RE: [PSUBS-MAILIST] internal pressure question

Philip,

Although the "cat" can be skinned various ways, I have decided to do what the books tell me. To paraphrase "the soft ballast tanks are designed to be of such volume as to render the ship at or near neutral buoyancy when fully flooded". Then forget about them until it's time to surface.

In my design, this means no air in any tanks whatsoever while submerged, excepting the small VBT at the CG. You manipulate this small volume much like a hot air balloon varies density and thus buoyancy. In a sub, thrusters and or hydrodynamic effect, make up the difference.

I think the Benjamin Franklin vented into the cabin then overboard...I don't know why.

In looking at your "proof of concept" idea, I think you are where I was late last year when I was trying to "wrap" my mind around the concept of submerging a vessel. No need to prove this out, it's been done awhile, just follow the previously laid out examples.

There are lot's of ways to "prove" a concept. One way, and the way I have chosen, is mathematically, and then design structures and systems to "fit the numbers". then go test. The best example of this approach is the space shuttle. Until Columbia flew in 1980, nothing with wings that big, heavy and fat had ever been hypersonic. They designed structures and systems to "fit the numbers". based on what had been done before.

Joe

From:  Philip Ridenauer <akula151@yahoo.com>
Reply-To:  personal_submersibles@psubs.org
To:  personal_submersibles@psubs.org
Subject:  RE: [PSUBS-MAILIST] internal pressure question
Date:  Sat, 18 Mar 2006 18:18:36 -0800 (PST)

Thanks, Joe. Sorry to burden you further. Can I use the vehicle's ballast venting system to dump the pressure? If so, would I do so periodically to prevent taking on more ballast or do I need a separate venting system?

Philip

Joseph Perkel <joeperkel@hotmail.com> wrote:




"will the pressure inside the cabin need to be vented in some way"




Yes Phillip, an enclosed dry ambient will need to provide for Boyles law and the subsequent expansion on ascent. If the rate of ascent / expansion exceeds the ability to vent, the weak point in the structure then becomes the weak link...most likely to fail first, tympanic membranes (eardrums) then...windows.

Clearly the control (buoyancy) profile of a dry ambient, needs to be on the mon!
ey.

Joe





From:  Philip Ridenauer <akula151@yahoo.com>
Reply-To:  personal_submersibles@psubs.org
To:  personal_submersibles@psubs.org
Subject:  [PSUBS-MAILIST] internal pressure question
Date:  Sat, 18 Mar 2006 16:35:51 -0800 (PST)



Hi All,

I'm working on the design of a proof-of-concept vehicle to test the ballast system of an ambient dry sub. I've figuered out that on descent air from the ballast tanks have to be vented thru the cabin in order to keep the pressure equal with the outside. On ascent, once sufficient water has been expelled from the ballast tanks, will !
the
pressure inside the cabin need to be vented in some way to prevent the sub from exploding as the surroundind water pressure lessens?

Any thoughts or suggestions are appreciated

Philip Ridenauer



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