The nuclear weapons of the united states navy 1945 – 2013 Don G. Boyer Haleiwa, Hawaii March 2013
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- MK 105 "Hotpoint" (and the W-34 Warhead)
- Part 7: Anti Submarine Warfare Weapons
- MK 105 Hotpoint
- MK 90 "BETTY" Depth Charge
- MK 101 "LULU" Depth Charge
- The MK 45 Astor Torpedo
- The ASROC (RUR-5A)
- The SUBROC (UUM-44A)
| Part 6: Still More Bombs
From the late 1940s to the mid-1950s, the U.S. Navy had slowly developed its nuclear delivery capability from carrier-borne aircraft delivery of very heavy weapons by large aircraft less than ideal for carrier deployment to the ability to deliver both "strategic" and "tactical" strikes from a large number of far more suitable aircraft. This section will finish up with the bombs that fit within this era of naval nuclear capability and then future sections will move on to the parallel development and deployment of specialized nuclear weapons for the anti-submarine role, fleet air defense and anti-shipping strike (roles that opened the nuclear option to fleet units other than aircraft carriers) and finally to what would evolve into a long-range strategic strike role with the advent of first the Polaris ICBM program and its descendants the Poseidon and Trident. MK 105 "Hotpoint" (and the W-34 Warhead) The Mk 105 Hotpoint bomb (a navy designation) was the first nuclear weapon developed for "laydown" delivery where the bomb would be dropped and retarded by a parachute until it would soft land instead of impact at high speed. The outer nose casing of this weapon would be blown off by a small charge just prior to impact and an inner reinforced steel "cookie-cutter" nose would absorb the shock of impact. Detonation of the weapon was via a time delay system that allowed for both airburst and delayed ground burst. The timer delay also allowed the Hotpoint to be used as a nuclear depth charge for anti-submarine and anti-ship use. (Underwater detonations were not only intended to be fatal for submarines, but as anti-task force weapons if needed, a fact made obvious by that famous film of the Operation Crossroads Baker detonation.) The MK 105 could be carried internally or externally on all the anti-submarine and most attack aircraft in the navy inventory, measuring either 8' or 12' long depending on how it was carried. The bomb was 19" in diameter and weighed about 1700 lbs. Yield was 10 – 15 kt. The MK 105, released in two Mods, used the W-34 warhead of which 600 were manufactured specifically for this bomb out of a total of 3600 W-34s manufactured between 1958 and 1962 for navy weapons that included the MK 101 depth charge and the MK 45 Astor torpedo. The MK 105 and the contemporary MK 101 "Lulu" depth charge (which had hydrostatic fusing) entered the navy inventory beginning in early 1958 and are historically significant in the nuclear weapons program because of the W-34 warhead used in both. This warhead was the direct result of a navy Bureau of Ordnance request in May of 1954 for development of a small depth bomb. The navy's weapons specialists (particularly famed WWII submarine commander CPT Henry Glass Munson who had earned a Master's degree in nuclear physics in 1952) contributed directly to the design of this warhead, demonstrating the increasing coordination between the military end-users and the civilian bomb makers, a working relationship of great importance to the strategic security of the U.S. in the years to come. The Los Alamos Laboratory was the prime developer of this weapon and conducted tests (Operation Teapot) at the Nevada Test site in February – May 1955 of a small boosted-implosion device also using a different method of initiating the neutron pulse that began the nuclear burning process among other system improvements. The W-34 warhead was also indicative of the great improvements being made in fielding weapons that needed very little "prep" time to have them ready to load on an aircraft and little maintenance required for keeping them active in the inventory until needed. Nuclear weapons have become more and more "canned" and ready to go ever since. The role of the nuclear weapons specialist, engaged in maintenance and care of deployed weapons, has all but disappeared from the navy as a consequence. The weapon used a fission design nicknamed "Python." As finally produced as the warhead for several weapons, the W-34 was by far the most scientifically elegant and utilitarian fission weapon of its day. In addition to its application to three navy weapons, the W-34 warhead was also used as the primary fission device in several thermonuclear weapons, including the MK 28 bomb. The W-34 also featured in several British weapons including a fission bomb and as the primary in a