<p>While structures and other 'hard' targets are best dealt with by classical 'bombs,' area targets such as troop and armor concentrations, truck parks and artillery batteries are more susceptible to cluster munitions. Many early cluster munitions were dispersed from containers retained by the aircraft. This had two major drawbacks. First, it increased aircraft drag, thus decreasing range. Also, the dispersion pattern of the bomblets was very dependent on speed and altitude, forcing the aircraft to maintain a predictable flight path during delivery—never a wise move in combat! For these reasons, only dispensers released from the delivery aircraft are used today. Once these are released from the aircraft, the dispenser shell breaks apart, scattering the bomblets. Most cluster bomb dispensers have 14-in (35-cm) suspension lug spacing.
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<p>Modern cluster bombs, like general-purpose bombs, are employed by all tactical fighters as well as B-52s. Unexploded cluster bomblets in general, especially the older ones used with the USAF's SUU-30 and the Navy's Mk 20, were the most difficult weapons to dispose of after the end of the 1991 Gulf War.
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<hi style=hdr1>M129 Cluster Bomb</hi>
<p>The <hi format=bold>M129</hi> cluster is used to deliver propaganda leaflets. Shaped generally like the M117 750-pound class bomb, but constructed of fiberglass reinforced plastic, it weighs 92 pounds empty and about 200 loaded. It splits longitudinally to dispense about 30,000 5-in x 7-in leaflets. Painted overall olive drab, the M129 is currently qualified for use with the B-52 and F-16. During Desert Storm, two M129s were mixed into loads of M117 bombs dropped by B-52Gs. Sixteen were also dropped over Baghdad by a four-ship of F-16s on 26 February 1991.
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<hi style=hdr1>Mk 20 Rockeye II Cluster Bombs</hi>
<p>The <hi format=bold>Mk 7</hi> dispenser was the basis of most Navy cluster bombs from Vietnam well into the 1990s. The $3,400 <hi format=bold>Mk 20 </hi>'<hi format=bold>Rockeye II</hi>' anti-armor weapon was the most widely used version of the Mk 7. Developed by the Naval Weapons Center and adopted by the Air Force, this subsonic-delivery dispenser first entered service in 1968 and was used extensively during both Vietnam and Desert Storm. This was the ONLY cluster bomb to bear the title 'Rockeye II'. (The USAF's CBU-87 was often mistakenly identified as Rockeye II during Desert Storm, but is a completely different weapon. The <hi format=bold>Mk 12 </hi>'<hi format=bold>Rockeye I</hi>' was a pre-Vietnam developmental 750-pound dispenser containing 96 anti-armor bomblets that wasn't produced.) Rockeye has been widely exported and used on all USAF combat aircraft except the B-1, B-2 and F-117. Although many later Navy versions of Rockeye were thermal protected for increased safety in case of a fire during carrier-based operations, non of the versions used by the Air Force have this feature.
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<p>The Rockeye II's <hi format=bold>Mk 118</hi> shaped-charge bomblets look very much like throwing darts and are designed to be effective against both tanks and ships. The detonation of each bomblet focuses a slug of copper against the point of impact with a force of 250,000 psi. All versions of Rockeye use the Mk 118 Mod 0 bomblet except for the Mk 20 Mod 4, which uses the Mod 1. The only difference between the two bomblets is that the <hi format=bold>Mk 118 Mod 0</hi> requires 1.2 seconds to arm after being dispensed, while the <hi format=bold>Mk 118 Mod 1</hi> only takes 0.5 seconds, allowing it to be used from the lower altitudes expected to be encountered in combat against the now defunct Warsaw Pact.
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<p>The <hi format=bold>Mk 20 Mod 0</hi> and <hi format=bold>Mk 20 Mod 1</hi> were probably preliminary designs, but never entered production. The <hi format=bold>Mk 20 Mod 2</hi> was used by both the Navy and Air Force and was the only Rockeye II lacking a fuze timer setting observation window for its Mk 339 Mod 0 fuze. It was also unique in having only a single fuze arming wire, which meant only the 4.0-second timer would function unless the fuze was manually reset to 1.2 seconds on the ground. Finally, it was also the only version to use a hat box-shaped fuze cover on the ground. Distinctive markings were a single three-inch wide, FSN 23538 or 33538 yellow band, centered 10±2 inches aft of the nose fairing joint. Early production USAF Mk 20 Mod 2 bombs were overall FSN 24084 olive drab, while all subsequent Rockeye IIs were FSN 27875 white, with all having a 0.5-inch FSN 23638 or 33538 yellow semi-band over the top half of the weapon to mark the center of balance.
