Mark 8x series conventional bomb
Mark 8x series of gravity bombs are a standard U.S. series, used by all U.S. military services[1], and many other nations. The basic munition is a "dumb bomb", with the minimal controls of substituting fins that maximize or minimize speed, and fuzes that mount either in the nose (i.e., instant destination) or tail (i.e., slight delay). One of the tail delay variants can deploy a braking parachute, so the aircraft can drop at very low altitude, but be far enough from fragments when the bob hits.
These bombs have casings that are aerodynamically designed for minimum drag, so, when they are carried on the external wing mounting points of aircraft, they create the least possible wind resistance.
The "X" indicates the approximate total weight of the bomb. Roughly half of this amount is actual explosive content; the rest goes principally for the casing, fins, and fuzes. While the original filling was trinitrotoluene (TNT), there is a program of replacement with more insensitive explosives to improve safety in crashes or emergency jettisons. Specialized explosives may be used, such as DIME Dense Inert Metal Explosive that concentrates the blast, minimizing damage to anything near the actual target.
There are ballistically similar bombs, such as the BLU-109, which have much stronger cases, accepting much less explosive in order to be able to penetrate more deeply.
While the basic Mk. 8x is guided only by the accuracy of the releasing aircraft, all can be equipped with the Joint Direct Action Munition (JDAM) kit, which replaces the fins with movable fins that can steer the bomb. Steering commands come from a guidance assembly attached to the nose, which can use inertial guidance, inertial+GPS, or, recently, home on a laser designator. Other, more intelligent, guidance and fuze designs are in development.
| Designation | Total weight | JDAM designation/Comments |
|---|---|---|
| Mk. 81 | 250 lb. | GBU-29 |
| Mk. 82 | 500 lb. | GHU-30, GBU-38 |
| Mk. 83 | 1000 lb. | GBU-32 |
| Mk. 84 | 2000 lb. | GBU-31 |
| Mk. 117 | 750 lb. | Higher drag, internal carriage |
| GBU-39 Small Diameter Bomb | 250 lb. DIME | delivers more explosive power in a smaller area than the Mk. 81; three can be carried in a pylon meant for a Mk. 84 |
- ↑ that have aircraft that drop bombs