After nuclear weapons were created in the United States, American experts predicted that the USSR would be able to create an atomic bomb no earlier than in 8-10 years. However, the Americans were very much mistaken in their forecasts. The first test of a Soviet nuclear explosive device took place on August 29, 1949. The loss of the monopoly on nuclear weapons meant that a nuclear strike could be launched against US territory. Although in the early post-war years the main carriers of the atomic bomb were long-range bombers, Soviet submarines armed with missiles and torpedoes with nuclear warheads posed a serious threat to large political and economic centers located on the coast.
After processing the materials obtained during the underwater nuclear test carried out on July 25, 1946 as part of Operation Crossroads, the US Navy admirals came to the unequivocal conclusion that a very powerful anti-submarine weapon can be created on the basis of a nuclear charge. As you know, water is a practically incompressible medium and due to its high density, the blast wave propagating under water has a more destructive force than an air explosion. Experimentally, it was found that with a charge power of about 20 kt, submarines in a submerged position within a radius of more than 1 km will be destroyed, or will receive damage that impedes the further performance of the combat mission. Thus, knowing the approximate area of the enemy's submarine, it could be sunk with one nuclear depth charge, or several submarines could be neutralized at once.
As you know, in the 50s, the United States was very keen on tactical nuclear weapons. In addition to operational-tactical, tactical and anti-aircraft missiles with nuclear warheads, even "atomic" recoilless artillery pieces with a range of several kilometers were developed. Nevertheless, the American top military-political leadership at the first stage confronted the admirals who demanded the adoption of nuclear depth charges. According to politicians, such weapons had too low a threshold for use, and it was the responsibility of the commander of an aircraft carrier strike group, which could be located thousands of kilometers from the American coast, to decide whether to use it or not. However, after the appearance of nuclear submarines with a high speed of movement, all doubts were dropped, and in April 1952 the development of such a bomb was authorized. The creation of the first American nuclear depth charge was undertaken by specialists from the Los Alamos Laboratory (nuclear charge) and the Naval Weapons Laboratory in Silver Springs, Maryland (body and detonation equipment).
Upon completion of the product development, it was decided to conduct its "hot" tests. During Operation Wigwam, the vulnerability of submarines to an underwater explosion was also determined. For this, a tested nuclear explosive device with a capacity of more than 30 kt was suspended under a barge at a depth of 610 m. The explosion took place on May 14, 1955 at 20.00 local time, 800 km southwest of San Diego, California. The operation involved more than 30 ships and approximately 6,800 people. According to the memoirs of American sailors who participated in the tests and were at a distance of more than 9 km, after the explosion, a sultan of water several hundred meters high shot up into the sky, and it was as if they hit the bottom of the ship with a sledgehammer.
Unmanned underwater vehicles equipped with various sensors and telemetry equipment were suspended on ropes under three tugboats, located at different distances from the point of the explosion.
After the combat characteristics of the depth charge were confirmed, it was officially adopted. The production of the bomb, designated Mk. 90 Betty began in the summer of 1955, with a total of 225 units delivered to the fleet. The anti-submarine aviation ammunition used the Mk.7 Mod.1 nuclear charge, created on the basis of the W7 warhead, which was widely used in the creation of American tactical bombs, nuclear bombs, tactical and anti-aircraft missiles. The bomb with a mass of 1120 kg had a length of 3.1 m, a diameter of 0.8 m and a power of 32 kt. The weight of the robust hull with hydrodynamic tail is 565 kg.
Since the nuclear depth charge had a very significant impact zone, it was impossible to use it safely from warships even when fired from a jet bomb, and anti-submarine aircraft became its carriers. In order for the plane to leave the danger zone after dropping from a height of less than 1 km, the bomb was equipped with a parachute with a diameter of 5 m. The parachute, unfastened after splashdown, also provided acceptable shock loads, which could affect the reliability of the hydrostatic fuse with a firing depth of about 300 m.
To use the Mk. 90 Betty atomic depth bomb, 60 Grumman S2F-2 Tracker anti-submarine carrier-based aircraft (after 1962 S-2C) were built. This modification differed from other anti-submarine "Trackers" by an extended bomb bay and an enlarged tail unit.
