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Topic review - Calling all Los Angeles SSN-688 class fans
Author Message
  Post subject:  Re: Calling all Los Angeles SSN-688 class fans  Reply with quote
Friedman's U.S. Submarines since 1945 says that the contract for integrating the TB-16 into the BQQ-5 system was awarded in 1982. So I think Tom is right that the older analog systems couldn't work with the new digital BQQ-5. It's conceivable that there was a standalone towed array processor, along the lines of the STASS or the BQR-15 towed arrays in earlier submarines which didn't have combined sonar suites. But I don't know.

As for the "ladder," I think it may be two pipes that are connected to the MBT 5 vents. You can see two raised circular object where the aft part of the "ladder" meets the hull, which are in the right pace for the two MBT 5 vents. The "rungs" might be rope or wire keeping the pipes/hoses together. What exactly the function of these pipes are I have no idea.

Jacob
Post Posted: Tue Jul 21, 2020 3:08 pm
  Post subject:  Re: Calling all Los Angeles SSN-688 class fans  Reply with quote
Thanks for the replies. For the time being, I will plan on modeling the earliest 688's without, but it seems hard to believe they didn't have any towed array since it placed a submarine at such a disadvantage to trailing. From what I can see through Navsource images, the last LA class to be launched without the TB-16 hull hump was SSN-699 (USS Jacksonville). SSN-700 (USS Dallas) is the first I could find with the hump at launch.

This overhead image of USS Jacksonville struck me as interesting as it is one of the few that I can find with a look at the stern of a 688 at launch during this time period (http://navsource.org/archives/08/700/0869914.jpg). The thing that caught my eye was the ladder like structure that is clearly affixed in some manner to the stern, aft of the lines connecting her to the dry dock. Any thoughts on what this is ? I recognize the flags on each horizontal plane to give a clear indication of where they were below the waterline while she was in dry dock . They did a pretty good job of hiding the top of the screw.

Not much else to go on though, but I thought I would share what else I had parsed out.

John
Post Posted: Tue Jul 21, 2020 11:15 am
  Post subject:  Re: Calling all Los Angeles SSN-688 class fans  Reply with quote
Adding to the above comment, one of the big changes from the Sturgeon to LA classes was the switch from analog to digital conversion in the Sturgeons to all digital in the Los Angeles class. The earlier LAs had to be backfitted as the first LA with the new Mk 117 digital system was Dallas. The earlier analog BQQ-2 sonar was replaced with the digital BQQ-5 sonar. The commitment to all digital eliminated a lot of A to D conversion electronics (which weighed ~3000 lbs.) Later boats received the more capable BSY-1. It is possible that the earlier analog towed arrays (STASS) were not compatible with the LA digital systems. So earlier boats may (and this is sheer speculation) not have had the towed array feature and were later retrofitted with the TB-16 in the forward ballast tank and the hull "hump" to stream it to the stern plane. I also have not heard or seen any evidence of a clip on towed arrays on the earlier LA boats.
Post Posted: Mon Jul 20, 2020 10:38 am
  Post subject:  Re: Calling all Los Angeles SSN-688 class fans  Reply with quote
That's a good question: Did any of the 688s use STASS? As far as I know, no, and I haven't seen any photos of that tow point on a 688. But I don't have any information to preclude the use of STASS on a 688 and you would think that the Navy would want some towed array capability on their latest submarine class. If I were you, I would probably leave the stern stabilizers bare if depicting a pre-TB-16 boat.

Jacob
Post Posted: Sun Jul 19, 2020 2:07 pm
  Post subject:  Re: Calling all Los Angeles SSN-688 class fans  Reply with quote
Just to clarify with regards to the initial, as launched 688 Flight 1's, is it likely they had the clip on STASS bracket on one of their aft planes? I know the other classes were using them but I can't nail down any information on these early boats sonar beyond the fantastic information here. I assume they would have had a similar bracket as those seen on the contemporary SSN's and SSBN's of the era but I wondered if anyone had more information.

I am trying to depict the USS Memphis during the service life of a late acquaintance who once commanded E Division aboard her between 1981-1985. I can tell from this video of USS Memphis coming into port in 1981 that she didn't have the towed array blister:

https://www.youtube.com/watch?v=207JMtbJS4Y

By May 1984, she had been updated:
http://navsource.org/archives/08/687/0868712.jpg

Any help is appreciated!

John
Post Posted: Thu Jul 16, 2020 8:44 pm
  Post subject:  Re: Calling all Los Angeles class (SSN-688) fans  Reply with quote
Woodstock74 wrote:
Regarding the LA's screw diameter, digging into this data base, here:
https://www.parttarget.com/?userguid=72 ... 92E6E12160

Looking at the 688's propeller entry, here:
https://www.parttarget.com/2010-00-106- ... 28E17F6A13

Says:

AGAV End Item Identification Propeller assy 216.000IN od 250.964IN pch rh

216 in OD...= 18'

But what's the 250.964" indicating (20.8')?

Pretty cool it gives diameter of the vortex attenuator (dissipator) at 5.5' and verifies the blade count (11).


