Wouldn’t the lid be sucked in when the differential pressure is not that big yet? Usually all that holds it in place is a feeble latch and the pressure from inside.
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The pressure canner I just picked up has 1/4" to half inch aluminum walls, and six decent sized latches. If it was under a vacuum and you dislodged the lid (somehow) it would hop up and spew its contents everywhere.
Of course if it came to be a serious vacuum, you might need to step drill the lid to get it off 
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Sweet! I’d love to have that one, for a vacuum chamber! If the lid would be replaced with a board of laminated glass, it would be even possible to see inside. (Of course a little webcam inside the enclosure could also do the job, with just a small hole for the wires.)
Yes, pretty much like this! (Such thin-walled vessel? Maybe it’d work though…)
Yeah, that one isn’t mine. And I’d splurge for an overbuilt unit when it comes to messing around with pressures.
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Same here. A potential problem with pressures is that an overpressure-resistant vessel can fail miserably when subjected to underpressure; see the spectacular failures of tanks, whether rail or car ones. The cylindrical walls are fairly resistant if not too thin, the flat bottom of the vessel can be however susceptible to caving in.
The advantage of vacuum is however that you can’t get much over one atmosphere of pressure difference vs the ambient.
…what if we added more power?
Yo dawg, I heard you like pressures so I put a vacuum chamber in yer pressure cooker
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Then it’s not ambient anymore.
Thought. We could sink the assembly into water. Then we’d get quite some additional pressure differential.
I was actually thinking about a design of an underwater vehicle that’d be totally filled with e.g. oil or gasoline, to avoid having to deal with heavy pressure vessels… And if the liquid was gelled, would be even leak-resistant both underwater and above, which would significantly reduce oil-dripping annoyances in storage/transport.
…turned out there are actually decades old guidelines for such designs, as this is the approach used for submarine hardware that goes outside of the inner pressure hull.
Ambient shambient, we’re blasting off for Venus!
BTW, and this is a little wacky, but would oxygen rich unclmpressable liquids be feasible for humans at deep sea depths? Like the Abyss? Or is recharging the oxygen and scrubbing the co2 from the liquids too crazy?
The ocean depths are also pretty interesting, and don’t require annoying amounts of rocket fuels. Think of all the shipwrecks, and virtual presence via remote controlled vehicles, or swarms of such vehicles making accurate 3d models for virtual walkthroughs…
Not that wacky, I’d say. Quite some research going into this. The big problem here is the much higher viscosity of the liquid in comparison to air, together with the large volumes needed to move. So I think some mechanical assistance to the lungs would be required.
…thought… why not gene-mod (or just surgically mod, with 3d-printed additional organs) the diver with gills?
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This might be excruciatingly uncomfortable (I sure know it was when I was in surgery) but a tube down the esophagus would be more practical.
Wait, what problem are we trying to solve? >:)
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It’s actually tube down the trachea. With esophagus they’d just inflate your stomach. The tube slipping is something that has to be guarded against.
Beats me! 
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Heh, I just got done making rice in a pressure cooker, as we’ve done for three generations now…
Maybe 1 or 2 failures in all that time? If that?
The trick, even with the “wobbling weight” ones is to ensure that the exit hole doesn’t get plugged. Put whatever you’re cooking in a separate container and cover it. Steam will escape easily; food particles pushed up by the pressure may not.
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For the same reason cannonballs and mortar shells generally go in one direction. Have you seen footage of a bullet cooking off? The shell goes one way, the bullet goes the other, and the particulate mostly follows the path of the bullet. That the food would follow the same path as the lid and not really splatter until it hits something isn’t surprising at least to me.
But yeah, the lid not deforming at all does seem suspicious.
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I believe this type of device is already used to de-shell and cook mollusks and crayfish industrially
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Because the dissolved oxygen content of water is barely enough to keep cold-blooded fish alive. You’d have to be circulating hundreds to thousands of gallons of seawater a minute to pull enough oxygen out of the water for a human doing something other than being comatose. It’d be faster and easier to simply electrolyze the water into HHO and just use the oxygen.
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I have a Fagor, similar to the one featured in the link. It was a gift, and though it was well-meant, it’s not ideal. It leaks copiously before the pressure comes up to seal the gasket, and I’ve tried a few different approaches (new gasket, oiling the gasket, calling Fagor, avoiding cooking foamy stuff like beans–the one thing I most need it to cook for us): it just leaks and is messy. Fagor’s lower part–the pot itself–is solid and I use it. I sure wish they’d redesign the lid/gasket/lock assembly though.
I also have one of these:
http://www.sunoven.com/products-page/sun-oven-package/global-sun-oven-duplicate
It’s kinda the opposite of a pressure cooker: very unfast. But even if you’re not around rotate it to face the sun optimally every hour, on a sunny day it cooks the hell outta most stuff. I love its “set it and forget it [until dinner time]” method here in Texas. It doesn’t really ever overcook, which is handy. Beans? Just put in the water, seasonings and soaked or unsoaked beans, then walk away. Hours later, grab the salsa and tortillas. We’ve cooked through power outages, out in the fields when we’re attending bees and fruit trees and chores, we’ve taken it car-camping (it’s lightweight but bulky), we use it when we don’t want to heat our house up in the summer. No complaints. It’s about 99% safe, as long as you don’t look right at the reflectors when you go to take your food out, unless you’re unloading it at sundown.
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If it’s been on the stove since the other day you might want to… uh… go outside and enjoy how beautiful your house is. At the moment. And stay out there for a while.
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