The torpedo developed rapidly. From a shore detonated galvanic underwater mine, to a contact mine, to an explosive spar protruding from the bow of a submarine, and finally, the self-propelled, gyro-steered progenitor of today's modern torpedo, they have changed very little over the last century.
As with all good naval weapons, a hull to carry them soon followed. The preferred delivery vehicle of the torpedo, the submarine, evolved quickly. The first submersible, David, was little more than a ship whose steam engine smokestack extended above the water's surface. In a spar torpedo engagement against the USS New Ironsides, in October 1863, she caused significant damage. Both the Confederate and Union navies recognized the tactical benefit of such a ship and set out to fully develop a true submersible. The Confederate effort, named for its designer the CSS Hunley, cost the lives of five crews. She was raised each of the first four times for study and engineering improvement and upon her glorious first success, she delivered a fatal torpedo into the hull of the USS Housatonic in February 1864-fatal for both crews. In all, 40 Federal ships were impacted by torpedoes during the Civil War; nine of them survived. Thus began the battles under the sea.
The torpedo defense problem is a worldwide challenge. At a NATO maritime tactics course in Halifax, Nova Scotia, tactical scenarios that fused the various nations and specialties together with a common mission were of particular interest. The aviators, submariners, and surface warriors from all countries represented agreed that defeating submarines is the most ominous task we face. Yet, the salient issues impacting our ability to survive not to mention win-in a hostile submarine environment remain largely unexplored. The primary reason submarines drive fear into the hearts of warriors is their ability to get close and attack without warning. How do we both hunt submarines and defend ourselves from them?
Many articles have decried the sad state of our antisubmarine warfare capability; a single submarine-or the belief that one is present-can cause an entire operation to shift focus and direction. The hard truth is that our first detection opportunity may be the detonation of an impacting torpedo. How can we gain the initiative without relinquishing inordinate assets to a nearly futile task? The answer lays in defeating the torpedo-the only weapon for which we have not developed an integrated defense system for our state-of-the-art warships.
As rival submarine forces continue to out-quiet each other, we ignore the fact that the silent service has become just that. The argument that we need to be quieter because they are quieter ad nauseam just does not matter. Silent enough to get within weapons-release range of a target-a point in the water getting farther away with each new weapon-is quiet enough. Better batteries, air-independent propulsion, and hull coatings will continue to compound the problem. As technology improves, the likelihood that a first detection will be the "whoosh" of a torpedo launch-or even worse, the "bang!" of an impacting torpedo only increases.
In a recent multinational exercise against an attacking diesel submarine, the surface ship sonar operators failed to identify and respond to an incoming torpedo. After the initial torpedo attack, the operators examined the data tapes and learned how to recognize the torpedo signature. Even with this advantage, however, in subsequent attacks, the torpedo still was the first indicator of where the submarine lurked. Without knowledge of the submarine's location, the initiative to attack belongs to him alone. These are the historical and recent empirical lessons that cannot be ignored: we will not always know where the submarine is located; we may not detect or recognize the attack; our countermeasures may not be employed successfully.
A torpedo defense system would aid the sonar operators in identifying and responding to a torpedo attack. Unlike the exercises, a second chance to evaluate the attack and examine why the first torpedo went undetected is unlikely, even if it missed its mark. In war, the enemy probably will shoot multiple torpedoes in rapid succession. There is no time to replay the tapes and prepare for the next shot. We must be ready—semper vigilans.
There are seven fundamental elements to a Torpedo Defense System, and most of them can be incorporated into the ships we sail today:
Torpedo Detection . The NATO course used the same instruction we have all experienced in learning torpedo evasion. "You have hydrophone effects off the starboard bow; what do you do?" The opening argument is defunct. Did the ship really hear (or see on the display) the hydrophone effects? Many of our sonar teams today would not.
The towed array is useful for torpedo detection, but it is still imperfect. The system has an integration time delay associated with its operation and system alertment is, therefore, time late. If the ship is maneuvering frequently, the reliability of the array as a detection asset declines sharply. There are also inadequate automatic displays to alert the analyst, and with unresolved bearing ambiguity, the optimal ship's course change may not be executed. Although not perfect, the towed array can be used to detect and evade torpedoes, after training. The complete loss of this sensor in future hulls, however, would only weaken our defense.
