SSN-775 pumpjet under construction pic

[bobcowan]

Just stumbled upon this on the navsource site, the stern unit for USS Texas including the pumpjet without shroud. Under wraps but visible. Best peek I have seen!

http://www.navsource.org/archives/08/0877704.jpg

Bob Cowan

[bobcowan]

I just tried that link

I just tried that link after posting my message and it's not working. Try navsource.org and look for SSN-777 North Carolina or...

http://www.navsource.org/archives/08/08777.htm

Bob

[d manley]

cool, very cool!
Makes me wish

cool, very cool!
Makes me wish I were building one, maby some day!


Dave Manley
Small World Models

[thordesign]

Dave,

We completed the prototype and

Dave,

We completed the prototype and ran her quite a bit. She is a pig. She combines the worst of the Los Angeles with the worst of Seawolf. I have never been so disappointed in the performance of a model. After the performance trials we shelved her. From what I have been able to gather the real boat has its problems as well and has been a real disappointment to the Navy. This happens every time we try and shove 10 lbs of crap in a 5 lb bag. Multirole anything is a massive collection of design compromises, which means the boat does a lot of things, but does not do any of them well.




Edited By ThorDesign on 1086922504

[bcliffe]

Bob,
I plan on being at

Bob,
I plan on being at the cottage for the first two weeks of August. You, Ted, and myself should get together and do a little underwater film work.

Matt,
I am curious what do you see as the best and worse attributes of the Seawolf and LA class.

Hope things are well for both of you gents.

Cheers
BC

[petn7]

Dave,

We completed the prototype and

Dave,

We completed the prototype and ran her quite a bit. She is a pig. She combines the worst of the Los Angeles with the worst of Seawolf. I have never been so disappointed in the performance of a model. After the performance trials we shelved her. From what I have been able to gather the real boat has its problems as well and has been a real disappointment to the Navy. This happens every time we try and shove 10 lbs of crap in a 5 lb bag. Multirole anything is a massive collection of design compromises, which means the boat does a lot of things, but does not do any of them well.

hahaha. i keep telling myself "i knew it, I KNEW IT!" you cheap out on anything now, you pay the price later

[anonymous]

True. You get what you

True. You get what you pay for. But, the really funny thing about that propulsor design is there is *nothing* cheap about it...

[thordesign]

The LA is a very

The LA is a very good boat with excellent speed, manueverability and stealth. The seawolf is a weapons platform monster that was built to rip the enemy's head off. She is swift and extremely powerful. Both designs were executed simply to destroy the enemy and they both perform the task quite well. Those who sail them admire both designs. However, the LA is sensitive at shallow depths and has a severe rolling motion. Seawolf turns poorly at slow speed and takes a bank of computers to keep her straight at flank.

[petn7]

sometimes learning can be so

sometimes learning can be so interesting!

thanks matt

[Guest]

This seems to be bad

This seems to be bad news for the US Navy. Will the Virginia Class be ended after North Carolina is finished due to the problems outlined by Mr Thor? Was there any backup plan in case Virginia and her sisters don't perform as advertised, or perhaps they will be refitted to remedy these problems somehow?

[anonymous]

http://www.continuum-dynamics.com/research/topics/smart_ducts/index.html


Interesting about your prototype Virginia

http://www.continuum-dynamics.com/research/topics/smart_ducts/index.html


Interesting about your prototype Virginia handling Matt. Was the main problem turning (left & right yaw) maneuverability primarily? We must have incomplete information.

I find it hard to accept these findings about Virginia (SSN-774) class designs based on what I am sure is a very accurate Thor model prototype. These maneuverability issues would have been identified in computer and model tests early. I firmly believe we do not have a complete picture of the Virginia's and Seawolfs true capabilities in handling. The Navy and it's contractors and designers simply cannot be that dumb!

I also find it hard to believe Newport News and the Navy would release such images of the PCU (Pre Commissioning Unit) Texas propulsor, yet they have. I have downloaded and burned a disk and put in a safe place should this image possibly disappear.

I believe the Virginia classes may use a 'smart duct' pump jet shroud technology. It would explain much if they did - based on your initial model handling reports Matt. I had illustrations of a Smart duct and filed them away till I saw the PJ arrangement image noted above shown here. The photo of Texas's PJ area image reveals it has a solid ring mounting forward, and like the smart duct illustrations, employs a 7 broad blade propulsor just like in the photograph giving more credence to the smart duct illustration by comparison. The article on the 'smart duct' work being done at Pennsylvania State University (Penn State) by 'Continuum-Dynamics' related that 'smart ducts' was a likely candidate for later follow on Virginia class units. I believe now based on this latest image that the smart duct is being used from the beginning first unit (Virginia SSN-774) onward from the very beginning of the program! This is my theory.

Steve Reichmuth




Edited By Dolphin on 1087008268

[PaulC]

From what I have gathered,

From what I have gathered, initial disappointment with SSN classes is not unheard of. When the 688's were introduced, many submariners preferred the older Sturgeons in regards to habitability and maneuverability. However, later LA flights were improved to overcome certain deficiencies. This will certainly happen with the Virginia's as well.

As far as I know, no plans have been made to reduce the number of boats already scheduled for the Virginia class. And if the LA's are any indication, we'll be studying them for a long time.

[anonymous]

First in class boats do

First in class boats do have their issues. Early reports suggested that there was an issue with weight/balance on SEAWOLF that wasn't uncovered until late in the program, amongst other issues.

Steve, excellent research on the smart duct. Interesting how Penn State is becoming more "vocal" with their work. I did note, however, that the model they seem to be using is a 5 blade highly skewed prop ahead of the rudder (at least that's how it appears from the flow streams and the pressure gradients), more along the lines of a surface craft (i.e. DDG or CG).

A deformable duct is an interesting concept, but I'm guessing that there may be too much noise from the actuation mechanism for sub use??

Chris

[anonymous]

http://www.dawnbreaker.com/virtual2003/briefings/ContinuumDynamics.doc


The Smart Duct is a

http://www.dawnbreaker.com/virtual2003/briefings/ContinuumDynamics.doc


The Smart Duct is a ducted propeller with a deformable shroud that redirects the propeller wash to provide direct steering force. The Smart Duct provides the ability for submarines and surface ships to maneuver while minimizing or eliminating cavitation-induced noise. In particular, the development of practical Shape Memory Alloy (SMA) actuation devices has matured quickly since the 1980's for underwater use which has opened the way for a deformable 'Smart Duct'.

The above address outlines in greater detail the smart duct, and it is what I believe Virginia class SSN's will or are employing.

The Virginia class SSN's are designed both for deep water and littorial shallow water fighting. The ability to maneuver slowly in littorial areas would require such a concept for effective turning ability. It flies in the face of the Virginia's mission and design not to use a smart duct.

Steve Reichmuth



Edited By Dolphin on 1087072121

[PaulC]

Steve,

Which boat is this?

Steve,

Which boat is this?