Part Eight: Torpedoes in the Cold WarII
When WWII ended, various reviews showed that U.S. Navy torpedoes had made a major contribution to winning the war in the Pacific. U.S. forces had sunk more than 90 percent of the Japanese ships lost during the war and torpedoes had been involved in over half of these sinkings. Most of the problems with straight running torpedoes bad been solved and three new homing torpedoes had been tried in combat. One of these was a successful air launched anti-submarine weapon, one an anti escort weapon, and the third a 21 inch, 20 knot/4000 yard anti-surface vessel torpedo. All that, however, was the past. Was there a post war threat and, if so, what was it? The answer bad begun to emerge during the war as an increasing fraction of the military/foreign policy community came to view the Soviet Union as the most probable and most dangerous post war enemy. An early post war milestone was the so-called long telegram sent by George F. Kennan, who was then charged’ affair at the Moscow Embassy, to the State Department on 22 February 1946. The crux of the message can be conveyed in a fragment from the first sentence of Part V: “… we have here a political force [the Soviet Union] committed fanatically to the belief that with U.S. there can be no permanent modus vivendi … “. The telegram was widely read; James Forrestal had copies distributed within the Navy and it seems probable that most flag officers read it. If there had been doubt before, there was no doubt after the telegram-the threat was the Soviet Union.
The emergence of the Soviet threat and concurrent demobilization produced conflict, turmoil and confusion in the U.S. defense establishment. It was, nonetheless, clear that one of the prime naval threats was the already large Soviet submarine fleet and its potential for growth and improvement based on captured German materiel. From this it followed that ASW should be a major mission of the U.S. Navy. Given the composition and relatively small size of the Soviet surface Navy, fewer than 150 significant surface combatants, and the lack of dependence of the Soviet economy on sea borne commerce, anti-surface vessel operations seemed less important. Weapons, including torpedoes, developed during WWII were judged to be adequate. In subsequent developments missiles became the anti-surface vessel weapon of choice, making torpedoes relatively less important for this purpose.
It is interesting to note that the Soviet Navy apparently viewed the situation in substantially the same way and concluded that because of NATO’s large surface fleet and dependence on sea borne trade that naval surface vessels, particularly Carrier Task Forces, Amphibious Task Forces, and merchantmen should be the principal targets for their submarines. As a result, they produced a large variety of increasingly sophisticated and increasingly lethal anti-surface vessel torpedoes in the four decades following WWII.
The importance of ASW was formally recognized in June 1946, when the Chief of Naval Operations, Fleet Admiral Chester W. Nimitz, initiated Project GIRDER, a major research and development project with the objective of dramatically improving ASW. Research and development in ASW has remained important ever since and, in fact, it was the Navy’s top R&D priority until the spring of 1950. GIRDER embraced surface, air, and somewhat wishfully, submarine based ASW. New and improved platforms, sensors, weapons and doctrine were sought. Our interest here is on part of that spectrum, the role of torpedoes primarily as post WWII ASW weapons, and we will focus rather narrowly on that subject.
ASW Torpedoes 1945-1958
The initial post WWII submarine threat estimate was 100 to 150 modem Soviet sea-going submarines. There were forecasts that this could grow to the order of 300 by 1950. These estimates include at least four Type XXI boats and the possibility of 20 more. U.S. Navy WWII ASW systems were moderately effective against the S and SHCH classes but could not deal with the Type XXI part of the threat. The Type XXI was rated at 17 .18 knots for one hour and in U.S. trials made 15.2 knots for 1.2 hours. Furthermore, the Whisky class of Soviet submarines was under development and began service in 1950. While not as capable as the Type XXI, it was a serious challenge to early post WWD anti-submarine forces.
The dominant U.S. ASW forces were destroyer type vessels and aircraft, both carrier and land based. Homing torpedoes, Mk 24 and later Mk 35, largely displaced depth charges and bombs as the principal airborne ASW weapons. These torpedoes were replaced by Mk 43 (ca 1951), Mk 44 (ca 1957) and later (ca 1963) Mk 46. The initial emphasis for surface vessel ASW was continued use of WWII weapons, improved forward thrown weapons and improved sonar. High speed, deep diving homing torpedoes were desired, but in the immediate post war years, they were far from adequately developed. Around 1950 the Mk 32 active homing torpedo was resurrected and put into production as a surface vessel ASW weapon. These torpedoes were launched over the side by a launcher reminiscent of those used in Pr boats. This was probably the first homing torpedo in service use on U.S. ASW surface vessels. At about the same time, the Mk 35 torpedo finally entered service. It was carried by destroyers equipped with fixed 21 inch tubes, usually in the after deckhouse or on the 0-1 level, and by submarines. Twenty-one inch tubes of various kinds were also used for launching Mk 35, Mk 37 and Mk 48 torpedoes from surface vessels without much real success. Currently the only surface vessel ASW torpedo in use is the Mk 46 launched from Mk 32 tubes.
