Introduction
The dramatic change in the international situation and the I rapid evolution of technology presents the submarine force W1 opportunities to expand submarine missions and to increase submarine military effectiveness.
Regional uncertainties have resulted in threats to U.S. mili-tary forces which are more complex and much less focused than at anytime in recent memory. In addition, the dramatic changes in the former Soviet Union have created a situation in which the world’s largest military force is potentially for sale.
Those nations with aggressive tendencies in the Third World can see from the Desert Storm experience the high leverage that can be gained by submarines for both defense against, and disruption of, a long-range intervention effort. They can also appreciate that a hole exists in their littoral defense without some anti-U.S. submarine protection.
It is not hard to imagine Third World countries buying former Soviet submarines and ASW systems in substantial numbers. Further, increased investment in underseas technolo-gies by these same countries could make the former Soviet systems even more effective.
This threat change challenges U.S. naval forces credibility, flexibility and deterrence capabilities. USN Battle Groups, Amplubious Assault and Military Sealift units can become seriously threatened by Third World submarine forces enhanced with ex-Soviet systems and technology.
The potential development of credible undersea warfare capability in a Third World adventurist nation is not necessarily limited to a regional, wholly defensive concern. Because submarine warfare is not dependent on sea control, or suprema-cy of force, offensive operations can be carried out much as the U-Boats did in two world wars. This potential creates the requirement to counter this threat with new approaches to U .S. submarine effectiveness – both offensively and defensively.
Submarine Fon:e Strenlibs and Vulnerabilities.
At this point in the development of U.S. submarines, the Force represents an overwhelming challenge to any threat or potential threaL At the technical-tactical level this is primarily as a result of superior sensor and stealth technologies, especia!Jy acoustic. At the strategic-operational level U.S. submarines are formidable force because of their self-sufficiency, mobility and multi-mission capabilities.
Nevertheless, there are vulnerabilities which cause some concerns. U .S. submarines, for example:
- operate out of a small number of easily approachable bases,
- are decreasing in force levels as budgets are cut, and
- employ weapons which are noisy and easily detected.
The March of Technologies.
It is reasonable to postulate that the push of technology will provide other nations with submarines and submarine systems with substantially increased capabilities. Without forecasting a specific date when these capabilities will be achieved, the list below describes some of them:
Stealth
- Radiated noise of 110 db or less at speeds below 15 knots.
- Target strength reduction (12 db stealth) coatings.
Sensors
- High gain (20 to 30 db) towed arrays.
- Narrow and broad band processing improvement (20db ).
Weapons
- Quiet launch, quiet run-out 30-inch weapons.
- Smart mobile mines with ranges of 100 to 300 om.
- Highly accurate cruise missiles with ranges out to 1500nm.
Off-Board Systems
- UUVs capable of penetration into harbors/anchorages with a variety of sensors and devices.
- UUVs with low speed/long range profiles capable of deploying hundreds of miles of low-loss fiber optic cable and sensors.
- Submarines capable of deploying and managing the opera-tions of such UUVs
- Swimmer delivery vehicles capable of delivering and re-trieving special warfare forces at ranges up to 100 om or more.
It is assumed that the US will where they do not presently exisl them through outright purchase, develop these capabilities Other nations will obtain barter and espionage, or through their own indigenous R&D programs. While any one of these programs would not in itself present an overwhelming problem, combinations of them would require restructuring of U.S. programs and would compel significant changes in operat-ing modes and tactical doctrine.
Implications of Improved Foreign Submarine Capabilities Submarine Quieting It is difficult to estimate precisely what quieting levels may be achieved by future generations of submarines. If, for instance, radiated acoustic levels do not exceed 100 or 110 db, then passive detection of them would occur only at extremely short ranges.
Even if the radiated noise levels of U.S. submarines were below ambient and even if U.S. submarines had detection and signal processing systems that provided a total of 35 db of system gain, ultra-quiet aggressor submarines could not be detected at ranges greater than 1 to 2 miles.
It should be noted that, modern U.S. submarines would still have a figure-of-merit advantage, and would be able to detect other submarines before we were counter-detected. However, all detection and counterdetections would occur at very short ranges.
Submarine Sonar Target Strength Reduction
Target strength is a measure of submarine wlnerability to detection by active sonars. As a result, substantial efforts have been made to develop coatings (among other techniques) to reduce active sonar target strength.
It is reasonable to postulate that non-U.S. submarine de-signers are intensely interested in coating technology. Eventual-ly, coating, the performance of which might achieve as much as 10-12 db reduction in sonar target strengths, will be available. A reduction of 12 db in sonar target strength will reduce the active detection range by a factor of 2.
