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Captain Ralph Enos was the Mk48 Project Officer from 1974 to 1977. He is currently with the Naval Undersea Museum in Keyport, Washington.

In the era of satellites, AA Vs, stealth aircraft, and C41, it is difficult to accept that the bumble torpedo is arguably the most sophisticated weapon of all. A modem torpedo is like a miniature submarine, minus the life support systems. It is, in effect, an autonomous underwater vehicle masking as an expendable weapon.

Torpedoes are difficult weapons to test realistically, and failure to test them realistically during peacetime caused great difficulties for American and German submarines during the Second World War. Stung by that failure, the United States Navy’s torpedo development and deployment communities went to extraordinary lengths to test torpedoes thoroughly and as realistically as possible in the postwar years, in the process erecting extensive and expensive test facilities and underwater ranges. Since the historical record of terrible German and American torpedo performance in the early years of WWII may have faded in the minds of a couple of generations of undersea warriors-who have not had to fire a torpedo in anger in more than a half century-I think it would be useful briefly to review that record, and what has happened since that bears remembering.

To begin with, the history of poor underwater weapon performance during wartime due to inadequate peacetime testing began in the First World War. British mines were unreliable when deployed. The British Elia contact mine was fitted with a mechanical detonator, rather than the German-designed Hertz-horn chemical-electric detonator. When these mines were planted, the mechanical linkage tended to seize due to marine organism encrustation. Two years passed before the British discovered these mines weren’t working. A program of mine stockpile surveillance, routine in the U.S. Navy today, would have revealed this defect well before the war. But the pre-war Royal Navy bad become complacent after nearly 60 years of peace (its last major combat was the 1854-56 Crimean War), and mine warfare was a low priority.

Mines are simple devices to test compared to torpedoes. Torpedo speed does not greatly exceed target speed, which puts a premium on estimating target movement and precise aiming. Modem torpedoes use homing to correct for aiming errors, but an acoustic-homing torpedo is susceptible to all the vagaries of sound in the sea-thermal layers, bottom or surface interference, counter- measures-as well as a target evading at high speed in three dimensions. On the other hand, torpedoes are recoverable after firing if they are programmed not to smash into the target.

Probably the most serious problem in test firing torpedoes is that they must not strike the target. This can damage the target and destroy the expensive torpedo. In the days of straight running dumb torpedoes, this was avoided by setting the torpedo to run deeper than the target’s keel. Since all torpedoes before WWII were air or steam driven and left wakes, observers had no difficulty in determining a torpedo’s path. Practice firing of torpedoes was concerned with aiming accuracy in azimuth, not in depth. No one knew, or cared, how deep the torpedo ran in practice firings. Depth control in torpedoes had been one of their most reliable features.

Testing a warshot torpedo entails its destruction and probably that of the target as well. This is a very expensive business and in peacetime years was avoided if at all possible. Components of the warshot weapon were tested separately and their sequential functioning assumed.

Between the wars, most navies developed magnetic exploders (called 11 pistols” in Germany and Britain) for their torpedoes. These devices promised to increase greatly the effectiveness of torpedoes by causing them to explode underneath a target’s hull. Such an explosion set up a huge gas bubble in the water which lifted the target’s hull; when the bubble vented into the atmosphere, the now unsupported hull underwent whipping which caused major structural damage, and for smaller ships, broke them in two. The magnetic pistol was set off by the change in the earth’s magnetic field sensed by the torpedo as it passed beneath the target’s steel hull. Depth of run now became crucial: too shallow and the torpedo would strike the target’s side, setting off the contact pistol but doing less damage; too deep and the magnetic distortion might be too feeble to detect.

Testing the magnetic exploder meant destroying a ship large enough to set off the device. In the U.S. Navy one such test was made-successfully-and the design was put under lock and key for security reasons. In the German Navy there were a couple of tests made; none was successful, but the device nonetheless was issued to the U-boats after the torpedo directorate had fixed the indicated problems. Neither navy tested their magnetic exploders in latitudes where the earth’s magnetic field differed greatly from the homeland.

