Xray Scintillation Lighting

A unique form of lighting I've been considering is using free electron xray lasers to strike artificially-grown scintillating crystals, causing them to glow. These free electron xray lasers dont need to be close to the scintillating crystals, which makes their glowing more mysterious.

Uranium-containing crystals could also be used to glow and provide lighting. Similarly to the crystals, one could use beautifully-sculpted glass to glow and gleam with no obvious source of light. Careful design to avoid exposing the xray beams to human bodies can make them surprisingly safe. As an additional safety measure would be to use lots of leaded glass, since lead is cheap and decent at blocking radiation.

Suffice to say, the only practical way to power all this is with nuclear power.

Moon Pool Elevators

As a sort of evolution of caisson ship locks, moon pool elevators are special multi-tiered moon pools that behaves like a caisson ship lock, using hyperbaric pressure of neon-oxygen breathing gas to push the seawater down, and reducing that pressure to allow seawater to rise in an elevator shaft.

To make this economical, this shaft should be big enough that several shipping barges to fit in one elevator ride. Why shipping barges and navigable canals underground and underwater? it's surprisingly convenient and just plain cool. Shipping barges from the surface can enter and exit a long elevator shaft that terminates at the surface in an artificial island cove. The cove is shrouded in mist, produced by liquified air and chunks of dry ice from dry ice machines, and protected by very powerful superconducting magnets in frequencies designed to jam common communications channels, including aviation and nautical communications and navigation. This is a protective measure against potential invasion or military raid. These powerful magnets could also be used to flux pin islands in place for purposes of communications using free electron xray lasers and xray flat panel detectors, as well as additional defenses providing complex hazards for aircraft.

Using this technology, you could artificially cause the surrounding atmosphere to cool and precipitate out all water vapor and form a permanent shroud of clouds and rain, which wrecks havok with many types of communication, including military communications. A light spray of seawater, such as with artificial geysers, can provide the condensation nuclei necessary for water vapor to condense into rain. These artificial geysers could be powered by the molten salt, and fog machines powered by the liquid neon.

To access the cove, you have to navigate a series of obstacles, and then manually activate one of six elevators, which are hidden in a secret harbor within the cove. The harbors have counterweighted locks which seal the enclosure and pressurize the chamber until the seawater begins to receded. This receding seawater level is part of a system of moon pools, and draws the vessel deep underwater, which then can travel along a network of underwater canals.

During the descent, the neon-oxygen atmosphere is traded for the natural atmosphere, so that as pressure increases the nitrogen is removed, and as the pressure decreases, nitrogen is slowly added. This is both to protect the vessel's occupants as well as to conserve expensive neon gas.

Thermal Storage

One thing of great value in subterranean and deep sea underwater habitats is heat. Heat is used for many industrial processes including the desalination of seawater. District heating for keeping living and growing spaces comfortable is important in such habitats, and storing this heat for later use is also important as a means of storing power. The approach I'm probably going to use is molten salt, specifically "Norwegian saltpeter" or calcium nitrate.

Storing this heat in this form makes a lot of other things pretty straightforward. If nothing else, using the temperature difference between molten salt and liquid neon with a bank of thermopiles can generate quick electrical power in a pinch.

Liquid neon can be used for a lot of other things, as well, such as cooling superconducting magnets and superconducting maglev high speed railways.

Liquified neon and molten salt are both so useful that they can be exchanged in an infrastructural grid, and provide both district heating and cooling for entire underground or underwater cities.

Aquaponics

The great thing about hydroponics is how flexible it really is. Hydroponics can easily be combined with aquaculture to make aquaponics. Aquaponics provides a more-or-less closed nutrient cycle between the hydroponics, which requires additional nutrients, and aquaculture, which requires filtering the excess nutrients out of the water.

This is especially relevant in the design, architecture and construction of an underwater or subterranean habitat. To produce the maximum amount of food per cubic foot of space, growing both fish and other aquatic livestock with food crops is essential.

One of the best aquaponics fish is tilapia, which produces a lot of food per fish, grows quickly, and is easy to breed from broodstock. Other options include oysters, crab, crayfish, prawns and lobsters.

For the plants, strawberries and blackberries top my list. Oats, barley, rice, beans and peppers are all favorites of mine. Although growing them in this neon environment may be tricky, coffee, tea and other money crops, such as sugarcane and cotton, are all valuable crops and may be able to offset some of the expense.

All plant life, including the crops, need carbon dioxide, but at such hyperbaric pressures, that of enabling moon pools in ocean depths of 4,000 to 6,000 meters (~13,000 to ~20,000 feet) below sea level, carbon dioxide is poisonous to humans, even at low partial pressures. For this reason, cryogenic liquifaction and fractional distillation of neon-oxygen breathing gas to extract the carbon dioxide exhaled by humans and livestock, including aquatic livestock such as fish and crayfish, and deliver that gas in liquified form, to sealed robot-farmed modules. These modules contain a much larger partial pressure of carbon dioxide, which is extracted and pumped from the exterior tunnel system.

This allows the plants to have plenty of carbon dioxide, while still having plenty of oxygen dissolved in the water to permit the plant to breathe. As an additional measure to reprocess the carbon dioxide, aquatic plants such as water hyacinths and watercrest can be cultivated to take up shallow wastewater troughs to help treat the water and consume the carbon dioxide. There are some NASA experiments regarding hyperbaric hydroponics that indicate that many crops grow exceptionally well under hyperbaric growing conditions.

Neox Breathing Gas

Today, my research led me to discover that the argon-oxygen mixture I was considering would not work for my purposes, that a neon-oxygen mixture would work better. This surprised me, but argon actually can cause a more severe decompression sickness than nitrogen! Hard to believe!

With multiple layers of moon pools and caisson locks for naval navigation well below sea level, it's important that the high-pressure gas used to push back the seawater be breathable, and the pressure changes be tolerable for humans. Argon is not a suitable gas for this. Rather, a breathing gas that is mostly neon, with just enough partial pressure of oxygen to keep the blood red, is more suitable.

To obtain neon, you must cryogenically liquify atmospheric air, and then use fractional distillation to separate the neon out. Neon is expensive for this reason: there is only so much of it. Liquifaction and fractional distillation of air is the only source of neon.

The multiple layers of moon pools and ship locks means that you can have navigable canals well below sea level and control the flow of seawater from the sea into subterranean tunnels. This seawater can be used for multiple things, including subterranean mariculture and saline aquaponics. It can also be used for desalinating into potable water, which can also be used for subterranean freshwater aquaponics.

If we want to construct a subterranean and submarine habitat, food and water production in a sustainable fashion is important. Fish is a wonderful source of food. Many animals, such as goats and chickens, can also be grown in a neox breathing environment. For growing plants, a carbon dioxide obtained from the animals and filtered out of the breathing neox gas can be given to the plants in a neon-carbon dioxide gas. Most crop plants should grow just fine this way. Whatever stuntedness the crop plants suffer because of the ultra-high pressure may be countered with careful aquaculture nutrient balancing.

One nice thing about the neon-oxygen gas is it can be stored fairly safely in liquid form separately, and that the balance of oxygen to neon can be tweaked in case of fire. Fires in submarine and subterranean habitats is an especially deadly threat, because oxygen can be consumed very quickly if not carefully managed. When a fire breaks out, carefully re-balancing the partial pressure of oxygen to provide enough for humans to survive during an incident while starving the fire outbreak is a necessary firefighting measure.