esmythe@atl.ge.com (Erich J Smythe) (08/30/89)
From: esmythe@atl.ge.com (Erich J Smythe) In a previous article tek@CS.UCLA.EDU (Ted Kim (ATW)) writes: >In article <8181@cbnews.ATT.COM> Dave Mead writes: >>I thought the new attack subs would have a *much* faster hull speed for >>quiet running (laminar flow?). All fast current subs make a lot of noise ^^^^^^^^^^^^^ >>when running near max speed and can only achieve ~6 knots or so quiet. New >>tricks and coatings allow the new subs to go *fast* and *quiet* at the >>same time. A big improvement. Today's attack boats (Russian and US) achieve laminar flow in the bow area, that is why the bows are so blunt. The flow becomes turbulent somewhere down the hull. Dolphins are believed to achieve laminar flow throughout the length of their bodies, and in the 60's there was a research program to make a submarine hull much the same as a dolphin, i.e., not a perfect cylinder. It seems laminar flow has a lot to do with shape. Politics killed off that idea, if I recall correctly. The book "Running Critical" by Patrick Tyler of the Washington Post (I don't recall the publisher) gives a short account of this project. The book is a detailed history of Electric Boat, its relationship with Adm. Rickhover, and the cost overrun scandal over the 688 (or LA class) boats. >The information I have heard, has Seawolf capable of going "silent" >upto ~15 knots (vs. ~5 knots for LA Class). The pump jet propulsion >unit is not supposed to cavitate at any speed the sub is capable of. >(Though, cavitation along certain hull points may occur at high >speeds.) I have heard LA Class screws start cavitating somewhere in >the 15-25 knot range. Most aspects of performance, including max speeds, max depths, silent speeds, and cavitation performance are classified, so I wouldn't bother throwing numbers around, as they are likely to be incorrect. When I worked for Electric Boat, they were often asked about the performance of the Trident (Ohio class) boats. The standard quote was that they would do "20 knots at 400 feet." I'm sure they can. So could the boats before them. As for the Seawolf, that one isn't off the drawing board just yet, and hydrodynamics can give you many surprises. Electric Boat has the lead ship contract, is currently experiencing severe labor problems, and is behind schedule on at least three 688 hulls. IMHO I doubt the SSN-21 (Seawolf) will be completed on schedule. -erich Erich Smythe esmythe@atl.ge.com GE Aerospace (609)866-6643 Moorestown, NJ
kiravuo@kampi.hut.fi (Timo Kiravuo) (08/31/89)
From: kiravuo@kampi.hut.fi (Timo Kiravuo) In article <27026@amdcad.AMD.COM> esmythe@atl.ge.com (Erich J Smythe) writes: >Dolphins are believed to achieve laminar flow throughout the >length of their bodies, and in the 60's there was a research >program to make a submarine hull much the same as a dolphin, >i.e., not a perfect cylinder. I read somewhere (SF author, but non-fiction; Asimov, Clarke?) that dolphins have "active skin"; the skin can adjust to pressure differences and prevent turbulences before they start. I suppose that with modern technology it might be possible to cover the hull of a submarine with a soft skin, underneath which there would be pressure sensors and some hydraulics to change the hydrodynamics of the skin when necessary. I also remember that the book said that dolphins move faster underwater than they should be able to because of the lack of turbulences. They use much less energy than anything man-made. So a softskinned submarine could be silent, fast and use less energy, with a strong hull under the skin. -- Timo Kiravuo Helsinki University of Technology, Computing Center work: 90-451 4328, home: 90-676 076 kiravuo@hut.fi sorvi::kiravuo kiravuo%hut.fi@uunet.uu.net