British thermonuclear weapon based on the MK 28. The W-34 warhead was 32" inches long, 17" in diameter and weighed around 320 lbs. With a yield of around 15 kt, the comparison to the "Little Boy" weapon with the same yield is indicative of the enormous advances made in ten years regarding the reduction of weapon sizes and weights while still achieving the required yields. (The W-34 warhead is also notable as the first warhead this writer ever worked on as a "newbie" nuclear weapons specialist at the navy's Nuclear Weapons Training Center at Sandia Base, New Mexico. ) The MK 105 could be carried by the AD in the attack role and the P2V, P3V, P5M, S2F and the HSS-2 helicopter in the ASW role. The MK 105 remained in the navy inventory until 1965, primarily as a laydown weapon, as the MK 101 Lulu had taken over the first-line role as the navy's nuclear depth charge. MK 15 Bomb The MK 15 (B15) bomb was the first "lightweight" thermonuclear weapon deployed and the first "production line" fusion weapon, some 1200 being produced between April 1955 and February 1957. (The production of 1200 megaton-range thermonuclear weapons in the space of two years says all that need be said regarding the capabilities of the weapons manufacturing infrastructure in the United States at the time.) During development the B-15 warhead was nicknamed "Zombie" and was tested in Operation Castle, shot Nectar, on 13 May 1954, yielding 1.69 MT, a yield that increased considerably in the production weapon. The MK 15 was still a somewhat limited weapon in that it was fused only for air and ground burst and had no retard capability. Produced in two Mods, the bomb entered service with the navy in April of 1955, with the last withdrawn from service in 1965. (The MK 15 was also supplied to Great Britain under Project "E".) The bomb weighed between 6850 – 7600 lbs. and was about 11' 8" long and 34.5" in diameter. Yield was 3.4 MT (about 150 times more powerful than the Fat Man bomb). The bomb could be carried by the AJ and the A3D. (In my estimation, the ability of the AJ to escape the blast of a weapon this size approached zero, and the A3D only slightly less so, a fact probably thoroughly depressing to aircraft crews, particularly with a weapon with no parachute retard capability.) With the deployment of this weapon to naval operations, the line between the "tactical" role expected of the navy in a nuclear war and the strategic role designated for the Air Force became subject to considerable blurring, a trend that would continue as the definition begin to apply more to what target was going to be hit with what weapon rather than a "role" of the services or the delivery vehicle. MK 27 Bomb The MK 27 bomb was the second thermonuclear weapon deployed by the US Navy, supplementing the MK 15. (The W-27 warhead was also used as the upgraded warhead for the Regulus I and II missile, the latter being canceled before it was ever deployed.) Designed for use against large strategic targets like its contemporary, the MK 27 was fused for air or ground burst. The A3 Skywarrior and the A5 Vigilante were the delivery aircraft. When employed for the A5, the bomb would have two expendable 275 gallon fuel tanks rigidly mounted to either end of the bomb. The A5 would use this fuel en route to the target and the entire package would be ejected aft on rails from the tube bomb bay of this aircraft. Theoretically, the tanks would help stabilize the bomb in its descent. This system never worked properly, and the A5 was later withdrawn from the attack role with this bomb, being converted to the reconnaissance/attack role (the A5 could still carry nuclear weapons on wing pylons if necessary, but this reduced speed considerably). The MK 27 was in the navy inventory from November of 1958 until October of 1964, its relatively short life due to the conversion of the carrying aircraft to other roles and the retirement of the Regulus 1. The bomb was 10' 5" to 11' 10" long with a diameter of 30" and weighed between 3150 – 3300 lbs. Bomb yield was 2 MT. Produced in three Mods, about 700 weapons were built in all. MK 28 Bomb The MK 28 bomb was the first to be designated as a "weapons system" because it was designed to flexibly adapt to many delivery options by being assembled into any one of five different drop "shapes," although the original version was built around the B-52 bomb bay which could hold four of the internal version of these bombs. Like all the more Modern bombs, delivery option settings became possible from the electronics of the carrying aircraft rather than by on-the-ground settings that couldn't be changed in flight. Because the MK 28 had an extremely long service life, it was produced in 20 Mods and variants and was in service long