For the mid-50s, the S2F Tracker was a very good anti-submarine patrol aircraft, with very advanced electronic equipment for that time. The avionics included: a search radar, which, at a distance of about 25 km, could detect a submarine periscope, a set of sonar buoys, a gas analyzer for finding diesel-electric boats going under a snorkel, and a magnetometer. The crew consisted of two pilots and two avionics operators. Two 9-cylinder air-cooled Wright R-1820 82 WA 1525 hp engines allowed the aircraft to accelerate to 450 km / h, cruising speed - 250 km / h. The deck anti-submarine could stay in the air for 9 hours. Typically, aircraft carriers of a nuclear depth charge operated in tandem with another "Tracker", which searched for the submarine using sonar buoys and a magnetometer.
Also, the Mk.90 Betty depth charge was part of the armament of the Martin P5M1 Marlin flying boat (after 1962 SP-5A). But unlike the "Tracker", the flying boat did not need a partner, she could search for submarines herself and strike at them.
In its anti-submarine capabilities, the "Merlin" was superior to the deck "Tracker". If necessary, the seaplane could land on the water and stay in a given area for a very long time. For the crew of 11, there were berths on board. The combat radius of the P5M1 flying boat exceeded 2600 km. Two Wright R-3350-32WA Turbo-Compound radial piston engines with 3450 hp. each, accelerated the seaplane in horizontal flight to 404 km / h, cruising speed - 242 km / h. But unlike the carrier-based anti-submarine aircraft, the Merlin's age was not long. In the mid-60s, it was considered obsolete, and in 1967 the US Navy finally replaced the patrol-anti-submarine flying boats with coast-based P-3 Orion aircraft, which had lower operating costs.
After the adoption of the Mk.90 atomic depth charge, it turned out that it was not very suitable for everyday service on an aircraft carrier. Its weight and dimensions turned out to be excessive, which caused great difficulties when placed in the bomb bay. In addition, the power of the bomb was clearly excessive, and the reliability of the safety-actuating mechanism was in doubt. As a result, a couple of years after the adoption of the Mk.90 into service, the admirals initiated work on a new depth charge, which, in terms of its weight and dimensions, should have been close to the existing aircraft depth charges. After the appearance of more advanced models, the Mk.90 was removed from service in the early 60s.
In 1958, production of the Mk.101 Lulu atomic depth charge began. Compared to the Mk.90, it was a much lighter and more compact nuclear weapon. The bomb was 2.29 m long and 0.46 m in diameter and weighed 540 kg.
The mass and dimensions of the Mk.101 depth charge made it possible to significantly expand the list of its carriers. In addition to the "nuclear" carrier-based anti-submarine aircraft S2F-2 Tracker, it included base patrol P-2 Neptune and P-3 Orion based on the coast. In addition, about a dozen Mk.101s were transferred to the British Navy as part of allied assistance. It is reliably known that the British hung American bombs on anti-submarine aircraft Avro Shackleton MR 2, which was created on the basis of the well-known World War II bomber Avro Lancaster. The archaic Shelkton's service with the Royal Dutch Navy lasted until 1991, when it was finally superseded by the Hawker Siddeley Nimrod jet.
Unlike the Mk.90, the Mk.101 depth charge was truly free-fall and was dropped without a parachute. In terms of the method of application, it practically did not differ from conventional depth charges. However, the pilots of the carrier aircraft still had to carry out bombing from a safe height.
The "hot heart" of the Lulu depth charge was the W34 warhead. This nuclear explosive device of the implosive type based on plutonium had a mass of 145 kg and an energy release of up to 11 kt. This warhead was specially designed for depth charges and torpedoes. In total, the fleet received about 600 Mk.101 bombs of five serial modifications.
In the 60s, the US Naval Aviation Command was generally satisfied with the service, operational and combat characteristics of the Mk.101. Nuclear bombs of this type, in addition to American territory, were deployed in significant numbers abroad - at bases in Italy, the FRG and Great Britain.
Operation of the Mk.101 continued until 1971. The rejection of this depth charge was primarily due to the insufficient safety of the safety-actuator. After the forced or inadvertent separation of the bomb from the carrier aircraft, it got up to a combat platoon, and the barometric fuse was automatically triggered after it was submerged to a predetermined depth. Thus, in the event of an emergency drop from an anti-submarine aircraft, an atomic explosion occurred, from which the ships of its own fleet could suffer. In this regard, in the mid-60s, Mk.101 depth charges began to be replaced with safer Mk.57 (B57) multipurpose thermonuclear bombs.
