needed. That something was the cluster munition. Cluster bombs were not new. The idea dates back to World War II, when both fragmentation and incendiary cluster bombs were used for many purposes, but suffered from restrictive delivery profiles and the lack of predictable dispersal patterns for the small bombs (called 'bomblets' or submunitions) carried in the cluster. To overcome these limitations, the U.S. Navy developed a new concept — the munitions dispenser.
The dispenser would be a 'truck' for the load of submunitions, which would be dropped like a normal GP bomb onto the target area. At a preplanned altitude, the fuze (proximity or time delay from aircraft launch) would activate, causing the outer skin panels of the dispenser to break loose. Then another charge (usually compressed air or a small pyrotechnic charge) blasted the load of bomblets loose into a preplanned pattern, which would then fall onto the target.
The Navy's first effort, which began in 1963, centered around a dispenser called the Mk 7. When activated by an Mk 339 time delay fuze, the dispersion charge has the effect of scattering the submunitions in an elongated, doughnut-shaped pattern whose size is controlled by the release height of the bomblets. Each submunition has its own fuze, which detonates upon contact with a target or the ground. When the whole package was put together, it was known as the Mk 20 Rockeye II Mod. 2. It carried a load of 247 M118 anti-tank munitions that looked for all the world like sadistic hypodermic syringes, weighed in at some 490 lb./222.7 kg., and was an instant success with American aircrews when it reached Vietnam in 1967. Adopted by both the Navy and Air Force, it was particularly welcomed by aircrews tasked with attacking SAM sites and AAA gun emplacements, which were particularly vulnerable to the deadly rain of cluster munitions. This classic piece of aircraft ordnance has been so effective that some 27,987 Rockeye IIs were dropped on targets during Desert Storm, more than any other cluster munition used. At only $3,449 a copy (in 1991 dollars), it is quite a bargain by current standards.
With the early success of the Rockeye, the Air Force quickly jumped on the bandwagon and started development of its own cluster bomb dispenser, the Suspension Underwing Unit (SUU-30H/B). A total of 17,831 SUU-30-series weapons were delivered by U.S. aircraft during Desert Storm. This dispenser became the basis for a whole family of USAF CBUs. Some of the versions currently in use include:
As you can see, the variety of submunitions and weapons effects is numbing. Again, fuzing is as critical to successful employment of the SUU-30 family as it is for the 80-series GP bombs. If the dispenser opens too soon, then the density of submunitions will not be high enough to ensure destruction of the target. Similarly, if the canister opens too late, then the bomblets will not spread out enough to cover the whole target. As might be imagined, it is a challenge for planners, ordnance technicians, and loaders to figure out the proper dispenser/submunition/fuze combination.
As good as the early CBUs were, they still imposed a number of restrictions upon fliers trying to deliver them. By the early 1980s the Air Force was beginning to realize that the early CBUs were shackled by a number of limitations in high-threat target areas. Most especially, the aircraft delivering them had to actually overfly the target in 'laydown' delivery profiles, exposing them to ground fire. Thus, a new series of submunitions was developed by the Air Force, with a larger dispenser that would get enough of them onto a target array to be useful. And so was born the SUU-64/65 Tactical Munitions Dispenser (TMD).
The TMD is a 1,000 lb./454.5 kg.-class weapon, with three versions currently in service with the USAF. All three share the basic TMD dispenser components, with only the submunition load and other minor details differentiating them. Starting at the front is the optional FZU-39/B proximity fuze, which is designed to tell the TMD its exact altitude at all times. There is also a time delay fuze, which can be used by itself, or in conjunction with the FZU-39/B. Just aft of the nose/fuze section is the cargo section where the submunitions are packed. This is a tubular body section, with equipment designed to cut the body into thirds when the submunitions are ready to be deployed. This is topped by a structure called a strongback, where the mounting lugs are attached. At the rear is a tail assembly, with spring-loaded guidance fins designed to stabilize the entire TMD assembly.
The three different variants of the TMD are shown in the table below:
On the CBU-87/B, the SUU-65 dispenser is loaded with 214 BLU-97/B Combined Effects Munitions (CEMs), and is planned to replace almost every type of CBU. About the size and shape of a beer can, each CEM is equipped with its own ballute, making each a tiny high-drag bomb. It is designed to have excellent weapons effects against armored vehicles and exposed infantry, as well as superb incendiary effects against targets like fuel and ammunition dumps. The BLU-97/B accomplishes this through the use of a unique triple-function pyrotechnic package. Its anti- armor capability comes from a shaped charge capable of penetrating the top armor of virtually any tank or armored vehicle in the world. Surrounding the shaped charge is a serrated steel case, which fragments into hundreds of 30- grain size (about 1/4 in./6mm.) fragments. Finally, at the rear of the CEM is a ring of zirconium. When fragmented and heated to incandescence by the explosive of the shaped charge, it ignites violently as soon as it hits the oxygen of air.
Armed with the finest general purpose submunition in the world, the CBU-87/B functions by delivering its load more accurately than any other dispenser in the inventory. Also, the CBU-87/B can be dropped from as low as 400 feet/121.9 meters, and as high as 40,000 feet/12,192 meters. This means that in addition to making tactical aircraft more survivable in high-threat environments, the CBU-97/B can now be used from bombers like the B-52, B-1B, and B-2. Some 10,035 CBU-87/Bs were dropped during Desert Storm, and in time, it will become the primary CBU in the USAF inventory.
The second TMD derivative to be fielded is the CBU-89/B, which is designed to replace the earlier CBU- 78/B in the mine deployment role. Composed of an SUU-64/B TMD, it is loaded with seventy-two BLU-91/B anti- personnel mines, and twenty-four BLU-92/B Gator anti-tank mines. The BLU-92/B Gator is an anti-vehicle mine with a highly sophisticated fuzing system, including the deployment of wire 'feelers' to detonate the warhead. Once activated, the Gator fires a self-forging projectile or 'spoon' into the belly of the target vehicle at a speed of over Mach 3, destroying the target. There were 1,105 CBU-89/Bs used during Desert Storm with great success.
The newest TMD variant to make it into the field is the CBU-97B, which is equipped with the new BLU- 108/B anti-armor submunition. First fielded in 1992, each CBU-97/B is composed of an SUU-64/B TMD, loaded with ten of the BLU-108/Bs. Known as a 'sensor fuzed weapon,' the BLU-108/B looks like an oversized coffee can when it is ejected from the TMD. Once clear of the TMD, each BLU-108/B ejects four small devices called 'skeets.' The skeets, which look a lot like jumbo-sized hockey pucks, are flung spinning from the BLU-108/B in four different directions to maximize their coverage. Once armed, each skeet scans the ground with a sensitive infrared seeker, tuned to look for the heat signature of an internal combustion engine. Should the skeet sensor detect the heat of a vehicle below, it fires a self-forging projectile or 'spoon' down into the engine compartment of the vehicle at a speed of roughly Mach 5! The projectile has so much energy, that it just punches through the vehicle, even if it is a tank, usually destroying whatever it hits.
With the coming of the SUU-64/65 TMD, most of the tactical limitations of previous types of CBUs have been eliminated. There is also a program, called the Wind Corrected Munition (WCM), which is designed to add a small, cheap, strapdown INS guidance system to the back of the TMD, along with guidance fins. The idea is that the inertial system would detect any course deviations resulting from crosswinds and correct for the wind drift. Given the hyper-accurate weapons delivery systems on various U.S. aircraft, particularly bombers like the B-1B and B-2, this would make truly accurate high-altitude CBU drops a reality.
