Thursday, November 1, 2012

SSBN(X) Update

The United States Naval Institute has a short article with a few details about the future SSBN(X). 

Here's a bullet list of features:

  • Single mission
  • X-stern
  • Electric drive
  • Virginia anechoic hull treatment
  • Virginia Large Aperture Bow Sonar array
  • Water jet propulsor
  • Dimensions 561 ft x 43 ft - 2 ft longer than Ohio
  • Crew of 155 - same as Ohio

The most interesting feature is the focus on single mission.  There has been a lot of discussion about using the SSBN(X) as a combination SSGN & SSBN or acting as a Special Forces platform.  It appears that none of that will happen.  This will be a straight up repeat of the Ohios with modernized equipment.

The next most interesting feature is the crew size which is identical to the Ohio.  Given a significantly greater degree of automation in this sub versus the Ohios, this seems odd.  I would have thought a reduction in crew size would have been part of the design.

I still don't get the why the sub is the same size (2 feet longer, actually!) as the Ohio when it has 33% fewer missile tubes. 

Cost estimates are unchanged from those reported in our previous post.  This is a very expensive sub!


  1. From what i've heard the extra is made up in more spacious living quarters. And more than likely duel quarters sense they will probably have both sexes.

    I can see why its so mission focused. A SSBN has but one mission. No one sees it till it launches. If its out there launching Tomahawks then it can be tracked. Would be nice if more mission focused approach was followed more often

  2. I understand the need to keep the SSBN dedicated to deterrence. They are the most secure leg of the triad because of their undetectability. The moment the SSBN surfaces to extract a seal team, as in the first and only episode of Last Resort I watched on ABC, it risks giving that away. Then it becomes easy for an adversary to take out the equivalent of a Minuteman missile wing with a single torpedo.

    I think new measures to improve the sub's acoustic signature over the Ohio will require more volume and weight. If it has an all-electric drive that will take up more space than mechanical drives. The Tullibee, Narwhal, and Lipscomb all experimented with forms of electric drive, with mixed results. From what I read these boats had larger machinery spaces than other nuke boats and were slower.


    1. WGM, please contact me via email at carr_manoratyahoodotcom. Substitute the appropriate symbols for the "at" and "dot" in the above. I write it this way to avoid having it identified by spambots. Thanks!

  3. No specific knowledge, but my guesses would be better living quarters and more perishables storage.
    Both of which will facilitate longer at sea patrols, and longer uninterrupted dives.

    I believe the argument in favor of multi use submarines was not that a submarine should carry ballistics, and cruise missiles, and special forces, but that it could carry ballistics OR cruise missiles OR special forces (or possibly cruise missiles and special forces).

    Special forces, I'm iffy on, its a lot of money to get 60 lightly armed blokes onto the beach, but 112 cruise missiles can debilitate nations.

    1. Actually, the overwhelming reason for similar displacement despite carrying 16 tubes vs 24 is probably electric drive. Electric drive is very bulky and occupy much more space than direct coupling with mechanical reduction gears. The one off Gerald P Lipscomb SSN was completed with Electric Drive and it displaced 6500 tons vs the 4600 tons of the Sturgeon class SSN from which it was stretched. The space from the 8 missing missing tubes more or less provides just enough space for a turbine generator set, a modest battery bank and a main propulsion electric motor. The other reason for the bulk is that, given the intent to operate the class for 40~42 years without a refueling overhaul, the reactor will have to be larger and less energy dense in the SSBN(X) to contain enough fissile material to go the distance.

  4. First of all, I am not overly concerned about the reduction in tubes. We are talking about 30 years into the future when this class will form the back bone of US Sea based Nuclear Deterrence. There is a very high probability that there will be another treaty further down the road which further limits the number of SLBM warheads. Hence, 192 is not a bad place to be. If this does not happen, 12 boats into the run it will not be overly difficult to add two or three more boats.

    The reason these boats are larger despite carrying a smaller missile load is probably the result of going with electric drive. Electric drive is bulkier for the same output; or conversely same size but lower output. The difference is not minor as we have seen in the Gerald P Libscomb class which used a turbo-electric drive -- 6500 tons vs 4600 tons of the Surgeon class from which it was stretched. 40% more displacement for essentially the same output and slower maximum speeds. Hence, at the same hull size with 33% less tubes probably just about make room for the additional machinery space & mass needed for a turbo-electric SSBN. The other probably has to do with the intent to have a 40 year no-refuel service life. The reactor will have to be larger and of a lower energy density to pack twice the amount of fissile material to go the distance.

    1. Your comments about the space needed for electric drive and a larger reactor sound plausible. I'm not a nuclear engineer nor a propulsion expert.

      Of course, you're correct about the Lipscomb, however, in the intervening years every mechanical and electrical system has gotten significantly smaller and more efficient. Likewise, the reactors have gotten smaller and more efficient. The Virginia uses an S9G with a 33 year unrefueled life. I don't know what the SSBN(X) will use.

      If you are a propulsion/reactor expert (or just reasonably knowledgable - that's plenty good enough for me!) then I'll gladly accept your theory at face value. If you're largely speculating, I'll reserve a bit of doubt with the suspicion that the extra length is being used for something else in addition to drive and reactor space alone.

      Regardless, thanks for chiming in!

    2. Then new SSBN-X will have a reactor that uses a system that uses direct water cooling, although the navy is not saying what that is other than is is very quiet. is is said to take up more room than the old closed loop system using loud pumps and recirc. systems, This and the fact that the navy is using females on boomers now and will be using more in the years to come, needs more room for seprate housing for this mixed crew. Hope this helps a bit.

    3. I'm not a nuclear engineer by any means but I was under the impression that naval reactors already used water cooling? I'm not sure what you mean by "direct". Experimentation was done with cooling using liquid sodium, if I remember correctly, which circulated by convection rather than pumps and valves. It almost sounds like that's what you're describing. I think the Soviets actually operated such a reactor on some of their vessels.

      If we're adding a significant chunk of space/cost (10%-40%) to subs just to accomodate women then we need to be taking a serious look at whether women on subs is really a worthwhile idea. Hmm ... Instead of Blue/Gold crews maybe we need to go to Male/Female crews!

      Thanks for stopping by!

  5. Not sure if my earlier comment posted but:

    Take a look at this report:

    It's lengthy but quite thorough.

    1. Thanks, Chris. I stay current on all the CRS reports for all the ship classes.


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