Monday, November 16, 2015

LCS ASW Tactics

Here’s a just-for-fun post.  Let’s speculate about LCS shallow water ASW tactics.  I don’t think the Navy has gamed out an LCS ASW concept of operations so let’s do it for them!  Now, before we go any further, let’s acknowledge that none of us has the background to discuss this authoritatively and if we did we probably wouldn’t be able to discuss it publicly.  So, as I said, this discussion will be just speculative fun.

Let’s start by summarizing what we think we know about the LCS as it relates to ASW.

  • Let’s start by recognizing that we’re focusing on shallow water ASW because there are better ASW platforms for deep water operations and the LCS hasn’t got the endurance to conduct sustained deep water ops.

  • The LCS is not built for ASW.  It does not have machinery quieting built in, it lacks a hull mounted sonar, its water jets make it an acoustic beacon (it’s a better target than hunter), and it has no ship mounted ASW weapons.

  • The only ASW weapon the LCS has is the helo and it can only operate one helo.  Reports state that the LCS-2 variant can operate two -60 type helos but I’ve heard that flight deck structural issues limit it to one helo.

  • The ASW sensor suite consists of a variable depth sonar (VDS), SQR-20 multi-function towed array (MFTA), and the MH-60R helo’s AQS-22 low frequency dipping sonar (ALFS) plus sonobuoys.

  • When deployed, the VDS limits the LCS to very low speeds.

  • The MFTA requires a pretty fair water depth in order to be towed without dragging on the sea bottom.  I don’t know what the minimum operational depth is but I’ve heard the general statement that the MFTA is not really useful in shallow water.  I’ve also heard that it is possible to only partially stream the MFTA in order to keep the array from sinking too deeply but then a partial array is only partially effective.

Now, let’s summarize what we think we know about the shallow water ASW environment.  Due to its nature, shallow water is a very noisy place.  Bottom flow, river discharge flow, numerous civilian an commercial vessels, surf/shore interaction, tidal movement, civilian craft, bottom debris including lots of wrecks and metal structures, and lots of biologics (animal life) all contribute to making shallow water a very noisy place.  Thus, detection is likely to occur only at much shorter ranges than in deep water.  Passive sonar is going to be far less effective resulting in an emphasis on active sonar which, again, is inherently shorter ranged.  Further, the mixing of fresh water from rivers with the salt water and the effects of solar heating will cause lots of transient thermal and density gradients which will further complicate acoustic detection and result in shorter range detections.

Finally, let’s summarize what we think we know about the SSK, the likely shallow water opponent.  SSKs are very quiet, slow moving, and quite deadly with long range, fast torpedoes.  Well, that wasn’t hard to summarize!

So, now we understand the LCS, the environment, and the enemy (hmm, the Navy has people study ASW for years and we just became experts in a couple of paragraphs!).  With that knowledge, what ASW tactics can we postulate that would emphasize our strengths, mitigate our weaknesses, and maximize our chances for success?

The helo is clearly the strength of the LCS.  It allows the ship to remain at arm’s length and is immune to counterattack (at least from the sub!).  Unfortunately, the helo is also an inherently weak platform when available in only limited quantities.  The old saying is that if you have one helo, you have none.  That’s in recognition of both the helo’s chronic maintenance issues and the limited endurance (Lockheed’s product brochure lists mission endurance as 3.3 hours) and small payload that requires frequent returns to the ship for maintenance, refueling, and rearming.  Remember that ASW is a very long term operation requiring persistence, patience, and endurance.  Even a functioning helo is only available for several hours out of each 24 hour cycle.  Thus, a ship with only a single helo will only have sporadic ASW helo coverage.  When you subtract the maintenance, refueling/rearming, and transit times, you quickly realize that the best a single helo can offer is 4-6 ours of actual ASW coverage per day.

The obvious solution to limited helo availability is to increase the number of ships, each with a helo, and pool the helos so as to maximize helo availability.  Four helos, and hence four ships, sounds about right to ensure one helo is always on station.  This, then, dictates an LCS ASW tactic of operating four ships as an ASW squadron.

How, then, do we utilize the four ship squadron, tactically?

We must first acknowledge that even four helos operating simultaneously can only provide a very limited coverage area.  Dipping sonars in shallow water are just not going to provide wide area coverage.  More realistically, as we discussed, one or two helos are going to provide extremely limited coverage.  Thus, in order to maximize our chance of detection, we’ll have to involve the ship’s sensors.  A reasonable approach to this is to stake out a square of interest with a ship at each corner and work in towards the center with the helos starting at the center and working back out towards the ships.  Hopefully, the constricting box will herd the submarine towards the center where the helos can locate it or, eventually, all four ships can combine to locate and prosecute it.

The alternative approach is for the ships to stand well off and let the helos work the area of interest alone but their limited coverage is unlikely to succeed.

