The SSBN
The Vanguard Class SSBN (Ship Submersible Ballistic Nuclear) provides the United
Kingdom's strategic and sub-strategic nuclear deterrent. The first Vanguard
class submarine was launched in 1993 carrying Trident II D5 missiles and is now
the cornerstone of our Defence policy and significantly contributes to the
Alliance's deterrent forces.
The SSBN Fact File
Trident D5 missiles
A credible nuclear deterrent depends upon the ability to threaten an assured and
effective response to aggression. The Trident II D5 missile has a range of over
4,000 nautical miles and an accuracy, which can be measured in metres. Each
missile is technically capable of delivering up to 12 warheads, enabling a
number of different targets to be engaged, and each Vanguard class submarine has
16 missile tubes. The missile is ejected from the submarine by high-pressure gas
and only when it reaches the surface does the rocket system actually fire.
Spearfish Torpedo
Weighing in around two tonnes, this is one of the world’s most advanced homing
torpedoes, effective against surface and underwater targets. Spearfish has an
impressive accelerating attack speed combined with considerable operational
range and is the mainstay of Vanguard’s conventional arsenal.
SSBN OPERATIONS
Ballistic missile submarines must at all times have a robust and reliable link
with their chain of command on the mainland. A comprehensive network of
communications installations connects Britain's nuclear fleet with the
Commander-in Chief at Northwood, the Secretary of State for Defence in London
and the Prime Minister in order to authorise the use of nuclear weapons and keep
them under firm political control.
The
tactical weapon system is used to “fight the boat” and has three functions: to
avoid detection; provide self-protection, and to enable effective
communications.
The Submarine Command System (SMCS) is the “brain” of the tactical weapon
system, controlling and co-ordinating its constituent parts. It receives
information from the various sensors, analyses the data presents it to the
ship’s Commanding Officer in a format, which enables him to make informed
tactical decisions. Once this is done, the command system provides the means
with which to “fight,” including the preparation, launch and guidance of
tactical weapons.
Pressurised Water Reactor (PWR)
The driving force behind the Trident submarine is the latest design in
pressurised water reactor. In simple terms, this is a collection of uranium fuel
elements that produce huge amounts of energy to power the vessel (a ton of
fissionable material releases the energy equivalent to 2.5 million tons of
coal). The entire process takes place inside a heavily shielded reactor
compartment, which completely protects the crew from radiation. Water coolant
travels round the reactor and is heated by the nuclear fuel elements and on into
the steam generator, in the steam generator the heat of the coolant is used to
convert water into steam, which is used to power the main turbine engines. From
there a system of clutches, gearing and propulsion transmits the power to the
sea. Steam is also used to drive turbo-generators, which supply the submarine
with electricity. Because of the large amount of energy stored in the uranium
fuel elements Vanguard class submarines can travel great distances and for many
years without refuelling.