X-Message-Number: 3383
Date:  Wed, 02 Nov 94 17:05:56 
Subject: SCI.CRYONICS High Pressure Cryonics

Ben Best's posting concerning high pressure cryonics contains some 
assumptions which could lead to consequences I don't think he 

First, the reason that high pressure storage has been proposed is to 
bridge the gap between toxic cryoprotectant concentrations and 
vitrifiable cryoprotectant concentrations, using current 
cryoprotectants. Other cryoprotectants might not have this gap.
Second, some practical engineering and physics considerations come to 

If we assume fabrication of a pressure chamber of 22" diameter using 
steel at 100,000 psi yield strength and a storage pressure of 2000 
atmospheres (30,000 psi), this results in a chamber with 3.3" walls. 
This ignores engineering practice and the question of the properties 
of steel (industrial strength) at liquid nitrogen temperature. Other 
problems are electrical and fluid feed-throughs. In a lot of ways 
this begins to look like a gun barrel. A recent example of this scale 
of fabrication was Gerald Bull's long range super cannon he was 
developing for Saddam Hussein! In particular the closure for this 
pressure vessel starts to look like a breech block.

A question that come to mind at this point is: Do you store 
people at this pressure? In which case the cost of storage per 
person will be very expensive. Or, since at low enough 
temperatures, the high pressure forms of ice can be stored at 
atmospheric pressure, do you process them down to - 196C and then 
remove them in a metastable state and store them at atmospheric 
pressure in liquid nitrogen with attendant transfer complications?

The crystallography of the high pressure forms of ice from X-ray 
diffraction studies was done this way.  The ice crystals were formed 
at high pressure, cooled to liquid nitrogen temperature and removed 
from the pressure vessel at -196C in a metastable state and X-rays 
were taken. Unfortunately, a lot of energy is stored in the ice.
There is probably somewhere an anecdotal account of dealing with 
"explosive ice".

We can estimate the amount of energy involved in the re-expansion of 
the ice as follows:

W = PdV 

thus 30,000 lb/in^2 x 0.08 in^3/in^3 = 2500 in-lb/in^3

which after appropriate conversion results in a value of 67 cal/in^3 
or 4.2 cal per gm.

The heat capacity of ice at low temperature is as follows:

 -200C                  0.156 cal/gm.
 -150C                   .246
 -100C                   .332
  -40C                   .435
   0                     .492

Assuming the transition takes place at -150C, the temperature jump 
from the released energy will be approximately 17C. "delivered by 
hammer" (Try pounding a piece of iron until it gets too hot to touch!)

For 14,000 atmospheres (another figure mentioned in Ben's posting), a 
vessel of 23" steel walls results, again ignoring engineering 
practice and strength vs. temperature.

The bottom line is that this is not a trivial project and can have 
some rather novel consequences. The resources that would have to be 
devoted to it would almost certainly be better expended in other 

Incidentally, I at this point do not share Bob Ettinger's confidence 
that cracking is not a problem for liquid nitrogen cryostasis.  
Although he may in fact turn out to be right, there is still work to 
be done in this area before we can reach that conclusion, (work which 
is still in progress here at Alcor). 

Hugh Hixon
Alcor Foundation

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