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Hello Jean.
You just missed the recent thread we had on this
subject. I had proposed something very similiar that further discussion made
clear to be although not impossible, pretty much impracticle.
I had proposed having a 1 atmosphere sub that could
convert to an ambient sub and back again. Some of the reasons I proposed
this were the same as your idea. To be able to leave the sub without having
to install
a diver lockout CHAMBER and to use the sub for
decompression after diving. Instead of building a seperate lockout chamber
within the sub which would take up a lot of space, I proposed just pressurizing
the sub and making
it ambient and then opening a bottom hatch to enter
and exit the sub.
Then I proposed after the diver reentered the sub, to make the sub 1 atmosphere again.
This all sounded well and good until Carsten asked me how I was going to get rid
of the pressurized air? You can't just let it bleed out of the sub. It will not
unless you
take on water to replace it's volume. As Carsten
wisely said you would have to have a compressor in the sub and actually suck air
from the interior into the compressor and compress it into a tank to bring down
the pressure from ambient to 1 atmosphere again.
Yes it may be possible but would take up more space than having a diver lockout chamber which
would defeat the whole purpose of doing it. By the time you had a
compressor taking up space to compress the air into a tank and make the interior
1 atmosphere again and
also kept the space
clear to have a bottom hatch which means another spot unusable because you would
have to have that area clear so you could open the hatch, it would take up about
as much or more room than just having a conventional diver lockout
chamber.
It's a great idea and would seem to work until you
start to think about how are you going to get rid of the pressurized air in the
sub. Once the interior is pressurized and ambient the interior is the same
pressure as the outside water as you know. The problem is
that now you cannot bleed off that air pressure
into the water because the air does not want to leave the sub because there is
no pressure pushing it out since the interior and exterior of the hull is the
same pressure at ambient. I suspose you could use the compressor
to suck air from the interior and instead of
putting in into a tank and saving it which would make sense, you could just use
the compressor to suck air from the interior and expell it out into the water if
you closed your bottom hatch when you did this. If you did not use a
compressor the only way you could depressurize the
sub would be to surface so the air could expand
as you accended with your bottom hatch OPEN and THEN air would bleed out
but only as you surfaced and would only become 1 atmosphere again when you were
either almost surfaced or actually
surfaced.
But don't feel bad, I missed the physics on that
one too until Carsten set me straight.
Kindest Regards,
Bill Akins.
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