The Royal Navy has unveiled a vision of what the British fleet could like in the future, including an enormous flying drone station based in the stratosphere and an underwater flagship vessel.
"In a future scenario if we find ourselves unable to compete traditionally in terms of mass, we must think differently if we are to regain operational advantage," said Vice Admiral Nick Hine.
"The young engineers who worked on this project are thinking radically and with real imagination and reflects how the Royal Navy is thinking too," added the Royal Navy's second most senior officer.
Some of the proposals are "eminently rational", explained Dr Sidharth Kaushal, a research fellow at RUSI who specialises on the impact of technology on maritime doctrine, while some others were "much more in the realm of very, very speculative thinking".
Young engineers from industry and academia responded to a challenge posed by UK Naval Engineering Science and Technology (UKNEST) – a forum for naval defence – to offer their proposals.
Their concept for the flying drone station has it attached to an enormous helium balloon sitting in the upper stratosphere, which the proposal suggests could be covered in material that would collect solar energy for power.
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It would harbour fast strike vehicles which would drop in free fall before their wings expanded and they glide, potentially even dipping under the waves, before striking a target using projectiles launched from forward-facing rail guns that skim over the surface of the water.
Currently "both the Chinese and the Americans use [stratospheric balloons] for surveillance, and it's not a long stretch to seeing them weaponised", said Dr Kaushal, "but having [a vehicle] launched from a stratospheric balloon, sort of entering the water… and then deploying weapons… that all seems a bit far-fetched to me".
The engineers proposed a new semi-submersible carrier stealth vessel that uses biofuel and wind power to run, and is capable of housing autonomous submarines.
Although the technology behind the carrier is speculative, the general focus on having more autonomous vehicles in the fleet is exactly the direction that maritime warfare is heading in, Dr Kaushal explained to Sky News.
The main big shift when it comes to warfare at sea "is the substitution of the few and the expensive for a combination of exquisite platforms, but also relatively cheap, unmanned, or optionally-manned platforms", he said.
The first reason for that is many of the surface ships that navies use, for example destroyers, lack the capacity to vertically lunch missiles – both to intercept enemy attacks and to launch offensive ones – which unmanned surface ships are able to provide.
The second reason is that "long range missiles like China's DF-21, the famous anti-carrier missile – but also a range of cruise missiles – make it more and more risky to concentrate the most valuable platforms in a surface combatant fleet in one place".
The most unusual vessel proposed as part of the UKNEST challenge was a vaguely-streamlined shaped minimally-manned submarine covered in an outer skin made of brain coral.
This ship would be capable of launching a large autonomous vessel equipped with "hex block" drones, manufactured inside the mothership itself, that can combine together to create larger structures to encase enemy drones or be weaponised to target enemy vessels.
"In terms of the conceptual side of it the idea of using unmanned platforms to take away some of the more mundane tasks from the fleet, things like resupply for example, seems to be eminently achievable. On the other side of the spectrum you had some ideas which were a bit more out there," Dr Kaushal said.
"Increasingly, relatively cheap, expendable, unmanned launch platforms will become more and more central to naval operations going forward," he added.
The Royal Navy is not doing too badly in this regard, compared to the major adversaries identified in the Integrated Review: Russia, Iran, and China.
"The Russians have generated a lot of combat capability at sea, particularly in terms of very accurate fast missiles, most recently the hypersonic Zircon missiles. But in terms of lethal autonomy, interestingly, they haven't necessarily sort of opted for much," Dr Kaushal said.
"The one exception, one might think of, is in the realm of underwater surveillance, where the Russians have built a pretty robust range of underwater vehicles for surveillance purposes, as well as which are capable of a range of tasks including the placement of deep sea underwater surveillance stations in in places like the Arctic."
The Iranians "do have some capability in the area of unmanned aerial assets as a combat tool", but Dr Kaushal said he had not seen much from Iran in terms of autonomous naval warfare.
"The Chinese are by far the most developed of the bunch. They have a range of unmanned underwater vehicles including unmanned gliders," he added and was continuing to develop more.
China's navy "appears to be experimenting with unmanned surface vehicles and unmanned underwater vehicles in the way that the US navy and the Royal Navy are", he said.
"In many ways, it's a peer competitor to the US navy in this space," Dr Kaushal added, noting that the Chinese research appeared to be more developing more robustly than the British ones.