[2.0] Cluster Munitions & Other Bombs

v4.0.0 / chapter 2 of 10 / 01 may 14 / greg goebel / public domain

* This chapter follows up on the previous chapter by discussing cluster munitions, napalm and fuel-air explosive (FAE) bombs, and more specialized dumb munitions.

Rockeye cluster bomb



* Exactly when cluster munitions were invented is unclear; they were clearly in service by the beginning of World War II. One of the most significant Luftwaffe tactical munitions of the conflict was the 2 kilogram (4.4 pound) "SD-2" antipersonnel fragmentation bomb, known as the "butterfly bomb". This weapon looked like a small can with a curved cover over one side. On release, the cover popped open, deploying two linked circular fins from the ends of the bomb and connected to the bomb by a short cable. The fins spun to slow the fall of the bomb. Interestingly, although it doesn't seem the US employed cluster bombs as such during World War II, preferring fragmentation bomb bundles, the US used a copy of the SD-2 butterfly bomb during the Korean war, under the designation "Mark 83".

butterfly bomb

Another important German tactical weapon was the 4 kilogram (8.8 pound) "SD-4" hollow-charge antitank munition. The SD-2 and SD-4 could be carried on racks or in cluster bomb canisters, such as the "AB-250" 250 kilogram canister, which split into halves on release to scatter its "splitterbombe (submunition)" payload. The AB-250 could carry 144 SD-2s or 30 SD-4s. It could also accommodate 224 tiny "SD-1" munitions, 17 "SD-10" bombs, 184 "B-1" incendiaries, or 116 "B-2" steel-nosed incendiaries. A bigger "AB-500" 500 kilogram canister was also used.

* The US military made extensive use of submunition dispensers during the Vietnam war, focusing on three types: the "SUU-7/A", the "SUU-13/A", and the "SUU-14/A", where the acronym SUU stands for "Suspension Utility Unit" or "Suspension Underwing Unit":

These dispensers could carry a bewildering range of submunitions, usually given a "BLU" designation, such as cans with various forms of pop-out fins, for example the BLU-3/B "Pineapple", so called because it resembled a pineapple fruit; minelets in the form of large wingnuts, such as the BLU-43/B and larger BLU-44/B Dragontooth; or in the form of little cloth packets, called "Gravel", that contained an explosive that became very touchy after being dispersed and drying out. There were also gas and smoke bomblets.

A-1 SPAD with SUU-14 dispensers, SUU-7 in front

A submunition dispenser with a given load of submunitions was given a "CBU" designation, for "Cluster Bomb Unit"; for example, a "CBU-1/A" was an SUU-7 dispenser with 509 BLU-4B anti-material submunitions. Cluster submunition dispensers were often used in Vietnam by search and rescue support aircraft, such the Douglas A-1 Skyraider. Riot gas loads were useful for interfering with the work of antiaircraft gunners, and a Skyraider could lay down a carpet of minelets behind downed aircrew on the run to block pursuers.

In the postwar period, the USAF obtained a clamshell canister, the "SUU-30/B", which was in widespread use up to its retirement from service in the 1990s. It had small pop-out tabs on its tailfins, apparently to set it to spinning before submunition release. The canister was popped open by a time-delay fuze, activated by a lanyard on release from the carrier aircraft, or by a proximity fuze activated at a specified altitude over the ground. Canisters of such general form are sometimes referred to as "sprinklers" or "tossed salad", while the cloud of submunitions are sometimes known as "black rain".

SUU-30/A canister

The most stereotypical submunitions carried by the SUU-30/A were various "grenades" in the form of spheres marked with spiral flanges that help set them spinning for arming and dispersal. Representative SUU-30/B configurations include the "CBU-24/B", with 670 BLU-26/B fragmentation submunitions, and the "CBU-54/B", with 670 BLU-68/B incendiary submunitions.



* Modern American cluster bombs, generally known as "cluster bomb units (CBUs)", are organized around two general types of canisters:

The Rockeye and the TMD canisters feature pop-out tailfins. The tailfins of the Rockeye and SUU-65/B TMD are canted a bit to impart a spin to the canister before it pops open to ensure scattering of the submunitions. The tailfins of the SUU-64/B and SUU-66/B canisters are straight, meaning these canisters don't spin. Both also have a thermal battery, which has a long shelf life and can be activated before a mission to power submunition electronics; the SUU-65/B does not have a thermal battery because its submunition loads don't have any electronics. The SUU-64/B is used to dispense mines and also has a switch to program mine arming conditions.

