<div dir="ltr">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. </div>
<div class="gmail_extra"><br><br><div class="gmail_quote">On Mon, Apr 14, 2014 at 8:40 PM, Vance Bradley <span dir="ltr"><<a href="mailto:VBra676539@aol.com" target="_blank">VBra676539@aol.com</a>></span> wrote:<br>
<blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex"><div dir="auto"><div>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.</div>
<div class=""><div>Vance</div><div><br>Sent from my iPhone</div></div><div><div class="h5"><div><br>On Apr 14, 2014, at 7:21 PM, "Sean T. Stevenson" <<a href="mailto:cast55@telus.net" target="_blank">cast55@telus.net</a>> wrote:<br>
<br></div><blockquote type="cite"><div><div style="font-size:12pt;font-family:times new roman,new york,times,serif"><div>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?<br>
</div><div><br></div><div>Sean<br></div><div><br></div><div><br></div><hr><div style="font-size:12pt;font-style:normal;font-family:Helvetica,Arial,sans-serif;text-decoration:none;font-weight:normal"><b>From: </b>"Vance Bradley" <<a href="mailto:VBra676539@AOL.com" target="_blank">VBra676539@AOL.com</a>><br>
<b>To: </b>"Personal Submersibles General Discussion" <<a href="mailto:personal_submersibles@psubs.org" target="_blank">personal_submersibles@psubs.org</a>><br><b>Sent: </b>Monday, April 14, 2014 4:03:39 PM<br>
<b>Subject: </b>Re: [PSUBS-MAILIST] Deep sea question<br><div><br></div><div>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.</div>
<div>Vance<br><div><br></div>Sent from my iPhone</div><div><br>On Apr 14, 2014, at 5:57 PM, <<a href="mailto:swaters@waters-ks.com" target="_blank">swaters@waters-ks.com</a>> wrote:<br><div><br></div></div><blockquote>
<div><div>I have a question I have never understood about really deep sea submarines. How do they go up and down?</div><div>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.</div>
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