SHIFTING FROM BLUE TO BROWN: PURSUING THE DIESEL SUBMARINE INTO THE LITTORAL

Editor’s Note: lieutenant Vlattas’ paper won 1he Naval Submarine League Essay OJntest for Submarine Officers’ Advanced Cass 98060.

In its 1992 White Paper, ” .. .From the Sea”, the United States Navy’s mission was defined as 11providing the initial, enabling capability for joint operations. ” In more precise terms, the Navy’s role in the joint arena was to project power into the littoral sea in order to open a door through which the heavy ground and air forces required to overwhelm the enemy would pass. ” As part of this strategy, the U.S. Submarine Force and its nuclear-powered attack submarines (SSNs) would play an integral part in securing the dominance of the undersea battlespace.

In the years hence, drawing from countless years of experience obtained from real-world operations and training exercises, the Submarine Force has become adept at operations in waters less than 100 fathoms deep. Our experiences in the Persian Gulf, South China Sea, and the Adriatic Sea have matured capabilities in mission areas such as intelligence and warning, special forces insertion, and strike warfare. But having said this, the Submarine Force has neglected to devote the necessary operational and training resources to what many consider to be a core competency: undersea warfare (USW) against a proficient diesel submarine operating in the
littoral environment.

The Submarine Force remains focused on the same paradigm: blue water USW predominately against the 3rd and 4th generation SSN or SSBN. The vast majority of submarine approaches and attack exercises continue to be conducted on nuclear submarines and when they do involve the diesel submarine, the platform is usually simulated as a non-proficient diesel with limited or non-existent USW weapons and acoustic-intercept capabilities. It is important to note that the failure here is two-fold. Not only are exercises weighted in favor of one target over the other (SSN/SSBN) versus proficient diesel), but when conducting USW on the simulated diesel, these exercises are normally done in a blue-water environment where the adverse acoustic characteristics of the littoral sea are not at issue. In so doing we take one of the inherent advantages away from the third world diesel, the added stealth and security that the diesel obtains while operating in the littoral sea.

To ensure the supremacy of the Submarine Force in the realm of littoral USW, a new operational and training paradigm needs to be developed. The distinct worlds of anti-diesel USW and littoral operations must be merged and put into practice. In short, there is no better way of learning than in doing. The training program and POM cycles must allow the SSN to venture into the shallow water environment to conduct USW against real-world adversaries. But training alone in the littoral sea may not be enough. We have to consider that Sun Tzu’s adage of “Know the enemy and know yourself and in a hundred battles you will never be in peril, “may ring true; that to be able to understand and counter a threat one should be able to pose that threat oneself. In the case of submarine warfare, this means developing the expertise to operate and tactically utilize the high-end diesel submarine. To develop this expertise the U.S. Navy should therefore purchase several high-end diesel submarines and integrate them in the force structure to act as
the real world OPFOR (opposing force).

The Diesel Submarine Threat

In February of 1996, the Office of Naval Intelligence released a report warning of the potential threat to U.S . forces from submarine proliferation. The report, Worldwide Submarine Challenges, noted that the threats posed by submarines “are more diverse and more complex than at any time during the Cold War. General John Shalikashvili, the then chairman of the Joint Chiefs of Staff, said in the report that the continued proliferation of capable, quiet diesel submarines was a serious concern to joint planners.” There are currently more than 150 submarines in the navies of potentially unfriendly nations outside of Russia. Forty-five of these are modem, non-nuclear types. An additional forty-five more submarines are on order worldwide, principally from Russian and German shipyards. By 2030, it is projected that 75 percent of the submarine inventory in the rest of the world will exhibit advanced capabilities.

Many of these potentially adversarial third-world countries have made· these submarines into the capital ships of their navies. Submarines are the ideal weapons for states which lack, or cannot afford the capability to assert sea control in their own (or others) water space. They are desired because they are a cost-effective platform for the delivery of several types of weapons; they counter surface forces effectively; they are flexible, multi-mission platforms (e.g., anti-surface warfare (ASUW), special forces, intelligence and warning, and ASW); they are covert and thus can be deployed with minimum political ramifications; and finally, they can operate without supporting escorts. The subs, which cost as little as $200 million each, provide developing countries a capacity to hit even the most sophisticated Western ships and land targets. Since diesel subs are most effective in areas where ships have little room to maneuver, they pose a particular challenge to the U.S. Navy in critical areas such as the Persian Gulf and other shipping chokepoints.

The utility and effectiveness of even a moderately proficient submarine in a maritime conflict were demonstrated in the Falkland’s War. On the British side, HMS CONQUEROR’s sinking of GENERAL BELGRANO forced the Argentine Navy to retire to its bases, greatly complicating Argentinean efforts to keep control of the islands. Conversely, as told by the U.S. Navy’s Summary report:

The Argentine submarine SAN LUIS was at sea, and at times in the area of the British force, for an estimated 36 days. The threat from the Argentine submarine was a continuous concern for the British Task Force commander, and numerous attacks were made against suspected submarine contacts, with a large number of ASW weapons being expended. In any event, SAN LUIS survived all British efforts.”‘

In short, the presence of one enemy diesel submarine significantly thwarted the tactics of a first-world naval armada.