There are a few standard combat configurations for each type of canister, with the munition delivered in prepackaged form as an "all-up round". Some sources hint that the SUU-30/B canister can be field-configured to carry leaflets and other payloads.

MK-118 Rockeye bomblet

The basic Rockeye cluster bomb was first fielded in 1968 for use in Vietnam, and is still an important weapon. It was used extensively in the Gulf War. Details of Rockeye configurations are a bit tricky to unravel. The current Rockeye II canister, preferred by the US Navy and Marines, apparently has alternate designations of "SUU-75/B" and "SUU-76/B", the different designations no doubt indicating some minor differences in detail. There appears to be three primary configurations:

The TMD canister appears to be the "standard" for the USAF at this time, and CBUs based on it include:

There is a "CBU-97/B", which carries the smart BLU-108 Sensor Fused Weapon (SFW)" submunition, and a "CBU-94/B" with "soft kill" submunitions to attack electrical power stations. There are also a number of TMD CBU configurations that include the "Wind Corrected Munitions Dispenser (WCMD)" guidance kit. These configurations fall somewhat outside the definition of typical cluster munitions and are discussed later.



* European nations, including France, the UK, and Germany, have built and used their own types of cluster munitions. The French contribution to cluster bomb technology is the "Belouga", which is optimized for low-level high-speed strike. Its canister is 3.3 meters (10 feet) long and is 36.6 centimeters (14.5 inches) in diameter.

The Belouga is loaded with 151 submunitions. It can dispense three different types: a fragmentation bomb for use against soft targets, an armor-piercing bomb for use against tanks, and a mine used for "area denial" operations. Each submunitions is 66 millimeters (3 inches) in diameter, and weighs 1.3 kilograms (2.86 pounds).

The Belouga is parachute-retarded after release. It is not a clamshell canister, instead ejecting the submunitions from launching ports covering the weapon's body. The submunitions deploy small parachutes after ejection. The pilot may select either a concentrated or dispersed submunition scatter pattern before release of the weapon. The Belouga was a follow-on to the "Giboulee", a dispenser that had 12 or 24 tubes that could store five bomblets each.

Western cluster bombs

* The British Hunting Engineering / Royal Ordnance Factory "BL-755" cluster bomb is 2.4 meters (7 feet 9 inches) long, 42 centimeters (16.5 inches) in diameter, and carries 147 fragmentation bomblets. Like the Belouga, it is optimized for low-level, high-speed strike. The initial BL-755 was introduced in 1972, and was followed by the current "Improved BL-755" in 1987.

The BL-755 is also not a clamshell canister. Its two side panels pop off, with the bomblets ejected by expanding gas bladders. The bomblets are 15 centimeters long (5.9 inches), about 5 centimeters (2 inches) in diameter, and combine an antiarmor hollow charge with a case containing a segmented metal coil for antipersonnel effect.

On deployment, the submunitions extend a small standoff probe detonator and pop out a retarding parachute. The initial version of the BL-755 used submunitions with a popout metal "crown" for stabilization. One BL-755 was dropped on Argentine troops in the Falklands, and quickly persuaded the survivors to put up the white flag. The BL-755 series has been popular in international sales, since it is both effective and relatively cheap. Hunting has developed a proximity fuze for the BL-755 to allow it to be released at higher altitudes.

Neither the Belouga nor the BL-755 were used in large numbers in the Gulf War. This was not due to any inherent defect in their design, but because they were designed for low-level strike. US cluster bombs were better optimized for high-altitude release and were a better fit for mission profiles.

* However, another Hunting Engineering weapon, the "JP.233" bomblet dispenser, was used in the Gulf War in its intended role, airfield attack. JP.233s were extensively used by RAF Tornado strike aircraft early in the air war to disrupt the operation of Iraqi airfields. The strikes were at low level and were extremely hazardous to the Tornado crews.

