3.6 Undersea Weapons

3.6.1 Warfighter Needs

With the shift in focus from global confrontation to regional conflicts in shallow water and littoral zones, a deficiency became obvious regarding the capability of undersea weapons to successfully attack threat submarines under such harsh environmental conditions. Moreover, the problem is compounded by low-signature diesel/electric submarines operating in the shallow waters armed with modern, lethal weapons. Technological superiority and affordability of next-generation undersea weapons is needed to ensure the ability to cope with an evolving threat in harsh environments. The return on investment includes the capability to provide deep-water-equivalent performance against the quiet, small diesel/electric targets in shallow water, which will be available in the mid term (i.e., 3 to 5 years). By employing broadband sensors and signal processing, the capability to defeat sophisticated countermeasures will be available in the far term. A new capability to disable incoming torpedoes will be available to the fleet in about 5 years. In addition, significant efforts are directed toward reducing cost of ownership through commonality of subsystem hardware and software and, where possible, entire systems over the next 3-10 years.

The end of the cold war drastically changed the outlook for production of all-up-round torpedoes and significantly reduced the planned inventory. DoD's assessment of industrial issues for torpedoes indicates all-up-round production is not needed now, but there are requirements for advancing weapon technologies, upgrading and maintaining the current inventory, and supporting torpedo operations. Planned block upgrade programs will continue to improve performance of the MK48 ADCAP and MK50 torpedoes through FY05. Technology transitions are currently planned for the Lightweight Hybrid Torpedo (LHT) with an IOC of 2002 and the hard-kill torpedo defense programs for both surface ships and submarines, which will reach IOC in 2002-05. Explosives and warhead technologies will transition explosives with increased performance for both bulk and directed-energy warheads. In addition, a MEMS-based (microelectromechanical systems) safe and arm device is being developed as a potential common unit for backfit into all torpedoes and possibly all undersea weapons.

3.6.2 Overview

The objective of the undersea weapons S&T program is to develop and demonstrate technologies that contribute to the neutralization of threat submarine targets, countering (both soft and hard kill) enemy torpedoes, and assessing tactical battle scene and weapon employment tactics. The effort is organized in four areas: torpedo guidance and control, torpedo countermeasure and counterweapon devices, undersea warheads and explosives, and combat control. Torpedo propulsion and UUV technologies are covered in the Ground and Sea Vehicles area (Chapter IV).

3.6.2.1 Goals and Timeframes. The underlying tenet of undersea weaponry is innovative technology leading to affordable, effective weapons. The program encompasses the technology process from basic research, through applied research and advanced development, and transitions the promising candidate technologies to weapon systems upgrades. It is focused, productive, and responsive to the needs and requirements of the warfighters. Some of the major technology development milestones (when the capabilities are available for transition) are shown in Table X-7.

3.6.2.2 Major Technical Challenges. The primary challenge is to provide undersea weapon performance in the adverse, harsh, shallow-water environment that is equivalent to deep-water capability. Quiet, slow, or bottomed targets operating in cluttered shallow water areas present a detection and classification challenge to both the platform and the weapon because of the reverberant, noisy acoustic conditions. Moreover, the clutter creates a plethora of false targets that must be recognized by identifying features of various false targets. As a result, simultaneous tracks must be maintained on several contacts. The reverberant, noisy, congested environment coupled with the quiet, slow target results in close-in engagements that demand fast reaction. Achieving this performance is a challenge that requires organizing and coordinating several undersea weapon technology areas including shipboard fire control, weapon sensors and signal processing, trackers, precision homing, and warhead lethality.

