Naval Systems: Lower Profile for Torpedo Defense

By Ed Walsh

Program officials said that present efforts are aimed at providing a comprehensive detection, classification, and localization capability to support torpedo defense for individual ships against threats that will emerge in the next decade. The system, if it survives, eventually would replace a current-generation system—now entering production—that represents the culmination of an effort that began with a U.S.-U.K. memorandum of understanding in October 1988. Even in 1992, a Navy official called the SSTD program "absolutely essential—one of the Navy's highest priorities."

The Navy plan now is to retain, for most surface combatants, key components of the present system, which consists of a processing suite called the multisensor torpedo recognition and alert processor (MSTRAP—"Mousetrap"), and a launchable-expendable acoustic decoy (LEAD), built by L3 Hycor. The MSTRAP, which is controlled by a standard Navy TAC-3 or 4 workstation, has been integrated with the surface Navy's mainstay antisubmarine warfare suite, the SQQ-89. The MSTRAP receives acoustic data from the SQR-19 towed-array sonar, the SQ1-28 ASW helicopter datalink, and the SQS-53 hull-mounted sonar, all of which are integral 'Q-89 subsystems. For ships not equipped with the '89, it would operate as a stand-alone. Twelve early-production units have been built.

The LEAD, which consists of an acoustic decoy fitted with a propulsion system, is built in two variants, one propelled by a rocket, and the second by a mortar round. The U.S. Navy's rocket-powered variant is designated the Mark 12, and the mortar-launched variant is the Mark 15. The Royal Navy's rocket-powered and mortar-propelled variants are the Mark 14 and the Mark 13, respectively. For U.S. Navy ships, the decoy would be launched from the Mark 36 Super Rapid blooming Off-board Chaff canisters, already installed on most surface combatants.

For torpedo-defense operations, the MSTRAP would process acoustic data and perform the detect-classify-localize sequence to recommend a course of action, ranging from evasive maneuvers to launching the decoy to confuse torpedo guidance system. The MSTRAP/LEAD system, program officials have pointed out, emerges from older technology. The twin system actually represents the third phase of a torpedo-defense effort that began in the early 1970s, when the Navy started work on an acoustic decoy, called Nixie, a fielded system that provides some capability to evade torpedoes. Phase 2, which started in the early 1980s, aimed at building a three part system: a towed acoustic device; an upgrade to the Nixie; and some classified countermeasures. That program eventually was replaced by the SSTD joint venture.

A contract award was expected this month for production of the LEAD propulsor. The acoustic decoy, which is built for the U.S. Navy by GEC-Marconi Hazeltine under a separate contract, will be government-furnished equipment.

The successful integration of the MSTRAP SSTD processor with the SQQ-89 sonar is expected to provide an effective system against currently recognized threats. Still, torpedo defense remains outside the surface Navy's current focus on air defense in all its dimensions: ship self-defense; cooperative engagement, and theater ballistic defense—all of which occupy the high ground in the surface warfare budget. While OpNav last year established a new office, N84, to refocus on antisubmarine warfare, it now seems unlikely that the next-generation torpedo defense initiative will continue into next year. 


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