A new attack submarine, the SSNX, has been conceived and its characteristics are being justified to insure the necessary funding for this program. However there has been no mention of how this SSNX complements its primary weapon — the anti-submarine torpedo. R. c. Gillette in his Submarine Review article of July 1983 noted the desirability of building a submarine to optimize the effectiveness of its major weapon, while Dr. Richard Pariseau in a Proceedings article of July 1983 suggests a different context for future use of the ASW torpedo then the expected one-on-one situation against what he terms, a “passive target.” These premises, which appear sound, suggest a need to examine the direction being taken with the SSNX designs relative to its ASW weapon compatibility, or conversely, the kind of ASW torpedo needed to best complement the SSNX.
The SSNX concept is basically an improved ASW submarine with capabilities for secondary missions. It will provide an even quieter submarine than today’s best attack boats. It will’ be faster than the 688. It should provide the improved acoustic capability necessary to meet the threat of likely sound quieting of enemy submarines and give good passive ranges out to the maximum employment range of the ASW torpedo. It should also be more able to handle an expanding number of missions including under-ice ASW. Bence, it appears to be a submarine which with the right weapons, is well designed to meet the threat of the 90s.
But what sort of primary weapon–the ASW one-is then indicated for use with this highly competent platform to best engage enemy submarines which are likely to aggressively counterattack and be protected by coordinated multiple forces, as described by Dr. Pariseau in his Proceedings article.
ASW Torpedo Stealth
The stealth of the SSNX seems to call for an ASW torpedo which is very quiet and covert. This means wakeless as well. The entire weapon system, platform plus weapon, can then miximize the element of surprise in its attack. With a growing capability of enemy submarines to countermeasure incoming torpedoes and counterattack with their own torpedoes, surprise is at a premium.
Today’s torpedoes are electronically guided, giving them increased hitting precision. This makes them particularly susceptible to countermeasures. The need to have a torpedo that is not detected in time for its target to adequately take countering actions is apparent. Although today’s highly sophisticated torpedoes have electronic means to counter most of a target’s countermeasures, past electronic warfare (EW) experience has shown that shortly after the introduction in way of a new electronic technique, the enemy has produced an effective counter to it. But sufficient warning time to counter efficiently bas been necessary. For example: when in WWII the Germans unveiled the radio-guided, bomb in a mass air attack against Allied shipping at Bar!, Italy, some 16 merchant ships were sunk and 9 badly damaged in the single attack. However, within two months, a similar type of attack on a concentration of Allied ships in Salerno Harbor was thwarted by 2 U.S. destroyer escorts who jammed the radio signals to the German bombs. The DEs had been hastily configured with high-power jallllling transitters which were set to the bombs’ guidance-frequency. Thus, just one ship was hit by a German bomb! In fact, the EW history of WWII as well as that for recent wars have shown the considerable susceptibility of electronically guided weapons to electronic countermeasuring. Even for covert high speed weapons which produce short warning times, EW countermeasures can be successfully activated. This was illustrated by the use of chaff in the Falkland Islands War to decoy Argentine, aircraft-launched Exocet mdssiles away from their targets.
The torpedo is a slow weapon. It takes six or more minutes to go 10,000 yards–a reasonably close firing range for today’s terminal-homing ASW torpedoes. This means that if the torpedo making noise in being launched and in its trajectory, gives its target sufficient time to carry out effective evasive maneuvers, i.e. run away at high speed from the torpedo as well as activate countermeasures coodination with target maneuvers. Moreover, when under the sea, more time is required for the effective use of countermeasures than in the environment of air. Getting off-board jammers or noise decoys into place well clear of a submarine takes a considerable period of time. Renee, a torpedo which is detected a few hundred yards away may still prevent effective evasion measures.
The element of stealth should also be built into the ASW torpedoe’s guidance and homing system. Thus, a quiet or passive method of guidance, i.e. wire guidance and three-dimensional passive acoustic homing, are best used, with a passive acoustic sensor on the submarine providing accurate ranges to the target. The employment of active acoustic target localization by either the firing submarine or torpedo should only be a last-second effort. A target which can be heard passively at long range by a firing submarine should be detectable by a torpedo at a much closer range. To fire at an enemy submarine whose position is so poorly known as to require an active terminal-homing system of several thousand yards deny the value of a quiet torpedoe’s inherent stealth.
Systems analysis has shown present ASW torpedoes to have a high hit probabilities against a “passive target” in the one-on-one situation. This has produced very favorable exchange rates for U.S. attack submarines. But given a competent alerted target, the probability of hitting decreases and exchange rates approach a one-for-one ratio. However, while high speed in a torpedo and extensive counters for enemy countermeasures improve hit probabilities — even against and alerted target — exchange rates are likely to suffer because high speed in the torpedo should provide its target with increased warning time. Counterfire from an elusive target or response from protecting forces are the consequences.
Quiet covertness in the SSNX; ASW torpedo system would be of 11 ttle value if major improvements in sound quieting were made by enemy subs. Similarly, a breakthrough in non-acoustic means for detecting the firing sub or its ASW torpedo would evidently impact on torpedo characteristics and tactics for its use. If this happens, salvo fire of very high speed torpedoes is indicated. But such ASW weapons are necessarily different from the stealthy ASW torpedo. Moreover, to try to incorporate characteristics needed for massed fire into the stealth torpedo would probably make it prohibitive in cost.