The challenge of platform survivability is met by a multilayer defense strategy that includes both smart, adaptive countermeasures and hard-kill counterweapons able to defend against attacking weapons of various capabilities, including salvos. Improved post-launch retargeting and countermeasure identification will be possible by development of bidynamic, intersensor processing whereby the weapon and platform sensors are simultaneously and cooperatively processed to better define the engagement environment. The weapon's challenge is fast, accurate target DCL (detection, classification, and localization), intelligent mission control, and precision homing to achieve selective warhead placement on the target to ensure target destruction. Increased lethality warheads enhance the probability of kill by development of explosive formulations that produce higher bubble energy and shock performance. Alternatively, standoff distances can be increased while still achieving effective mission kill. A major challenge is development of a common, small, reliable safe and arm device for various weapons while retaining the multiple environmental interlocks required to satisfy current safety standards.

3.6.2.3 Related Federal and Private Sector Efforts. Because of the broad, varied technology areas involved in developing undersea weapons, many federal and private sector performers are involved. In FY95 (a representative year), the undersea weaponry budget was $34.0 million, of which $6.5 million went to industry, $13.0 million to Navy warfare centers, and $14.5 million to university laboratories. Although most of the technology is Navy-unique, some funding is leveraged by participation with organizations interested in similar pursuits. For example, this program is participating with DARPA, universities, and industry to develop MEMS technology that has the potential to allow a common, low-cost weapon S&A. Other examples of technology areas where the program joins with federal and private efforts are sensor materials and arrays, simulation-based design, explosive formulations, signal processing, intelligent control, and COTS processors.

3.6.3 S&T Investment Strategy

S&T investments for undersea weaponry are selected in conjunction with OPNAV sponsors and PEO(USW) with emphasis shared between performance enhancement and reduction of cost of ownership. The program provides an integrated effort comprising basic research that supports an applied research program which, in turn, leads to current and planned ATDs and the advanced development undersea weaponry core line, which begins in FY97.

3.6.3.1 Technology Demonstrations. The undersea weaponry program has two ATDs in FY97: Shallow-Water Guidance and Control (FY97 is the final year) and Antitorpedo Torpedo (DTO WE.29.02) (FY97 is the first year). A Broadband Torpedo Sonar Demonstration (WE.32.02) is planned to begin to FY99 that will provide major improvements in shallow-water detection, classification, and countermeasure resistance. It is supported by 6.2 enabling technologies from FY97 through FY01. In addition, the 6.3 core line described in the following text supports the broadband demonstrations beginning in FY98 and continuing through FY02. The Shallow-Water G&C ATD relates to specific software upgrades for shallow-water performance enhancements that can be implemented in an efficient manner. The Antitorpedo Torpedo ATD addresses both surface ship torpedo defense (SSTD) and submarine torpedo defense (SMTD). Technologies developed and demonstrated will be transitioned to the Lightweight Hybrid Torpedo Program. Additionally, the Broadband Torpedo Sonar Demonstration supports DTO WE.32.02. The need for torpedo component prototyping and transition of technology improvements is addressed by the 6.3 core line for undersea weaponry. The 6.3 core line is the bridge between applied research and the industrial base.

Shallow-Water G&C Technology Demonstration. The goal is to demonstrate a torpedo guidance system capability to detect, classify, and home against a low-speed or bottomed diesel/ electric submarine in shallow-water environments with performance equal to or better than current deep-water capability. The effort involves embedding new detection, classification, and environmental adaptation processing algorithms within the structure of a fuzzy-logic-based torpedo intelligent controller. New sensors will be employed to provide high-resolution image processing against small shallow-water threat targets. Achievement of the goals would provide a 30-50% (site dependent) improvement in probability of hit for current weapons in shallow water environments. This capability significantly increases the capability of the Navy's air, surface, and submarine ASW forces to realize a single weapon kill against a diesel/electric submarine threat. Transition targets are the MK50 and the MK48 ADCAP torpedoes. These weapons contain software-based guidance systems and have block upgrade programs in place to insert these improvements.

