Re: [PSUBS-MAILIST] Thought experiment

[irox <irox@ix.netcom.com>]

A vacuum is only 15psi less them atmospheric pressure, if your VBT
can't stand a 15psi difference, then it's not going to be much use
for underwater activities (where is has to withstand a higher pressure
difference).  I'd guess you would still have some air in the tank any.

Ian.

-----Original Message-----
>From: Philip Ridenauer <akula151@yahoo.com>
>Sent: Jul 18, 2007 10:16 AM
>To: personal_submersibles@psubs.org
>Subject: Re: [PSUBS-MAILIST] Thought experiment
>
>Paul, 
>  A 1atm would be much more comfortable but from an expense standpoint ambient seems to be the way to go.  Don't know exactly what type of glide ratio I could expect, (that torpedo pool toy you can get at Wal-Mart looks to be better than 2:1) but if one could obtain 5:1 then a 1ft/sec descent would yield 5ft/sec forward or abt. 3kts.
>  Forgive my ignorance but how does a VBT work?  If you expell water from the tank with a pump aren't you left with a vacuum which would collapse the tank?
>  PR
>
>Paul Kreemer <paulkreemer@gmail.com> wrote:
>  Phillip, for a glider I've thought that 1atm would be good (at least for me with my bad ears).  I'd like to avoid the possible rapid pressure changes for health and comfort.  But maybe your normal ascent and descent rates wouldn't be too high. 
>
>How about an electric motor and pump for expelling ballast water at the bottom of your flight profile?  Maybe a setup that similar to a trim pump with a larger-than-average variable ballast tank.
>
>
>Paul
>
>  On 7/16/07, Philip Ridenauer <akula151@yahoo.com> wrote:    Vance, Frank thanx for the replies.  I guess I wasn't clear in describing the ascent phase using pos. bouyancy as "negative gravity" so that propulsion would be achieved on both descent and ascent.  I think Karl Stanley's sub (from what I could gather from the website) ballasted down to descend and provide propulsion then used air to ascend, which is what I'm trying to avoid.  Will check out your leads, Vance. 
>  Thanx again
>  PR
>
>
>
>
>
>       
>---------------------------------
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