This Is How A Nuclear Bomb Works

Let's investigate how a nuclear bomb works!


Since their first, devastating use back in 1945, nuclear weapons have been a huge source of anxiety and fear across the globe. For almost a century now, we’ve lived in the knowledge that our world leaders could plunge us into nuclear war with destruction on a scale never before seen in history.

But how likely really is this scenario? What was the biggest nuclear weapon ever dropped? And how does a nuke even work anyway? Slip your HazMat suit on and brace yourself for impact, because you’re about to get hit with a fat knowledge bomb.

History Of Nuclear Weapons

In 1938, just a year before the world was plunged into war, German scientist Otto Hahn was working in a lab in Berlin when he discovered something incredible: nuclear energy. By splitting the nucleus of an atom, the smallest unit of matter in the known universe, Hahn realized a monumental amount of energy was released.

nuclear energy

After word got out about his findings, US President Franklin D. Roosevelt was worried that the Germans would use this newfound energy to develop a superweapon. So, he tasked US scientists to develop one first.

When America joined World War II in December 1941, these efforts were doubled, and Roosevelt established the Manhattan Project. Based in Manhattan, New York, the project was a joint effort by the military and several hundred scientists to weaponize nuclear energy. Just four years after its formation, its goal was met.

On 16th July 1945, the US conducted the first ever test of a nuclear bomb, codenamed the Trinity Test. The bomb, containing one kiloton of destructive power, the same as 1,000 tons of conventional explosives, was dropped from a plane over Socorro, New Mexico.

This Is How A Nuclear Bomb Works

The resulting explosion stunned the US military and left the bombsite so irradiated that even today the area contains more than 10 times the normal level of background radiation. In other words, it was a resounding success!

Less than a month later, the US would put this terrifying new technology to horrific use. With the war almost over but Japan refusing to surrender, newly instated President Harry S. Truman ordered the atomic bombing of the city of Hiroshima.

When the bomb, named “Little Boy”, was dropped, everything changed. The plane chosen for the mission, a B-29 Superfortress bomber called The Enola Gay, reached Hiroshima at 9.14am local time on 6th August 1945.

The bombardier, Thomas Ferebee, dropped the near 10,000 lb bomb, then the pilot, Paul Tibbets, sharply turned and flew away from the city as fast as he could.

Little Boy release

43 seconds later, Little Boy exploded with the force of more than 16,500 tons of TNT. The nuclear explosion instantly vaporized anyone at its center, scorched the ground around it to temperatures hotter than 7,000°F, and sent a shockwave that smashed through buildings and obliterated land for miles around.

It was hell on earth. A daunting mushroom cloud soared in the air 20,000 feet above the city, blocking out sunlight to those below.

little boy mushroom cloud

But still, the Japanese Emperor Hirohito refused to back down. Surprised but unperturbed, Truman ordered the dropping of a second bomb, this time over the city of Nagasaki. This bomb, named “Fat Man”, was even bigger and more powerful than its predecessor.

Just three days after the bombing of Hiroshima, Fat Man fell from a US plane and exploded over Nagasaki, obliterating over 2 ½ square miles of the city. A second mushroom cloud was thrust high into the air, and radioactive rain burned down on anyone unfortunate enough to have survived the initial blast.

fat boy destruction

You might’ve been better off being vaporized than being a little further out when the bomb went off. Those not in the immediate blast suffered all kinds of nasty maladies, like burns, internal injuries, and blindness, and many succumbed to them.

Emperor Hirohito, seeing such destruction, finally announced the country’s surrender. At the cost of over 200,000 innocent lives, the Allies had won the war.

Perhaps unsurprisingly, the newly formed United Nations made one of their first acts to call for the elimination of atomic weapons. And, even less surprisingly, this was completely ignored.

In the years following the war, the US continued testing atom bombs. And the Soviet Union, under communist rule and firmly against the American way of life, accelerated their own nuclear program.