The technology for a stealth ASW torpedo exists today — but its speed would be marginal against targets operating at very high speed. For such targets the high speed of the firing submarine becomes critical for gaining an intercepting firing position.
ASW Torpedo Speed
The SSNX is a very fast submarine which can close virtually all contacts to a favorable firing position. Only a few of the latest submarines have greater speed. Such subs, however, pose a hitting problem for a torpedo with equal or lesser speed — if the target submarine is traveling at maximum speed. But this is highly unl~kely in war, since the noise created by very high speed operations makes the submarine particularly susceptible to destruction by airborne ASW systems.
The importance then of very high speed in a torpedo is lessened because of a capability of high speed in the firing platform. Torpedo trajectories to intercept a target rather than chase it, appear to be practical. This is particularly true if the target is not alerted in time for it to change course and speed to create a stern chase by the torpedo. (Torpedo detection devices were mounted in WWII U.S. submarines. Noisy straight running torpedoes could thus be detected in sufficient time to maneuver sa as to outrun the closing torpedo or make it pas hartalessly down the side. Similar torpedo detection devices may be used by enemy submarines today.)
ASW Tropedo Hitting Range
It seems imperative that the planned, great advantage in detection range for the SSNX over potential enemy submarines — despite recognized efforts at their sound quieting and improvement of their passive acoustic capability be capitalized on to maintain high exchange rates. This advantage and the continued capability for detecting submarines at long ranges, combined with a capability to use the ASW torpedo stealthily at long stand-off ranges, provide the means for combatting enemy submarines in other than one-on-one situations.
To this end, not only should the torpedo of the SSNX be covert, but 1 t should also have the guidance necessary to produce hits against a target which may change course and speed during the many minutes the torpedo is in the water. Thus, to be consistent, the torpedoes’ guidance should be covert and non-alerting. Wire guidance provides this sort of capability, but it should be two-way in the information carried by the wire, i.e. directions from the firing submarine for control of the torpedo in its trajectory, and target information derived by the torpedo’s sonar back to the firing submarine. The latter capability provides the means for an opera tor on the sub to evaluate the target’s acoustic countermeasures and then give the torpedo the necessary tactical instructions to thwart the enemy’s countering efforts. Wire guidance also makes practical the efficient use of a covert torpedo at such long ranges that the firing submarine is not likely to be subjected to counterattack by either an aggressive target or by supporting units in company with the target sub1DBrine. Since wire guidance of forward launched torpedoes requires the firing submarine to be locked into a closing course during guidance phase, it is particularly desirable to have firing ranges as great as possible.
It is significant that a wire guided ASW torpedo which leaves a wake may provides valuable tactical information to aircraft protecting an enemy submarine. The location of the firing submarine at the time of firing may be disclosed and aircraft attack follow .
Quietness in a torpedo facilitates wire guidance whereas a noisy torpedo tends to blank its target’s radiated noise making guidance more difficult.
With the SSNX designed basically for ASW, it needs an ASW torpedo with a warhead of sufficient power to destroy the submarines of the ’90s. The Soviets see their submarines as the first line units of their fleet. As such they are steadily increaing the hardness of their submarines -using double hulls of increasingly greater thickness and greater separation. Big warheads on ASW torpedoes are thus required if high explosives are used. If a nuclear warhead is contemplated, a smaller nuclear warhead on the torpedo, with its far greater power would be used.
The submarine launched missile-carried ASW torpedo in development significantly, has too small a warhead to insure single-hit destruction — though it may create sufficient damage to start an enemy submarine towards its eventual destruction. A tactical nuclear warhead on the missile-carrier torpedo thus appears necessary to meet criteria which calls for destruction of a submarine target.
When the SSNX is projected costs to the better part of a billion dollars, the cost of its primary weapon is of little comparison significance. As Admiral I. c. Kidd, a former Chief of Naval Material, writes: “The cost of the First Stage of this weapon – the submarine itself — makes it ridiculous to short change the Sunday punch of such a very valuable platform.” However, the lower the cost of the ASW torpedo the greater should be the numbers in the stockpiled and hence the greater the freedom to use the weapon in battle and accept the high expenditure rates of modern warfare.
Even if the SSNX maintains a significant quieting and acoustic advantage over enemy submarines, there are environmental conditions in which neither submarine is likely to hear the other until the range between them is small. For this situation something other then the heavy ASW torpedo is indicated. A Lightweight, very high speed weapon, used salvoes, with acoustic terminal homing.
The technology is at hand to develop an ASW torpedo which properly complements the SSNX. Given the same planning and timeliness — as used with the SSNX to define the torpedoe’s characteristics, it should be developed and be operational with the arrival of the SSNX in the fleet. To try to make this new ASW torpedo be an all-purpose torpedo — for melees, antiship, to destroy oil riga, to hit radically maneuvering submarines making 40+knots, etc. –will only tend to degrade its primary capability and make it far too costly for wartime applicationf As Admiral Kidd notes: “With the ever increasing costs of high complexity, high capability weaponry, there will become increasingly aggravated instances of perceived need to cram just as much capability iato a single item as possible. There is a point of diadnishing returns in this philosophy. ”