The Regulus missile submarines were a group of submarines operated by the United States Navy (US Navy) capable of carrying the Regulus cruise missile. Between 1959 and 1964, a total of five boats were used to undertake the first submarine-based nuclear deterrent patrols by the United States. Regulus submarines were used for this task until 1964, when sufficient ballistic missile submarines carrying the Polaris ballistic missile became available.
History Regulus missile development and submarine use In May 1947, the United States Army (US Army) awarded a contract for the development of a guided cruise missile, the MGM-1 Matador. The US Navy saw this as a threat to its role in the operation of guided missiles, and launched its own development program for a turbojet powered missile, which it called Regulus. In August 1947, specifications for the Regulus project were issued:
Be capable of carrying a warhead Have a range of Have a maximum speed of Mach 0.85 A CEP of 0.5% of the maximum range
The Navy had been experimenting with guided missiles since 1945, using the JB-2 Loon, an American copy of the German V-1. In 1947, a pair of s, and , were converted to allow operation of the JB-2, and a test program of submarine launches of the weapon began which ran until 1953.Regulus: The First Nuclear Missile Submarines documentary, Spark, 2002
The Regulus missile itself was long, in diameter, had a wingspan of , and weighed between 10,000 and 12,000 lb (4,500 and 5,400 kg). Guidance was provided by remote control, with at least two control stations required for operation of the weapon, which could be installed on submarines, ships or chase aircraft. The first Regulus launch took place in March 1951, using a specially converted test missile fitted with an undercarriage to allow for easy recovery. At the same time, the Navy began consideration of the use of submarines armed with cruise missiles, and in 1953 recommissioned a World War II vintage , , for conversion into its first cruise missile submarine. Tunny was initially employed as a more advanced testbed for the use of cruise missiles from submarines than the previous boats, Carbonero and Cusk, as she was fitted with a specially designed missile hangar located aft of her sail. This pressurised, watertight installation allowed Tunny to be able to submerge with the missiles on board, and was connected via an access trunk to the boat itself, allowing the missiles to be prepared while the submarine was still under water.
Missile submarines
Following her conversion, Tunny began a test program, which saw the first Regulus launch from a submarine take place on 15 July 1953.Stumpf, p. 111 At the time, Tunny had not had the missile guidance system installed, which meant she had to operate in conjunction with a ship or submarine capable of controlling the missile once it had been launched; the installation of the guidance equipment was undertaken in early 1954, following which Tunny was capable of independent operations with the Regulus. At this point, the boat began being used to develop and trial the operational use of Regulus. At the same time, plans began for the conversion of a second submarine, , for the carriage of the missile. Barbero was chosen as she had already undergone a conversion to a cargo-carrying vessel, and thus did not require major modifications to install the missile hangar or equipment.Stumpf, p. 124 Barbero was commissioned following her conversion in October 1955 and, following sea trials, entered operational testing alongside Tunny, conducting her first Regulus launch in March 1956.
At the time that Regulus began development, the US Navy was looking for ways that it could deliver nuclear weapons using its own resources. In the late 1940s, the Navy had planned a class of supercarriers, with the first ordered as . These ships would be large enough to carry strategic bombers of the size required to carry the nuclear weapons of the time, the specification of which crystallised into the Douglas A-3 Skywarrior. However, the difficulty in designing aircraft of the required size to carry nuclear weapons, but capable of operating from the deck of a carrier, which became more of an issue when United States was cancelled, led to the Navy looking at other options for nuclear weapons delivery, and focusing on the concept of submarine launched nuclear missiles, with Regulus a prime candidate. The missile was designed to be able to accommodate the W5 nuclear warhead, before it underwent a redesign to allow carriage of the W27 thermonuclear warhead. The capability of submarines to carry nuclear weapons was seen as significant, as it was possible for submarines to remain undetected on station, with the threat of nuclear retaliation potentially ever present without their presence being known. So, in 1953, the US Navy, with the success of the test programme conducted using Tunny and Barbero, ordered a pair of larger missile submarines capable of carrying twice the number of missiles each. Originally planned as sisters to the attack submarine , the two boats, and , were converted while under construction through the addition of a section containing the missile hangar onto the bow (as opposed to an external installation in the original Regulus boats).