In 1949 the Soviet Union became the second nation to successfully detonate a nuclear bomb. The Cold War had officially begun. Two nations with wildly conflicting belief systems, both harboring the most powerful weapons mankind had ever seen. What could possibly go wrong?

nuclear bomb usa and russia

In 1952, three years after the Soviet Union’s first successful nuclear test, and with Cold War tensions rising ever higher, the US took nuclear weaponry to a whole new level, by detonating the first ever hydrogen bomb.

Can you guess how much more powerful this hydrogen bomb was than the OG atom bombs? 10 times? 100 times? In fact, it was 1,000 times more powerful than the bomb dropped on Hiroshima. For when obliterating an entire city just isn’t enough!

When the bomb exploded over a remote Pacific Island, it did so with the monumental force of 10.4 megatons of TNT, that’s over 10 million tons of the stuff! The colossal blast made a fireball at least four miles wide that, by expert estimates, shone brighter than a thousand suns, and the heat was felt by observers standing as far as 30 miles away.

This Is How A Nuclear Bomb Works

But the Soviets were hot on the US’s tail, and if you thought what you just saw was big, strap yourselves in, because you’ve seen nothing yet.

Let’s put things into perspective for a moment. The bomb dropped on Hiroshima was 15 kilotons; the first hydrogen bomb was 10 megatons. But nine years later, in 1961, the Soviets tested a hydrogen bomb that was an unbelievable 57 megatons, that’s 3,800 times the power of the bomb that destroyed Hiroshima.

soviet hydrogen bomb

The absolute behemoth of a weapon was called the “Tsar Bomba” and measured in at 26 feet long, as well as weighing 27 metric tons, about 6 times the weight of Little Boy, and over twice the length.

The monstrous superweapon was so big that it didn’t even fit inside a plane, and had to be carried underneath instead! You’ve got to feel for the poor pilot – he and his crew were only given a 50/50 chance of surviving the test!

On October 30th, 1961, the plane carrying the bomb took off and flew towards the test site – an island in the Arctic Ocean called Novaya Zemlya. Once over the island, the crew released the payload and got the hell out of there as fast as they could!

To give them more time, the enormous explosive had been fitted with a parachute to slow its descent. Even so, when it detonated the blast was so powerful that its shockwave slammed into the plane, sending it plummeting over 3,000 feet!

bomb shockwave

Luckily, the pilot recovered control, but the explosion annihilated everything within 22 miles and created a massive mushroom cloud over 37 miles high. The bomber’s crew, still hurtling away as fast as they could, watched as the beautiful, terrifying plume pierced the sky where they’d been mere moments before.

In reality, the test was nothing more than Soviet Premier, Nikita Khrushchev, flexing his military muscle to show the US who was the boss. But the bomb itself, while undoubtedly impressive, was impractical and wasn’t as effective as dropping several smaller bombs, so no attempt by either side was ever made to make one bigger.

Even today the Tsar Bomba remains the biggest nuclear weapon ever created and used. Despite no single bomb ever matching the Tsar Bomba’s power, between 1945 and 1980, a combined total of 510 megatons of explosives were detonated around the world in nuclear tests.

nuclear blasts

That’s 170 times more blast power than was used in the whole of World War II! And, though easily the two biggest culprits, it wasn’t just the US and Soviet Union that were responsible for the barrage of blasts.

By 1980, the UK, France, and China had all waded into the fray with their own tests, albeit on a far smaller scale. With five nations all blowing the living daylights out of any barren patch of land they could find, you might expect there to be some environmental consequences, right?

We can’t be sure just how much radioactive material has been flung up into the atmosphere from decades of testing, but we know it’s a lot. And what goes up, must come down. Throughout the Cold War, one of the Soviets’ favorite nuclear test sites was a patch of land in Semipalatinsk, Kazakhstan, called The Polygon.