In addition to their rapid proliferation, the conventional submarine is undergoing a technological transformation. The diesel submarine has historically had two fundamental weaknesses relative to its nuclear counterpart-a lack of mobility and the requirement to recharge its battery. Air-independent propulsion technologies in the form of the Stirling engine and the closed-cycle diesel are already a reality in the form of the Gotland class submarine. The goal of air-independent propulsion is “to provide 100-400 [kilowatts) of power to allow slow-speed operations(~ knots) for extended periods and still maintain the battery charge. “5 These systems wilt allow 30 to 50 days of submerged endurance without surfacing or snorkeling. For the submarine that is in a defensive mode-not needing to travel great distances or operate at high speed-these technologies give the diesel submarine the endurance of the nuclear submarine in a regional theater. If we combine these propulsion technologies with a modern sensor suite and capable USW weapons the third world diesel achieves effective parity with the nuclear submarine.

The SSN. The Diesel and the Littoral Environment

The combination of air-independent propulsion, modern sensors, and weapons makes the 21st-century conventional submarine a potentially lethal adversary. When we combine this platform with the shallow water environment we generate a scenario that leaves no margin for error. The SSN that ventures into the littoral sea to conduct USW against such an adversary will face a negligible acoustic advantage. The diesel submarine will provide low target strength, smaller sizes to ping on, and consequently lower returns. When in motion it will have a lower electronic signature, minimal cavitation, and produce little Doppler. In addition, the shallow water environment will produce high fast-contact rates due to higher ambient sea noise, ray-path bending and reflections, and bottom debris. The shallow water zones close to shore will be areas where freshwater from estuaries mixes with the ocean water, creating unpredictable layers with gradients not seen in the oceans. 15 More than likely, the area will be unsurveyed since the Navy’s third-world environmental database is not very large or up to date.

It is in this environment that the SSN will be sent and expected to succeed. In order to ensure this success, the SSN commander and crew must be given the opportunity to train against this potential scenario. Most of the Pre-Overseas Movement Certifications (POMCERTs) and Tactical Readiness Exercises (TREs) that evaluate the combat readiness of our SSNs involve approach and attack scenarios that are executed on existing ranges which are principally in deep water. Submarine attack parties must have the opportunity to train in realistic environments against real-world targets. It is only in this way that the submarine can be ready for the difficult nature of the shallow water, anti-diesel problem.

The means of achieving this are twofold. First, submarine training must elevate the shallow water, diesel problem to an equal footing with that of the modern nuclear submarine. In all likelihood, this is the scenario that will be encountered in the real world. Attack centers and their computer modeling must be adapted to correctly reflect the shallow water environments. SSN needs the opportunity to test the diesel approach and attack tactics in the littoral environment. This may mean investing the necessary funds to allow these submarines to use these ranges or construct additional shallow water test ranges to meet the training requirements. Second, the SSN must be provided with a real-world target. The use of another nuclear-powered submarine in these training scenarios is unrealistic. Although the nuclear submarine can imitate a diesel’s operational patterns, it is hampered in its ability to mimic the true adversary because of its size and design. The nuclear submarine is four to ten times larger than its conventional counterpart. At best, a nuclear-powered submarine with an anechoic coating might be able to simulate an uncoated diesel submarine. The design of the nuclear submarine also prevents it from being as maneuverable in shallow water as the diesel and makes it unable to perform tactics such as bottoming which will be a part of the bag of tricks that any proficient diesel force brings to the table.

The only way for a commander to gain an understanding of diesel tactics is to actually hunt an operational diesel submarine. Today, we do this by relying on friendly nations through bilateral exercises. Unfortunately, these training opportunities are extremely limited and normally occur when the SSN is already deployed, the time when her commander and crew are supposed to be at their peak readiness. It is also unrealistic to think that even the friendly-nation diesel will expose its full range of tactics to the U.S. submarine. For these reasons, the purchase of a small cadre of diesel submarines to serve as aggressors should be considered.

Indigenously constructing these submarines is an unrealistic scenario, but purchasing a high-quality, top-of-the-line diesel submarine such as the German Type 209 or Swedish Gotland is easily accomplished. For the price of one NSSN, the United States could purchase four to six of these platforms and distribute them evenly between the Atlantic and the Pacific under the command of the development squadrons. In this environment, they could be used not only as training assets for the U.S. submarine and surface fleets, but as part of the Navy research and development efforts on USW weapons and countermeasures. Manning of these platforms is 20-25 percent that of a Los Angeles class submarine and innovative manning schemes like that of the dual crew system of the SSBN force could be used to minimize impacts on the crews and maximize operational time.

Some will argue that the presence of only four to six aggressor submarines will provide minimal training value to a fleet of 55 attack submarines, but even a one or two week training period with one of these platforms in a shallow water environment will be beneficial to the SSN and certainly is better than experiencing the shallow water diesel problem for the first time while on deployment. Supplemented with bilateral exercises from our allies and the experience garnered by the officers and crews who will man these platforms, the knowledge and tactics developed will provide a knowledge base that will rebuild our core competency in littoral USW operations.

Conclusion

No navy in the world today has the submarine or naval resources necessary to successfully challenge U.S. dominance in any littoral sea, and, more than likely, no navy will be in that position anytime in the near future. Nonetheless, it is essential for the U.S. Navy to study the potential benefit of acquiring a force of diesel, in order to effectively counter the real-world threat. The U.S. Submarine Force is by far the strongest and best-equipped fleet in the world today, and it will remain so well into the next century. We became this way by identifying the threat and dealing with it. The shift from blue water operations to littoral operations has changed some of the Submarine Force’s priorities and will continue to do so in the years to come, but if the Submarine Force maintains the focus on its core competencies there is no reason to believe that we will not be a success in the brown waters of tomorrow as we are in the blue waters of today.