enough to undergo an improvement program to the later versions that added new electrical equipment, better and more insensitive high explosives in the W-34 primary, and increased safety features including three versions of the PAL safety interlocks (Permissive Action Link, basically a safety system operated only by human intervention according to strict protocols and initiated only when the President has given the orders to go to war. The MK 28 had CAT A, B and D versions depending on the bomb Mod.) Production of this bomb began in August of 1958 and continued through May of 1966 with some 4500 bombs produced and an additional 1000 W-28 warheads produced for the Hound Dog and Mace missiles. MK 28s were supplied to Great Britain as part of Project "E" for the Valiant bomber. (The W-28 warhead was adapted by the RAF to their own bomb casing design.) Versions of the bomb were: MK 28 IN (free-fall internal carriage); MK 28 EX (free-fall external carriage); MK 28 RE (parachute-retarded external carriage); MK 28 RI (parachute-retarded internal carriage; and the MK 28 FI (fully fused internal carriage). In each case the basic warhead assembly remained the same and the changes involved adding different fusing and parachute packages to either end of the warhead as well as different fins when needed. The external versions had fins that folded and were deployed by a small explosive charge when the bomb was released from the aircraft. This improved aerodynamics for the carrying aircraft and of course kept the bomb tail away from the flight deck when the aircraft was catapulted. The bomb was easy to maintain but came with a lot of extra "baggage" in order to convert the weapons from one delivery version to another. Depending on the version, the bomb measured between 8' and 14' 2.5". Diameter was either 20" or 22". Weight varied from 1980 lbs. to 2349 lbs. Yields varied with the Mod and are listed as: Y1 – 1.1 to 1.45 MT; Y2 – 350 kt; Y3 – 70 kt; Y4 – no accurate figures but probably 15 kt.; and Y5 – same as Y1. For the navy, the carrying aircraft were the A-3, 4, 5, 6 and 7, the P2V and the S2F. In the inventory for some 34 years, longer than any other nuclear weapon, the older Mods started to be retired in 1975 as newer weapons entered the inventory and the last MK 28 completed disassembly in April of 1992. The MK 28 gained international attention on 17 January 1966 when a B-52 collided with a KC-135 tanker at 30,500 feet over Spain. Seven men were killed in the accident. All four Mk 28 INs carried by the bomber dropped out of the stricken aircraft, three landing near Palomares, Spain and one in the ocean, resulting in much bad PR and the purchase and cleanup of a large chunk of Spanish soil. The bomb that dropped in the ocean was finally recovered by the navy and photos of this bomb have been published; one notes the bombs ancillary equipment is pretty battered but the warhead casing itself is intact. MK 39 The MK 39 bomb was a direct descendant of the MK 15 with parachute retardation for low-altitude delivery and a new gas-boosted primary (probably the W-34, which had just entered production). The bomb had improved safety features such as the use of thermal batteries, which also improved maintenance and readiness. The MK 39 was another weapon supplied to Great Britain under Project "E" for the Valiant bomber. The bomb's warhead was tested at full yield three times during Operation Redwing in 1956 (Shot Cherokee) and Operation Hardtack 1 in 1958 (shots Teak and Orange). The MK 39 entered production in February of 1957 and remained in the inventory until 1966. Only the A3D could carry the bomb for the navy. Produced in two Mods, the bomb was 11' 4" long with a diameter of 35" and weighed either 6650 lbs. (Mod 0) or 6750 lbs (Mod 1). Yield was 3.8 MT. 700 MK 39s were built with an additional 60 W-39 warheads built for the Redstone and Snark missiles. MK 43 The MK 43 was a more versatile thermonuclear weapon than the larger weapons preceding it, and could be used by a wide variety of aircraft. Successor to the MK 12, and also for the MK 11 penetration bomb, the MK 43 was designed at Los Alamos in 1956, with quantity production starting in February of 1959; 1000 weapons in two Mods were produced by October of 1965 when production ceased. (MK 43s were supplied to Great Britain under Project "E" for the Canberra and Valiant.) The MK 43 had two nose configurations, an armored steel spike (Mod 0) for laydown (it could actually "stick" in the ground, and there are photos of test weapons in this Mode) and a Mod 1 nose containing radar fusing for air burst options. The MK 43 also had parachute retardation options which could be "selected out" if the free fall option was used. The MK 43 was also fitted