Even today, this area is one of the most radioactive places in the whole world, it’s been hit with about 450 nuclear explosions. And with every single one, masses of radioactive dust and dirt were thrown into the air and carried across to the neighboring communities as toxic fallout.

radioactive dust

A test in 1956 resulted in over 600 residents of the city of Ust-Kamenogorsk being rushed to hospital with radiation sickness and they were 250 miles away! If you’re ever subjected to a strong dose of radiation, the symptoms can be severe and quick to set in.

The invisible rays penetrate your body, so they don’t just damage your skin, but also your insides. The cells that make your hair die off, causing you to lose it. Your disease-fighting white blood cells die too, crippling your immune system.

Even your very DNA is attacked, causing it to break and mutate. You’ll feel sick, weak, and disoriented. Even if you survive the initial dose of radiation, years later you’re more likely to develop life-threatening illnesses like leukemia, or cancer.

This Is How A Nuclear Bomb Works

That’s exactly what happened to many of the residents of Ust-Kamenogorsk. But the tests didn’t just affect one generation of people. Because DNA mutations are often passed on, pregnant women at the time were more likely to give birth to children with learning difficulties or physical impairments.

Overall, the tests in Semipalatinsk alone are estimated to have affected over 350,000 people across three generations. But what actually is it that makes these monstrous weapons so preposterously powerful? How did we go from conventional bombs to colossal weapons of mass destruction in the space of just a few years?

The Technology Behind Nuclear Weapons

In 1938, German scientist Otto Hahn didn’t just discover nuclear energy, he discovered something called nuclear fission and it’s the entire reason that we’re now capable of our own Armageddon.

nuclear fission

Everything in the universe is made of atoms. You, me, the chair you’re sat on, even your gran’s false teeth. They’re so small you can’t even see them with a microscope, but they’re everywhere.

And inside every atom is a nucleus, containing a load of protons, which are positively charged, and neutrons, which have no charge. These are bound together tightly to the nucleus, which takes a great deal of energy to keep together, because naturally things that have the same charge repel one another.

Think about magnets. If you try and push two magnets together, positive to positive, there’s resistance. If you then let go of those magnets, they’d spring backwards, releasing kinetic energy as they did so.

magnetic resistance

It’s the same principle here. The protons are held together by a powerful force, but if that force is broken, all the energy being contained by it is released. This process is called nuclear fission, and it’s the principle behind both the Hiroshima and Nagasaki atom bombs.

To instigate fission, a neutron is fired at the nucleus of an atom. When it hits the nucleus, it smashes it apart, forming two smaller nuclei and releasing energy in the form of heat. At the same time, some neutrons are flung from the nuclei entirely and go on to hit other atoms, splitting their nuclei and creating a chain reaction.

neutron hitting nucleus

In this way, a massive amount of heat energy is produced that increases exponentially in just a fraction of a second. And it’s all reliant on reactions in the nucleus, nucleus, or nuclear. It’s the basic process that powers all nuclear weapons, and most nuclear power plants use it to generate electricity too.

However, just to throw a spanner in the works, there is another way of creating nuclear energy, called nuclear fusion. This is much more powerful than fission and is used to power hydrogen bombs. Here, instead of splitting atoms apart, they’re fused together. Fusion only works with small atoms, like hydrogen, the nucleus of which contains just one proton.

Naturally, two hydrogen atoms repel one another because they’re both positively charged. But if the force repelling them is overcome, they’re impelled to fuse with one another, creating a bigger atom and releasing a huge amount of energy in the process.

This Is How A Nuclear Bomb Works

So, how do you overcome the powerful force repelling the atoms, and fuse them together? Well, you need to compress them into as small a space as you can so they’re more likely to collide and blast them with an absolute butt-ton of heat.

This way they’re not only closer to one another, but the heat makes them move faster and when I say a butt-ton of heat, I mean, at least 180 million°F.

nuclear fusion

For comparison, that’s almost 7 times hotter than the Sun, which also runs off nuclear fusion! Because of the immense gravitational pressure at the Sun’s core, about 200 billion times greater than the atmospheric pressure here on Earth, atoms are crushed so close together that it doesn’t need to be so hot for fusion to occur.