The Submarine Force was initially left out of both ASW and strike warfare, the two major Navy missions and relegated to a fleet warning and protection role. This situation changed rather quickly. Submarines became an important part of strategic warfare, with SSGs and eventually SSBNs as platforms for long range missiles. SSKs and SSNs, improved sonar, new ASW torpedoes and new tactics led to a major role in ASW. The starting point was, however, inauspicious. As of August 1945 all of the submarines that operated in both Allied and Axis navies bad sunk 20 German and 9 other submarines during WWI and 83, including 20 Japanese and one U.S. Navy, submarines during WWII. Almost all of the submarines were surfaced and attacked by submarines that were either surfaced or at periscope depth. Thus most of these attacks were, in essence, attacks against surface targets that happened to be submarines. The exception was HMS VENTURER’s attack on U-864 while both were submerged to periscope depth. This remains the only known actual sinking of a submerged submarine by another submerged submarine. As of the end of WWII, there were no submarine launched weapons for use against submarines submerged below periscope depth. Furthermore, the involvement of submarines in ASW was opposed by the surface and aviation ASW communities and even by some of the submariners. Early post war submarine conferences did, however, discuss submarine based ASW and recognized several concomitant needs including new acoustic homing torpedoes. One result of these conferences was the establishment by the CNO of Project KAYO, which permitted the submarine service to organize “to solve the problems of using submarines to detect and destroy enemy submarines.” Perhaps the most significant response was the establishment of SubDevGroup Two, which combined scientific talent and operational submarines to tackle ASW problems. The first postulated submarine target was an eight knot, cavitating snorkeler. Since their depth was known (fixed by the snorkel), such targets were vulnerable to conventional straight running, set depth torpedoes (Mk 14 or Mk 16) or to the late WWII Mk 28 homing torpedo. The first true anti-submarine homing torpedo to enter service with U.S. Navy submarines was the passive homing Mk 27 Mod 4, which began service with the fleet in 1949. This torpedo, with its 15.9 knot speed and homing in both depth and azimuth, was potentially effective against fully submerged early post war Soviet diesel submarines operating at speeds up to about 10 knots. Its performance in exercises against tame targets was encouraging. The Mk 27-4 was soon joined by the faster, 27 knot, but enoanously complicated and expensive, passive/active homing Mk 35. Both remained in service into the early 1960s. About 4000 Mk 27-4s were produced and it was carried as part of the loadout by most submarines. Successes with the Mk 27-4 encouraged the development of the 26 knot Mk 37. The Mk 37, which entered service in 1956, was designed against the threat of Soviet diesel submarines with some classes capable of 16 knots sub- merged. The number of these submarines grew from under 200 to around 350 boats while the torpedo was being developed. In this role it was an effective counterthreat. The first Soviet submarine launched, homing anti-submarine torpedo, SET-53, did not enter service until 1958 at the earliest. This timing is consistent with a Soviet strategy of building a large submarine fleet while largely ignoring ASW.
ASW Torpedoes Since 1958
In September 1954, even before Mk 37 was issued to the fleet, USS NAUTILUS (SSN 571), was commissioned. The performance of NAUTILUS was nothing short of revolutionary. Further, in 1954 the Soviet military press began to discuss nuclear power including ship propulsion. The prospect of Soviet submarines with performance comparable to that of NAUTILUS put U.S. Navy ASW back to a position comparable to 1945 ASW with the threat Type XXI submarines. The new threat was highly maneuverable submarines with effectively unlimited submerged endurance at speeds in excess of 20 knots (23.3 knots for NAUTILUS). Existing U.S. ASW weapons were ineffective against NAUTILUS. It is sometimes said, not unreasonably, that nuclear powered submarines wiped out 10 years of ASW research and development. The Soviet threat materialized in 1958 when the first Project 627 (NATO November class) submarine (SSN) was completed. The November class, though noisy, was credited with 28-30 knots submerged, a speed then matched’ by only one service torpedo, the air launched Mk 44. In 1959 the first Soviet Project 658 (Hotel class) SSBN was completed. This development further exacerbatedthe ASW problem by requiring not only screening against SSNs, but also detection and tracking of stealthy SSBN targets. Strategic ASW had been born.