for the rigid fuel tanks of the A5 Vigilante system, but was never employed as such as the system never worked right. Depending on the nose option, the bomb was 12' 6" or 13' 8" long with a diameter of 18" and a weight of 2060 or 2125 lbs. There were five yields available. The Y4 yield used the fission primary of the bomb only and was 70 kt. The highest yield was 1 MT. The bomb was equipped with a CAT D PAL. Delivery aircraft were the A1, A-3, A-4, A-5, A-6 and A-7. MK 57 Bomb The MK 57 bomb was the smallest free-fall bomb in the arsenal. Designed for special tactical strikes as well as ASW operations, this lightweight, multipurpose fission bomb was the result of a specific design request by the Navy and Marine Corps. In addition to the wide variety of navy aircraft that could carry the weapon, three NATO aircraft were also certified to use the MK 57 – the British Nimrod, Dutch P-3 and Italian Atlantic. The RAF's Tornado could also carry the MK 57. Another Los Alamos designed weapon, characteristics for the bomb were approved in December of 1959 and quantity production began in 1963 with some 3100 weapons produced in six Mods. Production ceased in May of 1967. Several Mods, particularly the NATO weapons, had the CAT B PAL device. The bomb was removed from naval vessels in 1991, although dismantling of older Mods had started in 1975. The final MK 57 was disassembled by March of 1995. The MK 57 had selectable delivery options including free-fall air burst, parachute- retarded air burst, contact burst (bypassing the parachute) and parachute-retarded underwater burst (depth charge); the MK 57 was equipped with hydrostatic fusing and replaced the MK 101 Lulu in this role. The bomb had four yield options from 5 kt to a fully boosted 20 kt and was 9' 10” long and 14.75” in diameter, weighing between 490 and 510 lbs. Naval aircraft the could carry the MK 57 were the A-3, A-4, A-6 (Intruder), A-7, F-4, P-2, P-3, SH-3 (helicopter) and the QH-50C (DASH) drone helicopter. The DASH capability meant that the MK 57 could be carried by ASW ships such as the DASH-modified destroyers, the only time a bomb appeared at sea anywhere but on an aircraft carrier in the U.S. Navy. MK 61 Bomb Now the only nuclear bomb still available to the navy inventory, this weapon was designed as a lightweight multipurpose thermonuclear weapon used both tactically and strategically. It can be carried at high speeds by a large variety of aircraft and has been certified for use by aircraft flown by Great Britain, Italy, Belgium, the Netherlands, Turkey, Greece and Germany although none of these countries now have any of these weapons available to them. Produced in 11 Mods beginning in 1968, 3150 bombs were produced and about 1300 are still in the stockpile. The last Mod, Mod 11 was introduced in 1996 and is a reinforced casing intended as a penetrator weapon. It is reputedly capable of penetrating at least 15 to 25 feet before detonating. All remaining MK 61 weapons have been upgraded to the standards of the Mod 3/4 bombs with the most sophisticated of the security devices, full fusing options and PBX-9502 insensitive high explosives in the primary. Not only is the full range of fusing options electronically available to the carrying aircraft but also the yields, the MK 61 being called the “dial-a-yield-bomb”. Yield options range from .3 kt to 360 kt with variations between Mods as to which yields can be selected. Known yields are .3, 1.5, 10, 45, 60, 80, 170 and 360 kt. The MK 61 is 11' 10” long and 13.33” in diameter. Weight varies by Mod between 755 lbs. and 1250 lbs. for the Mod 11 penetrator. Highly versatile, modular and very efficient, this bomb will undoubtedly remain in service for many years. Four existing variations of this weapon are to be modified into one. An important new feature is a new tail kit with controllable flaps. The new system would dramatically increase the bomb's precision. Aircraft that could carry the MK 61 were the A-4, A-6 and KA -6, A-6, A-7, F-4, F/A-18 and the AV-8B Harrier. While the MK 83 megaton-range thermonuclear bomb is in the current US inventory, it is not a weapon currently used by the navy, and therefore the list of bombs used by the navy ends with the MK 61. Part 7: Anti Submarine Warfare Weapons While the earliest years of the U.S. Navy's involvement with nuclear weapons focused on the fleet developing the immediate capability to deliver nuclear bombs from aircraft carriers, early planning also included future development of weapons for specific roles other than tactical (or strategic) strike missions. Programs evolved within the navy planning structure beginning in the late 1940s to provide nuclear weapons for the anti-submarine warfare (ASW) role, ship-borne AA missile defenses