If having the intellectual curiosity to look beyond the data and ask “why” is a hallmark of insanity, then I take Randy's comment as a compliment.
The current question those concerned should be asking is why the BOREY Class Russian SSBN has a pump-jet propulsor while the new YASEN Class Russian SSN has an ”open” seven-bladed propeller as clearly shown by Internet images even though the screw was canvas-covered when imaged from the stern on a building way.
One advantage of a pump-jet propulsor is that the stator directs thrust developed by the rotor along the axis of the submarine which reduces the tangential thrust which, in turn, reduces torque on the hull which allows the stern area control surfaces to be smaller than would be the case with a conventional screw. This permitted the BOREY to use the stern section – including the control surfaces of a much smaller Project 971 AKULA Class SSN.
In fact, both the bow and stern sections of the lead BOREY Class, the YURI DOLGORUKY (K-535), were originally constructed for the COUGAR (K-337) which was never finished. Why was this cannibalization necessary? - because, as a result of the collapse of the Soviet Union, the Russians lost their capacity to produce the required steel; the plant was in the Ukraine.
I seem to remember there is a very slight difference (one degree?) in the angle of the port and starboard stern planes relative to the long axis of a single-shaft submarine when viewed from astern. This to compensate for the above mentioned torque developed by “open” propellers. Such torque is not an issue for submarines with two shafts because they turn in opposite directions: outboard.
So, one reason (the only reason?) the BOREY has a pump-jet is that that type of propulsor allowed the use of existing AKULA hull sections. (If a pump-jet had other important advantages, one would have expected to see it used with the YASEN.) 0ne might say that, as finally built, the BOREY represents a major compromise of the original late 1970s concept which was a twin-shaft submarine close to the DELTA IV. The BOREY appears to be yet another example of “Better is the enemy of good enough,” and, as noted earlier, using AKULA hull sections and main propulsion power train was "good enough."
Oh, by the way, Internet sources confirm the BOREY has a “double reduction planetary” gear system and a left-turning propeller shaft.
Also note that using an AKULA bow section means the BOREY has eight torpedo tubes: four 650mm tubes and four 533mm tubes. That's pretty nasty for an SSBN. All other Soviet/Russian SSBNs had either four or six tubes.
Bruce,
Welcome back.
Rick
Rick, et al.:
Back but only at rare intervals such as now with the discovery of a Russian website (linked below) that confirms – by machine translation - my earlier estimate on this site that the BOREY has a hybrid (TE/TR) propulsion system that uses, as previously noted, the same “planetary double reduction” gear as the AKULA. The two paras quoted below from that website provide many of the highlights; capitalization mine.
“The greatest changes in (the 955 BOREY) project related to the decision to use the BACKLOG OF UNFINISHED SUBMARINE THIRD-GENERATION (systems) and re-equipment (a new missile) of missiles, the Bulava. The architecture was also adopted doublecase (double hull). From the Project 971 (AKULA) submarine has inherited almost unchanged the whole nose and tail. Thus, eight torpedo tubes caliber 533 and 650 mm, as well as torpedopogruzochny hatch were moved to the bow of the hull.
“Main power plant vessel was to include the new CTS-6 reactor thermal power of 200 MW steam turbine and a new, common to all 4-th generation. Realistically, the project 09550 and 09551, due to the difficulties of technical and, above all, a financial nature, have been used in slightly improved power equipment Boat third-generation steam-generating unit OK-650V thermal capacity of 190 MW steam turbine block "Azurite 90. The latter includes the main unit with turbozubchaty single-flow steam turbine with an effective system vlagoudaleniya of the flow part, shunting device with a control unit, a PLANETARY DOUBLE REDUCTION, offline turbo, built-in steam jet refrigeration machines, ELECTRIC PROPULSION (not the thrusters). isolation coupling, the main thrust bearing, the system automatically speed control shaft and the pressure of live steam...”
So, driven by financial and material supply constraints, at least the first several BOREYs appears to be more third-generation submarines than, from-the-keel-up, fourth generation submarines.
I continue to be astounded by what is available open-source on the Russian submarine force. All that is needed is the interest to use a search engine.
Bruce
Bruce, by all means take my comment as a compliment. Few have lived and breathed acoustics as you have but enough of us were sufficiently consumed with it to appreciate your intellect on the matter. There are times I wish I could stand some very busy mid watches at Kef again!
There are times that I wish I could stand some very busy midwatches at Antigua or Guam again to!!
Busy midwatch at Antigua or Guam? 
Rick
Rick,
Is that like a busy watch at Barbers Point?? I always said the "down range sites" in the Atlantic and the slower action at some of the Pacific sites were more of a moral and discipline challenge for all. It was amazing to see the difference when we did get busy. We had to make training the key in keeping everyone engaged and motivated.
I do miss it, because of the people when the light bulb finally came on.
Chuck
Like the time we had a "147" running for a LONG TIME! None of us (Antigua) thought it was what it turned out to be!! ALL the navfacs jumped on the bandwagon and sent it out. Our Master Chief Maultsby looked at it and told us it was an OLD "Y" and we verified it with CWO2 Pope looking at it. Man did we ever have PA on that one!! It did make the watch go fast though!! So did the other "slow" facs!!
HA! I was posting a "funny!" Most of the "busy" mid-watches were being busy keeping our eyes open!! The actual busiest navfacs I was at was 1. Can't mention it and 2. Centerville Beach.
Dick
Randy.....not going to happen.....your wife won't let you stay out that late.
Sorry, pal.
Nick, she probably wouldn't, not to mention I couldn't stay awake. All my time lates would hover around 7 hours, until the day watch came in and woke me up.