Background
In the broader concept of general war with the Warsaw Pact and the execution of the Maritime Strategy in the Soviet littoral, some U.S. nuclear attack submarine (SSN) losses to air ASW were operationally accepted as a minor portion of total losses. This rationale wilt no longer survive a prudent examination of post-Cold War submarine employment.
If a major conflict had occurred between NATO and the Warsaw Pact, U.S. SSNs would have deployed en masse to the littoral waters of the Soviet Union (Barents Sea, Sea of Okhotsk, Sea of Japan, etc.) where an extremely target rich environment of Soviet submarine and surface units would have existed. The high rate of engagement with these units most likely would have resulted in a very rapid virtual destruction of the Soviet Navy. In spite of the large technological advantage held by U.S. SSNs, it was to be expected that this engagement would have involved significant U. S. losses, considered acceptable at the time, princi-pally due to reactive counterfire from attacked Soviet submarines and defensive anti-submarine warfare (ASW) mining. The percentage of these total losses caused by air ASW was rightfully considered too small to warrant the development of air defense capabilities for SSNs, particularly since any such devices would likely impact the number of offensive weapons carried and/or the employment of limited weapon launchers-capabilities badly needed in the expected target and engagement-rich environment.
U.S. Submarine Employment Within The New World Order
With the need now to deter regional war on a global basis rather than deterring global war on a regional basis, and to do so with fewer military assets, an evolving theory of The Great Black Fleet defines a key role for U.S. SSNs. As the only naval platform that by itself represents a survivable military capability across a broad spectrum (including reconnaissance, surveillance, strike, mining, injection of special warfare forces, ASW, anti-surface ship, etc.), and also unique in being invulnerable to threats of attack by highly proliferated chemical or biological weapons, the SSN is particularly appropriate for being the first warship on the scene as the far more powerful but less plentiful Carrier Battle Groups (CVBGs) transit to the crisis. It is not at all beyond the scope of imagination, particularly given the emphasis onjointness, that a scenario could exist where a distant on-station SSN, targeting through organic ELINT and COMINT capabilities, calls in a B2 air strike from Omaha, NE, to establish air superiority through destruction of early warning and C-cubed nodes for an approaching CVBGs strike aircraft to whom it passes post-strike bomb damage assessment.
Nuclear powered warships also have the enviable characteristic of being basically no more expensive to operate than they are to own. and for many reasons, an operating tempo of about 50 percent has evolved as a near optimum level for highest material and operational readiness, and for best crew morale. Typically. half the time a unit is at sea, it is at sea in relatively short local operations for training. For any given total force level. therefore. about 25 percent are forward deployed-typically for a period of about 90 days. For a force level of 60 SSNs, this equates to 15 units. If indeed the task is to deter regional conflict on a global basis with CONUS-based forces, and if this amorphous constella-tion of units were to move somewhat homogeneously throughout the world’s oceans, than statistically. an SSN would probably be within 1000 miles (2 days steaming) of any shoreline point, and many units could pile ·an within a few more days if needed. Analogous to antibodies distributed throughout a bloodstream. these quick reaction forces could watch, tag and commence a limited engagement of infections while full immune systems defenses are alerted, mustered and deployed. While so employed, individual SSNs would be in a familiar situation not unlike that expected and trained for. had the Maritime Strategy been execut-ed-alone, in potentially hostile waters, with no air cover.
However. with the collapse of the Soviet Union as a credible threat and employment of U.S. naval forces in such Desert Storm-like scenarios. the similarity of the employment algorithm stops there. It is unlikely that the target rich environments of the Soviet Bastions will exist, the far greater need to communicate with and to National Command Authorities (NCA) and other forces will impact the SSNs primary defensive suite-covertness. and it is clear that the only domestically acceptable loss rate for major naval vessels in such engagements is zero. In this light, even a small probability that an adversary’s fixed or rotary wing aircraft could attack or even detect an SSN unopposed is unacceptable. If submariners have no good response to the what if of airborne detection in the shallow waters expected of regional conflict scenarios, then the only acceptable alternative is that they not be so employed-a justified but unfortunate conclusion for such an intrinsically capable platform.
The Air-Delivered WeaJPOn Threat to On-Station SSNs
If a need exists for a submarine based air defense system, then it must be effective, reliable, and as inexpensive as possible. To be effective, the submarine must have the capability to launch such a device upon warning of an actual or imminent attack. Such warning must come from detection of either the air ASW platform before an attack (preferably) or its weapon following such an attack. To initiate an attack, the air ASW platform must detect and localize the submarine.