The Mk.57 tactical thermonuclear bomb entered service in 1963. It was specially developed for tactical aircraft and was adapted for flights at supersonic speed, for which the streamlined body had solid thermal insulation. After 1968, the bomb changed its designation to B57. In total, six serial versions are known with an energy release of 5 to 20 kt. Some modifications had a kevlar-nylon braking parachute with a diameter of 3, 8 m. The B57 Mod.2 depth charge was equipped with several degrees of protection and a fuse activating the charge at a given depth. The power of the nuclear explosive device was 10 kt.
The carriers of the B57 Mod.2 depth charges were not only the base patrol "Neptunes" and "Orions", they could also be used by Sikorsky SH-3 Sea King anti-submarine amphibious helicopters and S-3 Viking deck aircraft.
The SH-3 Sea King anti-submarine helicopter entered service in 1961. An important advantage of this machine was the ability to land on water. At the same time, the operator of the sonar station could search for submarines. In addition to the passive sonar station, there was an active sonar, a set of sonar buoys and a search radar on board. On board, in addition to two pilots, two workplaces were equipped for operators of search anti-submarine equipment.
Two General Electric T58-GE-10 turboshaft engines with a total power of up to 3000 hp. rotated the main rotor with a diameter of 18, 9 m. The helicopter with a maximum takeoff weight of 9520 kg (normal in the PLO version - 8572 kg) was capable of operating at a distance of up to 350 km from an aircraft carrier or a coastal airfield. The maximum flight speed is 267 km / h, the cruising speed is 219 km / h. Combat load - up to 380 kg. Thus, the Sea King could take one B57 Mod.2 depth charge, which weighed about 230 kg.
The SH-3H Sea King anti-submarine helicopters were in service with the US Navy until the second half of the 90s, after which they were supplanted by the Sikorsky SH-60 Sea Hawk. A few years before the decommissioning of the last Sea Kings in anti-submarine helicopter squadrons, the atomic depth charge B57 was taken out of service. In the 80s, it was planned to replace it with a special universal modification with an adjustable explosion power, created on the basis of the thermonuclear B61. Depending on the tactical situation, the bomb could be used against both underwater and surface and ground targets. But in connection with the collapse of the Soviet Union and the landslide reduction of the Russian submarine fleet, these plans were abandoned.
While Sea King anti-submarine helicopters operated mainly in the near zone, Lockheed S-3 Viking carrier-based aircraft hunted for submarines at ranges of up to 1,300 km. In February 1974, the first S-3A entered the deck anti-submarine squadrons. For a short period of time, the Vikings rocket-propelled guns replaced the piston Tracker, taking over, among other things, the functions of the main carrier of atomic depth charges. In addition, from the very beginning, the S-3A was the carrier of the B43 thermonuclear bomb weighing 944 kg, designed to strike at surface or coastal targets. This bomb had several modifications with an energy release from 70 kt to 1 Mt and could be used both for solving tactical and strategic tasks.
Thanks to the economical General Electric TF34-GE-2 bypass turbojet engines with thrust up to 41, 26 kN, mounted on pylons under the wing, the S-3A anti-submarine aircraft is capable of reaching a speed of 828 km / h at an altitude of 6100 m. Cruising speed - 640 km / h. In the standard anti-submarine configuration, the takeoff weight of the S-3A was 20 390 kg, the maximum - 23 830 kg.
Since the maximum flight speed of the Viking was about twice that of the Tracker, the anti-submarine jet was better suited for tracking down nuclear submarines, which, compared to diesel-electric submarines, had many times higher underwater speed. Taking into account modern realities, the S-3A abandoned the use of a gas analyzer, which is useless when searching for nuclear submarines. The anti-submarine capabilities of the Viking relative to the Tracker have increased many times over. The search for submarines is mainly carried out with the help of dropped hydroacoustic buoys. Also, the anti-submarine equipment includes: a search radar, an electronic reconnaissance station, a magnetometer and an infrared scanning station. According to open sources, the search radar is capable of detecting a submarine periscope at a distance of 55 km with sea waves up to 3 points.
