Asw

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ASW Operations

Submarines are the greatest threat to offensive CVBG operations. The stealth of modern submarines (anechoic coatings, possibly near-silent magnetohydrodynamic drives (http://www.explore-cars.com/motor_vehicles/M/Magnetohydrodynamic_drive.html) etc.), can allow a submarine extremely close to a HVU target. The move towards shallow-water operations has greatly increased this threat. The threat is such that even the suspicion of a submarine means a fleet must commit resources to removing it, as the consequences of an undetected submarine are too great.

Sonar Operation

The main detection equipment to both sides in ASW is sonar (http://www.explore-language.com/abbreviations/S/Sonar.html). In the ocean the main factor affecting sonar operation is temperature. Ocean temperature varies with depth, but at between 30 and 100 metres there is often an marked change -- the thermocline (http://www.explore-earthscience.com/oceanography/T/Thermocline.html), also simply called the layer. This divides the warmer surface water and the cold, still waters that make up the rest of the ocean. Regarding sonar, a sound originating from one side of the thermocline tends to remain on that side -- it is 'reflected' off the layer change -- unless it is very noisy (active sonar, cavitation (http://www.explore-technology.com/technology/C/Cavitation.html), firing weapons, explosions etc.). Pressure, salinity and the turbulence of the water also affect sound propagation.



Water pressure creates convergence zones (CZ). Sound waves that are radiated down into the ocean bend back up to the surface in great arcs due to the effect of pressure on sound. Under the right conditions these waves will then reflect off the surface and repeat another arc. Each arc is called a CZ annulus. CZs are found every 33 nm, forming an pattern of concentric circles around the sound source. Sounds that can be detected for only a few miles in a direct line can therefore also be detected hundreds of miles away. The signal is naturally attenuated but modern sonar suites are very sensitive.

As in all EW the issue with sonar is passive versus active. Modern active sonar is limited to 250 dB (decibels (http://www.explore-physics.com/physics/D/Decibel.html)), this level of noise can be detected at about ten times the range that is useful to the operator, acting as a beacon to any submarine in 100 nm. So a target needs to be nearby and preferably on the same side of the layer to be detected by active sonar; just where a commander would not like a submarine to be!

In passive sonar operation the thermocline is the major issue. On passive detection the radiated noise of a unit is only apparent across the layer in a narrow cone, undetectable unless units pass almost directly over or under each other. For a surface unit there is the option of towing a passive sonar array above or below the thermocline - variable depth sonar (VDS).

A VDS passive array can be put below the layer to detect approaching submarines and when the target is within strike range a brief and unit-selective move to active transmissions can quickly return a targeting solution. An added advantage of VDS is that while it is operating below the layer, a unit's hull-mounted systems can be used above the layer. Unfortunately VDS is a blue-water solution. In shallow water, the high levels of biological, wave and tide noise, the influx of fresh water from rivers and the lack of a thermal gradient -- and therefore CZs -- make it a truly formidable environment to detect a sub-surface threat. Passive detection is almost impossible and surface units are forced to use active sonar to search. Because of this naval commanders hate operating close to shore or in shallow water, doctrine is that a fleet must act as if they have already been detected and maybe even targeted.

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The ASW triad

For successful ASW, a fleet must combine surface, air and subsurface assets in the most tactically efficient manner - if these assets are present. ASW engagements occur in three phases:



Detected - From any source a submarine is possibly (POSSUB) or probably (PROBSUB) in the area.

Localized - A submarine contact has been localized to a sufficiently small area to allow an attack with some chance of success.

Targeted - The submarines bearing, range, course and speed are known with sufficient accuracy to attack with a high probability of success.

Area ASW is the coordination of search ahead of the main force, along the threat axis. Detection and localization are the objectives, with destruction if possible. At best, area ASW is conducted by units with endurance and potency: maritime patrol aircraft (MPA) at 150 nm out or towed-array equipped surface units 30-50 nm out are most common. If the air unit has magnetic anomaly detection (MAD) as well as sonobuoys (http://www.explore-airplanes.com/air_travel/S/Sonobuoy.html) then so much the better.

