Sci-fi question: Snowcrash: The Raft: Would a raft comprised of an aircraft carrier, an oil tanker lashed together then ties to several miles of smaller and smaller vessels actually be able to survive floating around the pacific gyre? How would the physics of this work?
Since it's a distributed platform, a wave or a storm would still affect it in a big way so that any portion of it could flip or fold. Would it actually stay in the gyre? I mainly want to know if it is possible and any ways to help me think of something this large so that I can grasp the idea. Would a solid ship of a mile or more in length and half a mile in breadth fare better or would it crack and break when a large enough wave hit it?
Posted Jan 8, 2020, 2:18 PM UTC
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Not a maritime engineer... but I feel pretty confident that you'd have to allow it to flex a lot. In civil engineering, even concrete overpasses have to allow for thermal expansion/contraction, etc.
As you scale up a ship, the stresses required to make it rigid against deflection increase with size, but material strength doesn't.
The most applicable design analogy I can think of would be a pontoon bridge
It'd likely be possible, but there would be some design challenges. Chiefly, I think there's a tough balance between required flexibility and too much flexibility leading to self collision hazards. Not sure what the maximum likely wave magnitude would be but it'd have to be able to survive that from any angle since you probably aren't gonna be able to turn it.
FYI, this is more of an engineering question than physics, and you'll probably get an actual maritime engineer to weigh in if you post this question over in r/askEngineers or r/engineering.
To a point, I think. Once your structure is significantly larger than the water effects you're riding on, deflection stresses don't get larger. Once you span, e.g. 3 full waves, getting larger shouldn't really required more strength. I'd be interested in what a Very Large square would do in wave though. It probably would be so big that it couldn't get pushed up or down, so there isn't really a place for waves to go under it. Would they just bounce off? I think so.
Actually, the best design is probably deep pontoons like a floating oil rig. With that, the waves basically just go between the superstructure and the floating supports, keeping it stable and mostly unaffected by whatever the water does.
The difference in nautical vs terrestrial is that your bridge needs to stay connected to the ground. As the two move with respect to each other, you have problems. However, on the water, you don't have any fixed points. The ship can get ten feet longer, and you don't care.
Thanks, I will. Find a new sub everywhere I look!
To be fair ships of this length have been proposed before, normally by people off their heads, but often they're also actual naval architects, so some people believe its possible, at least.
Notably I'm thinking of Project Habakkuk, a WWII-era, 2.2-million tonne displacement, design considered by the Royal Navy for a 1.2km long by 200m wide Aircraft Carrier made out of a permanently refrigerated iceberg (I didn't make that up, honest!).