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<p>The <hi format=bold>Mk 20 Mod 3</hi> (Mk 7 Mod 3) was also used by both services. It incorporated a fuze timer setting observation window, two access holes on the lower nose fairing, dual arming wires (enabling in-flight selection of either fuze setting), a streamlined fuze cover, and could use either the Mk 339 Mod 0 or Mod 1 fuzes. The single 'live' band was shifted to 14.5 inches aft of the nose fairing joint.
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<p>The <hi format=bold>Mk 20 Mod 4</hi> (Mk 7 Mod 4) was the primary (and last) version used by the USAF and had several unique features. Aside from using the already mentioned Mk 118 Mod 1 bomblet, the Mod 4 had two sets of 14-in suspension lug wells, a longer fin release wire and conduit, with additional cutouts in the conduit. It was also used by the USAF as the basis of the canceled GBU-1 LGB. Mod 4s were fitted with either the Mk 339 Mod 0 or Mod 1 fuzes. The 'live' band on these weapons was centered 11 inches aft of the nose fairing joint.
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<hi style=hdr1>Mk 7, SUU-58, SUU-75, and SUU-76 Cluster Bomb Summary</hi>
<row><c>Mk 20 Mod 2<c>Mk 7 Mod 2<c>247 Mk 118 Mod 0<c><c>490 lb.
<row><c>Mk 20 Mod 3<c>Mk 7 Mod 3<c><c>inflight fuzing option<c>
<row><c>Mk 20 Mod 4<c>Mk 7 Mod 4<c>247 Mk 118 Mod 1<c>primary USAF version<c>496 lb.
</table>
<hi style=hdr1>SUU-30 Cluster Bombs</hi>
<p>Developed during the Vietnam War, the SUU-30 family has been qualified for use by all present USAF combat aircraft up to the newer B-1, B-2 and F-117, and widely exported. Nine different versions of the subsonic dispenser were developed, but only five were actually produced. The original <hi format=bold>SUU-30/B</hi> was a redesign of the Navy's <hi format=bold>Mk 5</hi> '<hi format=bold>Sadeye</hi>' dispenser that reduced the size of latter's fins enough to permit carriage on MERs and TERs. The <hi format=bold>SUU-30/B(Mod)</hi> and <hi format=bold>SUU-30A/B</hi> featured a modified fin assembly, with fintip plates aligned with the air flow. The <hi format=bold>SUU-30C/B</hi> was externally identical to the SUU-30A/B, but featured some internal structural modifications. All of these SUU-30s were FSN 34087 olive drab with an 8-in (20-cm) diameter, 3-in (7.6-cm) wide FSN 33538 yellow band around the nose.
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<p>The <hi format=bold>SUU-30B/B</hi> was a complete redesign which resulted in a blunter nose to the dispenser. The <hi format=bold>SUU-30D/B</hi> through <hi format=bold>SUU-30G/B</hi> were used to test various fin configurations, but were not produced. The final <hi format=bold>SUU-30H/B</hi> configuration had drag plates attached to the trailing edges of the fins to stabilize the weapon during its separation from the aircraft. This was the final SUU-30 produced, and the only one used after the Vietnam War. These SUU-30s are FSN 34087 olive drab with a 0.5-in (1.3-cm) wide FSN 33538 yellow band around the front of the cylindrical portion of the dispenser.
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<p>Operational SUU-30H/B cluster bombs are filled with spherical bomblets with sharp-edged ridges called 'flutes' on their exteriors. These cause the bomblets to spin-arm and self-disperse. The <hi format=bold>BLU-61A/B</hi> is a grapefruit-sized fragmentation bomblet that weighs about 3 lb and detonates on impact. The <hi format=bold>BLU-63/B</hi> bomblet is similar in function, but is only orange-sized, weighing about 1 lb, with the <hi format=bold>BLU-63A/B</hi> having an additional incendiary capability. The <hi format=bold>BLU-86/B</hi> is functionally identical to BLU-63/B except that it features a random time delay fuze.
