Dear Evil Engineer: Could I live in a lair on the ocean floor?

Dear Evil Engineer,

I am a reclusive billionaire, seeking peace in retirement after a long and tyrannical career. Being even more misanthropic than the typical villain, I would like to live as far from human civilisation as possible: the bottom of the ocean.

Could you advise me how to build a lair on the ocean floor?

Yours,

An aquatic villain

Dear villain,

The bottom of the ocean is a prime piece of real estate for a villain who values solitude and aesthetic considerations: there is nothing quite like a goblin shark or a giant isopod floating past your toilet window to reassure you that you have (at last) found Hell on Earth. I’m pleased to say that an underwater lair is possible, from an engineering perspective, and – as a billionaire – you may even have the means to make it a reality.

We have come quite some way from the age of the diving bell. Derring-do French oceanographer Jacques-Yves Cousteau led the first ‘Conshelf’ project in 1962, which supported a crew for a week in a habitat 10m below the ocean surface. The flurry of efforts that followed came to an abrupt stop at the end of the decade after a death during preparation for Sealab III, which aimed to support a crew of aquanauts 190m below the surface. From then on, space became the only frontier that mattered. Today, there are three major underwater laboratories, all in Florida Keys, and a handful of submerged recreational facilities, such as restaurants.

It is possible to push larger, deeper, and for longer periods of time than we managed in the 1960s. Let’s look first at how to build a lair at the bottom of the ocean, and then consider how to live in it.

Building structures under water is possible – the oil industry does it – but it is complex and expensive, even for something as structurally simple as a pipeline. To build your lair, you will want to either divert water during construction, such as with caissons or cofferdams, or to construct it on the surface and then submerge it. The latter is probably more practical for a lair. A small habitat could be constructed on the ground and then submerged whole, while a larger one could be composed of pre-assembled modules designed to be put together underwater.

What should your underwater habit look like? Perhaps your main consideration is pressure: every 10 metres of depth adds another atmosphere of pressure, mounting a vast load on your habitat. The ideal shape, then, is a sphere, which takes an even distribution of stress over its surface, meaning there are no especially weak points. A practical and attractive design could use joined-up spherical ‘rooms’ for various purposes, made from steel and concrete (strong and corrosion-resistant). This has much in common with the proposed Sub-Biosphere 2 design by futurist Philip Pauley. He and his collaborators concluded from simulations that an underwater habitat comprising spherical modules – constructed on the surface then submerged with ballast tanks – would be quite cheap and safe relative to other designs.

Next, let’s think about how to sustain life underwater. Perhaps the first concern is generating power. Though it is fun to consider tapping into a nearby oil pipeline, burning fossil fuels would squander precious air. You could incorporate a miniature nuclear reactor into your lair, like a military submarine, or otherwise harness tidal or geothermal power.

Once you have secured power, you can start to think about the other resources essential for sustaining life: oxygen, water, and food. Oxygen and water are easy; you can extract them from seawater through electrolysis and desalination respectively. Food is a little harder. You could bring regular deliveries of food from the surface using miniature robot submarines or trained animals (dolphins were used to deliver to the 62m-deep Sealab II). You could farm sea plants and animals. Or you could grow your own food.

Space and deep-sea exploration are frequently compared, sometimes unfairly. However, it is true that the engineering challenges of creating self-sustaining habitats in space and underwater have much in common. In both cases, delivering supplies is expensive, and moving crew between the surface and the habitat is an expensive ordeal. Even if it were not for the misanthropy you mention, you will want to minimise how often you must return to the surface; the crew of Tektite I (just 13m below the surface) had to spend 19 hours decompressing to return to the surface.

Of course, the best way to avoid this is to produce everything you need on-site. The ISS is beginning to grow some of its own food, including lettuce and cabbage, in experiments that will teach us how to sustain larger and larger biospheres – in which plants grow, soil is fertilised, and water is recycled – to support permanent crewed habitats in space, such as on the surface of Mars. Look to these experiments for inspiration.

There are no hard technical barriers to building the seafloor lair of your dreams. We know what materials, structures and construction techniques work best, and we know quite a lot about what needs to be done to sustain life within. There are plenty of projects in the pipeline: for instance, Jacques-Yves Cousteau’s grandson Fabian Cousteau is pitching Proteus (“the ocean’s equivalent to the ISS”) which would contain a lab, greenhouse, and recreational facilities; while Japanese engineering company Shimizu Corporation has proposed a structure spiralling from surface to seafloor, capable of housing 5,000 inhabitants. Whether these will become a reality is, as usual, a question of means. Perhaps if you have a spare $26bn (its estimated cost) you could help Shimizu get its project off the ground.

Yours,

The Evil Engineer