International pressure is driving militaries to adopt alternatives to cluster bombs. The weapons are controversial because they leave unexploded ordnance (UXO) on a battlefield, where it can injure or kill civilians. Treaties may limit their use, and suppliers are looking at ways of adapting weapons to new requirements. These could include a shift toward unitary warheads, enhanced fuzes and fail-safe measures that eliminate UXOs.

The Oslo Treaty, probably the best-known initiative, seeks to prohibit the use and production of cluster bombs. The treaty does not concentrate on UXOs but specifies weight, banning weapons that distribute submunitions of less than 20 kg. (44 lb.). It was adopted by 107 countries in 2008, and will take effect when 30 ratify it. Seventeen have done so. Signatories include France, Germany, Italy, Spain and the U.K., but not the U.S., China or Russia.

The U.S. defense community, though, is anticipating a change in the weapon. A June 2008 memorandum from Defense Secretary Robert Gates affirmed that cluster munitions are "legitimate weapons with clear military utility," but set a target for a dud rate of less than 1%. Until 2018, use of weapons exceeding this rate must be approved by the combatant command. After this date, the dud rate becomes a requirement.

Robert Buckley, Textron's senior vice president of business development, asserts that the company's Sensor-Fuzed Weapon (SFW) is the only munition in the U.S. inventory capable of meeting the requirement. SFW releases multiple smart submunitions. Each submunition scans an area using a laser and infrared pattern-matching sensor. If it verifies a target, the submunition launches an explosively formed penetrator (EFP); if it does not verify a target, two electronic controls cause it to self-destruct.

Buckley says tests show that current versions of the SFW have a 99.6% reliability rate. Even if it fails to detonate, the unexploded weapon is inert.

"Removal procedure consists of throwing it in the back of a truck," he says. In contrast to conventional UXOs, it is virtually impossible to make an unexploded SFW round go off with a controlled explosion.

The SFW is designed for vehicular targets. For targets such as massed infantry, Textron offers the Clean Lightweight Area Weapon (CLAW). This is a 100-lb. bomb with a unitary warhead that detonates at a preset altitude. Its lethality is enhanced by the design of the warhead casing, which is scored to produce thousands of triangular or diamond-shaped fragments. Textron says it effectively covers an area 140 yd. across. CLAW, like SFW, has a redundant fuze and uses an insensitive munition that cannot be detonated by impact or burning.

Even a weapon with a contact fuze can be made safer. Instalaza of Spain has developed an approach it terms sDē, short for self-destruct and self-deactivation. Munitions with this technology are designed to detonate on impact. Any that do not detonate, self-destruct within 20 sec. If both mechanisms fail, the weapon automatically deactivates within 10 min. The deactivation process works by dissipating an electrical charge over time. Once the charge is gone, the fuze cannot operate.

"The percentage is absolute," an Instalaza spokesman maintains. The sDē is already used in the company's MAT-120 mortar bomb, which dispenses 21 dual-purpose antiarmor and antipersonnel submunitions.

The Pentagon, however, regards deactivated submunitions as UXOs, and the weapon would probably not be compliant with the Oslo Treaty.

The M26 rocket fired by the U.S. Army's Multiple-Launch Rocket System (MLRS) releases more than 600 dual-purpose grenades, potentially leaving a number of UXOs behind every time it fires. The hazard has led to the use of a guided rocket with a unitary warhead, but there is a still a requirement to attack area targets. The bomblets are small and have low unit costs, making it economically impractical to equip them with elaborate fuzing mechanisms.

The Army is exploring options through the MLRS Alternative Warhead program. These include technologies that might replace the current submunitions, such as kinetic rounds--darts, rods or flechettes. Another option is a single warhead with multiple EFPs, which are used in naval munitions. A single warhead would fire a large number of EFPs over a wide area, with greater armor-piercing effect than flechettes.

The Oslo Treaty and others may outlaw existing cluster munitions. But the situation is different from moves to ban land mines. For cluster munitions, technological fixes appear able to ensure that the same capability remains, even if the delivery system is altered.

Photo credit: USAF