JP.233 dispenser

Two 6.5 meter (21 foot 6 inch) long JP.233s can be fixed to the bottom of a Tornado. Each of the two dispensers consists of two sections, with the rear section carrying 30 "SG-357" runway cratering submunitions and the front section carrying 215 "HB-876" antipersonnel mines. Both submunitions are parachute-retarded. The SG-357 weighs 26 kilograms (75 pounds) and is a "two-stage" munition, something of a British specialty, with a hollow charge in the front to blast a hole in a runway, and a cratering charge that falls into the hole and then explodes.

The HB-876 munitions can detonate at random intervals, and can also punch an explosively-formed slug through a bulldozer or other vehicle that disturbs them. The HB-876 is a 2.5 kilogram (5.5 pound) munition that looks like a beer can, with a dimpled surface to promote fragmentation. The base of the HB-876 is surrounded by little curled spring-metal legs that are released to curl downward and pop the mine into a vertical position.

Two dispersal rates can be selected for the JP.233, one giving a short, broad swath and the other a long, narrow swath. There are no alternative submunition configurations for the JP.233, and so it is a specialized weapon, useful only for attacking airfields or other soft, distributed targets such as railyards or supply depots.

The JP.233 was originally conceived in the late 1970s as a cooperative program with the US Air Force, which wanted to use the weapon with its FB-111 strike aircraft. Rising costs forced the USAF to pull out of the program, but the British completed development on their own. Hunting developed a version of the BL-755 CBU that carries 49 HB.876 minelets as used on the JP.233. This weapon was named the "Hunting Area Denial System (HADES)". It is unclear if it entered operational service.

* Luftwaffe Tornadoes use a conceptually similar, but different in detail, submunition dispenser, the MBB-Diehl "MW-1" (where "MW" stands for "MehrzweckWaffe / Multipurpose Weapon"). This weapon looks something like a big bathtub strapped onto the belly of the Tornado, with submunition launch tubes facing outward on each side of the tub.

The MW-1 actually consists of four sections joined together, each with 28 launch tubes on each side, for a total of 112 tubes on each side. The submunitions are blasted out of the tubes by pyrotechnic charges, with the dispersal pattern determined by the size and firing order of the charges.

MW-1 dispenser on Tornado

The MW-1 can carry combinations of different types of submunitions:

Payload configurations can be defined to fit specific missions. For example, 4,500 KB-44s can be carried by a single MW-1 dispenser to saturate an area covering about 180 x 500 meters (590 x 1,640 feet). The entire payload can be ejected in about 0.6 seconds. Head-on photographs of a Tornado spewing submunitions its MW-1 are impressive and fearsome.

Initial deliveries of the MW-1 to the Luftwaffe began in 1984. The MW-1 was originally tested on Luftwaffe F-104G Starfighters and then F-4 Phantoms, but as with the JP.233, the Tornado is the only aircraft that carries it operationally. The USAF considered the weapon for its A-10 tankbuster, but didn't follow through. It appears the MW-1 has never been used in combat, which is just as well.



* The French have developed a pair of cluster munitions, the Thomson-Brandt "BAP-100" runway cratering bomb and the similar "BAT-120" antiarmor bomb, weighing 100 kilograms (220 pounds) and 120 kilograms (265 pounds) respectively. These weapons are only loosely cluster munitions, being unitary bombs carried in a rack of nine, with one aircraft carrying multiple racks. Details are unclear, but the BAT-120 appears to be a parachute-retarded fragmentation weapon. If so, the fragments are likely pretty hefty, since the weapon is intended to attack armored vehicles.

The Soviets of course developed their own cluster munitions, though details tend to be unclear for the time being. The primary Soviet-Russian cluster-bomb canister is the "RBK-500", a 500 kilogram (1,100 pound) clamshell canister that can be loaded with various submunitions:

The Russian "KMGU-2" canister is a larger unit, but details are unclear as well.

The Israelis have developed cluster munitions. Rafael of Israel introduced the "TAL-1" cluster bomb in 1981 for the Israeli Air Force, with this weapon carrying 270 bomblets. It was followed by the "TAL-2" in 1983, which raised the bomblet count to 315 and introduced an improved dispersal system. The TAL-2 superficially resembles the BL-755 but has conventional bomb tailfins, and is a "clamshell" canister. They appear to be out of production, no longer being found in the Rafael product list.