and ship or land attack missiles and then the final strategic role of submarines which developed as the last and largest nuclear weapons program in the navy and probably the world. ASW was an obvious candidate for nuclear solutions because submarines were, even in the days before nuclear boats, very difficult to locate, pinpoint and sink compared to their surface sisters. WWII had seen great strides in conventional ASW tactics, pioneered in those early dark days of war by the Royal Navy and the Commonwealth navies working with them against the deadly U- boats. Later, with the U.S. Navy fully involved in war and the learning curve behind them, these international ASW specialists cleared the seas of the submarine threat in three oceans simultaneously. German advances in submarine technology came too late in the war to affect the ASW picture. Post-war, however, it was obvious that advances in ship propulsion and hull shapes were once again going to complicate the issue for those tasked with the sub hunter role. A nuclear weapon, by virtue of its huge kill range in comparison to the conventional ASW ordnance of the day and also its potentially more rapid delivery to the target, seemed to be an excellent, if expensive, way to resolve current ASW issues in case of a nuclear war. Once again, submarines made the problem more difficult when the shift was made to nuclear powered submarines capable of very high speeds underwater, deeper diving depths and virtually unlimited range. Submarine attack capabilities were also enhanced by new weapons and sonars – very much improved torpedoes and far more sensitive sonar suites. Still, even with the advent of the nuclear submarine, a nuclear anti-submarine weapon had about the highest probability of a kill as any ASW weapon developed post-war. Of course they would never be employed in any but the direst of circumstances, so they supplemented the conventional ASW weapons cache rather than dominated it and ASW capabilities with conventional ordnance delivery systems proceeded apace. (One should also note that these types of weapons – usually referred to as "ASW weapons" or “depth charges” – could as easily devastate a fleet of ships, surface ships being highly vulnerable to the intense underwater shock wave generated by a nuclear explosion, as clearly demonstrated during the Operations Crossroads Baker test. Ships not sunk outright by such a blast would have a high probability of sustaining crippling internal damage from the twisting and bending of major structural supports and plates. Considering the potential for intense radiation poisoning from any base surge to go with the damage, ships in this situation would probably be left in an intensely radioactive environment with no escape possible. This would be thoroughly depressing for ship's crews, to say the least. With that as background, this section covers the U.S. Navy's ASW weapons themselves, i.e., the delivery systems for the ASW-dedicated nuclear warhead as well as the warhead itself, including the MK 90 Betty depth charge, the MK 101 Lulu depth charge, the MK 45 Astor torpedo, the ASROC (RUR-5A), and the SUBROC (UUM-44A). The MK 105 Hotpoint bomb, covered previously, was the first lay-down delivery bomb and had an additional role as a depth charge by virtue of being detonated by a delay-timer. This weapon, with its early MK 34 warhead will not be covered further here. Covered in the same section on bombs, The MK 57 bomb also had a primary role as a nuclear depth charge in addition to its roles as a tactical nuclear bomb, replacing the earlier MK 101 Lulu. Unlike the MK 105, the MK 57 was equipped with hydrostatic fusing as well as its other detonating options. It also had a parachute laydown/delay option and was the most versatile of all the ASW depth charges. The MK 57 was the last and best nuclear air-dropped ASW weapon in the navy's inventory, and could be carried by the majority of the navy's attack and patrol aircraft over the weapon's long life in the active inventory. The last MK 57 was retired in 1992. MK 90 "BETTY" Depth Charge Two years after the appearance of the MK 7 bomb, the navy fielded its first ASW nuclear depth charge, the MK 90 "Betty". The Betty was simply a MK 7 Mod 1 warhead married to a depth charge shaped "package", and included a parachute retardation option, an option that could be selected or by-passed for free fall. The MK 90 had hydrostatic fuses with a delay timer back-up. The Betty was 10' 2" long, 31.5" in diameter and weighed about 1243 lbs. The Betty was an excellent early example of adapting a nuclear warhead to more than one specialized function and drop-shape, but because the MK 90 used the early MK 7 warhead, it was somewhat limited by being a more maintenance-intensive weapon to prepare for use, requiring the nuclear capsule (stored separately) to be inserted in the weapon before loading out and having usual early problem of battery life for the electronic components, and "shelf life" of the weapon once prepped. This made the weapon slower to activate and deliver than would be desired in an optimal wartime situation, but was an acceptable limitation at the time the weapons were deployed with the navy's ASW forces, as it got a functioning weapon to the fleet at sea and on shore. 