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Self-sufficient Flying Vessel

Let's assume that something has happened to the Earth. I won't be going into detail about this, but assume that if any living organism comes within 2 miles above the surface of the Earth (accounting for changes in elevation on the surface), it dies immediately. There is no other effect on the atmosphere, or the surface temperature, aside from the fact that atmospheric regulation from algae and plant life is mostly lost.

The ship can still send drones, and machines down to the surface, but nothing living will survive.

Is it possible to sustain a population of, say, 1000, aboard a vessel like this? If so, how will the ship:

  • Produce power
  • Stay in the air
  • Produce food (aeroponics? hydroponics?)
  • Create medicine, and other hard-to-manufacture goods
  • Collect resources
  • Gather water
  • Something else that's important but I haven't thought of

Assume that the ship can

  • Be built of any material harvestable on Earth
  • Have more advanced, but not space-opera level (LFTR (Liquid Fluoride Thorium Reactor) fission, efficient solar, aeroponics, limited quantum computing, etc) technology
  • Have a crew with a perfect mental health, etc. Just worry about physical needs.
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    $\begingroup$ Hire Lando Calrissian? (Oh, nevermind. No space opera...) $\endgroup$
    – Qami
    Nov 14 '21 at 4:20
  • $\begingroup$ Seems doubtful. What is the lift capacity of your airship? 1000 people is about 75 metric tons and even the largest airships that were constructed only have ~20 metric tons of lift. $\endgroup$ Nov 14 '21 at 5:23
  • $\begingroup$ Give each person an area 10 ft. by 10 ft. by 8 ft. high, you need an 8 story ship100 ft. by 500 ft., not including hallways or dining areas. No mechanical rooms. either. That is a LARGE airship. $\endgroup$ Nov 14 '21 at 6:00
  • $\begingroup$ "Create medicine, and other hard-to-manufacture goods" is the hard part. I have a solution to everything else, but not that. That requires a massive industrial base. I am considering answering with a kilometer-scale airship, though...I think I, myself, have a question for the site. $\endgroup$
    – KEY_ABRADE
    Nov 14 '21 at 7:01
  • $\begingroup$ @JustinThymetheSecond Or, since mental health isn't a concern, just make it submarine-style. $\endgroup$
    – KEY_ABRADE
    Nov 14 '21 at 7:10
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Flotilla

To make the question easier for me, I would suggest to spread the facilities and people over multiple ships. A single big one doesn't seem realistic, as the sheer size can already put a lot of strain on the whole ship. Imagine having a sheet of normal paper, but making it 20m (65ft) big. It is unwieldy and rips itself apart due to it's own weight, strain and any added force of even a soft gust of wind. Making something bigger and bigger is much like that. There's ways to mitigate this, but several ships is much easier.

Maintenance

Every airship needs to be maintained. Rigid, semi-rigid or full on balloon style must all have regular inspections and repairs. As you mention you have drones that can do complex tasks autonomously, this can be done by them. A flotilla will help here. If any ship requires repairs for which it needs to land, you can simply move all passengers to the other ships and land. Potentially the people can stay inside compartments sealed off like a spacecraft or submarine during these repairs, so they can stay on the ship and survive below the 2 mile barrier.

Water and food

My initial thought was that water would be hard. I've seen designs of skyscrapers so tall a normal way of plumbing would require insane pressures to get it that high. The solution proposed was cloud harvesting. Big ducts allow clouds and random water particles to condense or climg to surfaces, allowing it to be caught. These are big things, so unfeasible on an airship.

But it's not that hard. Compare it to a spaceship. Here a relatively tiny amount of water is recycled again and again. From perspiration to urine, it can all be turned back into clean water. Your airships don't need such extensive recycling, as there's still plenty of extra water in the air to collect. This can immediately be used as ballast to have stable flights.

For plants much the same can be done. There's big pots of plants you can buy. Add a little water and seal it. Water vaporises from the plants, condenses on the glass and slide down again, where it's ussd by the plants again. These ecosystems can run for years, even decades if done correctly. For your hydroponics you can do much the same, but on a different scale. The water in this case is collected and stored to be released at the right time. Again, use drones to fully maintain and harvest the gardens. That way you require minimal space, lights and water.

Drones

The drones are a solution to most of your problems. Maintenance, resource gathering and farming can all be done by them. That means you don't need to do everything on the airships. You can setup fully automated facilities on the surface. Mining and production of non-organic goods are chief among them. With some automated transports you can still have a huge range for the airships to fly. With many leftover facilities from the olden days they might venture nearly anywhere.

This does heavily depend on a well automated system. It wouldn't seem a stretch if you have special fission and super efficient solar panels. Then again, we mastered fission and space travel with computers that barely could calculate the square root of something. It might all fall apart if you don't assume these super drones and automation of factories.

Power and staying afloat

You suggest fission reactors, but super efficient solar pannels might already to. In a pinch humans don't require a lot of energy. Look at spacecraft again. They have life support and a ton of other features, yet it's powered by a relatively small array of solar pannels. If they are super efficient, you don't require too much surface on the airships to produce it. Solar pannels don't work at night [citation needed]. Storage of surplus power can be done in special compartments or separate balloons by producing hydrogen. This loses a lot of power compared to batteries or flywheels, but can also be used to refill the gasbags to stay afloat. Any airship slowly loses its gas! Some people might refer to the Hindenburg, but I hope airships have become more safe with new technology. You might have a hydrogen and helium combination for more safety. Helium is not as easy to get, but can still be created over time. That way the hydrogen can be used for both a stable flight and as electricity in a pinch.