Israel Military Industries (IMI) later developed the "Anti-Tank Anti-Personnel (ATAP)" series of cluster munitions, including the "ATAP-300", "ATAP-500", and "ATAP-1000" weapons, the suffix giving the weight in pounds, meaning 135, 225, and 450 kilograms respectively. IMI produces two types of submunitions:

Exactly what mix of submunitions are used in the IMI cluster munitions is unclear. IMI's website has a puzzling lack of detail on these weapons, whether out of laziness or a reluctance to advertise cluster weapons to the public is unclear.



* While napalm is an old and familiar weapon, it has fallen into disuse, in the American arsenal at least. The unfinned 340 kilogram (750 pound) / 380 liter (100 US gallon) "BLU-1/B" napalm bomb and its finned variant, the "BLU-27/B", were used extensively and with devastating effect in Vietnam. US forces also used the "M35" and "M36" "Funny Bombs", which scattered thermite over a target area and proved lethal to trucks and area targets.

However, the only napalm bomb still in the US inventory is the 340 kilogram (750 pound) "Mark 77", which was used in the Gulf War. Why the use of napalm has declined is hard to understand, since it was apparently an extremely effective battlefield weapon. Although napalm did get a lot of bad press in the Vietnam war, it would be odd to call it inhumane and still use cluster bombs.

The US Air Force and Navy have been collaborating on a special incendiary fill for "agent defeat" munitions, designed to be loaded into penetrating munitions to destroy chemical and biological weapon stockpiles. This fill is a "titanium boron lithium perchlorate intermetallic" that burns at a very high temperature, decomposing chemical agents and killing biological agents. The fill also generates lithium, chlorine, and acidic compounds that kill biological agents. The fill does not generate high pressures when ignited, reducing the likelihood that it will disperse chemical or biological agents from the target.

* The US military originally evaluated fuel-air explosives (FAEs) in Vietnam, using an odd-looking weapon named the "BLU-76/B Pave Pat 1". This 1.18 tonne (2,600 pound) weapon looked like a big can with a cone nose and stubby fins in back. It was loaded with liquid ethylene oxide and had an equivalent explosive yield of about 9 tonnes (10 US tons) of TNT. It was apparently not very satisfactory and was used only in small numbers.

The Navy also developed the "FAE-1" series of FAE bombs late in the Vietnam War, which would be fielded as the "CBU-55/B" and similar "CBU-72/B" FAEs. Both these munitions contain three 45 kilogram (100 pound) "BLU-73/B" submunitions containing ethylene oxide. The three submunitions disperse a cloud about 20 meters in diameter (66 feet) and two or three meters (7 to 10 feet) high that is then ignited. The result is a spectacular fireball that is highly effective against exposed targets.

FAEs were dropped in the Gulf War, both to clear minefields and for psychological effect. After the war, the remaining FAE munitions in the US inventory were disposed of, but the military had by no means abandoned the technology, and in fact was considering what else could be done with it.

During the Afghanistan campaign in 2001:2002, the US Air Force performed combat evaluations of the new "BLU-118/B" bomb, which was developed under the "Hard Target Defeat" program. The BLU-118/B is essentially a 900 kilogram (2,000 pound) BLU-109/B penetrating bomb, discussed earlier, but filled with a type of enhanced FAE instead of conventional high explosive. Of course, the BLU-118/B can be fitted with the same laser or electro-optic guidance systems as the BLU-109/B.

The BLU-118/B is described as a "thermobaric" munition and not an FAE, the term indicating that the bomb produces both thermal and blast pressure effects, and is intended for attacks on underground tunnel targets. The bomb's FAE load is scattered as an aerosol by a dispersal charge and then detonated. In contrast with traditional FAEs, which generate a "big ball of fire", the thermobaric aerosol detonates with blast effect much more like that of an normal explosive filling. The result is a crushing high-pressure shockwave that propagates through the tunnel system, followed by an asphyxiating wave of intense flame.

The Air Force has been experimenting with a "solid FAE (SFAE)" filling that apparently disperses a fine cloud of aluminum particles, while the Navy has been working on an "interhalogen oxidizer" filling, possibly based on fluorine. Initial tests of the BLU-118/B were conducted in mid-December 2001, and by late winter 2002 the weapon was in use in Afghanistan, performing attacks on tunnels occupied by Taliban and al-Qaeda forces.