Airborne ASW since 1958 has involved fixed wing land based, fixed wing carrier based, and rotary wing aircraft. Fixed wing aircraft have been fitted with sonobuoys and magnetic airborne detection (MAD) gear. Rotary wing aircraft have carried sonobuoys and more recently dipping active sonar. The primary ASW weapon has been the lightweight homing torpedo. In 1957 the 30 knot Mk 44 began to replace the much slower Mk 34 and Mk 43 aerial torpedoes. Thirty knots is adequate for attacking 20 knot targets including most of the 1948 Soviet submarine fleet, but essentially ineffective against 30 knot targets, in particular the November class. The U.S. Navy established a panel of distinguished civilian experts to study, among other submarine issues, anti-nuclear submarine warfare. This study, known as the NOBSKA study, concluded that the only possibilities were effective 45 knot homing torpedoes or nuclear weapons (torpedoes, bombs, depth charges or missiles) that could be detonated close to enemy submarines. The high speed homing torpedo posed serious problems. It was not until 1966, more than 10 years after the NOBSKA study, that the 45 knot Mk 46 homing torpedo began replacing the Mk 44. Aircraft again had a reasonable chance of killing 30 knot submarines. The comparable submarine launched torpedo, the 55 knot Mk 48, did not begin to enter service until 1972. This balance was, however, precarious and from the U.S. viewpoint tilted the wrong way when the 45 knot Soviet Project 705 (Alpha class) submarines appeared. This class had a checkered history, but the threat, though ultimately short lived, was real. A 45 knot submarine requires a 65 knot homing torpedo as an effective countermeasure. The U.S. Navy response was the 65 knot Mk 48 ADCAP and SO+ knot Mic SO. As it turned out, subsequent Russian submarines have been slower. under 35 knots. but quieter. The Mk 50 was not procured in quantity and the Mk 46 remains the primary airborne ASW weapon. The current state of this cat and mouse game is quite properly classified.
Surface vessel torpedo ASW bad much in common with airborne torpedo ASW. Although the Mt 2 torpedo launching system with the Mic 32 and other torpedoes persisted for a time, in 1958 the Mk 32 torpedo tube. often in trainable triple tube nests. and the Mk 44 torpedo became the premier ASW weapons of destroyer type vessels. The problems were identical to those encountered with air launched torpedoes, mainly the Mk 44 was too slow to deal with 30 knot submarines. In due course the Mk 44 torpedoes were replaced by Mk 46 torpedoes launched from the Mk 32 torpedo tubes. The same tubes could also accommodate the Mk 50 torpedo, but it seems probable that none of these were issued to surface vessels for other than test firings.
There have been other surface vessel ASW torpedo launching systems including GREBE. RAT and ASROC all of which launched torpedoes. as payloads of missiles, into aerial trajectories. In this way it was possible to achieve large standoff distance and short deadtime. Of these. only ASROC became operational. It was a rocket launching system with a payload consisting of either a lightweight torpedo or a nuclear depth charge. The maximum range was 10,000 yards. The IOC for ASROC was 1960. It could be launched from box launchers or from some railed launchers on destroyers and cruisers. The nuclear version of ASROC was withdrawn from service in 1989 and the torpedo carrying version in the early 1990s.
Submarine based ASW suffered the same ignominious setbacks as other forms of ASW. Diesel submarines even with the new Mk 37 torpedoes were no match for targets capable of sustained submerged speeds in excess of 22 knots. The NOBSKA study’s conclusion that either nuclear warheads or much faster homing torpedoes were needed was also valid in submarine versus submarine engagements. There was, however, another consideration; the attacking submarine needed at least as much submerged speed and stealth as the target to get within and maintain torpedo range. It became apparent that the nuclear powered submarine threat required both nuclear powered ASW platforms and new torpedoes to counter it. The new submarine launched torpedoes were the Mk 45 heavyweight with a nuclear warhead (IOC 1960 approximately); the Mk 48 heavyweight (IOC 1972); and the Mk 48 ADCAP (IOC 1989). Here too the driver was the Soviet submarine threat, which included about 100 nuclear powered submarines of all classes. Heavyweight torpedo development seems to have lagged badly behind the submarine threat. Even since the end of the Cold War the silent conflict of submarine versus submarine has continued. At the present time this conflict seems likely to continue, though at a slower pace and with further changes in platforms and weapons.
Some current uses for torpedoes do not fall neatly into any of the categories we have used. One of these is the use of lightweight torpedoes as the payload for the CAPTOR (Mk 66) mine. CAPTOR is a moored, deep water ASW mine that detects and evaluates passing targets. Appropriate targets are attacked by launching a Mk 46 Mod 4 torpedo upward. Another application is the conversion of Mk 37 torpedoes to Mk 67 mines. The Mk 67 mine is submarine launched and self propelled for remote planting.