There are only a few submarine detection phenomenologies available to aircraft, all of which can be categorized as either passive or active in nature (either involve release of energy to the environment or not):
Passive Means Active Means
Acoustics Acoustics
Magnetic Anomaly Detection (MAD) Radar
Electrooptical (i.e., forward looking IR – FLIR) Electrooptical (i.e. , laser)
Visual
It is demonstratable that a properly operated SSN is generally assured of being alerted to and of having enough time to deploy a defensive device, before any of these detection methods result in a weapon being delivered from the detecting platform.
First, it is important to realize the significant tactical difference between detecting a submarine within some large volume of uncertainty involving tens or evens hundreds of square miles and then localizing that position to meet the attack criteria of + / -500 yards or so required to release a modem homing weapon. It is also important to note and accept the fact that very real tactical and equipment limitations preclude the aircraft, fixed or rotary winged, from releasing that weapon (essentially on top of the SSN), from an altitude of more than several hundred feet.
In addition, it is stipulated that any viable submarine launched air defense device will have the ability to be launched within a minute or less, and throughout an operating envelope of several hundreds of feet through likely on-station speeds, and would be autonomous after launch to permit full evasive action by the SSN. In short, if an SSN can be shown to have a reasonable probability of sensing an imminent attack some few minutes in advance, permitting the launch and deployment of a defensive weapon that would effectively mine the airspace several thousand feet above and several thousand yards around his targeted position. then it would have the general ability to preclude the consummation of that attack. If the unlikely event occurs where detection of the ASW weapon itself is the first indication of attack, than the release of a defensive anti-air warfare (AAW) weapon as an integral part of evasion tactics has significant value-added to the survivability of the SSN by largely precluding subsequent reattacks.
Since stealth itself is the submarine’s primary defensive suite, it is logical that it will employ every means to detect any active emission that represents a potential threat to this vital characteris-tic. Since basic laws of physics dictate that a given emission will be more detectable following one way transmission losses (from emitter to target) than following two way losses (from emitter to target and back to a receiver co-located with the emitter), then a generally true statement is that such active emissions will provide the submarine enough time to evade prior to detection, or if received signal strength indicates that detection is likely, to deploy a defensive weapon and commence evasion well in advance of any attack. Even the theoretical capability of employing high pow-ered, blue-green lasers to see several hundred feet below the surface (from directly above) is relatively easy for the submarine to technically counter through use of topside mounted broadband blue-green sensors.
As for passive sensors, the relatively short ranged MAD systems require that the searching platforms be at altitudes low enough that significant amounts of acoustic energy will be coupled to the water to permit passive acoustic alertment of the submarine at slant ranges of several thousands of yards. Particularly in the case of fixed wing aircraft, such initial detection does not general-ly result in an immediate release of a weapon, but rather a circling return to that spot (consuming many minutes) for a release at the next subsequent detection.
Although many submariners can claim they heard sonobuoys hit the water, this is not a reliable means of alertment. However, to have an accurate enough knowledge of these buoys positions to support weapon release, they too have to be released from an altitude low enough to result in a high probability that the submarine will key to the presence of the releasing platform. In addition, passive buoys often don’t provide sufficient positional granularity to meet attack criteria, and contact by these devices is generally followed up by a MAD pattern, the release of an active buoy or, for a rotary-winged aircraft, a cable suspended dipping active sonar from a hovering condition-all of which the submarine will react to before attack criteria can be satisfied by the aircraft.
Visual observation of a submarine at periscope depth is always a possibility, and probably still accounts for many if not most initial submarine detections. For no other reason than relative physical size of the target (periscopes and masts) and the seeker (the aircraft), a significant visual cross-section advantage lies with the properly operated submarine, and the aircraft that spots a submarine has most likely been under observation itself for some time. If the hazard of the aircraft’s presence turns into a threat of attack by a turn towards, then the submarine will react according-ly. At night, against a FLIR equipped aircraft, the visual cross-section advantage is largely nullified through a normal periscope. More and more, however, submarines are adapting technology to obtain an integral periscope IR capability themselves, if anything, providing an even greater advantage of relative detection of the hot aircraft engine exhaust over the near ambient temperature peri-scope. Many previous submarine defensive AA W schemes involved mast mounted weapons to be employed in such a scenario, but this approach fails to satisfy the need for rapid release from a broader range of operational depths and speeds.
