What is "little boy" and what was the structure of nuclear warhead which destroyed the Hiroshima ?

6^th August 1945, the black day or you can say the dooms day in the history of word war I, America was about to change the face of modern war by using the nuclear warhead first time in the history of war.

In the morning, clock was ticking at 8:15 am and the giant American war plane dropped “The Little  Boy” on Hiroshima. The Little Boy, it was the code name of the first ever American nuclear warhead.

It was weighing around 4400 Kg and was detonated on height of 564 m from the ground level (Approx.) and suddenly whole Hiroshima city was flattened. Out of 0.3 million people, 0.14 million people died a terrifying death within 10 minutes after the detonation.

That explosion created a huge mushroom shaped cloud of fire and radioactive dust and reached up to the height of 15000 meter in the sky. Before this, no single bomb could able to do such a huge demolition. The whole world saw what a nuclear bomb could able to do.

“The Little Boy” was the code name of first nuclear warhead. It was created under Manhattan Project. It was around 3 m in length and approx. 0.71 m in diameter and Uranium-235 (U-235) was used in it. The bomb was containing total 64 Kg of U-235 out of which only 0.6 gram was undergo the fission reaction. As per Einstein’s formula, the bomb had the capacity of 15000 tan TNT.

As compared to modern nuclear warhead, Little Boy was poorly engineered and designed. Let’s consider that the bomb was cylindrical in shape so its axis had another cylindrical barrel. A wedge shaped U-235 was placed at the tail side of the bomb and a cylindrical target of U-235 was placed at the other extreme end. The cylindrical shape was specially designed as it will hold the wedge shaped U-235 perfectly inside it as it was hollow inside.

Cut view of Little Boy Nuclear Warhead

A detonating material was placed behind the wedge shaped U-235. The bomb was being detonated by using radio signal remotely from the plane. When the bomb reached at the height of 564 m from ground level, the bomb was detonated which created tremendous pressure on wedge shaped U-235 and within fraction of seconds, it struck the other U-235 (Spherical shaped). Due to this, a chain reaction started and explosion happened. Reflectors were placed inside the bomb do divert the free neutron towards the U-235.

It was estimated that if the bomb was detonated after reaching to the ground then it would be causing less destruction. So, it was detonated above the ground level, at a considerable height to maximize the destruction and loss. Along with the U-235, the bomb was carrying traditional explosive materials like TNT.

 

Effects of Nuclear Explosion:

• Shock Wave: Due to release of tremendous energy and pressure in nuclear explosion, a shock wave is generated which travels hundreds of miles and destroy everything which comes in its way. 

• Heat or thermal wave: Due to fission reaction, lot of heat energy get released in the environment which travels as long as shock wave. Most of the time thermal wave is generated first followed by shock wave. Thermal wave burns everything completely and leave only ash and dust behind. 

• Fallout: Fallout happened when the surround environment becomes radioactive due to the nuclear explosion. Dust particles, lake water, soil, etc. get affected due to radiation and becomes radioactive. These things remain in the that area for many years, so made that area radioactive for long time after the explosion.

  

  If you want to know more about nuclear power then go through the book 'Nuclear Power' by Dr. Michael C. Horowitz. Dr. Michael C. Horowitz is Professor of Political Science and Associate   Director of Perry World House at the University of Pennsylvania. He is the author of several leading  articles on nuclear weapons, as well as the award-winning The Diffusion of Military Power (Princeton, 2010).

  

   Click the link to get the book:

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