This photo shows a replica of Little Boy — the first nuclear weapon used in war. It wasn’t really that “little” with a length of 10 feet, a diameter of 28 inches, and weight of 9,700 pounds. It was dropped on Hiroshima on August 6, 1945, and detonated with the power of 15 kilotons of TNT. The blast radius was around one mile, and it’s estimated that the bomb killed 66,000 people directly and injured another 69,000.
The bomb was a “gun type” design, where two sub-critical masses of uranium enriched to 80% with isotope 235U were slammed together with conventional explosives to a create a critical mass that self-detonated. Despite the damage it did, it wasn’t a very efficient design. The bomb contained 141 pounds of uranium, of which only 2 pounds actually underwent fission.
The second bomb, dropped on Nagasaki on August 9, was different design. Dubbed Fat Man for its bulbous shape, it was an implosion device with a 14 pound core of plutonium 239. The design was nearly identical to the one detonated on July 16, 1945 at the Trinity test site in New Mexico. It was 10.5 feet long, 5 feet in diameter, and weighed 10,300 pounds. The blast yield was estimated at 21 kilotons of TNT. This photo shows a replica of Fat Man:
Fortunately, nuclear weapons have not been used in combat since the end of World War II. There have been some concerns of late surrounding Russia and Ukraine, Pakistan and India, Israel and Iran, and the Koreas. So I thought it would be good to look at just how far nuclear weapons have evolved since 1945, and how much more dangerous they’ve become. New designs have made them smaller and lighter and more destructive. Check out this photo of the B61 bomb, an important component of our current nuclear arsenal:
It has a streamlined casing capable of withstanding supersonic flight, and is 12 feet long with a diameter of 13 inches. The weight of the B61 is about 700 pounds. It has an estimated yield of 400 kilotons of TNT! And that’s not even close to our largest weapons, which have yields measured in megatons of TNT.
With current events around the globe increasing the likelihood of the use of nuclear weapons, I just wanted to put things into perspective. Use of nuclear weapons on any scale would be devastating to the planet. And Earth is already contending with the effects of climate change.
Nuclear weapons served a role in the Mutually Assured Destruction (MAD) “strategy” during the Cold War against the former USSR. Today, the sanest use of those weapons would be to break the enriched uranium down to the point where it can be “burned” in nuclear power plants. It’s a process called de-enriching and is easily done. It would help offset the burning of fossil fuels and reduce carbon emissions.
Plus, it just might give peace a chance.
Next Week in Sky Lights ⇒ Physics of Candle Flames