The nature of U.S. Naval Submarine Warfare bas changed. In two global conflicts, the effective use of the attack submarine has proven its influence on naval warfare. Since the advent of the nuclear attack submarine, there have emerged certain traditional roles for these platforms, as summarized in Table 1. However, the capabilities required by the submarine force are not solely determined by these missions. Recently, mined shallow coastal waters were encountered in the Persian Gulf, in the only live engagement involving U.S. submarine forces since World War II. The ability to penetrate mined coastal waters is uniquely different from those capabilities required to counter the threat historically presented by the Soviet block. It has been shown in the Persian Gulf that submarine operations, in order to support all types of naval warfare, must also consider the mine threat in shallow coastal waters. Such waters are likely future sites of limited intensity regional conflicts.
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As the U.S. and whatever new federation comes from the Soviet Union struggle to create an alliance to maintain and control regional conflicts; release of previously constrained tensions will become increasingly more frequent. The proliferation of inexpensive and increasingly sophisticated weapons can only serve to increase the probability of these conflicts.
It is likely that the evolving Third World naval warfare strategy will continue to consider mine warfare a cost effective deterrent to potentially hostile naval forces. Mines are an inexpensive means of near shore, shallow water defense or area denial. They require no special platform for deployment and lend themselves to deployment from any craft of opportunity that might be readily available. This approach to mine warfare contrasts sharply with the specialized platforms developed to locate and neutralize them. Increasingly sophisticated mines are readily available on the international arms market, yet even the unsophisticated mine can take warships out of service, as experienced by the USS TRIPOLI in the Persian Gulf.
Attack submarine independent operations and minefield penetration. The independently operating attack submarine is a powerful force capable of supporting all types of naval warfare. It is imperative that the covert, independent nature of attack submarine operations is maintained, even in a mine riddled theater of operations. Deployed submarine forces must be able to penetrate regions defended by, or potentially defended by mines. The submarine will require a combination of onboard and oflboard sensors that can probe the field. The system must find any mines that are present, accurately figure out their location, classify them, and provide the means for penetration of the minefield or assist the submarine to maneuver around it. If the submarine is to maintain its independent role, the sensors and sensor data must be an integral part of the submarine warfare suite. The sensors must provide real-time tactical data that gives the commanding officer the assurance that he can safely continue the mission.
The required sensors, data processing, and supporting system are under development. DARPA (Defense Advanced Research Projects Agency), the Naval Laboratories, and industry are continuing the research and development efforts to provide the submarine force a minefield penetration capability. Analytical studies have proven the feasibility of a remotely controlled sensor platform for guiding a submarine through a minefield. Proof-of-principle demonstrations have been conducted, using an ROV (Remotely Operated Vehicle) operated from a host platform. DARPA is now nearing completion of an autonomous Unmanned Undersea Vehicle (UUV) prototype program, the Mine Search System (MSS), that will further prove the feasibility of leading a surface ship through a minefield with a tethered UUV sensor platform. A torpedo sized UUV system for application with attack submarines is a logical follow-on effort to MSS, once successful demonstration and validation is complete.
Communicating the position of mines to the host platform is a critical capability. The communications system developed for the MSS prototype will demonstrate a high data rate fiber optic tether for vehicle command, control, and data exchange. The tether is planned for use during the escort phase of the demonstration. The MSS vehicle was also designed to autonomously survey, accurately map, and transmit to the surface ship, the location of mine-like objects via an acoustic telemetry link. For the future, more advanced high data rate acoustic communications, and blue-green laser communications for long range, high data rate communications are also being researched.
Development is continuing on integrated precision navigation systems that can provide accurate, long-range, way-point navigation, with the precision necessary for work-station location and area minefield mapping. Integration of state of the art Doppler sonars or Correlation Velocity Logs is underway that will provide velocity vector data, critical to advanced navigation system precision. These modem navigation systems incorporate use of the Global Positioning System (GPS) for periodic position verification. Systems are being researched that will accurately find position relative to acoustic transponders or mapped bathymetric features.
