Fire needs three things: oxygen, heat, and fuel. Conventional explosives, like black powder, use a mixture of fuel and oxidizer. On the other hand, a thermobaric bomb uses fuel, a conventional explosive, and picks up an oxidizer as it goes. 

Many people have heard of MOAB. Not just the National park in Utah, but the Massive Ordnance Air Blast, better known as the Mother Of All Bombs. MOAB is the most well-known example of a thermobaric bomb.

What Is a Thermobaric Bomb?

A thermobaric bomb uses all the oxygen in an area for its own use. Because the explosion needs oxygen in order to work, a thermobaric reaction actively seeks out oxygen on which to feed. When conventional explosives detonate, a shaped charge acts upon a projectile of some sort. A shotgun shell is an example of this: the primer charge is ignited by the firing pin, which then ignites a contained black powder charge, which ejects pellets from the muzzle.

When a thermobaric bomb is detonated, a small conventional charge within a larger fuel vessel is ignited. The charge begins to ignite the fuel mixture, which produces pressure within the container. The container ruptures, allowing the heated fuel mixture to disperse. The dispersed mixture then burns as it comes in contact with oxygen, continually expanding until the fuel or oxygen is consumed.

The fuel mixture acts as a shock wave as it expands, creating terrific pressure waves. If a person is near the explosion they can either be killed by the heat or the pressure. In confined areas, the concussive waves bounce off walls and ceilings, creating overlapping pressure waves. The name thermobaric comes from the Greek “therme” (heat) and “baros” (pressure).

Mother of All Bombs

The MOAB, developed in 2003 by the Air Force Research Laboratory and Dynetics, a U.S.-based aeronautics company, was first used operationally in 2017. It is a 22,000lb bomb, 18,500lb of which is the explosives packed inside. Because the skin of the bomb is so light, the MOAB is not designed to penetrate, but to hit softer targets. 

The one time MOAB was used operationally was to destroy an Islamic State cave complex. While the target seems mundane considering the aura surrounding the bomb, its use sent a message to ISIS and the world. A message with teeth. 

The Russians developed a bomb called the Father Of All Bombs to rival the MOAB. The Russian version is considered a fuel-air explosive, using liquid fuel to create the blast. MOAB uses a nano-particle fuel mixture, with basically deconstructed particles of aluminum, TNT, and a chemical called cyclotrimethylene trinitramine (cyclonite).

How Does the Bomb Work?

The official designation for MOAB is the GBU-43/B. GBU stands for guided bomb unit, which means MOAB is a precision-guided thermobaric bomb. Most bombs are delivered by bombers, like the B-1, B-2, or B-52. The GBU-43 is too large to be mounted on conventional launchers, so it must be delivered in a novel way.

The bomb is palletized and loaded onto C-130 aircraft. When near the intended target, the pallet is released from the C-130 using a drogue parachute attached to the pallet. Once in the air, the pallet is pulled free by the parachute, guidance fins depl0y from the bomb housing, and the integrated satellite guidance package takes over directing the bomb to the target. 

Once at the target, the bomb is detonated using preset values. Whether that means air-burst, ground-burst, or timed-release depends on the mission and situation. Considering the bomb has only been used once in battle, there is not a lot of real-world data to point to. 

Why the MOAB?

The MOAB was developed as a successor to the “daisy-cutter” bombs used to clear foliage and landing zones in Vietnam and later in Afghanistan. As an air-burst weapon, it can be used to clear an area of everything. 

Most people have seen footage of fighter jets dropping napalms in Vietnam. Napalm is not a thermobaric, however. It is a fuel-gel mixture that is dispersed through an explosive charge. That burning mixture sticks to anything it touches, causing massive damage. Think of candle wax, dripping from the candle and sticking to anything. Now imagine that wax on fire. That is napalm. 

Operational Use

The MOAB dropped in Afghanistan in 2017 acted as a galvanizer to the world. Many criticized its use and condemned the U.S. for deploying it.

“[T]here was [no] need for such a dramatic military measure,” said Borhan Osman, an expert with the Afghanistan Analysts Network. A local man interviewed after the explosion described it as “the earth felt like a boat in a storm.” 

Whether the MOAB will be used in combat again remains to be seen. While massively destructive, the optics of a bomb like this make it a psychological weapon as well as a conventional one. Psychological operations are not new to the military and have been in use for millennia.

Having a bomb with the power of a nuke, without the radiation concerns, is a huge psychological weapon against the boots, or sandals, on the ground.