HMS Astute is a submarine like no other. She can glide around the globe without once surfacing or refuelling; she could detect the QE2 an ocean away, and she whispers through the water leaving no more sonar trace than a large dolphin. She is in effect an underwater military hotel – with big guns.

She was launched yesterday at a ceremony in the BAE Systems shipyard at Barrow-in-Furness. Instead of champagne, the submarine was inaugurated with a bottle of home-brewed beer (a tradition in Barrow) crushed on her underside by a sort of mechanised ironing board. She was named by the Duchess of Cornwall before rolling slowly into the sea at a stately metre a minute.

The Astute – 318ft (97 metres) of reinforced steel and lethal weaponry – is the first of a new species of nuclear-powered submarine. In theory, she could remain submerged indefinitely. She can make her own oxygen and drinking water from surrounding sea water, and the only factors that could force her to the surface are hunger, the sanity of the crew or a successful enemy attack.

She is the first of four 7,800-tonne Astute Class submarines in production at Barrow, and will carry more torpedoes and Tomahawk cruise missiles than any before her. The pressurised water nuclear reactor that powers her will last for the whole 25-year lifespan.

There is one other important difference between the Astute and earlier submarines. While far from roomy, the Astute will be surprisingly comfortable for her 98 crewmen (there are no women on British submarines). She will be the first in which each submariner has his own bunk, rather than having to “hot-bunk” in rotation with other crewmen. No fewer than five chefs will cater for the crew and every berth has its own iPod dock.

The captain has his own cabin with a wash basin, and although the room is minuscule by normal standards, it is spacious in submarine terms.

BAE boasts that the Astute is a machine more complicated than a space shuttle. “Think about taking a nuclear reactor, shrinking it, putting it in a highly corrosive environment, with the captain sleeping ten metres away from the nuclear core, and stuffing a load of explosive underneath, and you can see the engineering challenge,” Mike Sweeney, BAE press officer, said.

The Astute is the product of more than 700 designs and more than one million components, but she is not only an extraordinary feat of engineering, she is also extraordinarily expensive. The first three submarines are expected to cost £3.65 billion, far more than the original budget and 2½ years behind schedule.

No less a critic than President Castro has condemned the price-tag, claiming that 75,000 doctors could have been trained for the same money. Writing in Cuba’s state newspaper, he said: “It illustrates the sophisticated weaponry being used to maintain the unsustainable order developed by the imperial system of the US . . . it cannot be forgotten that England was for years, until a short time ago, the queen of the seas.”

The Astute, which is half the size of a Trident submarine, no longer requires a conventional periscope, but instead boasts an optical probe which can poke up above the surface of the sea for a few seconds, sweep the horizon using infrared and thermal imaging technology, then retract and dive, while the information is analysed by computer.

The submarine has only the most minimal sonar signature. Indeed, her very invisibility may be her weak spot, since she may appear as a sonar “hole” beneath the waves.

She is designed to ferry Special Forces, but one of her main functions will be intelligence gathering – she carries the most sophisticated interception equipment and can “hoover up” signals around the globe. In years to come she may be found lurking off coasts anywhere in the world, eavesdropping on the mobile telephone calls of terrorists.

While the Astute may be more comfortable than her predecessors, she remains an odd, hushed, sexless world, lit only by fluorescent bulbs. Submerged, the submariners cannot watch television. They cannot even play a DVD without permission. Silence remains essential while on deployment. “There is only very limited shouting, and quiet parties,” said Lieutenant-Commander Jeremy Greaves, a Navy spokesman. “And you still don’t want to drop a spanner.”

Alcohol is not banned, but strictly monitored. The only place of limited privacy is the bunk, a space 6ft long but with only 2ft of headroom, in a mess with 22 others.

The “ping” noise associated with submarines of old, and the staple of every submarine film, have gone and the captain need no longer shout “Dive! Dive!” since the push of a button on the vast bank of computer screens will do that for him. Yet in other ways, for all her additional size and menace, the Astute remains the strange, silent, stealthy place submarines have always been – an enclosed and artificial world that only a few could learn to live inside.

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