Having located a target, how do we attack it?  As we noted, the LCS has no ship mounted ASW weapons so the attack will have to be by helo.  There’s nothing wrong with this except for the helo’s limited availability and limited payload (two torpedoes, max).  We may have to make multiple attacks over several hours due to limited availability.  Maintaining contact on a very quiet target for that length of time will be a challenge and, again, multiple ships will be useful to track the contact.

Related side comment:  If I were the Navy, I’d have designed the LCS with the ability to share ASW tracks and data in a common tactical picture.  I wonder if they did?  I’ve not heard of such a capability.

Lastly, we have to recognize that asking an unoptimized, acoustically loud ship to play tag with an SSK is asking for LCSs to be sunk.  It’s a fact of combat.  Again, this argues for operating in multi-ship squadrons.  If one ship is sunk or forced to run, the others can maintain contact and continue the prosecution.

One of the weaknesses in this concept is the LCS’ inherent susceptibility to enemy aircraft since the LCS has only very short range AAW capability.  It would be nice if the group could combine AAW resources for self-protection but that isn’t possible.  In an area of likely enemy air activity a Burke may be a requirement for self-defense.  If so, the Navy should also think about incorporating the Burke into an LCS/Burke hunter killer group – but that’s a topic for another time.

Of course, all of the preceding discussion presumes that the LCS is operating alone in the ASW role.  It is quite possible that other air or submarine assets might join in which would necessitate modified tactics.  We can’t cover all the permutations in one blog post so we’ll stick with just the LCS.  This should also provide us with the tactical baseline from which to modify tactics as other assets enter the equation.

The sharp among you may be wondering about the value of 4 LCS/4 helos versus a single small helicopter carrier that could carry, say, 12 helos.  If, as we’ve described, helos are the key to shallow water ASW, then a helo carrier would be suitable and offer more helos.  For probably the same cost as four LCS, a helo carrier would provide 3X the helos.  Something to think about.


So, what do you think?  Anyone have a different idea about how to go after shallow water subs with the LCS?

19 comments:

  1. LCS's would use active pinging by their VDS for long-ish range detection, even in shallower waters. The submarine has to play by the same acoustic rules as the LCS. Shallows impact its ability to use sonar as well. Of course an LCS blasting away with its LFAS will be heard by everything around. It would be interesting to know if LCSes can operate their sonars in multi-static modes with helicopters. I don't know if this is part of the plan. If so, then some would ping, and the rest would listen.

    Now one has to realize not all littorals are shallow. So in some areas MFTA will be valuable, and some it won't.

    I would expect to use larger formations than just 4 LCS's. IIRC, 6-8 was the thinking a while back. This would permit up to two continuous ASW helicopter orbits.

    Also IIRC, the max towing speed for CAPTAS-4 is 30 kts. Certainly not high enough for the LCS to run full-speed, but not "slow" either.

    I don't think a helo carrier by itself is the right answer. The key is to get the right ratio of different sensors and shooters (e.g.. tails, helos, sonobouys, VLA). A carrier with 12 helos can only contribute one tail and one hull-mounted sonar.

    The Japanese have spent considerable time thinking about this problem. Their ASW "Escort Flotillas" consisting of 8 ships: 1 DDH, 2 DDGs, and 5 DDs, with 8 or more helicopters. Seven of these ships have tails. All have hull-mounted sonars and VLS.

    https://www.usnwc.edu/getattachment/845c374a-6615-4872-9c65-8dcf522739ee/A-New-Carrier-Race--Strategy,-Force-Planning,-and-

    The Takanami-class DD sure would be a nice substitute for LCS (though i'm sure it's much more expensive).

    ReplyDelete
    Replies
    1. "The Takanami-class DD sure would be a nice substitute for LCS ..."

      There are so many ships out there that would be nice substitutes for the LCS!

      Delete
    2. I've seen speculations that a multi-static mode of operation could be developed (it's mainly a software issue) but I have seen no indication that it's actually being done.

      I think you got this but I'll say it just to be clear - the post is about only the LCS in ASW mode. I'm not by any means saying that this would be the optimum way to conduct ASW.

      Personally, I wouldn't use the LCS for ASW at all. The combination of active sonar, noisy waterjets, no internal machinery acoustic isolation, lack of hull mounted sonar, and lack of ASW weapons renders the LCS about the least effective and survivable ASW platform I could imagine.

      If I were designing a surface ship ASW group, I'd lean towards a small 12-helo carrier and four small, dedicated, purpose built ASW destroyer escorts.

      Delete
    3. The original invincible concept would make good reading I think.
      However they existed to close the giuk gap, not crack open the Baltic sea, an exercise that may simply be impossible, or require carpet bombing the sea.

      Delete
    4. Some dumb questions before I can even begin to postulate:

      A) Can the LCS use multiple firescouts (say 2/LCS, or a FS and an SH60?) and could the firescouts be modified as a latter day DASH?

      B) Kind of a meta question: Given all the issues out there... has there ever been a good surface ship for shallow water ASW?

      C) What kind of threat environment are we talking about? Limited conflict ASW? Or full on war in the Persian gulf. I don't think the LCS lasts long at all in the latter situation.