In the tail section of the aircraft there is a retractable telescopic rod for the magnetic anomaly sensor. The flight and navigation complex allows you to perform flights at any time of the day in difficult meteorological conditions. All avionics are combined into a combat information and control system controlled by the AN / AYK-10 computer. The aircraft has a crew of four: two pilots and two electronic systems operators. At the same time, the Viking's ability to search for submarines is comparable to the much larger P-3C Orion aircraft, which has a crew of 11 people. This was achieved due to the high degree of automation of combat work and the linking of all equipment into a single system.
Serial production of the S-3A was carried out from 1974 to 1978. In total, 188 aircraft were transferred to the US Navy. The machine turned out to be quite expensive, in 1974 one Viking cost the fleet $ 27 million, which, along with restrictions on the supply of modern anti-submarine equipment abroad, impeded export deliveries. By order of the German Navy, a modification of the S-3G with a simplified avionics was created. But due to the excessive cost of the anti-submarine aircraft, the Germans abandoned it.
Since 1987, the 118 most "fresh" deck anti-submarines have been brought to the level of S-3B. But the modernized aircraft installed new high-speed electronics, large-format information display monitors, and improved jamming stations. It also became possible to use AGM-84 Harpoon anti-ship missiles. Another 16 Vikings were converted into ES-3A Shadow electronic reconnaissance aircraft.
In the second half of the 90s, Russian submarines became a rare phenomenon in the world's oceans, and the underwater threat to the American fleet was sharply reduced. In the new conditions in connection with the decommissioning of the deck bomber Grumman A-6E Intruder, the US Navy found it possible to convert most of the remaining S-3B into strike vehicles. At the same time, the B57 nuclear depth charge was removed from service.
By reducing the crew to two people and dismantling the anti-submarine equipment, it was possible to improve the capabilities of the electronic warfare equipment, add additional cassettes for shooting heat traps and dipole reflectors, expand the range of shock weapons and increase the combat load. In the inner compartment and on the nodes of the external sling, it was possible to place up to 10 227 kg Mk.82 bombs, two 454 kg Mk.83 or 908 kg Mk.84 bombs. The armament included AGM-65 Maverick and AGM-84H / K SLAM-ER missiles and LAU 68A and LAU 10A / A units with 70-mm and 127-mm NAR. In addition, it was possible to suspend thermonuclear bombs: B61-3, B61-4 and B61-11. With a bomb load of 2220 kg, the combat radius of action without refueling in the air is 853 km.
"Vikings" converted from PLO aircraft were used as carrier-based bombers until January 2009. S-3B aircraft struck ground targets in Iraq and Yugoslavia. In addition to bombs and guided missiles from the Vikings, more than 50 false targets ADM-141A / B TALD with a flight range of 125-300 km were launched.
In January 2009, most of the carrier-based S-3Bs were taken out of service, but some machines are still in use at the test centers of the US Navy and NASA. There are currently 91 S-3Bs in storage at Davis Montan. In 2014, the command of the US Navy made a request to return to service 35 aircraft, which are planned to be used as tankers and for delivering cargo to aircraft carriers. In addition, South Korea has shown interest in the overhauled and modernized Vikings.
In 1957, the lead nuclear submarine of project 626 "Leninsky Komsomol" entered service in the USSR, after which, until 1964, the Soviet navy received 12 submarines of project 627A. On the basis of the Project 627 nuclear torpedo boat, Project 659 and 675 submarines with cruise missiles, as well as Project 658 (658M) with ballistic missiles were created. Although the first Soviet nuclear submarines had many disadvantages, the main one of which was high noise, they developed a speed of 26-30 knots under water and had a maximum immersion depth of 300 m.
Joint maneuvers of anti-submarine forces with the first American nuclear submarines USS Nautilus (SSN-571) and USS Skate (SSN-578) demonstrated that the destroyers of the World War II type Fletcher, Sumner and Gearing can withstand them after modernization, but they have there is little chance against the faster Skipjack boats, whose submerged speed reached 30 knots. Taking into account the fact that stormy weather was quite frequent in the North Atlantic, anti-submarine ships conceived were not able to go at full speed and would approach the submarine at a distance of using depth charges and anti-submarine torpedoes. Thus, in order to increase the anti-submarine capabilities of existing and future warships, the US Navy required a new weapon capable of nullifying the superiority of nuclear submarines in speed and autonomy. This was especially relevant for ships of relatively small displacement involved in escorting convoys.