Immediately after war broke out in September 1939, U-boat commanders began reporting torpedo failures, particularly torpedoes equipped with magnetic pistols. In April 1940, all U- boats deployed for the invasion of Norway and immediately experienced torpedo failures on a massive scale. At first the problems pointed to the magnetic pistol which may have lost sensitivity in northern waters where the horizontal component of the earth’s magnetic field is relatively weak, a problem exacerbated by close proximity to iron-rich rock along the fjords . The boats were ordered to use only contact pistols in Norwegian waters, but soon U-boats in the open seas also experienced magnetic pistol failures. Then, reports cascaded in of torpedoes running deeper than set and of contact pistols failing to detonate when they clearly struck the target.

U-boat commander Admiral DOnitz was furious and in despair. He seriously considered withdrawing U-boats from combat until the torpedoes were fixed. He got navy chief Grand Admiral Raeder to convene a board of inquiry to look into the torpedo scandal and if culpable negligence was suspected to court martial the apparently guilty parties. The board convened within a week of the beginning of the campaign and found that both the magnetic and contact pistol designs were defective, and that the torpedo establishment had some knowledge of these deficiencies before the war. They also found that the depth measuring gear used in test firings had given misleading data and torpedoes’ depth-settings should be recalibrated. However, deep running torpedoes continued to plague the U-boats and it was not until two years later that the real problem was identified. A fix for the contact pistol was rushed into service, and the problem quickly faded. The magnetic pistol fixes didn’t work well at all, and in time, DOnitz ordered them deactivated.

The most serious finding of the board was that the prewar torpedo establishment had not sufficiently or realistically tested new torpedo designs before the war. Senior officials were tried and condemned by court martial, served time, and humbled and chastised, were returned to duty.

This pattern of torpedo failures repeated itself in the American submarine campaign in the Pacific. Reports of torpedo failures began to trickle in as soon as submarines returned from patrol in December 1941, most of them complaints that torpedoes ran deeper than set. Torpedo failures contributed significantly to the failure of American submarines to do much to thwart Japanese landings in the Philippines-much as German torpedo failures had vitiated U- boat defense against British landings in Norway.

For reasons that are not completely clear, submarine command reaction to these reports was muted. Torpedo failures were viewed as excuses for poor aiming or unaggressive attacks, admittedly serious problems in some early American submarine patrols. It took awhile to shake down the submarine community and weed out cautious skippers, a not unexpected phenomenon in a navy that had not fought a major campaign on its own in 43 years.

The Bureau of Naval Ordnance rejected contentions that the Mk 14 torpedo was deficient, and did not run tests. Fleet submarine commanders, citing a severe shortage of torpedoes, also failed to test the Mk 14 for depth reliability, although the weapon is recoverable from such exercises. Such tests had to wait for Rear Admiral Charles Lockwood’s arrival at Fremantle in June 1942 as Commander of Southwest Pacific submarines. Lockwood arranged simple depth tests by firing dummy warshot-weight torpedoes at fishing nets. These showed that Mk 14 torpedoes ran an average of 11 feet deeper than set!

BuOrd quibbled about the validity of the tests, so Lockwood repeated them with much greater care. Same results! After more than a month of quibbling, BuOrd admitted the Mk 14 ran an average of 10 feet deeper than set, and recommended fleet units make appropriate adjustments. Much later, the Bureau discovered its depth-recording exercise equipment had been miscalibrated when depth was tested before the war.

Fixing the depth-setting problem did not quiet reports of malfunctioning torpedoes. Suspicion pointed to the Mk 6 exploder, which had been designed and tested in so much {unnecessary) secrecy before the war. Fleet commanders felt that once the depth problem was solved, the magnetic exploder would begin to pay great dividends, particularly in economy of torpedoes expended to sink a target. A single Mk 14 (with a relatively puny warhead) could sink a large ship if detonated under the keel, whereas three or four torpedoes might be required to sink the same ship if detonated by the contact detonator against its side. In 1942, a shortage of submarine torpedoes was a most serious problem. Under these circumstances, submarine operational commanders-including Lockwood-refused to allow disconnecting the Mk 6 magnetic feature. Nonetheless, some skippers did so anyway.

The magnetic exploder slowly but steadily betrayed its advocates. By early 1943, with Lockwood now commanding at Pearl Harbor, its unreliability was generally conceded, and ComSubPac ordered its use discontinued. BuOrd-turned on to the problem to some extent by Lockwood’s private correspondence with Bureau Chief Admiral W.H.P. Blandy-worked very hard to discover the magnetic exploder’s design flaws. 2 The problem was assigned to several naval and academic activities, to little avail . The fleet never was issued a fully tested, reliable magnetic exploder during the war.