225 MK 90s were built beginning in 1955, and the last MK 90 was withdrawn from service in 1963. Wide variations in the yield of this weapon are found in the literature, with most stating something in the 5 – 10 kt range, but one authoritative source stated that the MK 90 had a yield of 32 kt (well within the MK 7s capabilities). 32 kt – about one and a half times the size of the Operation Crossroads Baker test – seems a bit massive for the intended purpose of sinking a submarine, but on the other hand, was admirably suited to the fleet destruction role, a role that was apparently one of the goals of the weapon designers. The MK 90 has always been "a depth charge" officially, but its other applications are obvious, the same applying in one degree or another to all the navy's nuclear ASW weapons. Naval aircraft capable of carrying the MK 90 were the A-1, P2V, P-3, P5M, S2F and the SH-3 helicopter. MK 101 "LULU" Depth Charge The MK 101 Lulu was the second of the navy's depth charges, and a considerable improvement over its MK 90 predecessor. The MK 101 utilized the outstanding W-34 "Python" boosted fission design as a warhead with a yield in the Lulu of around 10 – 15 kt. This greatly shortened the prep time for the weapon as the W-34 required minimal maintenance when deployed and had a readiness "shelf life" far more than sufficient to cover a combat tour. There was no parachute-retardation option with the MK 101. The MK 101 was deployed with the fleet from 1958 to 1971, slowly replaced by the multi-purpose MK 57 bomb. The MK 101 had a shape similar to an overgrown WWII Hedgehog, with a very heavy steel plate nose to improve the sink rate and was 10' 2" long, 31.5" in diameter and weighed about 1200 lbs. (of which only 320 lbs was the W-34 warhead). 2000 MK 101s were produced in five Mods. Naval aircraft that could deliver the MK 101 were the AD, P2V, P3V, P5M, S2F and the SH-3 helicopter. The MK 45 Astor Torpedo The MK 45 torpedo was the only nuclear torpedo designed and deployed by the U.S Navy, and was specifically created to kill fast deep-diving nuclear submarines. The weapon grew out of the perceived need to counter the threat of the Soviet navy's massive build-up in submarines during the early 1950s and was based on the existing design for a new "Anti-Submarine Torpedo" with a conventional warhead already on the drawing boards and designated the MK 45. Warhead development for this weapon was requested in 1957, and quickly settled on the already-proven W-34 warhead used in the MK 101 Lulu depth bomb and the MK 105 Hotpoint laydown bomb/depth charge. Production of torpedoes mated to the MK 34 began in 1961, with delivery to the fleet beginning in 1963. The torpedo was used on both the last of the retrofitted "Guppy" diesel-electric boats and most of the later nuclear attack boats and boomers. (Nuclear-capable diesel boats could usually be identified by the unique triple housing of the PUFFS sonar system on the main deck.) The MK 45 torpedo was 18' 9" long and 19" in diameter, weighing about 2680 lbs. Capable of 40 knots, the torpedo had a range of about 8 nautical miles. The weapon was wire-guided, which supposedly limited the torpedoes range somewhat, but more importantly required and active ping from the launching submarine to determine or update range and bearing data, an attack concept not in the least popular in the submarine force. The maximum range was no thrill either in the opinion of the men in the boats, who often gave the torpedo a PK number (probability of kill) of 2. Its destructive power (10 –15 kt) and extreme accuracy kept the weapon in the fleet as the primary nuclear ASW response aboard both SSNs and SSBNs. Deployed from 1961, the Astor was withdrawn from the fleet beginning in 1972. A total of 600 Astor torpedoes were built. The ASROC (RUR-5A) The ASROC was developed to provide a stand-off attack capability for cruisers and destroyers and ASROC would become the first and only nuclear anti-submarine system deployed on these types of ships (as well as smaller frigates). The ASROC grew out of an earlier navy program called RAT (for Rocket-Assisted Torpedo) which suffered from poor accuracy, short range and limited payload capacity. In 