[PSUBS-MAILIST] Deep sea question

[Douglas Suhr]

Personally, I am very much in favor of diving with slight positive buoyancy
and using downward thrust for diving as SeaMagine and many other seem to be
doing these days. Obviously this is a very power intensive way of diving,
but if you can spare the power (or better yet increase your power capacity)
I feel its the best (and safest) way to go. If a power failure occurs, you
are automatically on your way up, no drop weights wasted. Having dedicated
thrusters for this purpose is best because multitasking with horizontal
mobility would be difficult. ~ Douglas S.


On Mon, Apr 14, 2014 at 8:40 PM, Vance Bradley <VBra676539 at aol.com> wrote:

> I don't recall the specific mix for Alvin. You are right of course for
> comparable wall thicknesses, but the way I understand it from tabletop
> descriptions, steel compresses more. The Mirs are maraging steel and have
> seawater vbts to compensate buoyancy variables. The new Alvin iteration is
> equipped the same way. The Ti sphere Is 3.5" wall, I think, which I
> speculate to be effectively non or near noncompressable for the given
> operating pressure of 11,000 psi. Or so the story goes.
> Vance
>
> Sent from my iPhone
>
> On Apr 14, 2014, at 7:21 PM, "Sean T. Stevenson" <cast55 at telus.net> wrote:
>
> Vance - that doesn't seem accurate.  Compressibility of a material is the
> inverse of its bulk modulus.  For ASTM A516 grade 70 carbon steel, the bulk
> modulus is 140 GPa, and for ASTM B265 grade 5 titanium it is 110 GPa.  So
> the steel actually performs better in that regard.  Was the Alvin sphere
> made from some atypical alloy?
>
> Sean
>
>
> ------------------------------
> *From: *"Vance Bradley" <VBra676539 at AOL.com>
> *To: *"Personal Submersibles General Discussion" <
> personal_submersibles at psubs.org>
> *Sent: *Monday, April 14, 2014 4:03:39 PM
> *Subject: *Re: [PSUBS-MAILIST] Deep sea question
>
> Alvin carried steel drop weights which were dropped at depth. The new
> system is like the Mirs and the Pisces before them-- vbts and high pressure
> pumps. Titanium hulls don't compress at depth so are actually more buoyant
> at 20,000 feet than at the surface due to increased water density. All that
> has to be taken into account.
> Vance
>
> Sent from my iPhone
>
> On Apr 14, 2014, at 5:57 PM, <swaters at waters-ks.com> wrote:
>
> I have a question I have never understood about really deep sea
> submarines. How do they go up and down?
> Submarines that use compressed air at 3,000 psi like ours could only go so
> deep before the water pressure is to great for the HP air. What do
> submarines like Alvin do? This is probably a really stupid question, but I
> have never understood it.
> Thanks,
> Scott Waters
>
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