Almost simultaneously with the beginning of the mass construction of nuclear submarines in the USSR, the United States began testing the RUR-5 ASROC anti-submarine missile system (Anti-Submarine Rocket - Anti-submarine missile). The missile was created by Honeywell International with the participation of specialists from the US Navy General Armaments Test Station in China Lake. Initially, the launch range of the anti-submarine missile was limited by the detection range of the AN / SQS-23 sonar and did not exceed 9 km. However, after the more advanced sonar stations AN / SQS-26 and AN / SQS-35 were adopted, and it became possible to receive target designation from anti-submarine aircraft and helicopters, the firing range increased, and in later modifications it reached 19 km.
The rocket weighing 487 kg had a length of 4, 2 and a diameter of 420 mm. For launch, eight charging launchers Mk.16 and Mk.112 were originally used with the possibility of mechanized reloading on board the ship. So on board the destroyer type "Spruens" in total there were 24 anti-submarine missiles. Also, on some ships, the ASROK PLUR was launched from the Mk.26 and Mk.10 girder launchers also used for the RIM-2 Terrier and RIM-67 Standard anti-aircraft missiles and the Mk.41 universal vertical launch launchers.
To control the fire of the ASROC complex, the Mk.111 system is used, which receives data from the ship's GAS or an external source of target designation. The calculating device Мk.111 provides the calculation of the trajectory of the rocket flight, taking into account the current coordinates, the course and speed of the carrier ship, the direction and speed of the wind, the air density, and also generates initial data that are automatically entered into the onboard control system of the rocket. After launching from the carrier ship, the rocket flies along a ballistic trajectory. The firing range is determined by the moment of separation of the solid propellant propulsion engine. The separation time is pre-entered into the timer before starting. After undocking the engine, the warhead with the adapter continues its flight to the target. When the Mk.44 electric homing torpedo is used as a warhead, the warhead is decelerated in this section of the trajectory with a braking parachute. After diving to a given depth, the propulsion system is launched, and the torpedo searches for a target, moving in a circle. If the target on the first circle is not found, it continues to search at several depth levels, diving according to a predetermined program. The homing acoustic torpedo Mk.44 had a fairly high probability of hitting a target, but it could not attack boats moving at a speed of more than 22 knots. In this regard, a missile was introduced into the ASROK anti-submarine complex, in which a Mk.17 depth charge with a 10 kt W44 nuclear warhead was used as a warhead. The W44 warhead weighed 77 kg, had a length of 64 cm and a diameter of 34.9 cm. In total, the US Department of Energy transferred 575 W44 nuclear warheads to the military.
The adoption of the RUR-5a Mod.5 rocket with a Mk.17 nuclear depth charge was preceded by field tests codenamed Swordfish. On May 11, 1962, an anti-submarine missile with a nuclear warhead was launched from the Garing-class destroyer USS Agerholm (DD-826). An underwater nuclear explosion occurred at a depth of 198 m, 4 km from the destroyer. A number of sources mention that in addition to the Swordfish test in 1962, as part of Operation Dominic, another test of the Mk.17 nuclear depth charge was carried out. However, this has not been officially confirmed.
The ASROK anti-submarine system has become very widespread, both in the American fleet and among the US allies. It was installed both on cruisers and destroyers built during the Second World War, as well as on post-war ships: frigates of the Garcia and Knox types, destroyers of the Spruens and Charles F. Adams types.
According to American data, the operation of the PLUR RUR-5a Mod.5 with a nuclear warhead continued until 1989. After which they were removed from service and disposed of. On modern American ships, the RUR-5 ASROC anti-submarine complex has been replaced by the RUM-139 VL-ASROC created on its basis. The VL-ASROC complex, which entered service in 1993, uses modernized missiles with a launch range of up to 22 km, carrying anti-submarine homing torpedoes Mk.46 or Mk.50 with a conventional warhead.
The adoption of the PLUR RUR-5 ASROC made it possible to significantly increase the anti-submarine potential of American cruisers, destroyers and frigates. And also by reducing the time interval from the moment the submarine is discovered to its shelling, the likelihood of destruction will be significantly increased. Now, to attack a submarine detected by the GAS carrier of anti-submarine missiles or passive sonar buoys dropped by aircraft, it was not required to approach the “pistol shot distance” with the place where the submarine was submerged. It is only natural that American submariners also expressed a desire to obtain weapons with similar characteristics. At the same time, the dimensions of an anti-submarine missile launched from an underwater position should have allowed it to be fired from standard 533-mm torpedo tubes.
