Aug 12, 2015

Submarine-Based Missiles -US SYSTEMS

During the Second World War German submarines in the Atlantic brought the United Kingdom very close to collapse before they were ultimately defeated, while US submarines in the Pacific achieved a mastery which played a significant part in Japan’s defeat. However, only a tiny handful of people foresaw a potential marriage between submarines and the newly developed missiles, and once again this occurred in Germany. The original suggestion came from a visitor to the German rocket-development site at Peenemünde, who proposed that the A-4 (V-2) missile, in addition to being launched from land, might also be launched from a submersible barge towed by a submarine. With such a device, he suggested, the Germans would be able to bombard New York. The suggestion was seized upon by the staff at Peenemünde, but the land-based missile was given higher priority and only one barge was completed before the surrender in May 1945. A separate proposal to mount V-1 cruise missiles in submarines for use against New York was considered in 1943, but was rejected due to a lack of suitable submarines.

The nuclear-powered missile submarine (submarine, ballistic, nuclear – SSBN) and its weapon, the submarine-launched ballistic missile (SLBM), formed a truly innovative weapon system. It was in essence a missile base, but with the immense advantage over land-based ICBMs that not only was it mobile, but it could use that mobility to hide in the vastness of the oceans.

Some of the V-1 and A-4 missiles obtained by the US forces in 1945 were allocated to the US navy, together with a number of the German scientists who had been involved in their development. These missiles were immediately seen as having a seaborne role against land targets, and, of the two, the V-1 cruise missile seemed to offer the greater promise in the short term. As a result, two fleet submarines were converted by installing a watertight hangar abaft the sail with a stern-facing take-off ramp – an installation similar to that used by the Japanese navy for its aircraft-carrying submarines, of which the US navy captured a number in 1945. The submarines had to surface to launch the missiles, and the first of many test flights took place in February 1947. The navy also conducted trials with the A-4, including the first launch of a ballistic missile at sea, from the flight deck of the aircraft carrier USS Midway on 6 September 1947. Numerous tests were conducted with both types of missile until the programme ended in 1950, but it was a start.

Meanwhile, two exceptionally far-sighted submarine-launched cruise-missile programmes were initiated, one for Rigel in 1947 and the second for Triton in 1952, although both were eventually cancelled. A less ambitious cruise-missile programme named Regulus did, however, reach service. Powered by a turbojet, the subsonic Regulus I had swept wings, and served operationally aboard submarines from 1954 to 1964. It was armed with a nuclear warhead, but was relatively inaccurate and was targeted against large cities within 650 km of its submarine launch position, such as Beijing. A second cruise missile, Regulus II, was greatly superior to Regulus I and carried a nuclear warhead at speeds in excess of Mach 2 to ranges of 1,610 km. Although it was proving very successful, the programme was cancelled in 1959, as the concurrent Polaris programme held out greater promise.

The United States’ first SLBM and SSBN programme – known collectively by the missile’s name, Polaris – was one of the most successful defence projects ever undertaken. It was a huge undertaking, which incorporated an astonishing range of innovations in two parallel but interlocking programmes. On the missile side, these included solid-fuel propulsion, cold-gas launch from a submerged submarine, lightweight ablative re-entry vehicles, and small nuclear warheads. Alongside this was the submarine programme, which involved cutting a nuclear-propelled attack submarine under construction in two and inserting a 39.6 m ‘plug’ containing sixteen vertical missile tubes. The submarine system also involved new launch-control and communications systems, as well as novel systems for submarine navigation. This very ambitious programme was steered to completion by Rear-Admiral William Raborn of the US navy.