Antitorpedo Torpedo Demonstration. The goal is to demonstrate ATT homing and fuzing technologies that can be incorporated into existing and planned torpedo and submarine defensive warfare systems (SDWS). This will be accomplished by embedding the homing and fusing technologies developed in the applied research program into a prototype G&C system and demonstrating performance against torpedo targets in clean, CM, salvo, ship wake, and shallow-water environments. Technologies to be demonstrated include high-range-resolution waveforms, high-pulse-rate signal and image processing, adaptive CCM processing, integrated homing and fuzing, acoustic intercept receiver, data fusion, and torpedo-defense-specific tactics. These technologies and capabilities will be based on common hardware and software technology compatible with existing and future torpedo systems (i.e., 21-, 12.75-, and 6.25-inch diameter weapons). In this way, a significant and cost-effective warfighting improvement can be quickly provided for existing inventories and future weapons. Because of the open architecture design, COTS common processor, and homing and fusing software modules approach, the capability can be directly transitioned to current and planned torpedo and SDWS programs.

Broadband Torpedo Sonar Demonstration. The goal is to demonstrate bandwidths five times that of existing torpedo sonars. Broadband sensors and signal processing technologies will be developed in the 6.2 program, and demonstrated in-water in an ATD, planned for a FY99 start. The ATD will integrate broadband sensors and signal processing techniques developed in the 6.2 program into a test vehicle and demonstrate improved performance in shallow-water environments against artificial targets, real targets, and countermeasures. The demonstrations will show detection ranges increased by a factor of two and false-alarm probabilities reduced by a factor of two, relative to existing narrowband systems. These demonstrations will be concluded in FY01. The sensors and signal processing demonstrated will be capable of being inserted with minimal impacts into existing operational torpedo inventories and into any new torpedo developments, and would provide significant, cost-effective enhancements to warfighting capabilities.

Core Line Technology Demonstrations. Many Third World and some developed countries contribute to the proliferation of inexpensive, quiet, diesel/electric submarines equipped with advanced countermeasures and lethal underwater weapons. These armaments pose a significant threat, particularly in the shallow-water regions where their quiet, slow-speed, or bottomed tactics foster close-in, quick-reaction encounters. New, innovative technologies must be inserted into weapons to counter this threat and ensure survivability of U.S. submarines and surface ships. The 6.3 advanced development core program addresses the issue of maintaining superiority through affordable innovation. Moreover, through its programs, the core effort retains sufficient industrial base to quickly and efficiently reconstitute torpedo production. Selected efforts for component prototyping provide either significant cost reductions or performance enhancements. The transition candidates are applicable to heavyweight, lightweight, and torpedoes for SDWS. Three efforts will begin in FY97. First is identification of a fuel and closed-cycle cooling system to replace the current open-cycle Otto fuel engines used in a large number of U.S. torpedoes. Otto fuel is a toxic substance, pollutes exercise areas, and requires an engine teardown after each exercise use. Second is a simulation-based design capability to analyze system cost and performance interaction. Moreover, the customer will be able to interact with the simulation in near real time. The third takes 6.2 technology for broadband sensors and processing toward a demonstration of a highly capable broadband guidance and control system for lightweight and heavyweight torpedoes. This broadband demonstration is the basis for the Broadband Torpedo Sonar Demonstration DTO (WE.32.02).

3.6.3.2 Technology Development. Undersea weapons embrace those technologies that contribute to the neutralization of submarine targets, countering and hard killing of enemy torpedoes, and assessment of tactical battlespace/weapon employment tactics. The work is separated into four efforts:

Guidance and Control. This effort includes a broad regime of technologies acting together or singly to detect, classify, engage, and neutralize submarines and surface ships. Particular emphasis is directed toward the quiet diesel/electric submarine operating in the harsh, shallow-water environment and often at slow speeds or bottomed. Among the technologies are detection, classification, feature extraction, simulation and test, acoustic arrays, fuzzy logic, intelligent controllers, inference machines, COTS-based processors, simulation-based design, and CCM techniques. Reduction in false targets by application of intelligent control promises improved resistance to countermeasures. Three principal tasks compose this technology effort: shallow-water G&C technology, advanced G&C technology, and simulation and test. This technical area is the key enabling technology for both the Antitorpedo Torpedo DTO (WE.29.02) and the Broadband Torpedo Sonar DTO (WE.32.02).

