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Re: [PSUBS-MAILIST] Theory Question

Well, the first thing that came to my head was that if the craft is enclosed in a bubble with water rushing past the outside, maybe it would be possible to extend a small "rudder" or "elevator" for lack of better words and touch the water from the inside of the bubble.  The small amount of drag would cause the sub to move to what ever side had the increased drag.  But then again, this may alter the shape of the bubble and that wouldn't be good.  Something to think about though, and that's always fun.
----- Original Message -----
From: Captain Nemo
To: personal_submersibles@psubs.org
Sent: Tuesday, June 25, 2002 4:47 PM
Subject: Re: [PSUBS-MAILIST] Theory Question

Steering.  Hmmmm...Admittedly, I haven't thought much about supercavitation because I don't deal with it.  But you raise an interesting point.  I guess you could steer with thrust vectoring, but then, as you say, what will happen to the shape of the bubble when the sub changes direction?  The closest analogy that come to mind at this moment are airplane wings I've seen that were perforated with a zillion little holes through which a portion of the engine exhaust was pumped.  They say it reduced drag somewhat, but the hard part was maintenance: keeping all those little holes clean.  I think if it were set up to distribute the gas envelope properly along the hull, a supercavitation system could be made to work at all angles and through a useful range of maneuvering.  But like you, yeah this is all way beyond me. 
 
The closest I came to this kind of thing was a project for a high speed sub: I have the hull and the 454 ratmotor downstairs.  But I decided to sack it for reasons Herve expressed: how fast do I want to go when continually submerged in limited visibility?
 
Pat
 
 
 
From: James
To: personal_submersibles@psubs.org
Sent: Tuesday, June 25, 2002 1:11 PM
Subject: Re: [PSUBS-MAILIST] Theory Question

It seems anything having to do with supercavitation is pretty dangerous.  From some of the reading I did another problem is with the steering of the projectile within the cavitation bubble itself.  The projectile can start banging around inside the bubble along with some other issues.  I'm really not big into going as deep as possible anyway, reading about the pressures at depth make me nervous.  Being able to cruise around at 100 ft to watch the fish, or race around in a bionic dolphin is more my cup of tea.
----- Original Message -----
From: Captain Nemo
To: personal_submersibles@psubs.org
Sent: Tuesday, June 25, 2002 3:59 PM
Subject: Re: [PSUBS-MAILIST] Theory Question

James,
 
Somewhere in this thread, someone (you?) wondered if a sub wrapped in a supercavitation bubble might be able to operate at great depth without regard for pressure hull strength considerations.  I suppose in theory that's possible, depending on whether or not one could generate a bubble of greater pressure than would be encountered down deep.  However, I don't think it would be wise to rely on such a system, though; for the obvious reasons of what would happen if it failed at greater than design collapse depth.  Whammo!  Your barracuda becomes a flounder!
 
Pat
----- Original Message -----
From: James
To: personal_submersibles@psubs.org
Sent: Tuesday, June 25, 2002 12:29 PM
Subject: Re: [PSUBS-MAILIST] Theory Question

Oh I definitely understand that, I don't imagine that anyone would want to travel that fast near anything that would come even remotely close to the sub.  I was just wondering if the assumption that supercaviation =  less hull pressure was accurate.
 
James
 
----- Original Message -----
From: Herve
Sent: Tuesday, June 25, 2002 3:16 PM
Subject: Re: [PSUBS-MAILIST] Theory Question

Hi speed for underwater vehicles is suitable only with enough deep waters and "room" around, there is no way you can drive a mini sub at more than 10 m/h in shallow waters or with reefs and obstacle. it s like driving a car in the fog. Even with 100 Ft visibility once you SEE the obstacle the collision is at 5 seconds, 5 sec to make a sharp turn or stop is actually not easy at all. Add to that the momemtum  of the sub.
Herve