When the first Polaris submarine entered service, in 1960, it revolutionized strategic warfare. The Polaris A-1 missile carried a single 500 kT warhead over a range of 2,600 km and, using inertial guidance, achieved a CEP of some 1,830 m. Polaris A-2 also had single warhead, but this was both more powerful (800 kT) and more accurate (CEP = 1.2 km), while Polaris A-3 carried three RVs, each with a 200 kT yield and a CEP of 850 m. The Polaris A-3 also became the first (and so far the only) SLBM to be supplied to a foreign nation, when it was sold to the United Kingdom to arm that country’s Resolution-class SSBNs.

The Poseidon C-3 two-stage missile started life as an evolutionary development of the earlier missile (its initial designation was Polaris B-3) and, although having a greater diameter, it was able to use the same launch tubes by eliminating the guide-rings used on Polaris. The first Poseidon was launched in August 1968, and the system entered service in 1971. The most important innovation was that it was armed with MIRV warheads, of which a maximum of fourteen could be carried, though this was limited to ten 100 kT warheads under the SALT I agreement with the USSR. The potential accuracy of the MIRVs could have given them a counter-force (hard-target) capability, but, since this ran counter to contemporary US strategists’ view of SLBMs as a survivable, second-strike, counter-value (i.e. anti-city) system, the proposed high-precision stellar-inertial navigation system was not authorized by the Department of Defense.

At its peak Poseidon armed thirty-one SSBNs. Conversion of twelve of these boats to carry the Trident missile started in 1984, however, and by 1990 only ten Poseidon boats remained in service.

Development of Trident I began in 1972, the missile being essentially a Poseidon C-3 with a third-stage motor added to give a greatly increased range of 7,400 km – that range enabling the SSBNs to obtain more sea room. The Trident design was a much more efficient design than earlier SLBMs, maximising its use of the volume available, and making use of all the fuel. The designers were also able to include the stellar navigation package which had been forbidden Poseidon, thus enabling the warhead to be extremely accurate, with a CEP of 463 m. Trident I (C-4) was put into production even though it was known that Trident II (D-5) would become the definitive system, and it armed twelve SSBNs which had originally carried Poseidon as well as the first eight Ohio-class SSBNs.

Next came Trident II (D-5), which was the same diameter as Trident I but 3.6 m longer, giving it a range of 12,000 km and nearly double the throw weight of the earlier missile. As the Cold War ended, Trident II was coming into service aboard the twenty-four-missile Ohio-class SSBNs. Trident II was fitted with NAVSTAR satellite receivers, giving mid-course navigational updates to the inertial system, resulting in a CEP of 90 m, making this a genuine hard-target attack system, with a range enabling it to hit any target in the world from anywhere in any ocean.

In the late 1980s the US navy introduced the Tomahawk cruise missile into service, thus turning the wheel full circle, since the navy had started its Cold War development with a cruise missile – the Regulus – some forty years earlier. This missile was, however, much superior in performance, range and accuracy, delivering a 200 kT warhead to a maximum range of 2,500 km with an accuracy of 280 m. It was also smaller and lighter, being capable of being launched from a standard 533 mm diameter torpedo tube.

SLBM Launching
One of the keys to success of the US SLBMs was the use of a gas-operated system which blew the missile out of the launch tube towards the surface, thus avoiding the rocket-motor ignition taking place in the tube, with its attendant dangers to the submarine. In some missiles the first-stage motor to drive the missile up into the atmosphere fired below the surface, while in others (e.g. Trident) it fired when clear of the surface. The missiles were launched in sequence, Poseidon missiles being launched at a rate of one every fifty seconds.

The original submarines used by the US navy in the 1946–7 V-1 programme were standard Second World War diesel-electric fleet submarines with large cylindrical hangars abaft the sail, with a short, sloping launching rail. The next step was the Regulus I and II programmes, which involved five submarines. The first two of these were converted fleet submarines with cylindrical aft-facing hangars, but the other three were purpose-built, with the missiles stored in a large hangar in the bows, two of them being diesel-electric-powered and the third, Halibut, nuclear-powered. All ceased to operate Regulus when the system was discontinued in 1964 and were then employed on different missions.