'pch' stands for 'pitch': the (theoretical) distance the screw will travel forward in one revolution, as if the medium doesn't flow away, just like a wood screw into wood. 'rh' stands for 'right hand', the direction of turn (clockwise) when viewed from behind, the ship moving forward.

Pitch therefore determines the angle and twist in the screw blades.
Post Posted: Fri May 29, 2020 1:35 pm
  Post subject:  Re: Calling all Los Angeles class (SSN-688) fans  Reply with quote
Woodstock74 wrote:
But what's the 250.964" indicating (20.8')?


It's the pitch of the blades, which is typically given at 0.7R (70% the way from the central axis to the blade tips).
Post Posted: Fri May 29, 2020 12:10 pm
  Post subject:  Re: Calling all Los Angeles class (SSN-688) fans  Reply with quote
Regarding the LA's screw diameter, digging into this data base, here:
https://www.parttarget.com/?userguid=72 ... 92E6E12160

Looking at the 688's propeller entry, here:
https://www.parttarget.com/2010-00-106- ... 28E17F6A13

Says:

AGAV End Item Identification Propeller assy 216.000IN od 250.964IN pch rh

216 in OD...= 18'

But what's the 250.964" indicating (20.8')?

Pretty cool it gives diameter of the vortex attenuator (dissipator) at 5.5' and verifies the blade count (11).
Post Posted: Fri May 29, 2020 10:33 am
  Post subject:  Re: Calling all Los Angeles class (SSN-688) fans  Reply with quote
The first I ever head of the 11-bladed vortex dissipater (that's what they (crew) called it) was after the LA used one while she was in Pearl, after arriving in '78. Supposedly, it was removed after evaluation to add a little extra speed to what was already a fast quick and silent boat. --As in spooky silent.

They passively ranged us during a training exercise, and then proceeded to perform an under-hull, with us blissfully unaware just a few yards above. We had been told this op was going to happen but when it did, we were . . . blissfully unaware. The only way to detect them would have been to use our fathometer, but that was tagged out after diving, --as per the CO's Standing Order. After we returned to port, our CO was pretty pissed-off, but our equipment was NO match to theirs. That didn't prevent him from taking it out on any sonarman he crossed paths with for a long time thereafter.
Post Posted: Sun Mar 15, 2020 4:10 pm
  Post subject:  Re: Calling all Los Angeles class (SSN-688) fans  Reply with quote
Vepr157 wrote:
Woodstock74 wrote:

So do all 688i have the ring screw? Are there exceptions (that is, a 688i with the vortex attenuator screw)? And to clarify, "688i" and "Flight III" are synonymous designations?

Yes, sans vortex attenuator would seem to be a fourth then, thanks for pointing that out.


I haven't seen a 688I with a non-annular screw, and I have only seen the vortex attenuator on non-688I screws, but this is a sample size of only a handful of photos. Since submarine screws are made up of two main parts (the hub with the blades, and the boss cap) I assume that the vortex attenuator (that specific type of design is commercially called Propeller Boss Cap Fins) is just added on to the original screw design. Whether or not it's connected to the Russian interest to non-acoustic ASW, I don't know, but it certainly does increase propulsive efficiency. As for the annular screw, it may help with ice protection, but it also probably increases propulsive efficiency and decreases propeller tip cavitation by eliminating the blade tip vortices. The ring also might help reduce flexing of the blades.

And yes, 688I and Flight III are synonymous.


Thanks for the clarifications!
Post Posted: Tue Feb 18, 2020 12:15 pm
  Post subject:  Re: Calling all Los Angeles class (SSN-688) fans  Reply with quote
Woodstock74 wrote:

So do all 688i have the ring screw? Are there exceptions (that is, a 688i with the vortex attenuator screw)? And to clarify, "688i" and "Flight III" are synonymous designations?

Yes, sans vortex attenuator would seem to be a forth then, thanks for pointing that out.


I haven't seen a 688I with a non-annular screw, and I have only seen the vortex attenuator on non-688I screws, but this is a sample size of only a handful of photos. Since submarine screws are made up of two main parts (the hub with the blades, and the boss cap) I assume that the vortex attenuator (that specific type of design is commercially called Propeller Boss Cap Fins) is just added on to the original screw design. Whether or not it's connected to the Russian interest to non-acoustic ASW, I don't know, but it certainly does increase propulsive efficiency. As for the annular screw, it may help with ice protection, but it also probably increases propulsive efficiency and decreases propeller tip cavitation by eliminating the blade tip vortices. The ring also might help reduce flexing of the blades.

And yes, 688I and Flight III are synonymous.
Post Posted: Wed Feb 12, 2020 1:09 pm
  Post subject:  Re: Calling all Los Angeles class (SSN-688) fans  Reply with quote
Tom Dougherty wrote:
The vortex attenuator was added to the existing 7 blade propellers when it became apparent that the Russian submarines had wake detectors. I guess you could call that a variant. The ring propeller is on the 688I boats, which are capable of under ice operations. Earlier LAs are not, as their sail planes cannot rotate to the vertical (as the Sturgeon class) due to the small sail size. For the 688I, they received retractable bow planes, reinforced sails and ring props.