Local ASW is within the outer screen, 12-25 nm from the main fleet. Detection is strictly passive as the distance is still great enough for the HVUs to be safe. Once a contact has been made, helicopter ASW assets (with dipping sonar, MAD or sonobuoys) are rushed into the area. Three or more close passive contacts are enough for aerial delivery of torpedo (http://www.explore-weapons.com/weapons/T/Torpedo.html)es. Ship-mounted ASW weapons such as ASROC (http://www.explore-weapons.com/weapons/A/ASROC.html) are reserved for when a contact is too close -- generally less effective, their role is to distract the submarine from attacking and buy time for a more effective strike. In modern combat depth charges are never used, enormously ineffective they have been completely replaced by guided torpedoes.

If a submarine is detected after it penetrates to the inner screen the issue is getting weapons in the water, even if they are not accurately targeted. All and any efforts to distract the submarine from attacking the HVUs are made. Torpedo evasion maneuvers are also necessary.

A general maneuver tactic against submarines is a zig-zag. A submarine usually relies on passive detection, not risking active sonar or a periscope observation. So to determine where a unit is heading the submarine needs Target motion analysis (TMA). This requires several minutes of passive contact and if the contact starts to zig-zag this process must restart. The most effective unit to find and destroy submarines is another submarine. Called Hunter-Killers, they utilize the stealth advantage of submarines to track enemy submarines. The difficulty is that they have to be out of communication with the units they are protecting for most of the time to use this stealth. Usually therefore most submarines operate independently, having been given general rules of engagement (http://www.explore-society.com/warfare/R/Rules_of_engagement.html) (ROE) for reconnaissance, ESM and early offensive operations. Modern diesel submarines are almost as efficient as SSNs as Hunter-Killers. However diesel submarines lack the capability to stay with a fast moving battle group due to their slower speeds (~20 knots Vs. ~35 knots for SSNs) requiring them to be deployed long before operations in a particular area will commence, or force the battle group to slow down to allow there diesel submarines to keep up. Diesel Hunter Killer submarines or SSKs would generally be deployed along the “choke points” formed by landmasses or shallow waters to interdict enemy submarines long before they could attack the battle group while the SSNs would tend to stay with the battle group.

This article was derived fully or in part from the article Modern naval tactics (http://www.explore-military.com/cgi-bin/wart.cgi?v=Modern_naval_tactics&w=0) on Wikipedia (http://www.explore-military.com/cgi-bin/wart.cgi?w=1) - the free encyclopedia.

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http://www.fas.org/man/dod-101/sys/ship/docs/aswcncpt.htm#Littoral (http://www.fas.org/man/dod-101/sys/ship/docs/aswcncpt.htm#Littoral)


Littoral ASW


Littoral ASW operations protect naval forces, commercial and logistics shipping from enemy submarines, and thereby enable naval forces to project power ashore, conduct strategic sealift operations, and control or interdict sea lines of communications (SLOCs) that affect littoral objectives. In the context of US joint force operations, successful littoral ASW clears the undersea battlespace of hostile submarine influence and permits US and combined forces to maneuver at will to best employ their assets at the time and place of their choosing. In limited regional conflicts, the loss or crippling of a key ship could unacceptably disrupt joint or naval force operations. The political realities of many regional conflicts could allow an adversary to equate a stalemate at sea with a strategic victory.

The ASW systems and practices employed in the open-ocean are not necessarily those that work best in littoral waters. Littoral ASW requires a complementary set of capabilities that address the special circumstances of naval operations in littoral waters. The littoral battlespace’s complex, noisy environment undermines the effectiveness of acoustic ASW sensors optimized for deep water, open-ocean ASW. In this environment, increasingly quiet and capable submarines operated by potential adversaries further erode the position held by open-ocean ASW forces. Quiet threats operating in harsh environments increase the utility of non-acoustic and active acoustic sensor systems. To be effective, sensors must be able to automatically adapt to the environment.

Principles of Littoral ASW


Understand and prepare the battlespace for joint force's maneuvering upon the sea.
Deny enemy submarines influence in the joint operating area.
Prosecute enemy submarines as close to their operating bases as possible.
Emphasize integrated information connectivity and flexibility at all levels.
Adapt sensors and weapons to the operational environment to optimize effectiveness.
The accelerating rate of technological innovation gives increasing advantages to the navies that most quickly introduce appropriate new technologies into their fleets. This introduction process must be rapid, focused and include all aspects of procurement, training, operations, maintenance and support infrastructure. Close coordination of US Navy ASW concepts, programs, systems and operations will optimize the ASW force’s capability in a period of declining resource allocations.