Led by Rear-Admiral Raborn, the Fleet Ballistic Missile System (FBMS) programme started in the mid-1950s, and the first submarine, George Washington, complete with sixteen operational Polaris A-1 missiles, entered service on 15 November 1960 – an astonishing technical, manufacturing and managerial achievement.

To save time, the George Washington class was created by taking five Skipjack-class attack-submarine hulls currently under construction, cutting them in two, and adding a missile section containing sixteen vertical tubes abaft the sail. There were, of course, many minor changes, including the addition of missile control and launch systems, special navigation systems, and new communications. The system introduced many new concepts which subsequently became standard practice, including the sixty-day operational cycle, using two crews, designated Blue and Gold, one of which was at sea, the other ashore on rest, leave, training and, finally, preparing to take over for the next operational cruise.

The George Washington class was very quickly followed by five Ethan Allen-class boats, completed between 1961 and 1963, which were very similar to the George Washington class, but with the advantage of being designed as SSBNs from the start.

The range of Polaris (A-1 – 2,600 km; A-2 – 2,800 km; A-3 – 4,630 km) meant that all these SSBNs had to operate relatively close to Russian shores to meet the requirement to hit Moscow. So, in order to reduce transit times, the boats were forward based at Holy Loch (Scotland), Rota (Spain) and Apra Harbor (Guam). None of these ten SSBNs could be converted to take the Poseidon missile, and in 1980–81 all were either converted to nuclear-powered attack submarines (SSNs) by deactivating the missile tubes or were decommissioned.

The first of the Ethan Allen class had not even been completed before the next class was being laid down, and thirty-one Lafayette-class SSBNs joined the fleet between 1963 and 1967. All thirty-one entered service with Polaris missiles (the first eight with Polaris A-2, the remainder with A-3), and a further four were planned to bring the grand total of Polaris-armed boats to forty-five. These last boats were never built, and the thirty-one Lafayette-class were converted in 1970–78 to take the Poseidon missile. Twelve were later converted yet again to take Trident C-4 (1978–83), with the first of these, Francis Scott Key, sailing on its first patrol on 20 October 1979.

Finally came the Ohio class, the largest US submarine and the most powerful single weapons platform ever built – 171 m long, displacing 16,964 tonnes and carrying twenty-four missiles. Like most other strategic programmes, the Ohio-class programme was surrounded by doubts, and in particular by concern over its costs, but eventually the first submarine sailed on its initial patrol on 11 November 1981. The first eight, which entered service between 1981 and 1986, were armed with Trident I (C-4) missiles, and the remaining ten (completed in 1988–97) with Trident II (D-5).

Missile Numbers
When the first SSBN was being designed there was a major investigation into the optimum number of missiles. The minimum cost-effective number was twelve, but the maximum depended on the money available. The number of sixteen was simply the number that fitted in the largest submarine the US navy felt that it could persuade the Pentagon and Congress to pay for, and the majority of SSBNs subsequently built for both the US and foreign navies have been equipped with this number of tubes. There is, however, nothing magic about the figure of sixteen, and SSBNs have been built with twelve tubes (Soviet Yankee class), twenty tubes (Soviet Typhoon class) and twenty-four tubes (US Ohio class).

Availability of the later missiles aboard SSBNs remains classified, but in a US navy Polaris submarine fourteen missiles were available for 100 per cent of the time, while all sixteen were available for 95 per cent of the time.

Typical of its generation, the US navy’s Lafayette class usually spent sixty-eight days on patrol with the Blue crew, followed by a thirty-two-day refit before starting the next patrol with the Gold crew. There was also a sixteen-month yard overhaul every six years, giving an overall availability for each hull of 55 per cent. The Ohio class, however, offered a considerable increase in availability, with seventy-day patrols, followed by twenty-five-day refits, and with a twelve-month yard refit every nine years, increasing overall availability to 66 per cent.