Assuming U.S. sonar performance did not improve by a comparable amount, then the average range for active detection would be reduced to several miles or less. From the standpoint of enemy submarines being able to attack U.S. naval vessels employing sonars in the 3-10 Khz range, this would be a considerable advantage.
Other target strength technologies could cause similar concerns.
High Gain (20 to 30 db) Towed Arrays
At present, U.S. towed array technology is believed to be significantly more developed than that of other nations. Though considerable sophistication is employed in U.S. arrays, there is no intrinsic reason why eventually others can not field high gain towed arrays.
In principal, any modem Navy could develop and deploy very long towed arrays. Given the proven capabilities of fiber optic technology, there is no reason why they can not develop arrays with gains of 20 db or greater.
If several such arrays were multiplexed on the same cable, the effective gain could be on the order of 25-30 db. With such capability a non-U.S. submarine might have a significant capability against U.S. submarines. Detection ranges as great as 3-5 miles might be achieved.
Narrow and Broad Band Processing Capability
Foreign signal processing techniques have been considered to be behind those of the U.S. The most likely cause for this lag is probably related to deficiencies in computer processing technology.
Certainly, the principals of signal processing are no mystery to competent engineers and scientists. It would therefore be safe to assume that within the next 5-20 years the availability of 20 db of processing gain would increase their detection range proportionally to the number of db of improvement they might achieve.
In affect it can be assumed that the acoustic figure-of-merit of next generation passive sonar systems will increase signifi-cantly, and unless the radiated noise levels of U.S. submarines are reduced correspondingly, it will allow improved capabilities against U.S. submarines.
Quiet Launch, Quiet Run-Out Torpedoes
Submariners are aware of the importance of quiet weapons launch and run oul It would be prudent to assume that over the next 5-20 years some significant progress will be made toward the development of quiet launch, quiet run-out weapons.
At present, it is understood that the U.S. has a modest torpedo counter-measures program which is: (1) of limited effectiveness and (2) dependent on the capability to detect the launch of enemy torpedoes. If launch cues are lost as a result of a successful torpedo quieting program, the effect on the outcome of potential hostile encounters could be serious.
Submarine Launched Moblle Mines (100.300 mile Rauges)
While it is expected that much of a potential enemy’s mine effort is or will be defensive in nature, there is the possibility that they might develop an offensive mine warfare capability.
Long range mobile mines could be employed to mine the exit and entrance channels to any or all U.S. submarine bases prior to hostilities. While such activities would not effect U.S. submarines which were already at sea, it would interfere with port reentry and exits after hostilities commenced.
While it may be argued that great care is taken to examine submarine port entry and exit routes, it is obvious that the deployment and tactical use of smart mines, for example, would greatly complicate the problem.
Submarine Launched UUVs with Capabilities to Deploy and Operate Sensor Fields and other Devices aear U.S. Naval Bases.
The current state of the art probably does not allow anyone to launch UUVs that are capable of reliable performance in offensive actions against submarines in port However, the technologies do exist which could be used to develop such capabilities.
It is expected that a number of nations are deeply involved in UUV technology programs. For example, low loss fiber optic cables have been developed and are available from the French and Japanese. There is certainly no reason to assume that the importance of fiber optic connected sensor fields deployed by UUVs is not clearly appreciated by a number of potential enemies. One must assume that in the future, a number of them will have such capabilities.
Unless specific countermeasures are taken to defeat UUVs, the availability of such capabilities to potential aggressors will put U.S. ports at risk. Defending a port or submarine base against UUVs should not be difficult, but if efforts are not undertaken, a significant wlnerability will exist
Submarine Launched Swimmer DeUvery Vehicles (SDV)
The strong interest by several nations in Special Warfare is well established. There is every reason to assume that in the next 5-20 years there will be a continuous upgrade of SDV capabilities. Enhanced SDV capabilities will allow any nation, and especially those nations involved in terrorist activities, to undertake attacks on critical submarine shore facilities.
The effectiveness of such attacks would be limited if such facilities were defended. On the other band, if they were not defended, Special Warfare forces could have a significant impact on several aspects of U.S. submarine operations.
Scenarios
Diverse scenarios involving combinations of former Soviet and Third World Naval forces can be postulated. Two scenarios are chosen to illustrate the kinds of challenges which could confront future US submarines.
