Re: [PSUBS-MAILIST] Turtle

[Nathanael Henderson <jude@pconline.com>]

On Thu, 10 Feb 2000 SeaLordOne@aol.com wrote:

> tougher still.  From the moment the pilot closes himself off from the 
> outside, the air pressure in the cabin begins to increase.  As the Pilot's 
> body heat warms up the chamber, the pressure of the trapped air rises 
> proportionately."

    Hmmm...but proportionately to the Kelvin temp scale.   It should take
a fairly substantial increase in temperature before the rise in pressure
from it became a problem.   (Which would itself be easy to deal with by
equalizing your ears, something I imagine most of us know how to do from
SCUBA diving.)

> to get you back to the surface.  The pressure in your ears becomes a pounding 
> headache.  As more and more of the air gets used up, your breathing gets more 
> rapid.  Inhaling deeply brings no relief to the tightness in your chest."

    Carbon dioxide poisoning.    A 'proper' sub really demands it's own
life support system, which is surprisingly simple to do.  The rebreather
mailing list page at  http://nwdesigns.com/rebreathers/  has a lot of good
info on scuba diving rebreathers, including sales and technical info on
'sofnolime', a brand of scrubber chemical that absorbs carbon dioxide.

> boat.  I installed 10 portholes in the Undaunted, but the damn things fogged 
> up so much I couldn't see out of them anyway.

    Did you try a good defog (particularly the sort used for
scuba/snorkling masks)?   The primary cause of fog is just the temperature
difference between the air and the window causing the moisture in the air 
to condense on the port, but this effect can be 'fooled' by 'defog'
treatments that both clean the surface and fill in imperfections, robbing
the moisture of nucleation points to easily form on.    The number of
ports shouldn't have much effect on the fogging problem--if ten ports fog
up badly, so will one.  :-)    The problem would probably be reduced by
using thicker acrylic viewports (higher insulation value), or you could
rig something up to heat the viewport (since as long as the inside surface
of it is warmer than the inside air there shouldn't be condensation.)
You're probably already familiar with the heater wires put in car rear
windows to defrost/defog them--the principle is the same.