Oil rigs are super fascinating from an engineering perspective. Ironically, outside of space the ocean is probably the most inhospitable environment for man-made structures to be built where we still want them. Anybody wanting to build platforms/cities/anything else in the ocean would probably do well to start by looking oil rig construction.

> Anybody wanting to build platforms/cities/anything else in the ocean

For anyone interested I think the term is "Seasteading"

And for the SV crowd, a little pie-in-the-sky: https://en.wikipedia.org/wiki/Blueseed

That's an interesting point. The article says that the rigs were bought for $3.5 million each. At that price, it seems pretty obtainable for people interested in creating a floating city at sea to buy a few as a starting point.

I'm afraid maintenance costs will quickly eclipse any money saved by buying a second hand rig due to the rather hostile marine environment.

That's exactly why they are so cheap. They aren't an asset that you can mothball very easily. You have to either run it or scrap it.

I would expect the cost of running them for a year is far more than 3.5 million.

We've come full Armageddon.

Absolutely back when I worked in Hydrodynamics RnD we built a test rig that could simulate some aspects of that - 21 Cumecs flow rate! (fist time we turned it on its set the alarms of on Cranfield Universities Power supply)

Heck yeah they do. For anyone else interested who hasn’t seen it, check out “types” in the wiki article linked above for a nice picture of some variations in common use. Fun stuff to compute the wave induced motions of... The math is very similar to a circuit analysis (linear time invariant systems). But the properties of your “circuit” (your boat, craft, platform, whatever) are solved by hydrodynamics to account for the shape dependence, environment dependence, etc. and depending what you want to know - done in the time domain or frequency domain as well.

Check out Dockwise Vanguard

https://www.google.com/search?q=dockwise+vanguard&tbm=isch

I would love to see the modeling they must be doing to make sure that the floating rig is stable while 11mil lbs of rocket with 15mil lbs of thrust launches.

Oil rigs aren't build in place. They need to be moved to where the oil is.