tanks into the hull and other variables cause a
1 atm sub to not technically always be 1 atm. If that is true, then why do
we call them 1 atm in the first place?
I am trying to understand terms we use that
seem to not always fit the pressures they describe.
When you and Ray described pressure variations
to me that showed a 1 atmosphere sub to not always be 1 atmosphere, I
mirrored what you said back to you in trying to
understand why we call something a certain term
when upon close inspection that term shows to not always be an absolute.
Please understand, I am not trying to argue
with you or Ray, I am trying to understand susposedly specific terms that
upon close inspection appear to not
be absolute. From yours and Rays descriptions
of 1 atm subs frequently not being one atm, I wonder why we do not have an
accurate term that IS an absolute for
what kind of sub they are. Your definition said
1 atm was "at or close to surface pressure". What does "close to surface
pressure" mean? 1 pound of pressure? 10? 15? 100? How do
we determine a specific, accurate measurement for "close
to"?
That's kind of like attorneys arguing over what
is "Reasonable". As much as I am not very good at it, I think we need
mathematical figures here.
It would seem to me that the only accurate way
one could catagorize what type of sub would be to measure the pressures in
the boat during her sea trials during different situations and then
using 1 atm as the starting point baseline,
show those pressure variables as numbers and then catagorize the sub by a
baseline of 1 atm to whatever the largest of the numeric pressure variables
were.
That would then be an accurate term. For
example like this...."This sub is 1 atm to 16.2 lbs of pressure". The 16.2 being the largest of the pressure
variable spikes experienced during her sea trials.
Wouldn't that be more accurate than incorrectly
calling something 1 atm when it frequently is not?
Ian, you wrote..."I don't see any reason the ballast tank design of a submarine has any
effect on whether it's a 1ATM or ambient".
In the case of the Hunley with her open to the
hull interior ballast tanks it does make a difference and have an affect
Ian. I explained the reasons in an earlier post but will do so here for you
again.
I may well be wrong in thinking that the Hunley is a COMPLETELY
ambient sub, but she does have attributes and qualities of being ambient in
her design.
Let's analyze them.
1. An ambient sub allows water to enter its INTERIOR to dive. The
Hunley did this with her open top and open to the hull interior ballast
tanks.
2. The water pressure entering the sub's interior when an ambient sub
dives, compresses the atmosphere in the sub's interior just as it did with
the Hunley.
3. An ambient sub uses air to force water out of the
sub's INTERIOR to surface, just as they did with the Hunley.
In fact Ian, the Hunley has more in common with
an ambient sub than it does with a 1 atm sub. If they just had the ONE
addition on board of pressurized air tanks and left the ballast tank
valves open and used the air tanks to keep the water
from spilling over the open top, open to
the hull interior ballast tanks, she would have been COMPLETELY
ambient. She was just one step away from being a completely ambient sub. But
one off she was indeed.
The Hunley could CLOSE OFF her ballast tank's valves and thus
prevent outside water from freely coming in without just using air pressure
to keep the water out. WHEN the ballast tank valves were CLOSED OFF
the Hunley SWITCHED from being an ambient sub (letting water into
her hull INTERIOR and compressing her atmosphere), and
became a pressure hull sub.
Ambient subs do not prevent the water coming in by closing a valve
like the Hunley did. They are ALWAYS open to the water coming in and
keep it out by pressurized air pressure only. They have to use a pressurized
air tank in order to do this.
Since the Hunley did not have pressurized air tanks she could
not do this and deviated from what we consider to be ambient by being
able to close off any water coming in by closing her ballast tank
valves.
When she SWITCHED from ambient operation to pressure holding by closing
her ballast tank valves, she became a pressure hull and her
atmosphere was compressed and no longer at 1 atm.
IF we accept the above 3 listed ambient
qualities of the Hunley, then we have to conclude that when she dove with
her ballast tank valves open and compressed her atmosphere, she was acting
as an ambient sub at that time.
Then when she closed her flooded ballast tank
valves, she became a pressure hull.
Then when she opened her ballast tank valves
again and used her compressed interior atmosphere to pump the water
out, she was acting as ambient again. Then when the water was all pumped out
she closed her ballast tank valves again and
became 1 atm pressure hull
again.
She had to be switching back and forth from 1
atm pressure hull on the surface, to pressurized ambient upon diving, to
compressed atmosphere pressure hull, to ambient using her compressed atm to
pump the water out, then back to 1 atm again!
Unless anyone can correctly dispute the above
listed ambient qualities of the Hunley's design, then we must conclude that
she was in fact a hybrid having both qualities of an ambient, and a pressure
hull sub.
She also switched from being a 1 atm
pressure hull sub at the surface, to having her atmosphere compressed when
she dove making her no longer a 1 atm sub, then when she pumped the water
out of her ballast tanks, she became 1 atm again.
So we cannot call her a 1 atm sub, because she
sometimes was not. She wasn't a 1 atm sub, she also wasn't COMPLETELY
ambient. She was a combination of the two. A HYBRID.
It's all due to the Hunley's open top and open
to the hull interior ballast tank design.
Now do you see the reason Ian why the design of
the ballast tanks had an effect on whether the Hunley was ambient or 1
atm?
Comments?
Kindest regards,
Bill Akins.
Sent: Friday, June 10, 2005 7:50 PM
Subject: Re: [PSUBS-MAILIST] When is
ambient, ambient and 1 atmosphere, 1 atmosphere?
By your definition, there are no manned 1ATM submarines
in existance
(even breathing will change the internal cabin
pressure).
Definitions:
1ATM: Pressure resistant
hull, internal pressure is at or close
to
surface
pressure.
Ambient: Non-pressure resistant hull, internal
pressure
matches
external pressure.
I don't see any reason the ballast tank design
of a submarine has
any effect on whether it's a 1ATM or
ambient.
Ian.