Using a large unit for cryonics does have some complications. One would need to be able to be able to add people in at different times without disrupting the temperature. And when we eventually start taking people out they’ll need to be able to remove the the then repairable ones without disruption to the more injured/sick. I suspect that neither of these will be a large technical hassle. Maybe someone who knows more about low temp engineering can comment if that’s correct.
I envision a steady stream of new patients for one or more years after its construction. There would be a robotic system to place them, and they would be cooled prior to entry. Delivery mechanism could be as simple as lowering them on a chain, but I suspect getting them settled in stably would involve some kind of robotic mechanisms operating withing the container itself. It would make sense to stack with accessible spaces given to more repairable patients, But with high-precision robotic removal it shouldn’t be impossible to shuffle patients without shock. (They would be wrapped in something like fiberglass within their boxes to minimize this anyway.) On the other hand, it might be simpler to just take them out, assess them one by one, and place the ones that need to wait into a different dewar.
Maybe someone who knows more about low temp engineering can comment if that’s correct.
It’s not so much of a problem. Liquid cryogens such as LN2 will ensure the temperature stays constant until they have entirely boiled off, so you just open the thing up, put the body in, and close it again.
The largest imaginable is probably somewhere in the millions of cubic meters. Bringing in futuristic mass-beam tech (hey, it’s feasible with superconductors and you’re under cryogenic temperatures already) and you can go bigger than any building built to date, perhaps even hitting the kilometric cube—a billion cubic meters.
So we might say 30 meters is a relatively small one.
But even still, you are absolutely right that smaller ones are worth considering. In fact they are more worth considering because they can be done sooner. Every time you scale up by 1000, thermal transfer drops by 10. So if you just want to go from $22k to $2.2k, all other things equal, you can do this by going from 14 patients to 14000 patients.
The next wave of cryonics could take the form of relatively small (but still huge) urban cryo-centers that replace graveyards. A place like the UK where they are running short on grave spaces might be a good starting point for that.
Another important idea to look at is piggybacking cryonics onto other forms of cryogenic storage, or perhaps renting out storage in our cryogenic warehouses for other purposes as a source of funding.
I’m not quite sure I understand the math, but it sounds like you are saying that since there is a tenfold increase in volume per unit area that means not only does less heat reach the cryogen there is more of it to be reached. So the energy efficiency is 10 times, but the storage capacity is also 10 times. Or am I barking up the wrong tree?
100 times as much slack time between refills, wow. That reduces a lot of costs and risks.
The math is simply that the heat leak scales linearly with radius, not quadratically, because as you pointed out in your post, a larger container can have thicker walls.
If you scale outer radius at the same rate as inner radius, the thickness increases. And that impacts cost of boiloff by bringing it down by 100 times. Beautiful.
Using a large unit for cryonics does have some complications. One would need to be able to be able to add people in at different times without disrupting the temperature. And when we eventually start taking people out they’ll need to be able to remove the the then repairable ones without disruption to the more injured/sick. I suspect that neither of these will be a large technical hassle. Maybe someone who knows more about low temp engineering can comment if that’s correct.
I envision a steady stream of new patients for one or more years after its construction. There would be a robotic system to place them, and they would be cooled prior to entry. Delivery mechanism could be as simple as lowering them on a chain, but I suspect getting them settled in stably would involve some kind of robotic mechanisms operating withing the container itself. It would make sense to stack with accessible spaces given to more repairable patients, But with high-precision robotic removal it shouldn’t be impossible to shuffle patients without shock. (They would be wrapped in something like fiberglass within their boxes to minimize this anyway.) On the other hand, it might be simpler to just take them out, assess them one by one, and place the ones that need to wait into a different dewar.
Are there robots that operate at those temperatures?
It’s not so much of a problem. Liquid cryogens such as LN2 will ensure the temperature stays constant until they have entirely boiled off, so you just open the thing up, put the body in, and close it again.
I’m wondering whether the most efficient size isn’t the largest imaginable—that there’s some medium-sized unit which would be better.
The largest imaginable is probably somewhere in the millions of cubic meters. Bringing in futuristic mass-beam tech (hey, it’s feasible with superconductors and you’re under cryogenic temperatures already) and you can go bigger than any building built to date, perhaps even hitting the kilometric cube—a billion cubic meters.
So we might say 30 meters is a relatively small one.
But even still, you are absolutely right that smaller ones are worth considering. In fact they are more worth considering because they can be done sooner. Every time you scale up by 1000, thermal transfer drops by 10. So if you just want to go from $22k to $2.2k, all other things equal, you can do this by going from 14 patients to 14000 patients.
The next wave of cryonics could take the form of relatively small (but still huge) urban cryo-centers that replace graveyards. A place like the UK where they are running short on grave spaces might be a good starting point for that.
Another important idea to look at is piggybacking cryonics onto other forms of cryogenic storage, or perhaps renting out storage in our cryogenic warehouses for other purposes as a source of funding.
Wrong scaling. See my post: if you scale up by 1000 in volume, boil-off time goes down by 100. It’s better than you think!
I’m not quite sure I understand the math, but it sounds like you are saying that since there is a tenfold increase in volume per unit area that means not only does less heat reach the cryogen there is more of it to be reached. So the energy efficiency is 10 times, but the storage capacity is also 10 times. Or am I barking up the wrong tree?
100 times as much slack time between refills, wow. That reduces a lot of costs and risks.
The math is simply that the heat leak scales linearly with radius, not quadratically, because as you pointed out in your post, a larger container can have thicker walls.
So, heat leak ~ r
Volume ~ r^3
Volume/(heat leak) ~ r^3/r = r^2
Oh, that makes sense.
If you scale outer radius at the same rate as inner radius, the thickness increases. And that impacts cost of boiloff by bringing it down by 100 times. Beautiful.