Torpedoes are still important submarine weapons, though perhaps no longer totally dominant. They now compete with self propelled mines, tube launched missiles and vertical launch systems. Further, torpedoes themselves will continue to change, the Russians already have the jet propelled, SHKVAL reportedly capable of 200 knots. A Tomahawk launched torpedo has been proposed. There is a crying need for anti-torpedo defense and for this purpose short range, high speed torpedoes may be the best solution. The most significant current U.S. programs appear to be directed towards simplifying the inventory. The Light Weight Hybrid Torpedo is one step in that direction. U.S. torpedo program funding (total procurement and R&D) has declined from over $500M in FY96 to a requested $119.8M for FY98 and about $140M for FY99. However, Forecasting is difficult, especially when you try to do it for the future” so I’ll leave that to the courageous cadre who undertake such tasks.
The first of these eight articles appeared in the April 1996 issue of THE SUBMARINE REVIEW. They seem to have already provoked a significant amount of discussion and I hope it will continue. Torpedoes in the U.S. Navy have a fascinating history. They represent a microcosm of advanced technology. They played a major role in WWII. In addition to technical difficulties torpedoes have demonstrated most of the managerial and bureaucratic problems to which a weapon system can be subjected. A few of the lessons that seem apparent to me are:
- Weapons are the tools of the operating forces. Feedback as to operational performance must not only be accepted, but actively sought and used to eliminate defects and improve the performance of weapons.
- Inbreeding is very dangerous. It can lead to omissions and commissions and these produce faults and defects that are both difficult and embarrassing to rectify. The critical design review, among other tools, is aimed at avoiding such problems. To be effective the review must be independent and rigorous. The entire U.S. torpedo program from 1922 through 1941 suffered from this problem.
- Weapons must be tested, again independently. but also in as nearly as possible combat situations. Such testing is admittedly very expensive, but not testing can be even more expensive. Pre-WWII torpedoes were inadequately tested . Critical defects turned up in the Mk 10, Mk 13, Mk 14 and Mk 15 torpedoes and the Mk 6 exploder years after they were issued to the fleet or, in the case of the Mk 6 exploder, declared ready for issue. WWII homing torpedoes might also have benefitted from further testing. This criticism must. however, be muted because getting homing torpedoes into use during WWII, especially against submarines and escort vessels was critically important. The time from the beginning of development to first combat firing for these torpedoes was less than 18 months. Furthermore, early use in combat probably should be considered as operational testing. The crucial question is, are current production torpedoes being adequately tested?
- The risk of trying to do too much too soon must be recognized. Technical risk analysis must be particularly rigorous. Careful examination from many perspectives is crucial. Validating a single analysis is not enough. The Mk 6 magnetic influence exploder and the Mk 35 torpedo were striking examples of this sort of problem.
This is by no means either a particularly original or comprehensive list. These points have been made before and there are no other points or examples. What they have in common is that they all involve asking hard questions. There are now management tools for finding many of the hard questions and there are people who seemingly instinctively ask these hard questions. Both should be used rather than subverted or ignored. All this is well known to good program managers. Sometimes, however, even well known lessons are overlooked or must be learned again.
This series of eight articles is now finished and I would like to acknowledge the generous help that I have received from many people. It is impossible to cite all of these individuals and I apologize for oversights. I have had constant help, advice and encouragement from Richard I. Boyle, David E. Cohen, Captain Thomas D. Grimm, USN(Ret.), Thomas I. Pelick, Rear Admiral Maurice H. Rindskopf, USN(Ret.), Rod Rupert and Douglas A. Shireman all of whom are good friends and who contributed more than they know. With respect to specific points and issues Captain Frank Andrews, USN(Ret.), Captain Charles Bishop, USN(Ret.), Professor Harvey Brooks, Captain Harry Caldwell, USN(Ret.) Admiral I.J. Gallantin, USN(Ret.), Professor M. Gannon, Professor R. Gannon, Rear Admiral Jeffrey Metzger, USN(Ret.), Dr. Robert Plummer, Vice Admiral George P. Steele, USN(Ret.), also good friends, have generously contributed their expertise. NARA archivists especially Marjorie Ciarelli and Barry Zerby and the Upper Arlington Public Library librarians especially Christina Brawner; and Pam Lingbloom and Barbara Moe at the Naval Undersea Museum in Keyport provided important assistance in locating reference materials. Finally, our outstanding editor Captain James C. Hay, USN(Ret.) has been enormously helpful and a constant source of encouragement. As usual none of these is in any way responsible for errors of omission or commission which are mine alone.
A Persuasive Argument, 1904
“My beloved submarines are not only going to make it damned hot for the enemy .. but they are going to bring the income tax down to threepence in the pound.”
(Admiral Jack Fisher, 1904)