<p>The Honeywell tactical munitions dispenser (<hi format=bold>TMD</hi>) was developed by the USAF in the 1980s to replace the Vietnam-era SUU-30 and Mk 7 dispensers. Managed by Odgen ALC, both the CEM and Gator TMD-based munitions were widely used in the 1991 Gulf War. All TMD dispensers are capable of carriage and release speeds of 700 kt IAS/Mach 1.4. They used the FZU-39 airburst fuze, which can be set to function at any of 12 altitudes between 300 and 3,000 ft (91 and 914 m) AGL. There are two basic versions of the TMD: the non-spinning SUU-64 and -66 and the spinning SUU-65. The $6,000 <hi format=bold>SUU-65 </hi>dispenser's fins unfold after release and cant to spin it to a preselected rate before opening, permitting ideal bomblet dispersion, even when released from very low altitudes. It can be distinguished from the very similar $4,600 <hi format=bold>SUU-64</hi> and <hi format=bold>SUU-66</hi> by the large crossbar at the back of its fin assembly.
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<display id=\weapons\photos\cb870001.bmp>
<p>The $14,000 Aerojet General <hi format=bold>CBU-87/B</hi> combined effects munition (<hi format=bold>CEM</hi>) uses the SUU-65 TMD to dispense over 200 CEM bomblets. The CBU-87/B was rapidly qualified on British Jaguars during the 1991 Gulf War when their low-altitude BL.755 cluster bombs proved unusable for the high-altitude delivery tactics adopted. The <hi format=bold>CBU-87A/B</hi> features a factory-installed FZU-39/B fuze. The otherwise identical <hi format=bold>CBU-87B/B</hi> uses the BLU-97A/B bomblet. The change to the FZU-39(D-4)/B fuze results in the <hi format=bold>CBU-87C/B</hi>. Honeywell was the second source contractor for CEM.
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<p>Similar in size and shape to a beer can, the 3.4-lb <hi format=bold>BLU-97/B</hi> bomblet is stabilized by a tail-mounted ballute. It features an anti-material shape charge in the nose along with a body that explodes into anti-personnel and incendiary fragments. Because these bomblets suffered airburst malfunctions after being dispensed, a change from piezo-electric to mechanical firing mechanisms was made, resulting in the <hi format=bold>BLU-97A/B</hi>.
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<p>The $40,000 Aerojet General/Honeywell <hi format=bold>CBU-89/B </hi>'<hi format=bold>Gator</hi>' uses the SUU-65 to deliver a combination of BLU-91 and BLU-92 mines. The <hi format=bold>CBU-89A/B</hi> features a factory-installed FZU-39/B fuze.
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<p>Honeywell's $265 <hi format=bold>BLU-91/B</hi> anti-personnel mine weighs 3.75 lb and deploys trip wires that detonate it when they are disturbed. Aerojet General's $613 <hi format=bold>BLU-92/B</hi> anti-tank mine weighs 4.31 lb and senses magnetic disturbances to determine when and where to fire its self-forging warhead at passing tanks. Both mines eventually self-destruct. (US Army designations for these mines are <hi format=bold>XM74</hi> and <hi format=bold>XM75</hi>, respectively.)
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<p>The Textron Defense Systems <hi format=bold>CBU-97</hi> sensor fuzed weapon (<hi format=bold>SFW</hi>) entered low-rate initial production (<hi format=bold>LRIP</hi>) in mid-1992. In tests against formations of armored vehicles, kill rates of over 2.5 tanks per CBU-97 dropped have been demonstrated. SFW's ability to kill multiple targets per pass became crucial as the size of the fighter force shrank, leading to its identification as one of the four 'pillars' for halting a regional attack (along with the C-17, E-8 J-STARS, and military equipment prepositioning). Consideration has also been given to using the BLU-108 with the AGM-86C and BGM-109 cruise missiles. Initial plans had been to build 20,000 SFWs, but budget cuts dropped this to only 5,000. Originally expected to cost $186,000 per weapon, manufacturing improvements subsequently reduced this by as much as $72,000. Built at the Kansas Army Ammunition Plant in Parsons, Kansas, LRIP weapons were delivered in 1993, followed by the production versions in April 1994.
