmination of a massive effort and years of work by the Manhattan Project.

The people who were responsible for the research and development of the weapon, upon witnessing the explosion, knew that the world had changed at that moment.

Kenneth Bainbridge, a professor of physics at Harvard and responsible for the planning of the test said to Oppenheimer, "Now we are all sons of bitches."

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