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BLU-118/B Thermobaric Weapon

The BLU-118/B nomenclature was first reported on 21 December 2001, and this weapon is clearly unrelated to the BLU-118 500 lb. napalm canister used during the Vietnam war.

The BLU-118/B is a penetrating warhead filled with an advanced thermobaric explosive that, when detonated, generates higher sustained blast pressures in confined spaces such as tunnels and underground facilities. The BLU-118/B uses the same penetrator body as the standard BLU-109 weapon. The significant difference is the replacement of the high explosive fill with a new thermobaric explosive that provides increased lethality in confined spaces.

The BLU-118/B warhead uses a Fuze Munition Unit (FMU)-143J/B to initiate the explosive. The FMU-143 fuze has been modified with a new booster and a 120-millisecond delay. All weapon guidance systems and employment options currently used with the BLU-109 warhead are compatible with the new BLU-118/B warhead.

BLU-118/B payload candidates included PBXIH-135 [one of the Navy's new insensitive polymer bonded explosives], HAS-13, or SFAE [solid fuel air explosive] loaded into existing BLU-109 Weapon Bodies. Conventional high explosives (CHE) are characterized by a sensitivity to mechanical or thermal energy. Insensitive high explosives (IHE), on the other hand, require extraordinarily high stimuli before violent reaction occurs. Insensitive explosives reliably fulfil their performance, readiness and operational requirements on demand, but the violence of response to unplanned hazardous stimuli is restricted to an acceptable level. This means that when a munition is in a fire, hit by a fragment, bullet or high velocity projectile or subject to some other hazard the result will not be a detonation or a violent reaction of the explosive and propellant; no more than severe burning will ocur [such a deflagration is an exothermic reaction that occurs particle to particle at subsonic speed]. Some insensitive explosives are known to react in a different way to conventional explosives. For instance, detonation reactions are slower but more energy is released in a way that has the potential to produce a lot more damage.

The BLU-118/B bomb body can be attached to a variety of laser guidance system packages, including the GBU-15, GBU-24, GBU-27, and GBU-28 laser guided bombs, as well as the AGM-130 missiles.

BLU-118B weapon operational concepts include vertical delivery with the bomb detonated at or just outside portal, skip bomb with short fuse (1st or second contact), skip bomb with long fuse (penetrate door, max distance down adit), and vertical delivery to penetrate overburden and detonate inside the tunnel adit.

In October 2001 the Department of Defense accelerated a number of programs being pursued as Advanced Concept Technology Demonstrations (ACTD) that could be used in Operation Enduring Freedom in Afghanistan. The Defense Threat Reduction Agency (DTRA) organized a quick-response team on October 11, 2001, that included Navy, Air Force, Department of Energy and industry experts to identify, test, integrate and field a rapid solution that would enhance weapons options in countering hardened underground targets.

Explosive experts at the Naval Surface Weapons Center, Indian Head, MD, responded with a developmental explosive that provided enhanced internal blast effects. The Air Force Precision Strike Program Office at Eglin AFB, FL, led the team performing the weapon system integration, safety and flight clearances, and produced a modified fuzing system for the new warhead. The Indian Head facility conducted static testing of the fuze to demonstrate reliable initiation of the new explosive. Indian Head experts were called upon to provide the energetic solution, as PBXIH-135 was selected as the thermobaric bomb fill for the Air Force BLU-109 bombs. This new thermobaric bomb, designated as BLU-118/B, was developed within 67 days and subsequently supported Operation Enduring Freedom. Both static and flight tests were then conducted at full-scale tunnel facilities at the Nevada Test Site.

The BLU-118B was successfully tested at the Nevada Test Site on 14 December 2001. During that test, a Guided Bomb Unit (GBU)-24 laser-guided weapon using the BLU-118B warhead was dropped from an F-15E attack aircraft. The laser-guided bomb was "skipped" into a tunnel and exploded with a delayed fuze, which produced a significant growth in overpressure and temperature in the tunnel. When compared to the standard BLU-109 explosive, results showed the new thermobaric weapon generated a significant improvement in overpressure and pressure-impulse in the tunnel complex. The test culminated a two-month accelerated effort to rapidly transition a developmental explosive to improve lethality against underground facilities. DTRA weaponized and delivered (within 60 days) 10 thermobaric-filled air delivered munitions (BLU-118B) designed to enhance lethality in tunnel environments.

On 21 December 2001 Undersecretary of Defense for Acquisition Edward C. Aldridge officially announced that a small number of the weapons were being deployed to attack tunnels in Afghanistan. As of late January 2002, the Air Force had completed verification and validation of the technical data and operational flight clearances needed to deploy the BLU-118B warhead. Ten warheads were, as a result, immediately made available to the U.S. Air Force for deployment. These are compatible with the GBU-15, GBU-24, and Air-launched Surface-attack Guided Missile (AGM)-130 weapon systems for employment by U.S. Air Force F-15E Strike Eagle aircraft.

On or about Sunday 03 March 2002 a single 2,000-pound thermobaric bomb was used for the first time in combat against cave complexes in which al-Qaeda and Taliban fighters had taken refuge in the Gardez region of Afghanistan.

Pre-shot view of the BLU-118/B portal target at the Nevada Test Site
Post-shot view showing ejected rubble and debris following the successful and accurate BLU-118/B delivery and detonation
(photo taken under snowy conditions)

Class Bomb Live Unit (BLU)-118/B Thermobaric Warhead
  • GBU-15
  • GBU-24
  • AGM-130
  • Total Weight (lbs.) ~ 1975
    Length (in.) 98.5
    Diameter (in.) 14.5
    Explosive Weight (lbs.) ~ 560
    Fuze FMU-143
    Aircraft F-15E

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    Page last modified: 27-08-2013 19:18:27 ZULU