1955 the project evolved into the ASROC program and shipboard evaluation of the rocket began in 1960 aboard the test vessel USS Norfolk, a specialized one-off ASW light cruiser and test vessel, with operational capability achieved the next year when four destroyers were the first to be equipped with the now well-known ASROC MK 16 "pepperbox" eight-cell launcher. The warhead for the ASROC, the W-44, was not finally ready until late in 1960. The W-44 was quite similar to the primary used in the MK-43 thermonuclear bomb and measured 13.75" by 25.3", weighing some 170 lbs and with a yield of around 10 kt. (Over 12,000 ASROCs were built, but only 575 nuclear warheads were manufactured for them.) The ASROC was a basic unguided ballistic rocket (thus the navy's "rocket" designation of RUR) weighing 1000 lbs and was 15' long with a diameter of 12.5". The solid propellant rocket gave the weapon maximum range of 7 miles. The ASROC had three Mods, the Mod 3 carried the conventional MK 44 homing torpedo, the Mod 4 had the MK 46 Mod 1 homing torpedo and the Mod 5 carried the W-44 nuclear depth bomb. The torpedoes were fitted with parachute packs for descent to target, while the nuclear depth bomb was strictly a free-fall weapon. Some 262 U.S. naval vessels were eventually equipped with the ASROC system either as the pepperbox launcher or from a modified Terrier missile launcher. Later ships used VLS for launching ASROCs, but this version has no nuclear capability. Foreign navies also fielded the ASROC, but only in conventional types. The ASROC was one of the full-up nuclear weapons delivery systems to be tested when the USS Agerholm (DD-826) launched a nuclear ASROC as part of Operation Dominic, Shot Swordfish on 11 May 1962. The ship fired at a target raft at 4000 yards (2 nm) and the weapon detonated 4350 yards from the ship. As well as being a proof test, the shot was used to test the effects of a nuclear detonation on the ship's sonar and structures. As can be imagined, a nuclear detonation thoroughly messes up sonar reception for a time in the vicinity of the blast. One assumes that the Agerholm, shown stationary in the well-known photo of the test shot, got underway immediately after, as the ship would not want to have been anywhere near the base surge from the blast, which would have been intensely radioactive. Shot Swordfish was the last of five underwater nuclear tests conducted by the U.S. While the conventional ASROC is still in use from the VLS on many ships, they are conventional torpedoes only; the last W-44 was withdrawn from the active fleet in 1989. The SUBROC (UUM-44A) The SUBROC (SUBmarine ROCket) was a rocket-propelled nuclear depth bomb capable of being launched from submerged submarines from the standard 21" torpedo tube. SUBROC was a nuclear-only weapon. Development of SUBROC began in 1958 with a first test-launch (without warhead) made on 3 August 1959. The SUBROC was far more difficult to develop than the ASROC for several reasons, one of the main ones being it used a thermonuclear warhead and the others being the need for a specialized long-range sonar system to detect submarines out at a range of 40 miles and also a specialized fire-control system which could use the sonar data to program and prep the missile for launch. The weapon was an analog device and eventually only the Permit class of nuclear submarines would be fully equipped with SUBROC and its sonars and fire control equipment. The rocket itself went through a lengthy development process in order to work out the myriad problems of getting a rocket out of a torpedo tube, through the water and into the air, and then on to the target, problems that delayed getting SUBROC to the fleet until mid-1965. SUBROC was also another weapon that required and active sonar "ping" from the launching ship to lock in target bearing and range prior to launch. SSNs do not like to make active pings, for obvious reasons. The SUBROC system all up was 21' long and 21" in diameter, weighing about 4000 lbs. Using 2-stage solid propellant rocket motors, maximum range was 25 – 30 miles at Mach 1+. Guidance was inertial. The W-55 warhead was 39.4" long and 13" in diameter, weighing 470 lbs. Yield was given as "1 – 5 kt" which seems very low for a thermonuclear warhead, particularly one based on the Operation Hardtack 1 Shot Olive test device which had a yield of 202 kt. It has also been stated that the missile had a secondary airburst option for the warhead, which implies a much higher yield as well. 285 W-55 warheads were manufactured. Submarines were credited with being able to carry 4 – 6 SUBROCs on board. By 1989 the last SUBROC nuclear warheads had been withdrawn from service. 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