The high-stakes gamble: Can missile defence systems truly intercept nuclear warheads?

At present, there are approximately 12,100 nuclear warheads in existence. Nearly 88 per cent of these are held by just two countries, Russia and the United States, according to Statista.

Other nations that possess nuclear weapons include France, China, the United Kingdom, Pakistan, India, Israel, and North Korea. Russia holds the largest number of confirmed nuclear weapons, with more than 5,500 warheads in its arsenal.

Former Russian minister Andrei Kozyrev believes President Vladimir Putin is unlikely to use nuclear weapons against the West. However, Putin has made what some see as threats to use them if his invasion of Ukraine faces further interference.

Nuclear weapons are seen as the most destructive on Earth. When detonated, they cause massive destruction and release intense heat and radiation, leading to long-term environmental damage that can last for years.

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As reported by express.co.uk, a single bomb has the potential to wipe out an entire city, and the impact can be felt as far as 53 miles (around 85 km) away, depending on the bomb's size. People within this range may even experience temporary blindness if they are looking directly at the explosion.

Nuclear bombs have been used only once in history when the United States dropped two on the Japanese cities of Hiroshima and Nagasaki in 1945. While the exact number of deaths is uncertain, it’s estimated that around 140,000 people were killed in Hiroshima and at least 74,000 in Nagasaki.

The bombs released nuclear radiation that led to thousands more deaths from radiation sickness over the following weeks, months, and even years.

The creation of these powerful weapons started the Nuclear Arms Race, a competition for dominance in nuclear warfare between the United States, the Soviet Union, and their allies in the years that followed.

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This race continued throughout the Cold War, reaching its height in 1986 when over 64,000 nuclear warheads were believed to be in circulation worldwide.

But as the Soviet Union collapsed and the Cold War ended, tensions between the East and West eased, leading to the beginning of nuclear disarmament.

Since the 1980s, Russia's nuclear stockpile has reportedly shrunk by nine times, while the US arsenal is now six times smaller.

Can nuclear bombs be intercepted?

In short, nuclear bombs can be intercepted, but it's a very challenging task.

Ballistic missiles are used to carry and launch nuclear bombs along a specific flight path.

In the 1960s, during the height of the Nuclear Arms Race, the Soviet Union created anti-ballistic missiles to defend the USSR from ballistic missile threats.

These anti-ballistic missiles (ABMs) are designed to intercept and destroy nuclear missiles before they reach their target.

ABMs work by detecting and tracking an incoming ballistic missile, and then launching an interceptor to destroy it.

This is typically done using a booster rocket that either collides with the missile to destroy it on impact or uses a blast fragmentation warhead to detonate the missile's payload without causing a nuclear explosion.

Even if an ABM successfully destroys a missile, there’s still a chance that plutonium or uranium could be scattered in the area, leading to a radiation risk.

However, this outcome is still far better than the destruction of an entire city.

How do nuclear bombs work?

The effects of a nuclear explosion can vary widely based on several factors. These include the type of weapon (whether it uses fission or fusion) and its power. The location of the blast also matters—whether it occurs in the air (and at what height), on the ground, underground, or underwater. Weather conditions, environmental factors, and the nature of the target (such as a city, countryside, or military site) all play significant roles in determining the impact.

When a nuclear weapon explodes, it creates a fireball with temperatures as hot as the Sun's core or centre. The energy released spreads in different ways.

About 85 per cent of the energy from a nuclear explosion goes into creating a powerful blast and intense heat. The other 15 per cent is released as radiation. This includes immediate radiation within the first minute and lasting radiation over time, which can include local fallout.

Local fallout (radioactive debris that falls back to the ground) refers to the radioactive particles that settle back to Earth after a nuclear explosion.

Blast 

When a nuclear explosion occurs, extremely hot gases expand rapidly, creating a shock wave that moves outward at high speed.

The "overpressure," or intense pressure, at the front of the shock wave, can be measured in pascals (or kilopascals (kPa)), pounds per square inch (psi), and kilograms per square centimetre (kg/cm²). For reference, 1 psi is about 6.9 kPa or 0.07 kg/cm².

The higher the overpressure, the more likely a building will be damaged by the sudden force of the shock wave.

Another damaging effect is the "dynamic pressure," which is the strong, fast-moving (or high-velocity) wind that follows the shock wave.

A typical two-story, wood-frame house will collapse under an overpressure of about 0.35 kg/cm² (five psi).

Atmospheric pressure at sea level is about 14.7 psi (10.3 kg/cm²). A pressure of 5 psi (0.35 kg/cm²) is significantly higher than normal atmospheric pressure (14.7 psi is what we experience constantly). When a sudden additional pressure of five psi from a shock wave hits, it exerts a powerful force that can cause structural damage, leading to collapse.

A one-megaton (about 1,000,000 kilograms of TNT) explosion at 3,000 metres (10,000 feet) high can create this level of overpressure (5 psi) up to 7 km (about 4 miles) from the blast.

The strong winds following the blast can throw a person against a wall with several times the force of gravity.

The force of gravity is the pull that Earth exerts on objects, measured as 9.8 metres per second squared (m/s²).

Within 8 km (5 miles) of the blast, few people outside or in regular buildings are likely to survive.

The initial shock wave creates huge amounts of debris, like bricks, glass, wood, and metal, which fly at speeds over 160 km/h (100 mph), causing more destruction.

Thermal Radiation 

About 35 per cent of the energy from an airburst is released as thermal radiation, which includes light and heat. This can cause skin burns, and eye injuries, and start fires over long distances.

The shock wave can spread fires even more. If these fires are large enough, they can merge into a firestorm. This creates a huge column of hot air that pulls in fresh air from around it.

Winds rushing inward and the intense heat in a firestorm burn almost everything that can catch fire.

Initial radiation 

A unique aspect of a nuclear explosion is the release of nuclear radiation, which is divided into initial radiation and residual radiation.

Initial radiation, or prompt radiation, includes gamma rays and neutrons released within a minute of the explosion. It also produces beta particles (free electrons) and a small number of alpha particles (helium nuclei i.e., two protons and two neutrons bound together), but these usually don't reach the ground if the explosion happens high above the ground.

Gamma rays and neutrons can harm living things and remain dangerous over long distances because they can penetrate most buildings.

Although gamma rays and neutrons make up only about three per cent of the energy from a nuclear blast, they can cause a large number of injuries and deaths. They can lead to radiation sickness, cancer, and other serious health issues.

Residual radiation 

Residual radiation is the radiation released more than one minute after the explosion. In an airburst, this mainly comes from the weapon's debris.

If the explosion happens on or near the ground, dirt, water, and nearby materials are pulled up by the rising cloud, leading to local and global fallout.

Delayed fallout arrives after the first day. It consists of tiny particles carried by the wind, spreading thinly over large areas of the Earth.

A nuclear explosion creates a complex mix of over 300 different isotopes from many elements. These isotopes have half-lives ranging from fractions of a second to millions of years.

The radioactivity of fission products is very high initially but decreases quickly due to radioactive decay.

Seven hours after a nuclear explosion, the leftover radioactivity drops to about 10 per cent of its level at one hour. After 48 more hours, it decreases to one per cent.

As a simple guideline, for every seven times increase in time after the explosion, the radiation level drops by ten times.

For example, if the radiation level is 100 units one hour after an explosion, seven hours later it would decrease to 10 units. After 49 hours (seven times seven), it would drop to 1 unit.