What do submarines do

Submarine reactors are smaller than large-scale land-based nuclear power stations. Nuclear reactors famously require a lot of technology and expertise to manage safely, so why would you want to put one on an underwater vessel? A nuclear reactor allows the submarine to be less reliant on external supplies.

Diesel-electric subs need to refuel regularly, while a nuclear submarine — particularly one based on UK and US designs — might never need to refuel. Diesel-electric submarines also need to resurface often to turn on their diesel engines to charge their batteries.

The UK defence force claims their submarines can circumnavigate the world without resurfacing over a day period. This means there are functional advantages to keeping a nuclear reactor onboard, despite the additional safety risks. Because submarine reactors are similar but smaller versions of land-based reactors, a lot of the technical and safety considerations are the same.

If a nuclear submarine had an accident that caused it to have a slump and melt and drop out the bottom of the boat, I don't think we'd have a nuclear fleet any more. That would be the end of nuclear submarines.

It's that level of responsibility. A key distinction to grasp is between fast-attack submarines such as HMS Triumph, which are armed with conventional cruise missiles the UK has seven such boats in varying degrees of readiness , and the four nuclear-armed submarines, one of which is always on patrol, ready to unleash its Trident nuclear missiles if apocalypse beckons. The latter — called ballistic submarines or bombers — are, at m long, almost twice the size of Triumph, have bigger crews and are, according to the men who have served on them, deadly boring.

It is three months of suspended animation; men aspiring to the life of a flat fish, though a highly educated one — many are doing Open University degrees to pass the time and improve themselves. Another man tells me the crew on board one bomber used to amuse themselves by pretending to be motorbikes, and this rings true.

It means telling a tale — a tale that grows with the telling. Even on a fast-attack sub, if there is nothing to attack and you grow tired of listening to passing whales and pretending to target nearby destroyers, life can get repetitive, so the men slip into other worlds. One of the crew has a large tattoo on his back: "Never stop me dreaming," which might stand as a motto for all of them.

One evening, I wander into the control room at about midnight. The watch officer and sonar operators are discussing an important philosophical question: would it be more painful to be struck by a whole tuna or a tin of tuna? This is never resolved. These epistemological issues can be sustained over weeks. On my fourth day aboard, I make my greatest discovery: that a badger, washed into the bilge tank in Bahrain, is being kept back'aft. There is a roster to feed it, and somehow it is being kept alive.

I insist on seeing it — what a wonderful story! Of course, say the back'afties, come by this evening. After a couple of hours, even in my dim-witted, mind-clouded, headachy state, I realise I have been conned. Do they even have badgers in Bahrain? But the fantasy has become important to some of the crew. The ability to relax allows you, when required, to be on the ball. This is a highly segregated society, yet also a very organic one. There are three separate messes, for officers, senior ratings and junior ratings, each situated on the short corridor that serves as the men's living space.

The separate messes with their different atmospheres — the Xbox is never off in the junior rates mess — suggest division, yet everything else implies unity. What other organisation has that sort of ratio between top and bottom? And every crew member, officer or rating, has to know everything about the boat — the function of every one of the thousands of valves.

There are half a dozen trainees on the boat studying for their dolphin badges, and they are forgoing all sleep to memorise the handbook they have been given in time for a test that could be sprung on them at any time. Chief Petty Officer Paul "Jakie" Foran, the likable but occasionally terrifying Scot who oversees these tests, expects dedication, and woe betide any trainee AKA oxygen thief who is discovered having a cup of tea in the junior rates' mess when he could be unearthing the secret of the magazine spray drench system.

You learn early whether you will survive in this world. One young officer who wants to transfer from surface ships is aboard studying for his dolphins, and is reckoned to have too many airs and graces. The remainder is converted to energy.

Reactors in a nuclear-powered submarine are typically fuelled with uranium. Natural uranium mined from the ground consists mainly of an isotope called uranium, mixed with small amounts 0.

The degree of fuel enrichment is a crucial factor in maintaining a chain reaction that gives a consistent, safe level of energy output. Inside the reactor, uranium is bombarded with neutrons, causing some of the nuclei to undergo nuclear fission. The energy is given off as heat, which can be used to drive turbines that generate electricity for the submarine. One huge advantage of nuclear-powered submarines is they do not require refuelling. When one of them enters into service, it will be commissioned with enough uranium fuel to last more than 30 years.

The high efficiency of nuclear power also enables these submarines to operate at high speed for longer periods than conventional diesel-electric submarines. Armed with dozens of Tomahawk cruise missiles and torpedoes, the foot, 8,ton Virginia-class subs can cruise at more than 28 mph 46 kph and stay submerged indefinitely.

Their time underwater is limited only by the need to resupply provisions for the crew of The sub doesn't even have a periscope. Rather it uses a photonics mast -- a piece of electronic wizardry that includes high-definition and infrared video -- to monitor the battlespace.

The information is displayed on large screens in the command center, with a joystick controlling the whole show. The UK's four Astute-class attack subs are even faster than the US subs, capable of more than 35 mph 56 kph submerged, and like the US carry the Tomahawk cruise missile. It has a longer range than its predecessors well in excess of 1, miles , can be directed at a new target in mid-flight, and can also beam back images of the battlefield to its mother submarine," the Royal Navy's website says.

That's the kind of firepower and endurance Australia wants as it looks to protect its northern waters from any naval threats and project its naval power into the South China Sea, where it, along with the United States, looks to blunt Chinese influence and protect freedom of navigation.

Ballistic missile submarines. Their mission, essentially, is to stay at sea for months at a time, the vast majority of it submerged, and be prepared to launch a retaliatory nuclear strike should an adversary launch one of their own against the UK or US. The ballistic-missile submarine USS Pennsylvania returns home to its Washington state homeport following a strategic deterrence patrol in Ballistic missile subs are quiet beneath the waves and extremely hard to detect.

They are the linchpin of deterrence, assuring that an adversary of the US or UK would pay a horrific price for a first-strike nuclear attack. Each of the US ballistic missile subs can carry 20 Trident missiles 16 for the UK subs with as many as eight warheads three for the UK subs per missile.