* Along with a series of napalm bombs with the general designation of "ZAB", the Russians also have developed FAEs, and displayed a new 520 kilogram (1,150 pound) weapon in this category designated the "ODAB-500PM" at the Paris Air Show in 1995. The weapon looks something like a napalm tank with a ring tail, includes a parachute stored in the tail as a retarder, and is said to have an effective blast radius of 30 meters (100 feet) against exposed targets. There was some international outcry over the use of this weapon by Russian forces against Chechnyan rebels in 1999 and 2000.

* The US Air Force fielded an unconventional new cluster bomb unit designated the "CBU-94/B", mentioned earlier, during the NATO air campaign against Yugoslavia in the spring of 1999. The CBU-94/B used a TMD that contained 202 "BLU-114/B" submunitions, sometimes called "blackout bombs", which were filled with conductive wires that were dispersed to short out Serbian power stations.

According to US officials, the BLU-114/B submunitions are about the size of two beer cans stacked on top of each other. After the submunitions are scattered by the TMD, and then pop off a nose cap. 147 spools of conductive fibers are then shot out with a small explosive charge to unravel into a tangle that falls on power lines and other power-distribution equipment, shorting it out.

BLU-114/B blackout bomb

The US Navy used spools of such wire stuffed into Tomahawk cruise missiles to short out Iraqi power systems during the Gulf War in 1991. After the Gulf War, the USAF decided to develop a more formal weapon based on the concept.

The CBU-94/B will disable a power system for only a few hours, since the wires can be cleaned up easily enough, though if any are left lying around they can be blown back into the power station on the slightest breeze, shorting it out again. However, it is rumored that the US military has been working on a similar munition that is filled with fine conductive whiskers, which form a cloud and get into everything. They could be sucked into personal computers through cooling fans and would be very difficult to clean up.

After the 1999 attacks with the CBU-94/B, the Serbs working at the power plants collected samples of the threads, as well as remnants of the TMD and submunition cases, and passed them on to the Russians for analysis. The Russians report that the TMD cases were marked "CBU-102/B" instead of "CBU-94/B", and that the threads were actually made of glass fiber coated with aluminum, not carbon fiber as the US military stated. It appears that the CBU-102/B was a minor modification of the CBU-94/B. Reports also indicate that it took 500 people 15 hours to get a Serbian transformer yard back on line after being hit with the conductive fibers.

* The USAF also has been working on an "electromagnetic pulse (EMP)" or "high power microwave (HPM)" warhead that can, under optimum conditions, fry electronic equipment over an area the size of an athletic field. Details are unclear, but it appears this weapon was derived in the early 1990s from test devices developed by the US Los Alamos National Laboratories beginning in the late 1980s. The USAF refined the Los Alamos device into one that could fit into the nose of a cruise missile, with Boeing announcing tests of such a missile, designated CHAMP, in 2012.

One scheme for the USAF EMP / HPM weapon is described as consisting of a helical coil wrapped around a copper cylinder. A bank of capacitors supplies an initial current of a few hundred thousand amperes that creates a magnetic field in the gap between the coil and the cylinder. A conventional explosive charge explodes the coil assembly from the rear forward, compressing the magnetic field and generating a powerful electromagnetic pulse. The overall power of the pulse is not great. A simple antenna is used to focus it in a 30-degree cone to hit a target no more than a few hundred meters away. The weapon fires through a transparent window in the nose of the missile, with the window also used by targeting sensors.

Although it appears that extensive tests have been performed on EMP munitions, there's been no rush to field them. Some question their utility, seeing them as more pranksterish than lethal, and suggest they might be easily frustrated by simple countermeasures such as electromagnetic shielding. The military also likes to make sure that when they hit a target, there's as little ambiguity as possible that it is clearly destroyed. As a result, interest has shifted to "combined effects" EMP munitions -- conventional explosive bombs and warheads with an added EMP capability to boost their destructiveness. Despite defense cutbacks, work on EMP continues to move forward. It is possible they will remain under wraps until the first time the military uses them operationally.