Cluster Bombs - Background
Clustered bombs have been used extensively in trying to increase the effectiveness of air dropped munitions. These have been used since prior to World War II and basically involved the combination of a number of smaller bombs held together by some frangible or breakable link. These could be dropped together and would separate at the time of drop or during the descent so that they would have separated in distance from each other in the air and retain the capability, individually to damage or destroy the targets which they hit or which were in their area.
In time, it became apparent that it would be more advantageous to further reduce the size of these smaller bombs since computations, dating back to Leonardo DaVinci showed that anti-personnel effectiveness could be greatly improved by accomplishing this. Studies after World War II had shown that relatively small bombs, considerably smaller than those used in clustered bombs, could destroy tanks, armored vehicles, trucks and similar military vehicles. It soon became apparent that it was difficult and costly to place such larger numbers of much smaller bombs in clusters and reliably and safely hold them together for aircraft drop. This led to the placement of such clustered smaller bombs within the confines of a larger bomb, acting as a container for the smaller bombs, where, after drop from the aircraft, the bomb would open and somehow disperse the cargo of the contained smaller bombs over a target area.
The initial and continuing problem in trying to accomplish the ejection and dispersion of the cargo of such larger bombs has been the means of accomplishing this objective. Actually, two types of clustered dispensing systems came into being. One is commonly known in the U.S. as Slung Under Unit Dispensers or SUU Dispensers. These are hung under aircraft and directly used to dispense a cargo of munitions, through RAM air or propellants with the dispenser container retained on the aircraft. The United States Air Force has been using such SUU dispensers extensively. Here smaller bombs or other munitions are dispensed usually out of the rear end of SUU dispensers as a result of forces applied against the cargo to cause it to eject rearward. Thus Ram air was used frequently to eject the cargo of munitions.
The United States Navy was of the opinion that the aircraft dispensing of munitions, requiring a flight over the target would result in excessive losses to enemy air defenses. The Navy consequently developed an alternate form of dispensing clustered munitions, which would not require a flight over the target. Instead of leaving the dispenser on the aircraft during the dispensing of the munition, the dispenser itself was dropped from the aircraft and designed in a missile configuration, so as to fly toward the target, while the aircraft would turn so as to permit the aircraft to be out of gun reach of the defending gun positions. In one tactical use, this dispenser, which is now known as a cluster bomb, would be dropped from great altitudes at long distances from the target where the aircraft was out of reach of most air defense weapons. The forward velocity of the aircraft would to a large extent be retained by the aerodynamically shaped cluster bomb and would permit it to fly a long distance in the direction of the target before the cargo of munitions would be dispensed from that bomb to cover all or part of the target area.
In a second tactical use the aircraft would be flying at a low altitude. As it approached the target area, it would fly upward and release the cluster bomb on the "up-leg" of flight. This upward angle of flight of the cluster bomb would cause it to fly in a mortar shaped flight configuration. The cluster bomb, which is in effect a missile would fly a considerable distance toward the target area, to discharge the cargo of submunitions over the target area. The aircraft would turn and not be required to fly over the target area.
A major problem in the design of a cluster bomb as described above involved the complexity and resulting cost, as well the safety of such bombs. A cluster bomb had to be fuzed such that the dispensing of smaller bombs, mines or grenades could be conducted efficiently and reliably. Consequently, various designs of the cluster bomb were produced to properly contain and be able to discharge the cargo of munitions. These designs used a number of basic techniques, including combinations of such techniques to eject and disperse the cargo of munitions. This required the packing of the munitions such that they could be dispersed from the cluster bomb without damage. It further was a desire to pack the maximum cargo of munitions within the cluster bomb.
There has been a continuous desire to produce lower cost, easier to fabricate and safer to handle cluster bombs. Normally, the container main body of cluster bombs are fabricated from metal or plastic components and, therefore, cluster bombs can be manufactured competitively in a very large number of industrial organizations. Competition drives the cost down to a minimal amount. But, once energetic materials, such as propellants, explosives or pyrotective materials must be attached to that body or container, then the competition is effectively eliminated since only one or two special facilities in the locality can handle such energetic materials. Governmental restrictions severely limit the licenses given out to organizations authorized to handle explosives, propellants or pyrotechnic materials. These organizations need extra land and special facilities to store these energetic materials. Operators need special training and receive higher pay. Storage, handling and transportation requirements are severe and increase costs. There is always the potential of accidents with explosives, propellants or pyrotechnic materials. This forces special handling of loaded items. Even cluster bomb bodies containing small amounts of explosives require special handling and escort of police or similar protection during transportation, especially across bridges and through tunnels. All of these considerations cause a higher cost for energetically loaded cluster bomb bodies as compared to inert bodies which do not contain explosives or propellants.
Saturation of unexploded submunitions has become a characteristic of the modern battlefield. The potential for fratricide from unexploded ordnance [UXO] is increasing. Joint Publication 1-02 defines unexploded explosive ordnance as "explosive ordnance which has been primed, fused, or otherwise prepared for action, and which has been fired, dropped, launched, projected, or placed in such a manner as to constitute a hazard to operations, installations, personnel or material and remains unexploded either by malfunction or design or for any other cause." Although ground forces are concerned with all unexploded ordnance, the greatest potential for fratricide comes from unexploded submunitions.
Submunition function reliability requirement is no less than 95 percent. With a 95 percent submunition function reliability, one CBU-58 (with 650 submunitions) could produce up to 38 unexploded submunitions. A typical B-52 dropping a full load of 45 CBU-58/CBU-71, each containing 650 submunitions, could produce an average of some 1700 unexploded sub-munitions. The numbers of submunitions that fail to properly function and the submunitions' dispersion determine the actual density of the hazard area.
After the Kosovo conflict in 1999 much effort has been made to handle the mine and UXO problem in the region. According to the UN Mine Action Co-ordination Center (UNMACC) in Pristina the total number of mines and UXO cleared by 8 March 2001 was assessed at 84,046. More than 55,000 pieces of ammunition had been disposed of, including UXO produced through the failure of munitions to function (duds). The UK EOD unit of the Multi-National Brigade (Centre) carried out investigations of all strike areas in the area of responsibility and prepared statistics for the assessed failure rates. The average failure rates for sub-munition type BLU-97 was assessed at 7.1% and the failure rate for sub-munition type BL755 was assessed at 11.8%.
Studies that show 40 percent of the duds on the ground are hazardous and for each encounter with an unexploded submunition there is a 13 percent probability of detonation. Thus, even though an unexploded submunition is run over, kicked, stepped on, or otherwise disturbed, and did not detonate, it is not safe. Handling the unexploded submunition may eventually result in arming and subsequent detonation.
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