FMU-157/B Hard Target Smart Fuze [HTSF]

The Hard Target Smart Fuze enables precision bombs with penetrating warheads to detonate at a desired point inside buried or reinforced concrete targets such as underground bunkers and command centers. Detonation occurs after a sensor tells the fuze that the weapon has passed through a pre-programmed number of hard layers or voids in the target.

One of the newest weapons in the Air Force's arsenal of hard target penetrating bombs is the AFRL Munitions Directorate-developed Advanced Unitary Penetrator (AUP), equipped with the Hard Target Smart Fuze. The bomb and its smart fuze were a big hit during Operation Allied Force. The AUP mimics, in appearance and dimensions, the already combat-proven BLU-109 (Bomb Live Unit) warhead, a 2,000-pound hard target penetrating warhead used by the Air Force and Navy. The AUP is designated the BLU-116 and boasts twice the penetration capability of the BLU-109. The HTSF, designated the FMU-157/B, is an active decision-making accelerometer-based fuzing system capable of counting layers and voids (floors), as well as calculating distance traveled. When the weapon reaches the pre-determined floor it tells the bomb to explode. The HTSF is compatible with a variety of penetrating warheads.

The Hard-Target Smart Fuze [HTSF], developed at the Wright lab, is a microcontroller-based, in line fuze designed to be physically and electrically compatible with GBU-10, GBU-15, GBU-24, GBU-27, GBU-28, AGM-130, and general purpose MK-80 series weapons. The HTSF was designed for current and future penetrator weapons to define the fuze function point as either a desired distance within a desired void or a depth of burial beneath a hard layer. It operates in one of three modes: hard-layer detection, void detection, and path-length integration. It also has an adjustable backup time delay that is set in 1-msec increments with a maximum delay of 250 msec. The HTSF uses a void sensing technique to count layers within a structure to initiate fuze function, a depth of burial mode that causes the fuze to function a preset distance after it senses a hard layer, and an integral time delay backup. Initial tests of the fuse in 1995 and 1996 at New Mexico's White Sands Missile Range were failures, though modifications are under development.

The Advanced Unitary Penetrator used in Operation Allied Force used the hard target smart fuse, which gives it twice the penetration capability of a normal hard-target warhead. It's capable of counting layers and voids, or floors, calculating distance traveled and exploding when it reaches a predetermined floor.

In August 1998 Alliant Techsystems and an international team led by its Defense Systems Group was awarded a three-year, $16 million contract from the US Air Force Precision Strike System Program Office, Eglin Air Force Base, FL, for engineering and manufacturing development of the Hard Target Smart Fuze (HTSF). If exercised, production options would bring the total value of the contract to $54 million through 2006. Alliant is teamed with Thomson-Thorn Missile Electronics, Ltd., Basingstoke, England, on the HTSF program. Alliant will serve as the prime contractor and systems integrator and Thomson Thorn will develop certain electronic components for the fuze.

Motorola was the prime contractor until it abruptly abandoned the fuze business. The 1997 acquisition of Motorola's sensor and fuze business by Alliant Techsystems was a key factor in capturing the HTSF program. Motorola originally developed the HTSF technology and successfully demonstrated it with a variety of weapon systems and aircraft platforms. The acquisition of this technology was instrumental to Alliant Techsystems' participation in the competition as it has significantly strengthened the company's capabilities in military sensors and fuzes.

The training kit consists of a FMU-159(D-1)/B inert programmable bomb fuze, a FZU-60(D-1)/B dummy initiator, lock ring, adapter cables, lanyards, and associated hardware. The training kits are necessary to support FMU-159/B HTSF munitions build and load crew training requirements. The training kit consists of a FMU-159(D-2)/B inert bomb fuze, a FZU-60(D-2)/B dummy initiator, lock ring, adapter cables, lanyards, and associated hardware. The training kits are necessary to support FMU-159/B HTSF munitions build, load crew, and Explosive Ordinance Disposal (EOD) training requirements. Delivery of the initial procurement of training kits is required by December 2001 to support Air Force initial operational capability in February 2002. Additional option deliveries shall be completed within 12 months of option exercise. The training kits must meet the following requirements: a) capable of duplicating every action of the operational fuze system during programming with the ADU-833/E HTSF Ground Setter Unit (GSU). b) capable of duplicating every action of the operational fuze system during weapon build up and loading; c) identical components and packaging (fuze, FZU, lock ring, lanyards, adaptor cables, associated hardware, and M548 container dunnage); d) identical external component characteristics (dimensions, materials, electrical connections, appearance); e) weight and center of gravity within 10 percent of operational fuze system; f) meet the same storage and operating environmental qualification requirements for ground operations and captive carry flight;