Torpedo Countermeasure and Counterweapon Devices. The objective is development of affordable technologies that provide submarines and surface ships with a robust layered defense capability possessing a high degree of protection against torpedo attack to ensure platform survivability. These technologies include hard-kill (i.e., a counterweapon and supercavitating guns and projectiles), soft-kill (both sonar and torpedo acoustic countermeasures), and shipboard DCL capabilities to quickly identify and track threat weapons. Some of the challenges include defense against a salvo of attacking weapons; provision of advanced countermeasures that support an effective layered defense strategy; fuzing in or near the wake with a fuze that conforms to the restricted space available in a small counterweapon; the quick-reaction required by the close-in encounters in cluttered, congested littoral zone engagements; and detection of and precision homing on an attacking torpedo with closing speeds near 120 knots. These technologies are important enabling technologies for the Antitorpedo Torpedo DTO.

Undersea Warheads and Explosives. This effort is structured to address the top priorities identified in the PEO(USW) document "Science and Technology Needs for Undersea Weaponry" dated September 29, 1994. The effort will provide explosives formulations meeting both operational performance requirements and the Navy's insensitive munitions requirements. None of the explosives in current undersea weapons meets the insensitivity munitions requirements. Consequently, these explosives are operating under waivers. New explosives technology to be developed under this task will transition to the Insensitive Munitions Advanced Development (IMAD) program for qualification and subsequent insertion into the fleet. The warheads development effort will provide design tools and concepts, which will permit computer-aided design and performance evaluation of warhead modifications. Six tasks that are essential non-DTO enabling technologies are the foundation of the warheads and explosives effort:

• Investigation and evaluation of novel explosive mixes that promise improved performance.

• Development of technologies needed to design and implement underwater explosives specifically formulated to maximize performance for a specified requirement.

• Development of theoretical and experimental methodology capable of describing the behavior and detonation characteristics of explosive formulations.

• Development of a small, reliable, MEMS-based fuzing safe and arm device.

• Development of fully coupled fluid/structure interaction models to simulate effects of underwater explosions near solid structures.

• Development of advanced concepts for a common torpedo warhead.

Combat Control. Technologies produced by this effort are applied to enhancing the undersea warfare effectiveness of submarines and surface ships by exploiting available information, reducing system response times, working toward better use of warfighting assets, and ensuring increased own-ship survivability. In addition, affordability is addressed through software upgrades to existing tactical systems, reduction of manning and training requirements, and pursuing commonality across submarine and surface ship equipment and software. There are three tasks. The first is undersea warfare tactical engagement information management, which seeks to develop and demonstrate the technologies and capabilities that produce an accurate, unambiguous, and timely platform-level tactical picture. The second task is vehicle pre- and post-launch management, which directs efforts toward assessing and classifying the threat and then rapidly placing weapons to best counter the enemy. The final task's objective is to develop a situational awareness for responding effectively and to survive close-in, quick-reaction torpedo encounters.

3.6.3.3 Basic Research. Much of the basic research (6.1) relating to undersea weapons is under the direction and responsibility of the same scientists involved with undersea weaponry applied research (6.2). They have responsibility for 6.1 and 6.2 resources, participate in formulating and managing ATDs, and are involved with the 6.3 core line. This link provides a key influx of high-quality science into undersea weaponry that carries through to the fleet. In addition, other ONR basic research program managers are encouraged through technology area workshops to focus basic research tasks on topics with application to undersea weaponry technology. In this way, innovative science programs are influenced to contribute ultimately to the undersea weapon technology base. Some relevant research areas are: