[ExI] Essential Upload Data (was: Subject: Boltzmann brains)

spike at rainier66.com spike at rainier66.com
Fri May 15 16:01:16 UTC 2020



> On Behalf Of John Clark via extropy-chat
Subject: Re: [ExI] Essential Upload Data (was: Subject: Boltzmann brains)


On Fri, May 15, 2020 at 10:31 AM spike jones via extropy-chat <extropy-chat at lists.extropy.org <mailto:extropy-chat at lists.extropy.org> > wrote:


>>…It's simple and cheap to store a brain at -196C, you just put it in a big thermos and pore in some liquid nitrogen, but to evenly store it at -135C would be complex and expensive, you'd need all sorts of fans and heat exchangers and sensors and a computer network to manage it all, and that is a lot of places where a catastrophic failure could occur…


> On the contrary.  Storing at a stable -135C is cheaper and easier than -196C: -135C is below the critical point of argon.  Liquid argon gradually boils off at -135C when held around 30atm


At atmospheric pressure the boiling point of liquid argon is -186C, and I think it would be a very bad idea to have large containers full of brains pressurized at 30 atm. And liquid nitrogen cost about 30 cents a liter but liquid argon costs $2.25 a liter.


John K Clark




Regarding cost of argon vs nitrogen, that wouldn’t matter if the cycle is closed-loop: it doesn’t actually use up the material.  When we were fooling with it in the 80s, we had an open-loop system, but a full recovery re-condensation dual cycle is possible, as well as a hybrid system which uses liquid air as the heat sink for the argon condenser.


The motive for using argon is that -135C is still below its critical temperature.  I can see big advantages to that.  The big disadvantage I can see is the risk of catastrophic loss of pressure, which would cause the temperature of the stored bio-material to drop quickly to -186C.  That would be a bad thing.


I may not have understood the reason why -135C came up to start with, but the process control part of that problem caught my attention.  Process control is one of the coolest (interesting and fun, not specifically about temperature) fields of engineering I know of.  It unleashes the inner inventor in a prole.



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