A solution exists. Detection is critical in executing current evasion tactics and-more important-in winning the undersea battle. Initial torpedo detection depends on the sonar operator's ability to identify a torpedo launch or even better, indications of an impending launch. A real-time, automatic, hull-mounted detection system would help eliminate these problems. Possible solutions may be the WLR-9 and/or BQR-22. Removing these systems from decommissioning submarines and installing them in surface ships is a start in the right direction. They are standalone acoustic detection systems that can be installed and operated very economically. They provide immediate cueing and classification for torpedoes and other underwater acoustic signals.
At present, operational testing and evaluation are ongoing in the Arleigh Burke (DDG-51) with the SLX-I MSTRAP (multisensor torpedo recognition and alertment processor) system. Designed to cue on torpedo signatures received by either the SQR-19 or the hull-mounted SQS-53C sonar, this system includes such additional features as recommended evasion maneuvers and countermeasures employment.
High-frequency sonar also will become increasingly important to defense systems as the weapon technology results in later detection and thus, closer defense. A high resolution, high-frequency sonar used for queuing and targeting in conjunction with the onboard torpedo detection and queuing would provide a highly accurate torpedo detection and tracking system. This system would be capable of handing off a targeting solution for the defensive countermeasures and an offensive high-energy torpedo destruction capability.
Torpedo Safety . We have compounded the difficulty of reacting to an incoming torpedo further by limiting the water in which we can respond to the threat. We call it waterspace management; perhaps, more accurately, it should be called waterspace confinement. The driving logic behind this self-imposed restriction on our warfare is the need to prevent shooting ourselves (friendly fire is not friendly). Have we considered alternative solutions before imposing such restrictions on our survival? Is it reasonable to expect commanders in the heat of a torpedo attack to not shoot back unless they are in "good" water?
The same system that detects torpedoes would be able to classify the incoming as one of ours. An acoustic IFF would improve such an evaluation. Even a rudimentary transmission and response system would allow us to prevent the ills of friendly fire under the water. An encrypted system with changing codes would make this element even better. The final transmission to a torpedo identified as friendly could result in either deactivation for later recovery in a training environment or self-destruction, maybe even redirecting toward the target, in war. With only software modifications this system could be introduced today. There is no need to restrict the water and the warrior when we can restrict the weapon.
Torpedo Defense . Forging beyond the age-old analysis of whether to shoot the arrow or the archer leads to several acceptable alternatives-some of which already exist. In addition to defeating the archer (ASW) and the arrow (Anti-torpedo torpedo), ancient warriors often relied on shields and deception to survive on the battlefield. Deception equipment exists in the form of decoy devices. The shield concept, however, has no recent testing. After World War II, the U.S. Navy experimented briefly with kevlar nets that would protect convoy ships against rear-approaching torpedoes. These proved too brittle and the torpedo that was fortunate enough to aim directly for it would still burst through successfully.
A softer approach will work well. A nylon net with or without explosive detonation chord woven at regular spacing should prove much more effective. The net would entangle the torpedo propellers and the explosive would only have to damage the acoustic transducer to be successful. Calculations confirmed by Naval Undersea Warfare Center show that we could mount such a system of rocket-fired nets on the transoms of our ships. Floats and weights would keep the net vertical at a predetermined depth.
Prudence also requires the capability to shoot the arrow. Technology allows us to go beyond the traditional kinetic metal-against-metal approach. Breakthroughs in physics allow for a system of pulsed energy-a focused pressure wave-through the water that would destroy a torpedo. A pulsed plasma beam generated by a bank of transducers would emanate from a submersible phased array mounted within the hull of the ship. Similar technology exists today for commercial underwater applications to drill and crush rock.
For the torpedo that manages to escape all of these countermeasures, a double hull insulated with pressurized foam could minimize damage. The light inner hull would only require enough strength to restrain the foam pressure and detonate a fused torpedo. The foam would flood immediately the same compartment through which a penetration came. Less dense than water, most of it would remain inside the hull and cause less shift in the centers of gravity. It also would defeat any fire created by the explosion of the warhead by immediately displacing oxygen and breaking the fire triangle. Primarily a damage control element, the foam also serves as a ship-quieting feature, decoupling the inner hull and its machinery attachments from the sea.
Command and Control . While the concept of a sea combat commander is still in its infancy as a part of the battle group, it incorporates many long overdue changes. One commander applying all the resources of platforms that perform several missions can best decide where the focus of effort lies. The as yet unsolved aspect is that of the communications concerning several warfare areas now flowing on fewer radio channels. When the battle group needs to know why a surface ship is screaming toward the carrier at 31 knots and the radio nets are clobbered because of the patrol boats approaching from the West, how does the mail become prioritized? The best solution is to digitize communications using technology already available off-the-shelf.