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Coordinated, Multiplatform ASW Concept

Littoral ASW operations during periods of armed conflict should exploit defense-in-depth to maximize the flexibility of joint forces. These operations could occur against enemy submarines at their base (preemption), as they exit or return to port (port interdiction), as they approach the area of operations, threaten littoral sea lines of communication (SLOCs), and within the area of operations.

Preemption prevents the employment of enemy submarine forces by neutralizing submarines at their piers, and by attacking fixed support facilities essential to the effective employment of submarine forces. Because preemptive attacks deny adversary forces the ability to maneuver, preemption, if politically permitted, may offer the best balance between ASW effectiveness and economy of force.

Port interdiction offers opportunity to engage, monitor or tag adversary submarines before they can submerge. However, harbors and harbor entrances are particularly demanding environments for the employment of ASW systems. Thus, coordinated employment of appropriate sensors and weapon systems will be required to achieve optimal effectiveness in port interdiction operations.

Outside the area of operations, ASW forces have the flexibility to exploit maneuver and mass to defeat adversary submarines. This permits commanders to employ techniques such as barrier defense, defensive minefields and denial of logistic support opportunities. It also permits placing ASW forces at points along the threat axis where sensors and weapons may enjoy the benefits of more favorable environment, resulting in a higher probability of success.

SLOC protection may require ASW forces to protect large areas while placing a special premium on the effectiveness of coordinated ASW operations near chokepoints. These areas have noisy, cluttered environments that geographically concentrate both friendly naval forces and adversary submarines.


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Within the area of operations, finding and neutralizing enemy submarines will demand the assignment of significant forces to the ASW effort. Effective operations in the area of operations require numerous, coordinated ASW assets. Mêlée and flaming datum situations will fully stress our ASW systems.

Each scenario relies on coordinated, multiplatform ASW. The range of possible threats places a premium on timely and accurate information about adversary submarine operations, thus ASW commanders will require a responsive command and control architecture to effectively coordinate their forces. The concept requires commanders to balance the operational capabilities of available assets with mission objectives. These operational capabilities will depend on the assigned forces’ combat systems and materiel, training, doctrine, organization and leadership.

The mission objective of forward operating area ASW battlespace dominance directly supports the national military strategy. Successful achievement of this mission rests upon properly shaping and employing the manpower and equipment provided to implement the national military strategy.

Capabilities and Constraints

Task Imperatives. To conduct littoral ASW, naval forces must be able to:


detect, locate and target enemy submarines in littoral waters reliably,
respond rapidly and decisively to enemy submarine contacts that may last only a moment (fleeting contact),
employ integrated ASW systems (people, sensors, weapons and communications) with very high probability of neutralizing the target, and
provide all commanders with a common tactical picture of the undersea battlespace.
Programmatic Realities. Continuing ASW program budget constraints, and the increasing capabilities of the evolving submarine force threat, place additional imperatives upon all ASW programs. ASW programs must:


increase operator proficiency in the face of reduced manpower and equipment numbers. For example, through improved training programs,
shorten training pipelines by designing operator and technician "friendly" systems,
incorporate appropriate leading-edge technologies through shorter, innovative procurement processes, increased use of commercially available technologies (COTS), and adaptation of technologies not traditionally applied to ASW; and
reduce the acquisition and life-cycle support costs of systems so a greater portion of ASW resources can be focused on at-sea operations.
Within these constraints and in the most challenging ASW operations, coordinated, multiplatform ASW operations promises to provide the capabilities required of littoral ASW.

Coordination and Command, Control, Communications, Computers and Intelligence (C4I). Coordinated, multiplatform operations ensure the most effective sensors and weapons are used when and where they are most needed. Continuous awareness of the common tactical picture among ASW assets is essential to this concept. Assured C4I connectivity enables ASW forces to respond to fleeting contacts, integrate their collective knowledge to form this common tactical picture to best exploit their weapons’ capabilities.

All sensors, including those not historically associated with ASW, must be integral to the C4I network. For example, surveillance systems previously associated with only strategic indication and warning missions must also provide tactically useful information directly to ASW platforms.

Materiel and Weapon Systems. Optimization of materiel assets capable of capitalizing in a "plug and fight" environment is essential to coordinated, multiplatform ASW.


