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Subject: Supercavitating submarines?
EW3    11/8/2006 10:24:12 PM
way cool. http://www.defenseindustrydaily.com/2006/11/the-need-for-speed-all-aboard-the-underwater-express/index.php The Need for Speed: All Aboard the Underwater Express! Posted 09-Nov-2006 12:08 | Permanent Link Related stories: Americas - USA, Coastal & Littoral, Contracts - Awards, DARPA, Design Innovations, Engines & Propulsion - Naval, General Dynamics, New Systems Tech, Northrop-Grumman, R&D - Contracted, Science - Basic Research, Submarines "We feeeel the need..."DARPA's Underwater Express Program has a characteristically brief description. It is intended to: "...demonstrate stable and controllable high-speed underwater transport through supercavitation. The intent is to determine the feasibility for supercavitation technology to enable a new class of high-speed underwater craft for future littoral missions that could involve the transport of high-value cargo and/or small units of personnel. The program will investigate and resolve critical technological issues associated with the physics of supercavitation and will culminate in a credible demonstration at a significant scale to prove that a supercavitating underwater craft is controllable at speeds up to 100 knots." James Bond is officially jealous, Q's insurance division is cringing, and a pair of American defense contractors could be $78.6 million richer if the contracts they've just received pan out. We explain "supercavitation," and detail the contracts involved... Continue reading...
 
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mithradates       11/8/2006 10:30:22 PM
I do wonder about the range of such a craft.  The energy expended to create the supercavitating bubble is enormous,and increases exponentially with the total surface area of the bubble.

The Russian Schyval(spelling?) supercavitating torpedo contains more fuel than an exocet but can only travel 300 meters at high speeds underwater.  It would seem to me that the smaller the bubble, the more fuel efficiency can be acheived.  It would almost be better to construct some sort of smart super-cavitating bullet that can travel a few kilometers underwater at those kind of speed than to move an entire sub.
 
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mithradates       11/8/2006 10:32:22 PM
I do wonder about the range of such a craft.  The energy expended to create the supercavitating bubble is enormous,and increases exponentially with the total surface area of the bubble.

The Russian Schyval(spelling?) supercavitating torpedo contains more fuel than an exocet but can only travel 300 meters at high speeds underwater.  It would seem to me that the smaller the bubble, the more fuel efficiency can be acheived.  It would almost be better to construct some sort of smart super-cavitating bullet that can travel a few kilometers underwater at those kind of speed than to move an entire sub.
 
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gf0012-aust       11/8/2006 10:32:25 PM

 It would almost be better to construct some sort of smart super-cavitating bullet that can travel a few kilometers underwater at those kind of speed than to move an entire sub.
the USN has been working on supercav rounds for the last 6 years.


 
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gf0012-aust       11/8/2006 10:35:39 PM

 It would seem to me that the smaller the bubble, the more fuel efficiency can be acheived. 

its the shape of the bubble - not the cubic space it takes up that counts.
 
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EW3       11/8/2006 10:39:00 PM

Isn't there a 30mm(?) supercavitating round that is supposed to be deployed from an MH-60R for anti-mine warfare?
A supercavititating sub has pitfalls, such as noise, but I'm glad to see the research being done.  Never can tell what it will spawn.  (Curiously there is a bit on TV right now about the CSS Hunley)
Isn;'t there a 30mm(?) supercavitating round that is supposed to be

 It would almost be better to construct some sort of smart super-cavitating bullet that can travel a few kilometers underwater at those kind of speed than to move an entire sub.

the USN has been working on supercav rounds for the last 6 years.





 
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gf0012-aust       11/8/2006 10:54:38 PM


Isn't there a 30mm(?) supercavitating round that is supposed to be deployed from an MH-60R for anti-mine warfare?
A supercavititating sub has pitfalls, such as noise, but I'm glad to see the research being done.  Never can tell what it will spawn.  (Curiously there is a bit on TV right now about the CSS Hunley)
yes there is. there are actually a variety of rounds, starting from 20mm.
the inventor is a nice bloke - he did get screwed around by some USN contractors on the beltway though. 


 
 
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mithradates       11/8/2006 11:32:34 PM



 It would seem to me that the smaller the bubble, the more fuel efficiency can be acheived. 


its the shape of the bubble - not the cubic space it takes up that counts.


Well, the energy is wasted on the drag between the surface of the bubble and the surrounding water.  A small perfectly spherical bubble would still outperform a large ellipsoid bubble.



 
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gf0012-aust       11/9/2006 1:51:31 AM
Well, the energy is wasted on the drag between the surface of the bubble and the surrounding water.  A small perfectly spherical bubble would still outperform a large ellipsoid bubble.
thats an oversimplification of a complex process and also a contradiction of how we already know how these things work. Its also a small portion of the process that contributes to the overall effect.
 
I do however wish you luck in developing and validating your new theory on fluid dynamics.
 
 
 
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Galrahn       11/9/2006 1:51:31 PM
 
I think you are refering to the MK258 APFSDS-T 30mm Anti-Mine Ammo used by the Mk44 Bushmaster 30/40mm Automatic Cannon on a MH-60S.
 
The Underwater Express program is the latest in bids in supercavitation, a bid another few years ago was about steering and homing capability for supercavitating weapons, something the US and French know how to do, maybe the Russians too, but no one else knows. If I remember correctly, didn't we talk about this last year on this forum?
 
I don't see the advantage of supercavitating manned submersables, although I have seen more than one interesting ideas for supercavitating technology in LCS ASW design boards. One such unit would be about the size of NETFIRES and include 15 - 2 stage super cavitating torpedo weapons that would intercept heavier torpedos, acting as a point defense underwater weapon. This would enhance the envisioned role of the LCS as a major ASW close defense asset operating within 6000 meters of  high value assets. I have no idea where the development for that program is, but if it happens it was slated for around the FY2010 timeframe, roughly 2 years from now.
 
 
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gf0012-aust       11/9/2006 5:09:21 PM

 

I think you are refering to the MK258 APFSDS-T 30mm Anti-Mine Ammo used by the Mk44 Bushmaster 30/40mm Automatic Cannon on a MH-60S.
 

Yes, the ex RAMICs programme

 The Underwater Express program is the latest in bids in supercavitation, a bid another few years ago was about steering and homing capability for supercavitating weapons, something the US and French know how to do, maybe the Russians too, but no one else knows. If I remember correctly, didn't we talk about this last year on this forum?

  

Yes, agree, and we did go through this last year.

 
I don't see the advantage of supercavitating manned submersables, although I have seen more than one interesting ideas for supercavitating technology in LCS ASW design boards. One such unit would be about the size of NETFIRES and include 15 - 2 stage super cavitating torpedo weapons that would intercept heavier torpedos, acting as a point defense underwater weapon. This would enhance the envisioned role of the LCS as a major ASW close defense asset operating within 6000 meters of  high value assets. I have no idea where the development for that program is, but if it happens it was slated for around the FY2010 timeframe, roughly 2 years from now.

 


agree, and I think you'll find that that is the USN/NAVSEA/DARPA position.  There are far more useful benefits for supercav weapons than sticking the design philosophy onto the hull of a sub.
 
eg an underwater version of a claymore to act as an ant-torp CIWS weapon.  the US already leads the field in that area so its not as if we're talking about greenfields solutions. If top mounted, it can still serve as a normal PDS.
 
in fact, I can't think of a more gross waste of technology practicality than adding the tech to a sub hull.
 

 
 
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