Digitized voice communications have many advantages: storage, repeat and retrieval of administrative reports, prioritized start codes for transmissions of varying importance, and reduction of unnecessary radios (and thus, personnel) through multiplexing several digitized circuits onto the same frequency carrier, just to name a few. Complex warfare requires sensible information management.
System Automation . In order to further achieve reduced manning objectives, we should not overlook this element. Many of the actions an ASW team is trained to conduct could be expedited through automated steps.
Initial torpedo detection and classification by the WLR-9 should result in a digitized voice transmission within the ship and over the external communications circuit; the helm automatically steers to the optimum course; the deception elements launch at prescribed points in the maneuver; the anti-torpedo net is rocketed out from the transom; finally, the pulsed energy array extends below the hull and directs its beam toward the incoming torpedo the close-in weapon system for torpedoes. The equivalent air defense capabilities have existed for two generations of ship development. It is past time to consider such integration and automation for torpedo defense.
Platform Agility . The destroyer originally was designed to counter the torpedo threat. Its heritage began in the 1890s with an emphasis on speed to maneuver quickly into position and destroy torpedo boats. In essence, it was itself an outgrowth of the torpedo boat-the torpedo boat destroyer. During the World Wars, the same characteristics of speed and maneuverability proved the destroyer as the best platform to attack enemy submarines. These early destroyers were capable of speeds in excess of 37 knots. At 2,000 tons and less, they displaced less than a quarter of today's destroyers. Still, they could outrun most of the torpedo threats encountered even today.
Now a century later, we have endeavored to build ships capable of doing it all. The cost is in size and therefore a loss in speed. A small concession in size will yield ships that are again capable of outrunning the modern torpedo. If we assume, as we must, that the enemy will quickly develop even faster weapons and tactics that take advantage of these proposals, the agility built into our ships should go even further.
To counter a torpedo detection system optimized for a beam or stern shot, the enemy will undoubtedly learn to shoot effectively from the bow. As such, a 60-70 knot closure rate between the ship and the torpedo should be anticipated. Accounting for the ship's speed lost in a turn, our next destroyer should be capable of completing a 180degree turn in about a minute and with a turning radius of less than 500 yards to preclude losing the speed advantage to a transfer distance that would continue to close the torpedo in an evasive maneuver. In short, building a larger number of smaller, true destroyers designed to fight as bulldogs in the littoral against enemy submarines will prove most effective in neutralizing the torpedo threat.
Training. Finally, our training must include realism. Beyond the basic training to operate a torpedo defense system, we must expose the ASW team to real situations. There is little value in watching a green flare streak skyward several thousand feet from the ship. The value lies in actually being fired upon and learning how to recognize a real torpedo. Our operators and equipment must be tested against an attacker with the freedom to employ his fullest capability. With the requirement for submarine commanders to fire torpedoes regularly, it would stand to reason that every surface combatant has an opportunity to experience such a test with periodic frequency.
The school houses must go beyond the traditional approach of "You detect a torpedo, what do you do?" This approach is defensive and defeatist in nature. Courses should focus on the tactics of formation design, single ship aggressive ASW, choke point transits and littoral area clearing operations. Instruction by experienced commanders of other nations, and specifically, diesel submarine skippers is premium. To teach this in a classroom requires realistic, scenario-driven problems that teach the student to think before the attack. Red cell reactions and countermoves performed by seasoned veterans will add to scenario realism. The future warrior must operate in a manner to confuse the enemy with aggressive tactics before he can seize the initiative. Thus, we must train to understand more than the initial responses to an enemy attack we must train to prepare for our own attack.
Yes, we have come a long way toward quieting our submarines and ships-but so has our foe. With primarily acoustic sensors, we will most likely be victim to an attack before we detect the launching submarine. Our newest systems still to fail to adapt to the shifting balance of power under the sea.
The torpedo never has been challenged adequately. Since the American Civil War, when the torpedo claimed its first victim, there have been no innovations restoring the war-fighting advantage to surface ships. The torpedo remains as the cheap and overwhelmingly effective kill. Our ships continue to react to them instead of acting against them. The default initiative rests with the submarine. With confidence against the undersea threat-and thus, boldness in action-the initiative will shift to the surface combatant. As Admiral Farragut said during the Battle of Mobile Bay, "Damn the torpedoes... "
Lieutenant Capen is the Operations Officer in USS The Sullivans (DDG-68) and a frequent contributor to Proceedings.