The development of such a weapon began by Goodyear Aerospace in 1958, and trials ended in 1964. According to the American admirals responsible for the development and testing of missile systems intended for arming submarines, the creation of an anti-submarine missile with an underwater launch was even more difficult than the development and refinement of the UGM-27 Polaris SLBM.
In 1965, the US Navy introduced the UUM-44 Subroc anti-submarine guided missile (Submarine Rosket) into the armament of nuclear submarines. The missile was intended to fight enemy submarines at long range, when the distance to the target was too great, or the enemy's boat was moving too fast, and it was not possible to use torpedoes.
In preparation for the combat use of the UUM-44 Subroc PLUR, the target data obtained using the hydroacoustic complex were processed by an automated combat control system, after which they were entered into the missile autopilot. The PLUR control in the active phase of the flight was carried out by four gas deflectors according to the signals of the inertial navigation subsystem.
The solid-propellant engine was launched after exiting the torpedo tube, at a safe distance from the boat. After leaving the water, the rocket accelerated to supersonic speed. At the calculated point of the trajectory, the braking jet engine was turned on, which ensured the separation of the nuclear depth charge from the rocket. The warhead with the "special warhead" W55 had aerodynamic stabilizers, and after separation from the rocket body, it flew along a ballistic trajectory. After immersion in water, it was activated at a predetermined depth.
The mass of the rocket in the firing position slightly exceeded 1850 kg, the length was 6, 7 m, and the diameter of the propulsion system was 531 mm. The late version of the rocket, which was put into service in the 80s, could hit targets at a range of up to 55 km, which, in combination with nuclear warheads, made it possible to fight not only with submarines, but also strike at surface squadrons. The W55 nuclear warhead, 990 mm long and 350 mm in diameter, weighed 213 kg and had a yield of 1-5 kt in TNT equivalent.
PLUR "SUBROK" after being put into service went through several stages of modernization aimed at increasing the reliability, accuracy and firing range. These missiles with nuclear depth charges during the Cold War were part of the armament of most American nuclear submarines. The UUM-44 Subroc was decommissioned in 1990. The decommissioned anti-submarine missiles with an underwater launch were supposed to replace the UUM-125 Sea Lance missile system. Its development has been carried out by the Boeing Corporation since 1982. However, the process of creating a new PLUR dragged on, and in the mid-90s, due to a sharp reduction in the Russian submarine fleet, the program was curtailed.
In addition to the SUBROK missiles, the armament of American nuclear submarines included anti-submarine torpedoes with a nuclear warhead Mk. 45 ASTOR (English Anti-Submarine Torpedo - Anti-submarine torpedo). Work on the "atomic" torpedo was carried out from 1960 to 1964. The first batch of Mk. 45 entered the naval arsenals in early 1965. In total, about 600 torpedoes were produced.
Torpedo Mk. 45 had a caliber of 483 mm, a length of 5.77 m and a mass of 1090 kg. It was equipped only with an 11 kt W34 nuclear warhead - the same as the Mk.101 Lulu depth charge. The Astor anti-submarine torpedo had no homing; after exiting the torpedo tube, all of its maneuvers were controlled by the guidance operator from the submarine. Control commands were transmitted by cable, and the detonation of a nuclear warhead was also carried out remotely. The maximum range of the torpedo was 13 km and was limited by the length of the cable. In addition, after the launch of a remotely controlled torpedo, the American submarine was constrained in the maneuver, since it had to take into account the likelihood of a cable break.
When creating the atomic Mk. 45 used the hull and electric propulsion system of the Mk. 37. Considering that Mk. 45 was heavier, its maximum speed did not exceed 25 knots, which could not be enough to target a high-speed Soviet nuclear submarine.
I must say that American submariners were very wary of this weapon. Due to the relatively high power of the W34 nuclear warhead when firing the Mk. 45 there was a high probability of launching your own boat to the bottom. There was even a gloomy joke among American submariners that the probability of sinking a boat by a torpedo was 2, since both the enemy boat and their own were destroyed. In 1976, the Mk. 45 were removed from service, replacing the Mk. 48 with a conventional warhead.
