How Do Nuclear Weapons Actually Work?

Over 2,475 Nuclear bombs have been detonated on planet Earth to date. Two of them had the misfortune of being detonated on a human population. On July the 16th of 1945 in Alamogordo Bombing Range, New Mexico the first-ever Atom bomb was tested. There are mainly two types of weapons when people refer to Nuclear bombs, Atomic and Hydrogen bombs. A-bombs work on fission and are less efficient, whereas, H-bombs are fission-fusion based and are more efficient.

The basic principle on which both bombs work is loss of mass. When we say that there is “conservation of mass” in every chemical reaction that isn’t entirely true. When Uranium-235 goes through fission, it loses 0.1% of its mass. The famous E = mc² equation in effect shows us how this loss of mass radiates tons of energy in the form of photons, heat and gamma rays.

Atomic Bomb

Bombarding Uranium-235 (let’s call this initial radioactive atom Tom) with neutrons splits its nucleus into 2 smaller nuclei which weigh less than their composite in Tom at the beginning. Tom releases 2 more neutrons due to this, which go ahead and collide with another U-235 atom (call it Cathy) surrounding it, Cathy again splits into 2 neutrons and loses some of its mass. This happens on and on inside a bomb that releases immense energy, this is the fission chain reaction. All of this happens in a bomb in picoseconds which is about 0.000000000001 seconds.

1 Kilogram of Uranium-235 going through fission losses about 0.1% of its mass.

E = mc²; E = 0.001Kg * (3*10⁸)²; E = 90,000,000,000,000 (9 * 10¹³) J

More than 21,000 TNTs being exploded simultaneously in under a second. Actual bombs use more than just 1 Kg of U-235. The bomb “Fat Man” was almost just as explosive as the above reaction which was dropped on Nagasaki on 9th August 1945.

Summed up in a simple yet bleak manner (Fission/Atomic Bombs) —

Bombardment of the nucleus (of a radioactive atom) with neutrons → split into 2 nuclei (of smaller mass) → change in mass causes explosion (heat, photons and gamma rays)

But there must be a minimum amount of mass to start this chain reaction which is called the Critical Mass. This is needed to produce enough neutrons to follow through and split all the other surrounding atoms.

After being dropped from a plane or guided missile. There is an altimeter that measures the distance from the ground, for the greatest impact N-bombs explode a few hundred meters from the ground. Reaching a specified height, an explosive drives the sub-critical masses (small sets of masses needed to reach critical mass) into other target masses creating a supercritical mass. In which free neutrons are introduced and fission takes place, releasing energy.

Hydrogen bomb

It relies on the same principles of E = mc² for an explosion. But the loss of mass is accounted for by the process of fusion and fission. Fusion combines 2 nuclei into 1 nucleus which has a lower mass than the original 2. This change in mass causes energy to be released.

How is this facilitated? a small fission reaction is started first which causes an explosion. This heat release causes Deuterium and Tritium (atoms present in the bomb) to fuse and hence release energy. This is more efficient than A-bombs as 0.63% rather than 0.1% mass change is observed causing more energy release.

The process is started by electrical charge detonators (which lay on a layer of explosives) on the surface of the bomb. These go off at the specified height and cause an implosion inside the bomb itself.

The implosion causes compression to the last layer inside the bomb containing Polonium with Berilyium which fuse and release neutrons and cause fission. This heat and pressure then cause fusion in the hydrogen isotopes. This happens in a secondary fusion bomb.

All of this relied on physics and chemistry from the 20th century. But today there are N-bombs that possess 3,333 times the power of the Nuclear bomb which was dropped on Hiroshima. In the last 40 years, fission and fusion have advanced significantly making them far more efficient. These have been the worst-best creations of mankind. It has the potential to power and destroy homes at the same time.

Over 15,600 N-bombs are held by 9 countries in the world. The science of all of it is absolutely puny to the actual cost of human lives. One death is one too many. A solid quote from Einstein sums it up -

“Mankind invented the atomic bomb, but no mouse would ever construct a mouse trap”

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Disclaimer — I am not an advisor nor a qualified professional on the above discussed matter. Information provided in the post may or may not be correct. None of the images shown in the post are mine, they belong to various sources listed under “My Citations” and underneath the images themselves too.

My Citations

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YouTube, YouTube, 7 Oct. 2016, Accessed 5 Mar. 2022.

TheInfographicsShow, director. YouTube, YouTube, 20 Apr. 2021, Accessed 5 Mar. 2022.

“Atomic Bomb.” Encyclopædia Britannica, Encyclopædia Britannica, Inc.,

“Thermonuclear Bomb.” Encyclopædia Britannica, Encyclopædia Britannica, Inc.,

Gadgets February 6, 2021 5 min read, et al. “How Does a Hydrogen Bomb Works/Explodes.” The Polar Fox, 3 Dec. 2020,

“Unlocking Fusion Energy — Our Path to a Sustainable Future.” NI,

What Kind of Triggering Device Did the First Atomic Bombs …

Godfrey, Author Andrew. “Atom Bomb Hits Hiroshima.” Nostalgia and Now, 26 Feb. 2014,

Graham Templeton on November 9, 2015, at 9:47 am Comments. “Extremetech Explains: How Does Nuclear Energy Work?” ExtremeTech, 9 Nov. 2015,



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