Re: [PSUBS-MAILIST] Buoyancy control

[Jon Wallace <jonw@psubs.org>]

Hi Alan,

Some do, and its a viable design. The Atlantis tourist submarines remain 
slightly positively buoyant and use thrusters to force itself down to 
depth. The couple of cons that I can see are you'll likely have more 
power requirements since you'll need to use your motors to keep you at 
depth, and lack of reserve buoyancy if you get in trouble and need to 
come up quickly, and/or want to pick something up and surface with it.

I don't believe freeboard is an issue. Even with a K-sub you could 
maintain a slightly positive buoyancy and use the thrusters to force the 
sub underwater.

Jon



Alan Clifford wrote:
> I’m sorry if this sounds like a stupid question but here it is.
>
> Virtually all submarines and submersibles have some metal ballast and 
> one or more ballast tanks that are filled with water to submerge and 
> cleared with compressed air to surface. Why not just add metal ballast 
> until the vessel has slightly positive buoyancy and use dive planes to 
> “fly” down to whatever depth you want? This eliminates the complexity 
> of tanks, lines, valves, and compressed air.
>
> I realize that the submarine would not be able to hover at a specific 
> depth and could not descend vertically. Is this important?
>
> I can see that a military submarine would need to dive quickly but 
> that doesn’t apply to a personal submersible.
>
> A submersible with slightly positive buoyancy would not have much 
> freeboard. Is that the problem?
>
> If the load was changed, the ballast would have to be changed. That 
> doesn’t seem to be a problem with a personal submersible.
>
> Thanks for your help.
>
> Alan




************************************************************************
************************************************************************
************************************************************************
The personal submersibles mailing list complies with the US Federal
CAN-SPAM Act of 2003.  Your email address appears in our database
because either you, or someone you know, requested you receive messages
from our organization.

If you want to be removed from this mailing list simply click on the
link below or send a blank email message to:
	removeme-personal_submersibles@psubs.org

Removal of your email address from this mailing list occurs by an
automated process and should be complete within five minutes of
our server receiving your request.

PSUBS.ORG
PO Box 53
Weare, NH  03281
603-529-1100
************************************************************************
************************************************************************
************************************************************************