On Earth however, we need to make up for the lack of pressure by ramping up the heat. And you know what generates a lot of heat? Yes, nuclear fission. Therefore, hydrogen bombs, otherwise known as thermonuclear weapons, explode using the heat from a fission reaction to kickstart a more powerful fusion reaction.

In other words, when a hydrogen bomb goes off, it burns 7 times hotter than the Sun.

hydrogen bomb heat

Now we know the basic reaction powering the bombs, but how do the bombs themselves actually work?

Let’s start with the fuel inside them, which is either uranium-235 or plutonium-239. These are both radioactive metals, meaning their atoms have unstable nuclei. An unstable nucleus has too many neutrons or protons inside it and will eject them to try and become stable.

This is called radioactive decay, and it produces energy in the form of radiation. Atoms with unstable nuclei are also easier to split with nuclear fission, hence why they’re used in nuclear weapons.

radioactive decay

In fact, Little Boy’s design was very simple. The bomb had two separate pieces of uranium-235 inside it, the plug and the target. Upon detonation, several thousand pounds of conventional explosives were set off inside the shell, which fired the plug down a barrel and into the target.

The two pieces of uranium smashed together, compressing the atoms close enough to instigate a fission reaction, which grew in power exponentially until it exploded out from the bomb’s shell in a fearsome fireball.

Little Boy’s design

All nuclear weapons produce this fireball, and it expands so fast that in a one megaton hydrogen bomb, which is far more powerful than Little Boy was, it can reach 440 feet across in less than a millisecond.

Furthermore, Little Boy was actually pretty inefficient, which is why nobody ever made any bigger, more powerful versions of the weapon. Fat Man, the bomb dropped on Nagasaki, had a very different design. Instead of uranium-235, Fat Man was powered by plutonium-239.

Fat Man power source

However, the plutonium-239 used had trace amounts of plutonium-240 in it. This is a different kind of plutonium, called an isotope. Plutonium-240 has a higher fission rate than plutonium-239, which means if the same gun-type design as Little Boy was used, it would’ve begun fission before the two masses of plutonium had been brought together.

This would’ve made it so inefficient it wouldn’t have been worth using, so another design was thought up. For Fat Man, one plutonium sphere was held in the center of the bomb. Around this, a layer of uranium was placed. This layer of uranium held the plutonium in place and helped reflect neutrons back into the core, improving the efficiency of the fission reaction.

Blocks of conventional explosives were then precisely placed around this to produce a symmetrical implosion when activated, which would compress the plutonium sphere. Once compressed, a device inside the plutonium was crushed and injected neutrons into the radioactive metal, kickstarting the fission reaction and setting off the nuke.

fat man design

But there’s one more thing that needed to be considered for both bombs: how the detonation would be triggered in the first place. Impact with the ground would’ve done the trick, but the ground would also have absorbed a lot of the explosion and limited its radius.

Instead, for maximum destructive potential, the bombs had to be detonated in the air. To do this, both were equipped with specialized circuitry that could detect their height from the ground and detonate at just the right moment.

bomb detonator

As well as affecting more area, an aerial explosion sends out a shockwave that smashes into the ground, rebounds, and then combines with the initial blast to form an even bigger shockwave. So, the crews of the planes dropping the bombs really had to skedaddle fast!

In the modern world, we don’t have to drop these deadly destroyers from planes anymore, we can fire them straight into the air on automated missiles! Ballistic missiles are about 20 times faster than traditional bombers and can carry hydrogen powered nuclear warheads far deadlier than the atom bombs dropped on Japan. Luckily, we’ve also got some pretty nifty anti-missile defense systems.