Disconnecting the magnetic exploder was not the end of it. Throughout 1942 and the first six months of 1943, submarine skippers filed disconcerting repons of torpedoes that failed to detonate when impacting the target in the contact mode. The issue came to a head when USS TINOSA, commanded by LCDR Dan Daspit, on July 24, 1943 fired IS torpedoes at the dead-in-the- water 19,000 ton whale factory ship TONAN MARU ill, in broad daylight. Eleven of the torpedoes were observed to hit the target and fail to detonate. When Daspit returned to Pearl Harbor with his evidence, it was clear to everyone that there was a big problem with the contact feature of the Mk 6 exploder. Again, Lockwood arranged tests and discovered that the contact firing pin mechanism was insufficiently robust to strike the firing cap before the warhead was crushed in a dead-on 90° impact, supposedly the ideal situation. At shallower impact angles the number of duds decreased. A fix was kluged in the fleet and by October 1943, U.S. submarines-finally-deployed with decent torpedoes (albeit without a magnetic feature).

Similarities in German and American torpedo experience in World War II are remarkable. Torpedoes running deeper than set, malfunctioning contact exploders, magnetic exploder designs that did not work although tested and accepted before the war, one problem masking another, torpedo development establishments that insufficiently tested their designs before issuing them to the fleet-these were present in both navies. The principal difference between the two was the prompt German response to the crisis of April 1940, although this did not necessarily assure timely fixes. In contrast, American operational commanders were slow to react.

One of the most egregious aspects of both American and German pre-war torpedo establishments was that there was no independent test and acceptance organization. The same organization designed, tested, and accepted the weapons. We see now how this kind of system can breed complacency, arrogance, uncritical confidence in tested designs, a tendency to cut comers, and an incestuous insularity. Mindful of that, the post-war American Navy established an independent operational test and evaluation command.

BuOrd had little to do with fixing the bad torpedoes. They stonewalled admitting there was a problem and when this tactic was no longer realistic, were slow to provide a workable design. The fleet took the lead in operational testing and in designing a contact exploder fix. The magnetic exploder was simply bypassed. BuOrd’s poor response to a real fleet problem was felt keenly by Bureau Chief Blandy. In an often quoted mea culpa, he wrote:

“Even with the relatively meager funds available in time of peace, much of the work now being done after more than a year and a half of war, could and should have been accomplished years ago … That the work was not accomplished during peace or earlier during this war, or, so far as the Bureau’s records disclose, that no one either in the Bureau or at Newport apparently questioned the inadequacy of the design without such tests, shows a lack of practical appreciation of the problems involved which is incompatible with the Bureau’s high standards, and reflects discredit upon both the Bureau of Ordnance and the Naval Torpedo Station, Newport. The Chief of the Bureau therefore directs that as a matter of permanent policy, no service torpedo device ever be adopted as standard until it has been tested under conditions simulating as nearly as possible those which will be encountered in battle.”

The legacy of our WWII torpedo troubles has been a generation of mistrust between submariners and BuOrd and a proclivity for massive testing of torpedoes at all stages of development and production.

This massive testing became extraordinarily complicated when acoustic-homing torpedoes appeared late in wwn. Shallow, basically two-dimensional, test ranges-adequate (with a reliable depth recorder) for testing straight running, anti-surface torpedoes-don’t work for homing torpedoes. These torpedoes home in three dimensions, demanding much deeper water for testing and complicating recovery of heavy units. Their post-launch trajectories, even when the torpedo is functioning normally, are unpredictable. In the mid 1950s, the torpedo community began to build three-dimensional underwater test ranges, using torpedo and target transponder sound signals tracked by hydrophones in fixed bottom-mounted arrays. The first such range was installed in 1955 at Dabob Bay in the Hood Canal, near the torpedo test station at Keyport, Washington. In time, the need for greater operational area and depth, fleet training, and varied water conditions stimulated building additional underwater tracking ranges elsewhere.