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<p>Each CBU-97 spreads 10 <hi format=bold>BLU-108/B</hi> orientation and stabilization devices (<hi format=bold>OSD</hi>) over an area of 1,200 x 600 ft (365 x 183 m). Each OSD descends by parachute until properly aligned above the target area as it extends four 'skeet' explosively forged penetrator anti-armor sub-munitions from its body. As they deploy from the OSD, each skeet actively searches for targets with a passive, two-color infra-red sensor. When targets are detected, the parachute is released and a rocket fires to spin the OSD, stopping its descent and flinging the skeets along a horizontal trajectory. When positioned over a target the skeet explodes, transforming a flat 5.25-in (13.3-cm) diameter copper plate into a 6,000 ft (1,828 m) per second kinetic energy projectile directed at the target. The direction of this 1-lb slug is controlled within the sensor's 0.5 degree field of view so as to penetrate reactive and/or main battle tank armor, destroying the interior of the tank and killing its crew.
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<p>By the spring of 1994, with about 100,000 TMDs of all versions in existence, plans were announced to buy about 40,000 inertial guidance kits to provide 'PGM-like' accuracy from delivery altitudes as high as 40,000 ft (12,192 m). The wind corrected munitions dispenser (<hi format=bold>WCMD</hi>) will correct ballistic and wind errors with a combination of a processor to accept target data, pop-out, moving tail fins and actuators, and nose ballast to maintain weapon CG limits. Each kit is expected to cost $20,000-$30,000. This modification will primarily be applied to the CBU-97 SFW, with funding beginning in FY96. While initial plans focus on use of the 8-nm (14.7-km) range WCMD with the B-1B and B-2A, any aircraft fitted with a 1760 databus will be capable of employing it, including the F-15E and Block 50/52 F-16C/D. Initial plans called for WCMD to become operational with the bombers at about the turn of the century. By mid-1994, consideration was also being given to equipping the WCMD with 'Kit 2' carbon fiber warheads, like those used by BGM-109s during the 1991 Gulf War.
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<p>The TMD-based <hi format=bold>CBU-98</hi> direct airfield attack combined munition (<hi format=bold>DAACM</hi>) contained a mix of BLU-106 boosted kinetic energy penetrators (<hi format=bold>BKEP</hi>) and HB.876 area denial mines. The 5.5-lb Hunting <hi format=bold>HB.876</hi> is used as part of the British JP.233 anti-runway munition used successfully by British and Saudi Tornado GR.Mk 1s during the 1991 Gulf War. The $1,200 mine has a ring of curled springs legs around its base which help rotate it to an upright position after landing. It then sits, waiting to greet a disturbance with a detonation. After a preset interval, the HB.876 self-destructs. The 45-lb Textron Defense Systems <hi format=bold>BLU-106</hi> was similar in concept to many other runway penetrator munitions in that it was parachute retarded long enough to point it earthward before its rocket motor fired, driving beneath the runway where it exploded, heaving the runway upward. At least, that is how the $5,100-class submunition was supposed to work. Textron was never able to make the BLU-106 work reliably and, with the end of the Cold War, the need for runway-cratering munitions that required manned overflight of a highly defended airfield disappeared, as did the $119,000 CBU-98.
<row><c><c><c>24 HB.876<c>JP.233 area denial mine<c>
</table>
<hi style=hdr1>Cluster Bomb Fuzing</hi>
<p>Once again, fuzing is of critical importance. Two types can be used, time delay and proximity. A time delay fuze is set on the ground, and requires bomb release at a specific altitude and airspeed to produce optimum bomblet dispersion. Proximity fuzing uses a radar in the fuze to sense height above the ground, providing much greater latitude in delivery parameters. All CBU fuzes are nose-mounted and serve to split open the dispenser, releasing its payload.
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<hi style=hdr1>USAF Cluster Bomb Fuzes</hi>
<table>
<tblhdr><c>Fuze<c>Type<c>Remarks
<row><c>FMU-56<c>proximity<c>SUU-30H
<row><c>FMU-107<c>timer<c>M129 (also called AN-M147A1)
<row><c>FMU-110<c>proximity<c>SUU-30H
<row><c>FZU-39<c>proximity<c>SUU-30H, -64, -65, and -66