So do all 688i have the ring screw? Are there exceptions (that is, a 688i with the vortex attenuator screw)? And to clarify, "688i" and "Flight III" are synonymous designations?

Yes, sans vortex attenuator would seem to be a forth then, thanks for pointing that out.
Post Posted: Fri Jan 31, 2020 9:42 am
  Post subject:  Re: Calling all Los Angeles class (SSN-688) fans  Reply with quote
The vortex attenuator was added to the existing 7 blade propellers when it became apparent that the Russian submarines had wake detectors. I guess you could call that a variant. The ring propeller is on the 688I boats, which are capable of under ice operations. Earlier LAs are not, as their sail planes cannot rotate to the vertical (as the Sturgeon class) due to the small sail size. For the 688I, they received retractable bow planes, reinforced sails and ring props.
Post Posted: Fri Jan 31, 2020 9:15 am
  Post subject:  Re: Calling all Los Angeles class (SSN-688) fans  Reply with quote
I'm trying to catalog the number of different screws for the LA class, and I've come up with three.

OG:
Image


Vortex Attenuator:
Image

Image


Ice ring guard:
Image

Image

Are we aware of any others? Is there any understanding of the timeline of introduction? The Ice Ring Guard variant, is that swapped on and off as needed? And what are current LAs running?
Post Posted: Thu Jan 30, 2020 8:54 pm
  Post subject:  Re: Calling all Los Angeles class (SSN-688) fans  Reply with quote
Just to add to the previous post. I actually have a coffee mug with a very nice (and still quite crisp) color rendition of the Augusta with the WAA. The caption says "USS Augusta SSN-710" and "AN/BQG-5", with the three WAA blisters on the submarine's side. Picked it up when I was living in the Groton area.

Tom
Post Posted: Tue Jan 21, 2020 1:56 pm
  Post subject:  Re: Calling all Los Angeles class (SSN-688) fans  Reply with quote
JordinR wrote:
Just out of curiosity, I was wondering if any body has knowledge about the USS Cheyenne SSN 773. I recently ran across a picture online of the sub in dry dock and it has the three large sonar panels on the sides like the Virginia Class subs. I have not found any of the other Los Angeles subs with them yet so I was wondering if any one knew when they were added.


Actually the WAA (Wide Aperature Array) was prototyped on USS Augusta (SSN-710). We did an underhull on her in the Bahamas back in 1988 and could clearly see the individual sonar array bulges.

I'm not certain if Cheyenne had a WAA (never operated with her) ... but from my discussions w/ some of crew she was the test bed for the propulsor that was eventually used on the VA class.
Post Posted: Mon Jan 20, 2020 7:36 pm
  Post subject:  Re: Calling all Los Angeles class (SSN-688) fans  Reply with quote
pascalemod wrote:
Vepr157 wrote:
Pascalemod,
Do all LA classs boats sit lower by the stern, so the muck line is NOT parallel to the red lower half of the hull it seems. Can you confirm this and why this is?


Yes ... 688's sit at a 1-1/2 degree up-bubble pierside. this is due to the center of gravity being located aft of the center of buoyancy ... basically, they have a "heavy" reactor & engine-room aft.

When they come up to speed the hydrodynamic forces on the hull cause the bow to suck down to a zero bubble. ... and of course, when submerged, the boat is trimmed to a zero bubble.
Post Posted: Mon Jan 20, 2020 7:20 pm
  Post subject:  Re: Calling all Los Angeles class (SSN-688) fans  Reply with quote
Cold Warriors by Roy Manstan (p. 209) claims that an engineering development model of the WAA was installed on the Cheyenne, which implies it was done in the '90s:

https://play.google.com/books/reader?id=kZWmAwAAQBAJ&printsec=frontcover&pg=GBS.PA180.w.3.0.15

I still don't understand how the Cheyenne had enough margin for the heavy arrays, but obviously they were able to lighten the boat enough.

Jacob
Post Posted: Sat Sep 14, 2019 12:32 pm
  Post subject:  Re: Calling all Los Angeles class (SSN-688) fans  Reply with quote
Yep, those are definitely WAA panels. I wonder it was the advancements in COTS sonar equipment as well as the Light Weight WAA (LWWAA) that allowed for enough margin to carry those arrays.

Jacob
Post Posted: Sat Sep 14, 2019 12:10 pm
  Post subject:  Re: Calling all Los Angeles class (SSN-688) fans  Reply with quote
And lastly, here is a few of the pictures from April 2014 which say they are part of the Cheyenne Project. https://scontent-ort2-2.xx.fbcdn.net/v/ ... e=5E0A29C1 https://scontent-ort2-2.xx.fbcdn.net/v/ ... e=5E0F176C https://scontent-ort2-2.xx.fbcdn.net/v/ ... e=5DF2E98A
Post Posted: Sat Sep 14, 2019 12:03 pm

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