In addition to their being built to accommodate an increased number of missiles over Tunny and Barbero, the boats were also designed to be able to test what was intended as the second generation cruise missile, which was being developed under the name Regulus II. The rationale for the development of a new missile came from the limitations of the original Regulus - subsonic speed, low range, and the remote control guidance system, which meant that the missile had to stay within range either of its launch vessel, or a platform containing the remote control installation. So, the US Navy ordered the development of a new missile system that eliminated these issues. Regulus II had a range of , could fly at Mach 2, and was equipped with its own inertial navigation system that required no input either from the vessel that had launched it, or any other vessels or aircraft en route to its target. The size of the missile meant that the new submarines could only carry a pair of Regulus II missiles each, as opposed to four of the original Regulus airframes. In September 1958, six months after commissioning, Grayback conducted the first successful launch of a Regulus II from a submarine.
However, in spite of the success of the Regulus II test program, the disadvantages of cruise missiles were becoming evident, particularly as the project to develop a submarine launched ballistic missile (SLBM), which had begun in the mid-1950s, was achieving success with the UGM-27 Polaris. As a consequence, the US Navy elected to end the development of nuclear armed cruise missiles for use on submarines, and cancelled Regulus II at the end of 1958.
A further submarine designed to accommodate Regulus, , was laid down in 1957. Halibut was originally designed as a diesel-electric boat, but during the design stage, this was changed to a nuclear propulsion system. Designed from the start to operate cruise missiles, Halibut had a refined hangar design compared to that of the Grayback-class. Halibut was also planned as a platform for the Regulus II, but this was cancelled just over two weeks prior to the boat entering service. When Halibut eventually entered service, she was capable of carrying up to five Regulus missiles, and undertook the first launch of a guided missile from a nuclear submarine during her initial shakedown cruise in March 1960.
Regulus submarines as nuclear deterrent In 1956, while the test program was still under way, the US Navy instituted a policy of keeping one of its then existing cruise missile submarines in each ocean. Tunny was deployed to the Pacific Fleet at Pearl Harbor, while Barbero was sent to the Atlantic Fleet home-ported at Norfolk.Whitman, p. 32 As part of the testing phase, both boats undertook the first submarine based nuclear deterrent patrols. Subsequently, with the ramping up of the nuclear arms race between the United States and the Soviet Union that came following both superpowers successfully launching SLBMs, in 1958 Barbero was moved back to the Pacific to join Tunny, and the newly commissioned Grayback and Growler, to form Submarine Squadron One. Both Cusk and Carbonero were also retained as part of the Regulus programme and transferred to Pearl Harbor, as they had retained the guidance equipment to control the missile, despite having the launching equipment removed. This formed a major part of the US Navy's contribution to the nation's overall strategic deterrent, with the policy to continually have a minimum of four Regulus missiles at sea in the Western Pacific at all times.Whitman, p. 33
Following the constitution of Squadron 1, Tunny departed on the first operational deterrent patrol on 23 October 1959. Halibut meanwhile joined the Pacific Fleet in November 1960, becoming the fifth and final Regulus submarine to serve in the US Navy. The policy of keeping four missiles at sea at all times meant that Grayback, Growler and Halibut could undertake Western Pacific cruises alone, while Tunny and Barbero, both only capable of accommodating a pair of missiles, had to be at sea simultaneously. The system was found to have significant limitations, not just concerning those inherent in the Regulus missile itself. In order to launch a missile, the submarine was forced to surface and have a missile removed from the hangar to be loaded onto the launcher. This operation was undertaken manually on the two smallest boats, was partly automated on the second two, and fully automated on Halibut, but still took approximately 15 minutes to complete,NWIRPD, p. 8-112 during which time the submarine was on the surface and potentially vulnerable to air and sea attack. Once the missile was launched, the submarine was able to dive, but had to remain at periscope depth in order for the remote control system to operate and guide the missile to its target. Additionally, although the nuclear-powered Halibut was able to maintain station constantly for the duration of her cruise, the four diesel-powered boats needed to make refuelling stopovers during the periods that they were at sea, in order to maximise their time on station - these stops would usually take place either in Adak in Alaska, or at Midway Island. Nevertheless, between October 1959 and July 1964, when Halibut returned to Hawaii following its final patrol, the Regulus force had maintained at least one submarine constantly on station in the Western Pacific in the strategic deterrent role.