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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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