General-purpose bomb

General-purpose bomb

Characteristics

General-purpose (GP) bombs use a thick-walled metal casing with explosive filler (typically TNT, Composition B, or Tritonal in NATO or United States service) composing about 50% of the bomb's total weight. (The British term for a bomb of this type is "medium case" or "medium capacity",(abbreviated to MC). The GP bomb is a common weapon of fighter bomber and attack aircraft because it is useful for a variety of tactical applications and relatively cheap.

General-purpose bombs are often identified by their weight (e.g., 500 lb, 250 kg). In many cases this is strictly a nominal weight, or caliber, and the actual weight of each individual weapon may vary depending on its retardation, fusing, carriage, and guidance systems. For example, the actual weight of a U.S. M117 bomb, nominally 750 lb (340 kg), is typically around 820 lb (374 kg).

Most modern air-dropped GP bombs are designed to minimize drag for the carrier aircraft.

In low-altitude attacks, there is a danger of the attacking aircraft being caught in the blast of its own weapons. To address this problem, GP bombs are often fitted with retarders, parachutes or pop-out fins that slow the bomb's descent to allow the aircraft time to escape the detonation.

GP bombs can be fitted with a variety of fuses and fins for different uses. One notable example is the "daisy cutter" fuse used on Vietnam-era American weapons, an extended probe designed to ensure that the bomb would detonate on contact (even with foliage) rather than burying itself in earth or mud, which would reduce its effectiveness.

GP bombs are commonly used as the warheads for more sophisticated precision-guided munitions. Affixing various types of seeker and electrically controlled fins turns a basic 'iron' bomb into a laser-guided bomb (like the U.S. Paveway series), an electro-optical guided bomb, or, more recently, GPS-guided weapon (like the U.S. JDAM). The combination is cheaper than a true guided missile (and can be more easily upgraded or replaced in service), but substantially more accurate than an unguided bomb.

Modern American GP bombs: the Mark 80 series

During the Korean War and Vietnam War the U.S. used older designs like the M117 and M118, which had a higher explosive content (about 65%) than most current weapons. Although some of these weapons remain in the U.S. arsenal, they are little used, and the M117 is primarily carried only by the B-52 Stratofortress.

The primary U.S. GP bombs are the Mark 80 series. This class of weapons uses a shape known as Aero 1A, designed by Ed Heinemann of Douglas Aircraft as the result of studies in 1946. It has a length-to-diameter ratio of about 8:1, and results in minimum drag for the carrier aircraft. The Mark 80 series was not used in combat until the Vietnam War, but has since that time replaced most earlier GP weapons. It includes four basic weapon types:

* Mark 81 - nominal weight 250 lb (113 kg)
* Mark 82 - nominal weight 500 lb (227 kg)
* Mark 83 - nominal weight 1,000 lb (454 kg)
* Mark 84 - nominal weight 2,000 lb (908 kg)

Vietnam service showed the Mk 81 "Firecracker" to be insufficiently effective, and it was withdrawn from U.S. service. However, recently precision-guided variants of the Mk 81 bomb have begun a return to service, based on U.S. experience in Iraq after 2003, and the desire to reduce collateral damage compared to Mk 82 and larger bombs (e.g., when attacking a single small building in a populated area).

Since the Vietnam War, United States Navy and United States Marine Corps GP bombs are distinguished by a thick ablative fire-retardant coating, which is designed to delay any potential accidental explosion in the event of a shipboard fire. Land-based air forces typically do not use such coatings, largely because they add some 30 lb (14 kg) to the weight of the complete weapon.[citation needed]

In the Mk 80 series bomb bodies is also used in the following weapons:

* BDU-50 A practice (no explosive) version of the Mk 82 bomb body
* BDU-56 A practice (no explosive) version of the Mk 84 bomb body

Paveway II p1230135.jpg
Smart bomb kits

Dumb Mk 80 bombs could be smart bombs with attached kits:

* GBU-12D Paveway II (Mk 82) laser guided.
* GBU-16B Paveway II (Mk 83) laser guided.
* GBU-24B Paveway III (Mk 84) laser guided.
* GBU-38 JDAM (Mk 82) INS/GPS guided.
* GBU-32 JDAM (Mk 83) INS/GPS guided.
* GBU-31 JDAM (Mk 84) INS/GPS guided.

Snake Eye
Retarded versions

* Mk 82 Snake Eye was a standard Mk 82 with folded, retarding petals.
* Mk 82 Retarded was a standard Mk 82 with a ballute.
* Mk 83 Retarded was a standard Mk 83 with a ballute.
* Mk 84 Retarded was a standard Mk 84 with a ballute.