X-Message-Number: 2006
Date: Mon, 22 Mar 93 19:21:05 GMT
From: 
Subject: CRYONICS

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re W. Dye's question about huge economy of scale, here are the
thoughts of another lurker. I fear you might have been hoping for
something a bit more informed, but here goes anyway.

I guess the cost curve flattens out at about that of the LN2 required
to fill the volume per patient, plus the cost of excavating this
volume of ground, since a sufficiently large facility has negligible
boil-off. How large a facility is this? Using round figures, I get
that a spherical shell of foam (inner radius Ri=20m, outer radius
Ro=30m, thermal conductivity K=0.02 W/m/deg) initially filled with LN2
would take almost 100 years to boil dry, or 1000 litres a day to
maintain.  The scaling is very favourable - lifetime goes as linear
dimensions squared. Cost of materials: 30M$, assuming 300$/m3 for both
LN2 and foam (perhaps there would be a bulk discount!). This spherical
model might approximate to a cuboid shaped pit, with loading by crane
from above. If one could fit in 30000 patients (one per m3), the cost
would be $1000 each, or $3 per person per year to maintain. Even with
a somewhat lower patient density, this is competitive with a
conventional funeral/burial. Does anyone know of a suitable hole in
the ground, or what it would cost to dig one? For still larger
scales, the lifetime could be longer and the proportion of the total
volume which is foam lower, so that the limiting cost is just that of
the initial LN2 and of the hole.

While this scale of project might be rather remote from the current
concerns of cryonics, perhaps its possibility would help to counter
a couple of common criticisms:

1. I think most people assume that the world could never afford
storage for everyone, and that therefore cryonics is unethical. It
seems that in principle it could cost a few hundred dollars or less
for almost indefinite storage if everyone was doing it.

2. Doubt that any organisation could have the integrity to keep
expending resources on unresponsive clients continuously for
centuries. Above the 30000 patient level they need be trusted only to
not sell off the LN2.

Above figures use the following formulae:

heat loss = K DT 4 pi Ro Ri / (Ro-Ri)

-> lifetime = (1/3) (C/(K DT)) Ri^2 (Ro-Ri)/Ro

where DT is the temperature drop across the shell, and C=175MJ/m3 is
the heat needed to boil off LN2.

--Bobby Hesselbo

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