In all, a modem submarine can reasonably be expected to detect the presence of an ASW aircraft in advance of that platform being positioned to actually drop a weapon. Equipped with an appropriate autonomous defensive AAW weapon, the submarine could effectively prevent that platform from safely achieving the low altitude on-top status required for release of its ASW weapon.
Operational Employment of An SSN Air-Defense Weapon Many scenarios could be constructed to highlight the employ-ment of a defensive AA W system by an SSN. For the sake of brevity, however, the entire set of such scenarios can be summarized by consideration of a few first principles:
- The SSN would employ in either a deliberate or a reactive sense:
- Examples of deliberate use:
- Mining vicinity where SSN will surface to disembark special forces
- Mining a datum generated by launch of offensive weapons such as Tomahawks or torpedoes
- Mine near-water airbases’ end-of-runway to engage low level departing or arriving aircraft
- Dispersed mining of larger areas where opposing air ASW forces are likely to conduct general searches to discourage same
- Examples of reactive use:
- Upon receipt of off-board real time intel message that ASW aircraft or helo alerted and enroute
- Upon visually spotting or ESM intercept alert of ASW aircraft or helo coming in
- Upon acoustic detection of low pass by ASW aircraft or helo
- Part of tactical evasion guidance if active sono-buoy lights off (prevent a first attack)
- Part of tactical evasion guidance if air delivered torpedo lights (prevents a second attack).
Characteristics of An SSN Air-Defense Weapon
To complement and summarize the preceding discussions, any device considered for the SSN defensive ASW requirement should adequately address the following concerns:
- Cost . A principal concern, and to reduce or eliminate developmental expenses, maximum use of existing developments should be stressed by employing commercial off-the-shelf(COTS) and government off-the-shelf (GOTS) technologies .
- Autonomous operation. Since it is operationally unsatisfactory to be required to target, release or guide any weapon from a vulnerable position (i.e., periscope depth), any considered device must be autonomous in nature, and upon release form a reasonable operational envelope (depths to 300 feet and speeds through 15 knots) be capable of independently detecting, classifying and engaging specified targets of interest.
- Information or control links to the releasing platform are not desirable for a number of reasons including cost, post launch constraints on the releasing platform, and salvo size.
- Passive operation. Since the device must be able to be employed in a prophylactic manner (i.e., to establish an air defense umbrella just prior to deployment of special forces or a Tomahawk launch), any search, acquisition or tracking phenomenologies employed must be passive in nature.
- Low observables. To preclude the device itself from either initiating or confiming a detection event, it must have credible prefiring counter detection envelopes which lie significantly within its capability to detect, classify and engage any threat.
- Target selectivity. Since operations could involve areas where non-valid targets exist, the device’s imbedded acquisition, targeting, and weapon release logic must include provisions for selectivity of engagement.
- Self-sanitization. Provisions (i.e, scuttling by means such as dissolvable salt plugs) must be included which limit the time duration of the threat established by the device. Such provisions shall also destroy or otherwise render inoperable any contained armament. A broad time to scuttle selection is not required, and all expected employments could be met through the selection of either a short (30 minutes or so), or long (2 hours or so) option.
- Detection/engagement envelopes. Subject devices should be capable of detecting and classifying appropriate threats at slant ranges of at least 8000 yards, and of engaging such threats to ranges of at least 5000 yards and to altitudes of at least 4000 The device should have intrinsic physical capability limitations which would allow safe overflight by friendly or innocent parties at reasonable altitudes.
- Platform capability. Subject devices should be compatible with planned characteristics of SEAWOLF and CENTURION SSNs, and should be back fittable, at reasonable ~st through either internal or external launching means, to Los Angeles and Sturgeon Class SSNs. Compatibility with some existing or planned countermeasure launchers is particularly desirable. Possible SSBN employment is a separate issue with a potentially different set of require-ments and considerations, and although likely, is not addressed at this time.
Conclusion
The U.S. SSN represents a far too cost effective and effective component of a post-Cold War National Strategy to allow artificial constraints on its employment due to the lack of a response to a definable, albeit, an unlikely threat to its survival. The synergistic melding of existing sensor, weapon and countermeasure technologies should provide an affordable and effective solution to this problem.
