A daisy cutter is an explosive device (the term is an understatement, see also daisy).
It is commonly reported to be a thermobaric bomb, but this is not the case. The BLU-82B is a conventional explosive device incorporating both agent and oxidizer (ammonium nitrate, aluminum powder, and polystyrene). It is fitted with a fuze extension to provide detonation 1-6 feet above ground, minimizing the cratering effect and maximizing the blast effect. The daisy cutter was originally used to create an instant clearing in dense jungle for a helicopter landing zones. It can also be used to clear minefields of pressure sensitive mines or as an anti-personnel bomb relying on its extreme blast effects. The United States Air Force has a 15,000 lb daisy cutter bomb, the BLU-82, which must be parachute launched from the back of a transport plane, typically a C-130, because of its large size. The Air Force is currently (Dec 2002) lobbying for the development of an even larger, 30,000 lb weapon, which would be deployed from a traditional bomber (i.e. B-52, B-2, B1). (See Massive Ordnance Air Blast bomb)
Daisy cutter bombs were first used by the United States during the Vietnam War. The concept for the bomb is attributed to an Air America employee who grasped the idea during a night of drinking. Shortly thereafter, his drinking buddy, a Royal Lao Air Force airman at Louang Phrabang, gathered the needed materials for the prototype and started welding used aircraft gun barrels directly into the nose fuse cavity of bombs.
When used gun barrels were in short supply, water pipes were requisitioned for the task. The welded pipe versions had several adverse effects, such as vibration, pipe weld separation / breakage while in flight and wind drag due to the barrels not being capable of being aligned perfectly, so that phase of development eventually gave way to threaded steel water pipes screwed into the nose cavity of the bombs, leaving only the tail fuse for detonation.
The Daisy Cutter became better known to the public when it was used in the 2001 U.S. Attack on Afghanistan.