Gbu-144 Thumper Mk4

A thermobaric weapon, which includes the type known as a "fuel-air bomb", is an explosive weapon that produces a blast wave of a significantly longer duration than those produced by condensed explosives. This is useful in military applications where its longer duration increases the numbers of casualties and causes more damage to structures. There are many different variants of thermobaric weapons rounds that can be fitted to hand held launchers such as rocket-propelled grenades and anti-tank weapons.

Thermobaric explosives rely on oxygen from the surrounding air, whereas most conventional explosives consist of a fuel-oxidizer premix (for instance, gunpowder contains 25% fuel and 75% oxidizer). Thus, on a weight-for-weight basis they are significantly more energetic than normal condensed explosives. Their reliance on atmospheric oxygen makes them unsuitable for use underwater, at high altitude or in adverse weather. However, they have significant advantages when deployed inside confined environments such as tunnels, caves, and bunkers.