Additional DARPA programs are in place to develop other key technologies needed to support this mission and other UUV missions under evaluation. Software and supporting hardware are in development that can monitor the offboard sensor system and recognize unanticipated mission events. The system will be capable of autonomously assessing mission impact, directing corrective action, and replanning or aborting the mission. This effort, appropriately termed Autonomous Control Logic, completed the first phase in 1990 and commenced a 48 month Phase ll effort in mid 1991. Integration into a UUV and demonstration at sea is planned for Phase m, around the middle of the decade ..
Energy systems are considered to be on the critical path for these UUV systems. Therefore, one of DARPA’s key technology thrusts is the development of high energy density systems. DARPA’s goal is to increase specific energy density by a factor of 2, to possibly a factor of 10, over existing silver-zinc battery systems. This development effort will span the next several years. Presently, liquid oxygen and hydrogen are to be used as oxidant and fuel for a Proton Exchange Membrane (PEM) fuel cell. Similarly, liquid oxygen is used in a parallel development of an Aluminum-oxygen semi-cell. Development of alternative methods of storage may be necessary if the submarine community judges cryogenic storage of fuel and oxidants to be unsatisfactory. An aluminum silver-oxide primary battery is also under investigation by the Naval Undersea Systems Center, funded by the Office of Naval Technology.
Increased emphasis is applied to reducing the integrated vehicle system acoustic and non-acoustic signatures as the systems evolve. Non-magnetic materials, acoustically quiet motors and thrusters, and use of anechoic materials are just some technologies under investigation. These technologies will potentially enhance the covert operational capabilities and reduce the likelihood of unintentionally detonating a mine with the UUV platform.
While some critical technical challenges to providing a minefield penetration capability have been addressed, several challenges remain. For instance, UUV launch and recovery from a moving submarine will probably be required. If the system is to be recovered, conditions will likely mandate a dry maintenance capability, with minimum impact upon submarine combat readiness. In existing SSN configurations, launch and recovery through a torpedo tube become the most logical solution. Launch is perhaps easier than recovery, since the UUV can be designed to be impulsed or to propel itself out of the torpedo tube. Vehicle control, capture, and safe recovery, while minimizing impact on both the torpedo tube and vehicle is an imposing challenge. If a tethered system is used, then joint host-tether-sensor platform control while underway, compounds launch and recovery problems. Lateral launch systems and alternative shelters are under study and appear to have significant design challenges. Industry and U.S. Navy resources are pressing forward with proof of principle demonstrations as prototype systems are evolving.
As the large DARPA prototype vehicle systems progress, miniaturized components and subsystems are in development for the next generation torpedo tube sized vehicles to follow. Control and data interface display consoles along with the vehicles and their payloads must be packaged to minimize the impact to onboard maintenance. Servicing must not adversely affect submarine combat readiness or affect crew or submarine safety. Integration of vehicles and payloads into modular future submarine designs may be essential to an effective solution to providing these capabilities.
Closing on the solution. Even with the technical issues identified and many achievable solutions on the horizon, enabling future submarines to penetrate a minefield effectively is not a trivial task. Several more years of development work are required to field systems that will meet mission needs. Funding ceilings presently constrain current efforts. Continued industry and government support is essential. Minefield detection and penetration is a multi-mission capability that supports many naval warfare communities. Not limited to exclusive use as an SSN adjunct, similar systems can be deployed from surface ships and aircraft.
Offboard sensor systems will extend the battle space of the host platform, assist in achieving mission objectives, and improve weapon system performance. The oflboard sensor system will accept the platform risk when the host can not or should not. These systems need to be developed as adjuncts to existing combatant platforms and avoid the perception of being an offsetting force, competing for limited capital resources in an increasingly sensitive political arena.
The role of the submarine force will not be replaced by unmanned platforms. Instead, the additional capability will reinforce the utility of the existing and future submarine force. Government and industry should both recognize the need for an affordable force adjunct that enhances submarine effectiveness. The attack submarine must remain effective in all areas of naval warfare, including shallow coastal water regional conflicts. Mission effectiveness may very well hinge upon the ability to independently enter a mine denied combat theater. The integrated offboard sensor system for minefield penetration is an achievable solution now in development for the attack submarine.