As with land-based missiles, there were repeated attempts in the USA to discover a form of sea-borne basing that was either less expensive or more survivable – or, preferably, both. Designs took a variety of forms.

In the immediate post-war period the USA examined the German plan to launch A-4s from submersible barges, and carried out some tests, using ex-German A-4s and US-built barges. The result was always that the rocket efflux destroyed the barge, resulting in a somewhat erratic launch. Nevertheless, the idea was re-examined in 1961–5 as a possible alternative to Polaris, under the code-name Project Hydra, and was looked at yet again in the early 1980s as an alternative to both Trident and the Peacekeeper (MX) ICBM. Project Hydra showed that the technique was perfectly feasible, although it found that the most effective way of launching was simply to put the missile in the water without any form of protective container. The missiles needed to be waterproofed, and those with a specific gravity greater than 1.0 needed a flotation collar to make them float, the collar being shed on launch. The plan was for such missiles to be taken to sea aboard a converted merchant ship and lowered into the water, where they would be left until they were activated and the launch command was signalled from a headquarters ashore.

The 1970s plan was for thirty fast merchant ships, each capable of rapid changes in appearance, to operate out of two bases, one on the Atlantic and one on the Pacific. Each ship would have carried ten missiles, and two plans were considered: one to offload the missiles into the sea in peacetime, the other to offload them only in a crisis. In fact the project foundered on the deployment issue, as the system was judged to be far too vulnerable and susceptible to accidents, but there was never any doubt as to its technical feasibility.

There were a number of proposals in the late 1970s to use small diesel-electric submarines, operating on or near the continental shelf. One proposal involved a design displacing some 450 tonnes, based on the West German-designed Type 209; another was for a larger boat displacing between 500 and 1,000 tonnes. Such submarines would have carried two (or, in some proposals, three) Minuteman III missiles in external, horizontally mounted containers, from which the missile would have been floated out, brought upright by its ballasted rear end, and then ‘wet launched’ as with Project Hydra. Force levels varied between 100 and 138, with manning figures ranging between five and fifteen men per submarine. The most serious drawbacks were that, being diesel-electric powered, slow and with relatively short range, the submarines would have needed protection by a strong ASW force, while if they operated within the limits of the continental shelf they were vulnerable to attack by a relatively small number of Soviet missiles.

The Hydra plan was for surface ships to place missiles in the sea for a water launch, but there were other plans to use the surface ships themselves as launch platforms. The most serious of these was the ‘Multi-Lateral Force’ (MLF) proposed by President John F. Kennedy in 1961. This proposal was for a fleet of twenty-five surface ships to be built in west-European yards, each armed with eight Polaris A-3 missiles, supplied by the United States. Both ships and missiles would have been jointly owned by the nations concerned and jointly manned (as, for example, happened later for the E-3 Airborne Warning and Control System (AWACS) force).

One curious event, possibly linked to the MLF proposal, was associated with the Italian cruiser Giuseppe Garibaldi. This ship underwent a major refit in the early 1960s and emerged in 1962 as a guided-missile cruiser, its principal weapons being US-supplied Terrier anti-aircraft missiles. It was, however, also equipped with four vertical launch tubes for Polaris A-3 missiles. Dummies were successfully tested, but real missiles were never embarked, nor were live Polaris missiles ever made available to the Italian navy.

The most significant feature of the MLF proposal was that the warheads would have been under NATO control, with release authorized by a NATO body to be set up for that purpose, and signalled over a NATO-owned ‘permissive link’ to the ships. The MLF never came about, but the question of NATO control over nuclear weapons led to the setting up of the Nuclear Planning Group.
There was also a proposal for a NATO-operated ballistic-missile submarine force. This was, however, quickly scotched, since the US would not reveal its nuclear-propulsion secrets and a diesel-electric submarine would have lacked the essential stealth.

 SLBM family: UGM-27A, UGM-27A, UGM-27C, UGM-73A, UGM-96A, UGM-133A