You wrote..."With ambient subs, getting a diver in an out doesn't require a hatch -
just leave a hole in the floor. Although, I can't imagine why you'd
bother trying to accomodate divers with an ambient design."
One reason for accomodating divers and having a
hole in the floor with an ambient design would be if you saw
something down there that you wanted to pick up and
bring into the sub. A second reason would be to
further
explore something interesting that you see, but
that you cannot get close enough to by virtue of being inside the sub.
A third reason would be for normal entry and exit
doing away totally with needing any kind of a standard type hatch.
A
fourth reason would be to do away with the need for
a scuttle valve. A fifth reason that goes along with the fourth,
would be for an easy bail out in case of an emergency. A sixth reason would
be in case a diver was injured or ran out of
air or had a 1st stage regulator malfunction and he
had been compressed too long so that he could not immediately accend
without certain decompression sickness and possible death. He could come back inside the sub, breath
the air in the sub,
hopefully attend somewhat as best as possible to any injuries until the sub could surface and seek
proper medical attention,
and do all this as the sub slowly accended to avoid
decompression sickness.
"imagine". Smile. Bill Akins.
----- Original Message -----
Sent: Wednesday, February 15, 2006 12:25
AM
Subject: Re: [PSUBS-MAILIST] Dif. Between
Ambient & 1ATM
Ambient implies that the pressure within the hull is the same
as the
pressure outside the hull at all times. Essentially, an
ambient sub is
just like going for a SCUBA dive, only dry. The hull
in this case does
not need to withstand pressure differentials in any
direction, which
makes for much simplified construction, but then you are
subject to
decompression requirements just as when diving.
A 1ATM
sub maintains normal surface pressure within the hull at all
times,
eliminating the need for decompression regardless of dive
duration.
This means that the hull needs to be built to withstand the
external
pressure at the design depth. The interior pressure will never
be
higher than the exterior pressure in this case.
Diver lockouts
incorporate a separate chamber within the pressure hull
which can be
internally pressurized to match the external (ambient)
pressure. In
this case, when pressurized the only part of the chamber
that has a
pressure differential across it will be the bulkhead which
separates the
lockout from the rest of the sub interior. Diver enters
the lockout,
interior hatch is closed, chamber pressure is increased to
match ambient,
exterior hatch is opened, and diver exits into the
water. The
advantage of reasonable size lockouts like this is that they
can also be
used as decompression / recompression chambers, maintaining
the returned
divers at pressure even if the sub subsequently surfaces.
When space is
at a premium, and you can't use a dry chamber that a diver
can exit the
water to, you can use a wet trunk just large enough to
accomodate the
diver and permit him to close the hatch, but when blowing
or pumping the
trunk dry, you need to do this at constant pressure (i.e.
by venting at
ambient pressure), and then reduce the trunk pressure
slowly enough that
the ascent rate is reasonable - just like when
diving. This is more
difficult to accomplish with a small volume. Same
idea though - once
dry and returned to 1ATM, open interior hatch.
With ambient subs,
getting a diver in an out doesn't require a hatch -
just leave a hole in
the floor. Although, I can't imagine why you'd
bother trying to
accomodate divers with an ambient design.
-Sean
C & L
Hendkids wrote:
> Guys,
> From my understanding, the
differance between ambient hull designs and
> 1ATM is that ambient is
non-pressurized (resisting the pressure by
> structural strength) and
that 1ATM is pressurized (resisting the
> pressure by structural
strength *&* by internal air pressure, kinda
> like a 2L bottle of
pop before you take the lid off. :o) ).
>
> Also, I was
wondering if it would be feasible to have a submarine wet
> for diver
entry and 1ATM after they are in. (It would be underwater,
> and the
diver would open the hatch, get in, close the hatch, and then
> blow
all the H2O out of the cockpit).
>
> Am I confused, or
what?
>
> Just wanting a little clarification,
> Alan
Hendrickson, Oregon,
USA
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