Capable C4ISR systems are required to collect and evaluate battlespace information.
Environmentally adaptive sensors, used for cueing and targeting, must efficiently find targets in an ambiguous battlespace environment and help ensure weapons reach their targets.
Effective ASW weapons, either lethal or nonlethal, and tags that overtly or covertly mark an adversary submarine and report locating data to various sensors, are required to neutralize the submarine threat.
Coordinated, multiplatform littoral ASW draws from the experiences and knowledge gained through open-ocean ASW. When appropriate, the equipment and practices employed in open-ocean ASW must be used in littoral operations.

The best sensor and weapons systems are those operated
outside the target's sphere of influence on our forces.

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Training and doctrine. Effective training and doctrine are required to achieve the close coordination and responsiveness necessary for successful littoral ASW. The training must be challenging and focused to develop and maintain ASW expertise. Many area specific, political, warfighting and environmental differences make littoral ASW noticeably different from open-ocean ASW. This mandates littoral ASW doctrine be continually developed, evaluated, revised and promulgated as the Navy’s experience, systems, operations and goals evolve. Successful execution of both new and existing doctrine requires proper training to develop and maintain proficient operators.

(New Equipment) x (Zero New Doctrine and Training) = ZEROOrganization and leadership. The organizational leadership structure required to support littoral ASW may also require modification from that of parallel open-ocean ASW structures. Organizations must be able to work towards the visions of the leaders while maintaining or improving an operational capability.



Conclusions and Recommendations

This concept addresses the capabilities required to conduct successful ASW and broadly defines the enabling capabilities required to achieve the mission objective of forward operating area ASW battlespace dominance. Much innovation is required to attain this goal of conducting fully integrated, multiplatform, ASW concurrently with power projection and other military operations. The limitations of current day systems and doctrine restrict today’s ASW to platform-centric operations conducted as an enabling phase distinct from the main warfighting effort to prevent unacceptable losses to enemy submarines.

As improved equipment and updated tactics, techniques and procedures are developed, the state of ASW will evolve from the sequential, platform-centric reality of today to the concurrent, network-centric construct of the future. To accomplish this evolution, we must:


Increase the emphasis on updating the tactics, techniques and procedures for ASW to optimize the employment of today’s equipment in the conduct of coordinated littoral ASW operations. This aggressive development and implementation of updated doctrine must continue to drive the evolution of concurrent, network-centric ASW as more capable equipment becomes available.
Establish a synergetic, systems approach to ASW in a Navy ASW Strategy to focus the efforts of the various resource sponsors to most effectively develop the required ASW capabilities.
Develop an ASW transition plan that provides a path from current and near-term capabilities through mid-term improvements and to the far-term to achieve the necessary future operational capabilities.
Establish an assessment process based on ASW warfighting tasks that is independent of platform. The "ASW System" should use this process to measure the effectiveness of current ASW capabilities and to identify and prioritize future ASW capabilities.
Update the training and doctrine to include networked, coordinated, multi-platform ASW capabilities concurrent with technological advances and tactical developments. Additionally, continue to develop, evaluate and revise training and doctrine as experience, systems, operations and objectives evolve.
Evaluate both current and emerging technologies, including those not typically associated with ASW applications, to identify and develop appropriate technological "advances" to achieve the required future ASW capabilities.
Definitions

Anti-Submarine Warfare:"Operations conducted with the intention of denying the enemy the effective use of submarines." Joint Pub 1-02

Battlespace: "All aspects of air, surface, and subsurface, land, space, and the electromagnetic spectrum that encompass the area of influence and area of interest." NDP-1

Battlespace Dominance: "The degree of control over the dimensions of the battlespace that enhances friendly freedom of action and denies the enemy freedom of action. It permits power projection and force sustainment to accomplish the full range of potential missions." NDP-1

Concept:

"A notion or statement of an idea, expressing how something might be done or accomplished, that may lead to an accepted procedure." Joint Pub 1-02

A concept is a recommended solution to an opportunity or challenge. "Concepts provide the foundation for evolution." Joint Vision 2010

Littoral: "Those regions relating to or existing on a shore or coastal region, within direct control of and vulnerable to the striking power of naval expeditionary forces." NDP-1

Littoral Anti-Submarine Warfare: as used in this paper, refers to issues pertaining to the neutralization of the littoral submarine threat.

Undersea Battlespace Dominance: The ability to deny threat submarine operations in the joint forces maneuver areas and their associated sea-based logistics support."

Undersea Warfare: "That segment of naval warfare which involves sensors, weapons, platforms, and targets in the subsurface environment." NWP 1-02