Other concerns

Although you mention for this question the people are in good health both mentally and physically, it is still a major concern. Weight is valuable in an airship, meaning smaller compartments. This can be physically limiting, which affects both the mind and the body.

The 2 mile barrier is also problematic, as airships generally operate below that height. Airships need to become even lighter and/or the gasbags bigger for yours to operate above that. They might be able to fly in the death zone, as you need well protected living quarters if uou fly above the two miles anyway. Still it is something important to consider. It might be easier to build big sealed buildings on the ground with a special infrastructure for people to survive.

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  • power production

Your airships dont seem to need to go anywhere fast. That is great, since you can use wind energy. 2 miles up there is a lot of wind in all directions. You would let the wind push the turbines and ship in one direction, then shift height to another wind direction to make sure you keep a healthy energy production. If the drones build masts with loooong cables they could also anchor the ship.

Other power solutions: ground based drone-operated facilities create stored power, hydrogen power for example. Then export this to the airship where it can be used for power. High-end batteries/capacitors could also be brought up and down from such facilities for stored power.

  • stay in the air.

This requires volume, and airships have a great advantage in this area. This is the one exception where the square cube law is favorable. A larger ship means more volume of lifting gas compared to its outer surface area. That means that larger airships are less affected by the wind as the wind has to push more total mass with effectively less surface area per mass.

The lifting gas used would most likely be hydrogen rather than helium due to hydrogen being easier to come by in large quantities. Hydrogen is flammable and people are fond of pointing to the Hindenburg so lets install some safety measures:

  • don't vent flammable gas to lose altitude. This can be done by using vectored thrust and wing surfaces for a portion of your lift.
  • don't use a flammable envelope. If the Hindenburg's envelope wasn't flammable and remained intact when exposed to heat then only a flame would have appeared at the hole in the ship. This flame might even peter out since the gas inside isnt under pressure and uses osmosis to leak out. Even if the flame can keep itself going it would mean the ship wont crash as fast or engulf its passengers in flame, and it would give you hours to fix the hole and stop the burning before the ship crashes.
  • use multiple gas bladders. The Hindenburg already did this actually, but since the ship itself was flammable the other envelopes could also catch fire. Multiple bladders means the loss of one or two bladders does not mean the ship is lost. Bladders are located inside the envelope.
  • add a second gas bladder on the outside of the hydrogen gas bladders. These can have an inert gas inside, like a small amount of helium. This means any hydrogen gas leakage will (initially) be mixed with gases that reduce the flammability of the hydrogen as there is less oxygen to mix with.
  • add more electronic measurements. This should be easy for your drones. The Hindenburg had very little to gauge the status inside and outside of itself. A leakage would be far easier to trace in the modern day.
  • use modern materials. Modern materials can provide a lot of benefits in weight reduction, self-sealing capabilities, strength, fire safety and reduction in natural gas leakage. The Hindenburg had limited viable materials available, hence it used a material that was quite close to rocketfuel as its outer envelope.

As mentioned you can also use a heavier-than-air airship by utilizing vectored thrust and wing surfaces. This is what modern companies trying to bring back airships use. Since your ships never land but do fly at a height they can use the wind up high to stay aloft, reducing the need for lifting gas and making it easier to shift height when necessary. Vectored thrust by letting your engines point in any direction can also help the ship change heights or stay aloft in downdrafts. Although its likely that you use drones to plot the air movements ahead and avoid downdrafts as much as possible so your ship isnt pulled beneath the 2-mile height.

Production of the hydrogen could easily be done by drones on the ground. A modern nuclear/fusion reactor could provide plenty of energy to create hydrogen for fuel and lifting gas purposes.

  • produce food.

The big problem here is that there is no food production possible at the surface of the planet. This means you need to bring everything you need to produce food up in the air. If you've read anything about vertical farming and artificial light sources you might notice it is inefficient for your purposes. You need to have enough energy for light, bring the soil and have the plants all above the 2 mile limit to survive. That is an aweful lot of mass, space and energy to create food, but there are alternatives. Such as this (very very early) suggestion to use bacteria to convert biological waste and carbon in the air into food: https://onlinelibrary.wiley.com/doi/abs/10.1002/bit.260060406

Key factors here: its suggested for long-term space travel where all of the food has to be essentially recycled and it uses hydrogen as important catalyst in the cycle. Since you likely already have the infrastructure in place to produce large quantities of hydrogen and store hydrogen on the ship for fuel and lifting gas is makes the supply chain much shorter. This reduces the amount of surface area, weight and onboard energy you need to create food since the bacteria use chemical processes to convert the materials to food. For variety you can assign a portion of the ship to create other foodstuffs but it will just be to create flavor rather than the main foodsource.

A big advantage is that any food can be purified and stored by hanging it below the 2 mile limit where everything dies. If necessary through a small drone airship or by ground based facilities operated by drones.

  • create medicine

I'm not sure why you are asking this one. You are going to need to find, extract, refine and build the medicine. That means the only solution is to have drones that can do this. You can have some refinement facilities onboard, no idea how big they would be. But it would likely be smarter to use scanning equipment to locate materials, send drones to collect it and have a ground station somewhere which creates bulk medicine, to be collected at intervals as the airship passes overhead.

  • collect resources

Same as medicine.

  • gather water

Molecular sieves, the water created through burning hydrogen or automated facilities on the ground which filter the water without the need to prevent biological contaminations and then bring it up using the drones.

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