Britain’s Ship Submersible Ballistic Nuclear (SSBN) fleet is “fragile” according to Admiral Lord West of Spithead, the Times of 12 November 2015 reported.
“I am extremely worried about the fragility of these boats because we have extended them for so long” Lord West continued.
The Trident II D5 armed Vanguard class of SSBNs entered service in 1993 with the expectation of them being replaced in the early 2020s. However, building a nuclear submarine takes about ten years – followed by two years of seaworthiness trials before entering service. As a new four-strong fleet of Successor SSBNs has yet to be ordered by Her Majesty’s Government, there is a risk that the third decade of the 21st Century will see Britain without a continuous at-sea nuclear deterrent for the first time since June 1969.
A senior Whitehall source said of the incumbent Vanguard fleet: “They could keep running like a Swiss watch, or they could develop a major fault, and the whole thing could be a problem. The more you go past 2028, the bigger the risk.”
The cost of a replacement Ship Submersible Ballistic Nuclear fleet could cost £ 40 billion until 2030 and follows a number of large scale defence procurement programmes that have run spectacularly over time and budget. Perhaps the most galling of these was the plan to build 21 Nimrod MR4 aircraft to hunt enemy submarines. These were expected in service in 2003 at a cost of £ 2.8 billion. In fact nine aircraft were produced by 2010 at a cost of £ 3.8 billion. And then scrapped and not yet replaced by a nation which twice in the 20th Century was nearly brought to its knees by submarine warfare. However, The Sun of Sunday 14 February 2016 reported that “RAF chiefs have ordered £2 billion of of Poseidon jets [American built Boeing P-8 Poseidons, based on the 737-800 series airliner] to replace Nimrod but they will not be in service until 2019 at the earliest.” David Wooding continued to write in The Sun by saying that the P-8s would be incompatible with RAF in-flight refuelling tankers meaning they would have to turn back and top up every four hours.
Shadow defence secretary Emily Thornberry said “These figures are yet further evidence of the damage done by the Tories in the 2010 Strategic Defence and Security Review, and their failure to address the problems it created”. The MoD said “The Nimrod programme was 11 years late, £ 800 million over budget and no planes had been delivered. We are buying planes that work and are providing maritime surveillance by working closely with our allies”.
Although a new Successor design of SSBN might incorporate a number of proven off-the-shelf components it is likely to feature an advanced pressurised water nuclear reactor and fin carefully sculpted to reduce its sonar signature. Active stealth equipment could also include electrodynamic shakers, generating a vibration exactly out of phase with any machinery noise to cancel this tell-tale signature out.
Proposed Successor designs have also been drawn around the provision of 12 missile tubes wide enough to accommodate a larger replacement for the current Trident II D5. This would not be a problem as Trident missiles are already slightly smaller than the compartments provided for them on the Vanguard Class SSBNs. When being loaded ready for use, the 7′ diameter Tridents are held in place away from the tube walls by teflon-coated polyurethane rings and then covered by a styrofoam diaphragm below the missile hatches themselves. Once a missile tube hatch has been opened before firing, the diaphragm stops sea water rushing down the sides of the missile while at the base of the tube a gas generator, like a small fixed rocket engine, pressurises the space below the missile with a mixture of hot gas and cooling water. Once enough pressure has been generated against the lowest of the polyurethane rings, the 60 ton missile slides up the tube, breaks through the diaphragm and pops out of the submarine like a cork from a champagne bottle, breaks the surface and ignites its first stage rocket motor, which has a movable nozzle to steer the missile.
At this point too, a telescopic aerospike extends from the rounded nose of the 44′ long Trident missile to punch a hole through the air for it, thus reducing drag and extending its range. By the time that the missile has reached space and jettisoned its first stage, the Trident has also calculated its position by observing the stars.
This is in addition to data which would be available from GPS satellites and from the launching Submarine’s own Inertial Navigation System (SINS). Before a patrol begins, the SINS gyroscope is set spinning and adjusted to the submarine’s known latitude and longitude. From this point on, highly sensitive accelerometers measure the “boat”‘s every forward, lateral and vertical movement. These changing values are fed with other data into a computer which constantly plots a precise track for navigation, and gives the fire control computers the vessel’s position relative to true north and missile targets. For a Trident submarine patrolling the English Channel, these targets could be as far away as North Korea.
To ensure absolute reliability, a typical SSBN would have two or three independent SINS, all of which would also feed into a computer on board the missile itself which would be constantly updated until the last moment before launch. As the flight progresses, the three stage Trident would also use its own gyro stabilized guidance system and accelerometers to adjust it to the intended course – which is also calculated to include the Earth’s rotation during the flight time of the missile. Similarly, the onboard computer would command the missile to jettison the first stage and then ignite the second before staging for a second time and separating the two halves of the nose fairing. This would reveal a number of Multiple Independently Targeted Re-entry Vehicles (MIRV) each of which would ultimately free fall with a thermonuclear warhead to a separate target. Each cone shaped Trident MIRV can have a yield of up to 100 kilotons, compared to the 15 kiloton fission bomb which destroyed Hiroshima in 1945.
Meanwhile, back aboard the submarine, the hatch of the now-empty missile tube would be closed and the sea water now filling it pumped out until only the same weight as the departed Trident missile is left inside.
The first American SSBN, the Polaris fitted USS George Washington (SSBN 659) first went on patrol with its 16 missiles on 15 November 1960 while the 41st -USS Will Rogers (SSBN 659) – followed on 4 October 1967. As the decades progressed, Polaris was replaced by more capable and longer ranged Poseidon and Trident while the first generation of SSBNs reached the end of their working lives and were also replaced by more technologically advanced submersibles. The latest SSBNs have quieter engines than their antecedents to make them less detectable to increasingly sophisticated anti-submarine ships, aircraft and helicopters while the increased range of their missiles allows them to hide in a far greater area of ocean or even fire their missiles from their home ports.