An acoustic tracking range tests the homing performance of a torpedo fairly well-provided the dynamic behavior of the exercise weapon matches that of the warshot. But this test-as done in the overwhelming majority of peacetime torpedo firings-merely determines that an exercise-configured torpedo is able to acquire and home to a certain stand-off distance from a mobile torpedo-like target that acoustically and dynamically emulates a submarine. The torpedo is oot tested as to whether it homes close enough to actuate its warhead detonator, nor whether that would set off the warhead charge, nor whether a warhead so detonated would destroy the target. This is where the pre-WWII German and American torpedo communities singularly failed to do their jobs. We have done better since WWII-influenced in no small way by that failure-and SINKEXs are regularly held that evaluate the condition of our torpedo weapon inventory. Is this enough?

Sinking a stationary surfaced bulk with a noise-emitting source to attract a torpedo (a typical SINKEX scenario) is fine. It exercises the explosive train and one not particularly important acoustic mode. But it is far from a realistic test. The target is not underway, not evading, not using countermeasures, and most particularly, not submerged. The exclusively ASW torpedo Mk 46 can’t be tested realistically against a surface target at all. So bow do we test an ASW torpedo 11 realistically 11 as Admiral Blandy decreed so long ago?

The short answer is that we can’t test it in a way that simulates actual operational conditions that its users would encounter in battle. We must test the weapon system piecemeal. The best we can do is test those aspects of a weapon’s performance that we can observe directly and simulate those aspects where we cannot economically observe performance directly, being very careful to validate these simulations wherever we can.

We must rigorously and skeptically evaluate the results of these tests and simulations. We must continually ask “What if?” We must set conditions where our simulation can be extended to other situations-which the German torpedo designers did not do with their magnetic pistol. We must not assume one success validates a design-which the Americans did do with their magnetic exploder.

We should not be afraid of failure. No weapon design team is going to produce a perfect weapon straight off the drawing board. A weapon has to be shaken down in fleet operations for some time before its little flaws are revealed. The German depth-keeping balance chamber design was flawed because its seal permitted build up of pressure over time as the boat cycled its internal air pressure, biasing torpedoes so exposed to run deep. This defect was discovered accidently in January 1942, nearly two and a half years after the torpedo design first went to war.

In the U.S., post-war Navy, there is a tendency-driven by politics and funding issues-to bias test and evaluation for success. Failures are unwelcome. Any technical program manager knows how to rig tests to be successful, but do we learn anything that way? It is a truism, but we really learn through failure. If a weapon performs as predicted, we’ve learned nothing new. Only if it does the unexpected do we break new ground.

All this rigor, skepticism, simulation, validation, and testing increasingly sophisticated weapons against realistic targets on elaborate underwater ranges costs a great deal. The cost of building and maintaining test and evaluation ranges and testing torpedoes on them is large and some budget analysts question whether we can afford it, especially in an era when military downsizing is rampant and undersea warfare is in decline.

This was the situation in the 1930s when German and American torpedo designers were getting ready for WWII-on a shoestring. They scrimped on expending torpedoes on destructive tests; they extrapolated equivocal results in the most favorable way; they were not skeptical about their own testing gear; the same people who designed the torpedoes tested them and later proclaimed them fit for issue.

The early WWII torpedo troubles of the German and American navies is a cautionary tale of the problems that can arise when a navy takes its combat weapons for granted during peacetime. I suggest that the conditions for a repeat or this experience are growing in our undersea magazines. (Editor’s Note: Emphasis added.) We haven’t used torpedoes in combat in more than 50 years; virtually every other kind of non-nuclear ordnance has been combat tested during that time. I don’t think we can afford to make these mistakes again.


1. Bacon, Admiral Sir R.H., The Concise Story of the Dover Patrol (London: Hutchison & Co., Ltd, 1932), pp. 65-66; Sims, Rear Admiral William Sowden, The Victory at Sea, Classics of Naval Literature (Annapolis, MD: Naval Institute Press, 1984), p. 26.

2. Clay Blair, Jr., Silent Victory: The U.S. Submarine War .Against Japan (Philadelphia and New York: J.B. Lippincott Company, 1975), pp. 277, 403-404.

3. Cited in: Buford Rowland and William B. Boyd, U.S. Navy Bureau of Ordnance in World War H (Washington, DC: Bureau of Ordnance, Department of the Navy, 1943), pp. 105-106.

4. Clay Blair, U-Boat War: The Hunters, 1939-1942 (New York: Random House, 1997), p. 485.

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