Nuclear Weapons Around The World

Which countries have nukes today? Any guesses who has the most? Because of how secretive the world’s governments are about their nuclear stockpiles, we can’t be 100% sure on the exact figures.

But as of 2021 estimates, Russia has the most nukes with a world-ending 6,255. Hot on their heels in second place we have the USA, with a considerable 5,550. The other 7 nuclear-capable nations have a lot less, with North Korea owning the least, somewhere between 40 and 50.

This Is How A Nuclear Bomb Works

Even though 40 nukes don’t sound like much compared to over 6,000, that’s still enough firepower to completely wipe New York City off the map, and then some. Which makes us wonder what would it be like if the unthinkable happened and the world really did descend into full-blown nuclear warfare?

As a global community, we’re currently sat on over 13,000 nuclear warheads. However, this number is a little misleading. Due to disarmament efforts, only 3,000 – 4,000 are actually active, and the rest are decommissioned. This is relatively low compared with 1986, when the total number of active warheads hit a whopping world-high of 70,300!

Of course, 4,000 nuclear missiles could still do a pretty hefty amount of damage. If even a tenth of them found their target, the loss of human life would be catastrophic. And not just from the explosions and radiation from huge firestorms too! As if nuclear weapons weren’t bad enough!

At Hiroshima, all the individual fires caused by the explosion amalgamated into one, terrible tempest of flames. Hot air rose and created burning, hurricane strength winds that turned inward towards the fire and fanned it. This made it rage even harder, destroying everything in its path for almost 4 ½ square miles before eventually dying out.

nuclear weapon firestorm

One apocalyptic theory, called Nuclear Winter, claims that if enough bombs went off, thousands of these furious firestorms would burn their way across the globe, kicking up hundreds of millions of tons of smoke and ash as they did so.

This would form a thick belt of particles encircling the Northern Hemisphere, plunging our world into darkness. Lack of sunlight would cause dramatic falls in temperatures and destroy much of Earth’s vegetation and animal life.

With crops failing, animals dying, and cities and infrastructure destroyed, surviving humans would be left in a cold, irradiated wasteland, and the dark clouds could remain for a whole decade. In other words, it wouldn’t be very fun.

Nuclear Winter

Armageddon: The Odds of Nuclear War

Hold on though! Before you go and spend your life savings on a fallout shelter and a thousand tins of beans, you should know that we’re probably not heading into Armageddon anytime soon. Mankind has possessed the power to destroy itself since the end of World War II.

Despite this, no nuclear weapon has ever been used outside of a test since 1945. Why? Well, nuclear warfare doesn’t benefit anyone. If one country launches a nuclear attack on another, the defending country is likely to launch a counter-nuclear attack in response, and both parties would be sent to their doom.

We call this Mutually Assured Destruction, and it’s not ideal. This worked pretty well during the Cold War, but today it’s a bit more complex. With countries around the world developing blisteringly fast hypersonic missiles, conventional defense systems just won’t cut it anymore.

Not only do hypersonic missiles fly faster than a mile a second, they’re also more maneuverable than their ballistic counterparts, making them supremely tough to defend against.

hypersonic missiles

Even so, Mutually Assured Destruction still applies. The US, Russia, and China are all developing the technology, alongside a number of other countries. Because of this, ironically, an attack is far less likely than if just one country had the power.

Furthermore, the modern world is much more focused on using nuclear energy for constructive uses rather than destructive. In fact, about 10% of the whole world’s electricity is now nuclear. And that’s a good thing; it doesn’t pollute the atmosphere, and it’s about 10 million times more efficient than burning fossil fuels.

Nuclear research has also helped doctors in the fight against cancer, allowing them to predict the amount of radiation needed to kill tumors without damaging healthy cells. We even use radiation to kill harmful bacteria on our food!

kill harmful food bacteria with radiation

So, it’s not all doom and gloom, and thanks to nuclear technology we’re actually taking some steps towards creating a better world. Let’s just hope we don’t blow that world into smithereens before we get there.

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