The first scenario involves Third World country aggression that provokes a U.S. response in which U.S. submarines provide the first significant capability to respond. Depending on the situation, submarines would provide crucial surveillance followed by attack on key enemy military forces. U .S. smart weapons would be capable of inflicting significant damage as demonstrat-ed in the Persian Gulf War.
The enemy could counter this U.S. submarine threat with a variety of ASW systems including ultra-quiet submarines with improved sensors and weapons augmented by sea-bed based sensors and weapons. A second scenario involves high technology, sea-based attacks against U.S. naval facilities. Such a scenario might develop out of the confrontation in scenario one, or a com-pletely separate situation.
In any event, the kinds of threat systems which employ Standoff Weapons, Special Forces, UUVs or cruise missiles to conduct attacks against virtually undefended U.S. bases offers the potential for significant political as well as physical damage. These would have to be met with ASW forces that include the most modem SSN capabilities available.
U.S. Countermeasures to Improvements In Foreign Submarine and ASW Capabilities
In general, foreign anti-submarine improvements may be countered in part by changes in U.S. tactics or doctrine. However, when long lead procurement or substantial funds are required, it is doubtful that the U.S. could respond in a timely fashion unless programs are already in place and well along.
Defensive Barriers In CoasCal Areas
In order to attack in and around defensive barriers in Third World littoral seas, their high technology systems will have to be countered by even higher technology U.S. submarine systems.
Achieving these capabilities will require considerable investment in U.S. systems. Some of the most significant of these are discussed below as counter-measures to Third World systems.
Improvements in Enemy Surveillance and Long Ranee ASW Weapon Systems
Fundamentally this capability can be countered by:
- Avoiding areas where the enemy may have covertly installed a sensor field,
- Reducing to a minimum the detectibility of communications from submarines,
- Reducing the signature (acoustic, radar and beat) of weap-ons launch, D
- Development of decoys to confuse sensors and increase system noise.
Two of the approaches listed here are primarily operational and two are technical. Limiting operations is achievable and the investment in technologies should be affordable
Quiet Torpedoes
There are few countermeasure to a torpedo that is so quiet that it cannot be detected. Counters to weapon quieting are:
- Not allowing enemy submarines to detect U.S. SSNs first – acoustic advantage,
- Quieting U.S. torpedoes so that their launch and run-out does not cause the enemy submarine to counter-fire,
- Improving sensitivity of systems that detect weapons launch,
- Developing a family of hard kill and soft kill devices to counter torpedoes.
All of these approaches are believed to be at least in the development stage.
Enemy Quieting, Improved Sensors and Improved SignalProcessing
Assuming that it were not possible to recover the figure-of-merit and initial detection ranges the U.S. enjoyed in past years, the U.S. Navy might invest in:
- UUVs as decoys and to extend submarine sensor baselines,
- ASW Stand-Off Weapons and targeting to support them,
- Bi-static active sonars.
Increasing the Security of U.S. SSNs and SSBNs in and Around U.S. Ports
As indicated above, U.S. naval forces and critical facilities may be at risk to attacks by: Standoff Weapons, Cruise Missiles, UUVs, and Special Forces.
The basic countermeasure is also probably the lowest cost. Any number of schemes can be envisioned but the preferred option appears to be dispersal to alternative facilities. This factor alone would greatly complicate targeting problems if an aggressor wished to attack U.S. naval forces in port.
Attacks by Mobile Mines and UUVs While Entering or Exiting Port
Countering this problem is essentially a problem in sweeping future high performance mines. Mine hunting is difficult at best. It is not possible without an adequate number of highly capable search platforms equipped with mine neutralization vehicles. Internationally there is considerable high resolution mine hunting technology available and under development. Unmanned mine neutralization vehicles are also available.
For the U .S. Navy the mobile mine and UUV problem would be manageable if an appropriate investment were made in establishing and maintaining a competent mine hunting force. In the past, and for the foreseeable future, the problem will be one of investment and commitment to resolve the problem.
Enemy Intercept at Port Entry and Exit
In the vicinity of port entry and exit channels the U .S. Navy may resort to:
- Extensive patrolling and monitoring of these areas,
- Extensive use of decoys and escorts,
- High resolution detailed surveys of exit routes to detect emplaced sensors or other devices.
Recommended U.S. Actions
In sum, over the next five year defense plan and beyond, the U.S. should implement the suggested courses of action outlined above.
Priority should be given to:
- Continued development of UUVs and Undersea Warfare,
- Maintenance of control of port exit and entrance channels,
- Development of effective torpedo counter-measures,
- Development of a quiet launch, quiet run-out torpedo.
