As MPs prepare to vote on replacing the country’s nuclear weapons, we break down what you need to know about them
TODAY the UK Government will propose a vote in Westminster to extend the life of the Trident nuclear weapons system and the submarines that house them.
Known as the Successor-class, it is a replacement for the Vanguard-class of ballistic missile submarines which entered Royal Navy service in the 1990s.
The Conservative government claims it to be necessary if the Royal Navy is to maintain a continuous at-sea deterrent (CASD).
The Scottish Government, Greens and some Labour MSPs in Holyrood oppose Trident, and the SNP’s 54 MPs at Westminster intend on voting against renewal.
Ahead of the vote, we look at some key points in the case for Trident.
The system is not British owned
The 58 Trident II D-5 ballistic missiles operated by the Royal Navy are American made and the US maintains and provides the satellite intelligence to target them.
The government has admitted that three components of each warhead (the neutron generator, gas transfer system and arming fusing and firing systems) are purchased from the US.
The fourth component, the thermonuclear bomb, is manufactured at facilities near Aldermaston on a design modified from an American original.
The number of nuclear weapons in the overall stockpile is anticipated to fall to less than 180 in the 2020s.
The independent use of Trident is in doubt
According to a US diplomatic telegram released by WikiLeaks in 2011, President Obama handed over the unique serial numbers of the UK's missiles to the Russians as part of an arms reduction deal.
As a result, the Russians now know exactly how many missiles the UK has and what they can do.
Given the complexities of the US-designed electronics and computer programmes embedded in every aspect of the Trident system it seems unlikely that a British prime minister could launch them – unless a US president gives authorisation.
The cost is unclear
Costs vary according to who you talk to. For example, the Royal United Services Institute (RUSI) estimated in 2013 that a new system would cost between £70bn and £80bn for its lifetime.
However, the secretary of defence has said it will cost £31bn to replace Trident.
Of that, between £12.9bn and £16.4bn would be spent on the new Successor class submarines themselves, of which £1.2bn has been spent on the concept design stage already.
The cost according to anti-Trident campaigners
The Campaign for Nuclear Disarmament Scotland (CND) has arrived at the round £205.3bn figure by two routes.
One is to take the Ministry of Defence (MoD) intention to spend 5-6 per cent of its defence budget on running its nuclear deterrent: CND Scotland estimated that at £2bn to £2.4bn per year multiplied by 40 because of the lifespan of servicing the submarines.
It estimated £57bn in running costs, plus £13bn to decommission the submarines and weapons in the 2060s.
Add to that the upper end of estimates for building the submarines, at £26bn, and another £1bn for conventional military forces to protect them.
CND also adds more than £3bn for the cost of upgrading nuclear warheads and then replacing them in the 2030s.
The submarines
The four current Trident-armed Vanguard Class submarines are due to retire by 2028 but the missiles on them are having their operational lives extended to 2042.
All four UK submarines were built to an American design at Barrow-in-Furness, and are designated ‘Vanguard Class’.
Each submarine was originally built with 16 missile silos but, according to the 2010 strategic defence and security review, the number of operational silos will fall to eight.
How many of the world’s nuclear warheads does the UK have?
According to the Federation of American Scientists the UK has 1.4 per cent of the world’s nuclear warheads.
In contrast, Russia has 7,300 warheads and the US has 7,000.
Command and control: how would nuclear weapons be used?
The prime minister, or a designated survivor in the prime minister’s place if the circumstances require it, can authorise the chief of defence Staff to order the missiles to be fired.
The message is sent by CTF 345 operations room at Northwood, which communicates with the Vanguard commander on patrol.
Two personnel are required to authenticate each stage of the process before launching, with the submarine commander only able to activate the firing trigger after two safes have been opened with keys held by the ship’s executive and weapons engineering officers.
How destructive are they?
Most of the warheads have a yield of 80-100 kilotons, equivalent of TNT; but a small number have lower yields.
The bomb on Hiroshima had a yield of 16 kilotons.
Each of these bombs is around eight times as destructive as the bomb which flattened Hiroshima in 1945, killing over 140,000 civilians.
Picture courtesy of Defence Images
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