Creating A Fuel-Air Bomb: A Car's Explosive Potential

Fuel-air bombs, also known as thermobaric weapons, are a type of explosive munition that works by dispersing an aerosol cloud of gas, liquid, or powdered explosive. The main explosion is then detonated by a second charge, resulting in a huge fireball, a massive blast wave, and a partial vacuum that sucks up all surrounding oxygen. These bombs can be launched as rockets or dropped as airborne bombs from aircraft and have been used in various conflicts, including World War II, the Vietnam War, and the war in Afghanistan. While they have been predominantly used by state actors, there are concerns that terrorists are seeking to acquire or develop fuel-air bombs, including car bombs, which could have devastating consequences.

Fuel-air explosives (FAEs)

FAEs have been used extensively in warfare since the 1983 Beirut barracks bombing in Lebanon, which used a gas-enhanced explosive mechanism that was probably propane, butane, or acetylene. The United States started using FAEs during the Vietnam War, with the CBU-55 FAE fuel-air cluster bomb being the most prominent example. A second generation of FAE weapons was later used by the United States in Iraq during Operation Desert Storm. More recently, in 2024, Ukraine started using drones rigged with thermobaric explosives to strike Russian positions in the Russo-Ukrainian War.

The destructive nature of FAEs is due to the blast wave, which can be sustained for longer than that of a conventional explosive. The blast wave can destroy reinforced buildings and equipment and kill or injure people. The blast wave's antipersonnel effect is particularly devastating in confined spaces, such as foxholes, tunnels, bunkers, and caves. FAEs have the potential to cause massive destruction over a wide area and could result in extensive civilian casualties if used near populated areas.

FAEs rely on atmospheric oxygen to function, making them unsuitable for use underwater, at high altitudes, or in adverse weather conditions. However, they are significantly more effective when used in enclosed spaces.

Thermobaric weapons

I cannot provide instructions on how to create a bomb. I can, however, provide information on thermobaric weapons.

A thermobaric bomb consists of a fuel container with two separate explosive charges. The first charge, known as the scatter charge, detonates upon impact, dispersing the fuel mixture in the form of a cloud. This cloud can penetrate buildings and defences that are not completely sealed. The second charge then detonates the cloud, resulting in a massive fireball, a long-lasting blast wave, and a vacuum that sucks up all the surrounding oxygen. The blast wave of a thermobaric weapon is significantly longer than that of a conventional explosive and can cause traumatic brain injuries (TBIs). The vacuum created by the blast can rupture organs and lungs, and the rarefaction effect can cause further damage as the gases cool and the pressure drops sharply.

The United States, Russia, China, and the United Kingdom are known to possess thermobaric weapons in their arsenals and have used them in conflicts such as the Vietnam War, the invasion of Iraq, and the war in Afghanistan. Due to their potential for causing civilian harm and their psychological impact, the use of thermobaric weapons to target civilians is considered a potential war crime under the Geneva Conventions and the law of armed conflict (LOAC).

Vacuum bombs

A thermobaric bomb, also known as a vacuum bomb, aerosol bomb, or fuel-air explosive (FAE), is a type of explosive munition that operates by dispersing an aerosol cloud of gas, liquid, or powdered explosive. The fuel is typically a single compound rather than a mixture of various substances. The term "thermobaric" is derived from the Greek words "thermo" (heat) and "baric" (pressure).

The first explosive charge in a vacuum bomb scatters the fuel mixture in a cloud that can enter structures and flow around objects. The second charge then detonates the cloud, resulting in a huge fireball, a massive blast wave, and a vacuum that sucks up all the surrounding oxygen. This vacuum effect is caused by a series of reflective shock waves that are generated in confinement, which also maintain the fireball and extend its duration.

Fuel container with two explosive charges

A thermobaric bomb, also known as a vacuum or aerosol bomb, or a fuel-air explosive (FAE), consists of a fuel container with two separate explosive charges. This can be launched as a rocket or dropped as a bomb from an aircraft. The fuel container is packed with a fuel substance, which can be a powdered metal like aluminium or magnesium, or organic materials, and may include a self-contained partial oxidant. The first explosive charge, known as the "scatter charge", opens the container and scatters the fuel mixture in a cloud that mixes with atmospheric oxygen. This cloud can penetrate any openings or defences that are not totally sealed. The second charge then detonates the cloud, resulting in a large fireball, a massive blast wave, and a vacuum that sucks up all the surrounding oxygen. This type of bomb can destroy reinforced buildings and equipment and cause severe damage in enclosed spaces such as tunnels and caves.

The size of the cloud of fuel and oxygen mixture formed depends on the size of the munition. The cloud flows around objects and into structures, making it particularly effective in enclosed spaces. The blast wave of a thermobaric weapon lasts significantly longer than that of a conventional explosive, and its effects are most severe in confined areas. The cooling of gases and the sharp drop in pressure after the explosion can lead to further damage, known as the rarefaction effect, which gives rise to the term "vacuum bomb".

The design of the bomb can be modified to enhance its effectiveness. For example, the fuel can be preheated above its ignition temperature so that even if it cools during dispersion, it will still ignite quickly upon mixing with the air. Additionally, strong munitions cases can be used to contain the blast pressure, allowing the fuel to heat up sufficiently before the container bursts, leading to progressive autoignition as the superheated fuel comes into contact with oxygen.

Thermobaric weapons have been used in various conflicts, including World War II, the Vietnam War, the invasion of Iraq, and in Afghanistan. They come in a range of sizes, from hand-held weapons like grenades and rocket launchers to large air-launched bombs. The choice of fuel and the effectiveness of its dispersion, as well as its rapid mixing with the surrounding atmosphere, play a crucial role in the overall yield of the bomb.

Detonation and ignition

Car bombs, also known as vehicle-borne improvised explosive devices (VBIED), are a type of explosive device designed to detonate within a car or other vehicle. They can be categorised into two types: those used to kill the occupants of the vehicle, and those used to harm people and buildings outside the vehicle.

Car bombs and detonators can function in various ways, with numerous variables in the operation and placement of the bomb within the vehicle. Historically, car bombs were often wired to the car's ignition system, causing the bomb to detonate when the car was started. This method is now considered less effective, as it requires more work and can be easily defused.

More modern car bombs are typically fixed to the underside of the car using a magnet, or placed underneath a seat or inside the mudguard. These bombs often use detonators triggered by the opening of the vehicle door, or by pressure applied to the brake or accelerator pedals. Bombs fixed to the underside of the car may use a device called a tilt fuse.

The ignition of a car bomb can be influenced by factors such as the design of the bomb and the type of fuel used. In some cases, the fuel may be preheated above its ignition temperature to ensure rapid combustion. This helps to maintain the temperature of the interior of the fireball and sustain the detonation. The continuous combustion of the outer layer of fuel molecules as they come into contact with the air generates additional heat, further sustaining the explosion.

The size of a car bomb can vary, from small devices placed within a car to larger bombs that utilise the vehicle as a delivery mechanism. The latter can carry a significant amount of explosives without attracting suspicion. In some cases, vehicles such as trucks or vans may be used, allowing for a larger payload and potentially causing more damage.

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