The British Royal Navy aircraft carrier HMS Queen Elizabeth (R08) put to sea for the first time earlier today from the Scottish town of Rosyth where she was built for sea trials.

The massive 65,000-tonne vessel—which features a four acre flight deck—and her yet to be completed sister ship Prince of Wales are the two largest warships ever built by Britain.

“Today marks an historic day for the UK as HMS Queen Elizabeth, the nation's future flagship, goes to sea for the first time,” the Royal Navy stated on its Twitter account.

Like her U.S. Navy Nimitz and Gerald R. Ford-class counterparts, HMS Queen Elizabeth will have to undergo a series of sea trials before she is formally commissioned into service later this year.

Sister ship Prince of Wales is expected to be commissioned in 2020, affording the Royal Navy a significant power projection capability.

The Queen Elizabeth-class ships are significantly different from U.S. Navy aircraft carriers.

Firstly, the British ships are considerably smaller than the current generations of American carriers. They are not nuclear-powered—instead the Royal Navy chose conventional integrated electric propulsion.

The British ships are powered by a pair of Rolls-Royce Marine Trent MT30 48,000hp gas turbine generators, two Wärtsilä 15,000hp diesel generators and two 12,000hp generators. Those engines generate electricity to turn two propellers that are powered by four 20 megawatt advanced induction motors—giving the ship a top speed of around 25 knots.

Moreover, unlike U.S. Navy carriers, the Queen Elizabeth-class vessels are designed to operate short take-off/vertical landing aircraft with the aid of a ski-jump. Originally, the vessels were intended to be able to be modified with catapult launch systems and arresting gear—but that has proven to be far too costly. Instead, the British will rely on the Lockheed Martin F-35B Joint Strike Fighter for their fix-wing aircraft contingent.

The carrier will have the capacity to carry a maximum of 36 F-35Bs and four Crowsnest airborne early warning helicopters according to the industry consortium that builds the ships.

Alternatively, Queen Elizabeth’s air wing could be configured to carry up to 12 Chinook or Merlin helicopters and eight Apache gunships. It’s not yet clear what the exact configuration of a British carrier air wing will ultimately look like, but the U.S. Marine Corps has signed an agreement with the U.K. so that it might supply a contingent of F-35Bs to operate from the Queen Elizabeth.

Another difference from U.S. Navy flattops—or any other carrier for that matter—that is immediately noticeable is that Queen Elizabeth has two islands. The forward island will be used by the vessel’s 679-person crew for navigation and other ship functions while the second island will be used to control flight operations. The total ship’s complement rises to 1600 with the air wing embarked.

In terms of overall dimensions, the Queen Elizabeth is visibly smaller than a Nimitz or Ford-class carrier. The British ships are roughly 920ft in length with a flight deck width of 280ft.  While Queen Elizabeth currently displaces 65,000-tonnes, the ship could is designed with a growth margin so that she might eventually displace 70,000-tonnes as upgrades are added though her time in service.

Dave Majumdar is the defense editor of The National Interest. You can follow him on Twitter @DaveMajumdar.

Image Credit: Creative Commons.