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The Yacht (I am using the term Yacht for the design style/aura I have in mind) needs to produce enough food and water for a crew of 40 permanent residents and up to 30 additional passengers at a time. Material concerns are hand waved by sufficiently advanced metals and power concerns are hand waved by onshore facilities delivering power/fuel.

Assume 30% of resulting size is devoted to food production in hydroponic bays complete with specialized lights (i.e. lights that only emit photons that plants need to grow and produce food).

Tank-less water heaters will be onboard negating the space needed for those operations.

edit: The location is Lake Erie and desalination is unnecessary as Lake Erie is fresh water. Normally the yacht imports food from the shore but has backup food production in the event of disasters. External support is standard for a ship it's size (i.e. more fuel, more replacement parts, laundry etc. etc.)

Let's be generous and say that fishing is half of the required food intake. Considering using solar power since that fits the character's developing take on protecting the environment.

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    $\begingroup$ What tech level? What external support are they getting? Do they need to recycle organic matter or can they get fertilizers, for example? Are they on salt or sweet waters? $\endgroup$
    – Mołot
    Commented Nov 17, 2017 at 18:25
  • $\begingroup$ Can they fish? Can they use desalination to get fresh water? And if onshore facilities deliver power, why can't they deliver fresh food? (Alternatively, solar power might be workable, especially if they use sails for traveling.) $\endgroup$
    – Peter Shor
    Commented Nov 17, 2017 at 18:31
  • $\begingroup$ @Mołot fertilizers and limited capabilities in recycling organic matter (i.e. no Trek replicators only what we can do of 2017). $\endgroup$ Commented Nov 17, 2017 at 18:51
  • $\begingroup$ Even if they don't need desalinization, they'll probably need reverse osmosis to get clear water, which can be large and expensive (to run, maintain, and fix). Just sayin'. :-) $\endgroup$ Commented Nov 17, 2017 at 19:14
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    $\begingroup$ Why would a ship in a lake want to grow its own food on the ship? It's completely uneconomical. It takes like an acre of land to sustain 1 person from just growing crops, nothing prevents you from building an aircraft carrier size ship and farm off it but that's just a plain waste of money. $\endgroup$ Commented Nov 17, 2017 at 20:05

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The yacht should probably be a small fleet. One human occupied floating residence and multiple hydroponic barges under small-crew or wireless control. With vertical farming, each barge could feed several people while remaining anchored far off shore. Additional barges could be included to store winter food stores, emergency rations, fuel and replacement parts. That leaves the yacht itself for the now more manageable task human occupancy. For that simpler task, the yacht could just be a re-purposed small cruise-liner, such as the Independence.

Additional vessels in the fleet might include some small ex-military patrol ships for servicing and defending the barges and a small cargo vessel for interacting with the shore.

During stormy weather and other threats, the barges could be designed to scuttle themselves in the shallow waters at the west end of the lake, then pump them selves back to the surface when conditions clear.

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Some napkin math.

It takes at least 100 square meter to feed one person. We discount that to 50 through fishing. So 40 people need 2000 square meters to farm. A standard shipping container is about 30 square meters of floorspace, so about 70 of them are required. This works out to needing a ship capable of shipping 2000 tons.

This appears to mean vessels about 250-300 feet long. But if we need to make it three times bigger to accommodate not being just a floating farm. It will be bigger, in like a 350-450ft range.

The power requirement of all that indoor agriculture is serious. 900 watts/meter (for peak growth) means we need nearly 2 megawatts to run this operation. That is a little more than the engine of the boat I linked to can handle, but in the same order of magnitude.

But that is a little silly. You would be burning nearly 200L an hour to make that power, which is more than a ton a day, much more than the food you are making. So we need some sustainable power. On lake Erie that's wind power, people are planning that amount of wind power there already. Mounting one of those turbines on a ship is left as an exercise to the reader; they would be about 300 feet tall and weigh about 400 tones.

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  • $\begingroup$ googles at power requirements damn. have an upvote for figuring out the power/size requires. $\endgroup$ Commented Nov 17, 2017 at 21:16
  • $\begingroup$ Perhaps the ship can use nuclear fusion or fission? Or does that conflict with the characters take on protecting the environment. E.g. lockheedmartin.com/us/products/compact-fusion.html $\endgroup$ Commented Nov 19, 2017 at 16:45

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