      I guess what I'm thinking is that if the LCS is our ship by default, then it would be nice to leverage the VDS as much as possible. FS might help with adding numbers, thought they have issues with range.

      Overall my feeling is that this is a really tough job for the LCS crew.

      Delete
    5. One more thing... would it be technically possible to put SOSUS lines in shallow water areas we might need to cover?If you had some in the PG, for example, you might gain enough knowledge of the signal to noise ratio over time to make all of your sonar's better in that area.

      Delete
    6. SOSUS lines, probably no. But there were a number of distributed fixed/semi-fixed sensor networks that were proposed and/or developed. Unfortunately most died on the vine.

      Delete
    7. " there were a number of distributed fixed/semi-fixed sensor networks that were proposed and/or developed. Unfortunately most died on the vine."

      That's a shame

      If they were feasible it seems like it would be a really powerful tool in time of war.

      Delete
  2. One ASW asset in any network should be a Virginia class sub. What assets can coordinate the prosecution of ASW with any subs ?
    I agree that the LCS has a acoustic signature problem with regard to ASW.

    ReplyDelete
    Replies
    1. Historically, it's been very difficult to communicate with subs on a real time tactical basis. This has somewhat or largely precluded subs from operating with surface ships. Typically, a sub would be assigned an area and all friendly ships and subs would keep out. That's quite a bit different from co-operative sub/surface tactics. Submarine communications have improved but I'm not aware that we can yet communicate on a continuous real time basis.

      Trying to distinguish a friendly sub from an enemy based on occasional "whiffs" of sound is extremely challenging.

      This is also why subs don't typically "hunt" together.

      How would you envision a sub being part of an ASW team other than by being assigned an area?

      Delete
    2. . The big "if" in having a sub as part of any ASW prosecution is communications with all assets. If some communication were possible with other assets then the sub could be directed to prosecute the enemy contact.

      Delete
    3. Submarines dont play well with others.
      They might be modern battleships by name, but they just dont function in a fleet battle.

      Assign them a kill box and leave them to kill everything in the box.

      They cant do their job if they are tied to a surface flotilla.

      Delete
  3. Partially agree with your assessment, since you overlooking the utility of helo periscope detection radar (ARPDD). Diesel subs have to expose masts and snorkels fairly often for observation, comms and battery recharge. Not as much of an issue for AIP boats of course.

    I'd say sending any sort of combatant (LCS, DDG, etc.) into the littorals to fight a modern diesel sub is dumb. You're in his medium, vulnerable to his weapons, and the active sensors you use give away your positon. It's akin to shining a flashlight in a dark room looking for a bad guy with a knife.

    The best approach is to use maritime patrol aircraft. Flood the area with periscope detection radar and multi-static active buoys - which if they work as designed should provide good capability in littorals.

    ReplyDelete
    Replies
    1. You may be overestimating the exposure frequency of a modern diesel-electric sub. Even the classic Russian Kilo is credited with a submerged endurance of 5.5 days cruising at 3 kts.

      ASW aircraft would be great to have but in real combat they will be tied up in higher priority areas. The LCS will be assigned to lower priority areas and largely left on their own, I suspect.

      I've stated repeatedly that the LCS will make a very poor ASW vessel. However, the premise of the post is that the Navy plans to use them that way so we discussed it that way. Please understand that the discussion does not mean that I believe the LCS is right way to conduct ASW or even a good way. It's not!

      When someone develops a FUNCTIONAL multi-static system and tests it in realistic shallow water conditions then I'll factor it in to my thinking. Until then, it falls in the same category with so many other systems that looked good on paper and never panned out. The Navy is trying to make it work but is so far unsuccessfully. That doesn't mean it won't someday work but it hasn't yet.

      Here's the DOT&E summation:

      "[Offers capability in] select scenarios in some
      environments but it does not meet the program’s requirements
      in other operational environments or scenarios."

      Delete
    2. 2 LCS mini squadron. One that is a drone that drives around in circles pinging. The other one nearby with its engines off but a Helo aloft. When the first LCS explodes the 2nd can prosecute....

      Delete
  4. This is why the US' western pacific allies have been buying SSKs, small flat tops, and frigates.

    Not sure why the USN has been buying LCS mind you

    ReplyDelete
  5. I think the conclusion that one must inevitably reach is that the LCS is of limited, if any use in ASW against a competent enemy.

    That isn't a conclusion that the USN agrees with, but it's one based on what the evidence suggests.

    SSKs, although not invulnerable, and not without their drawbacks seem to have a considerable advantage over what ASW assets exist today. Perhaps that is why AIP SSKs have proliferated.

    ReplyDelete
  6. AIP is a lot less cut and dry than it appears at first.

    The T-212 has a 2850kw diesel engine, and a 2x120kw fuel cells.
    It can stay under water for up to three weeks, but it is virtually immobile and blind whilst it does so.

    Three weeks isnt a long time in a war, its especially not a long time in the build up to a war.
    AIPs dont use their AIP normally, they snorkel, and are tracked by enemy ASW assets from the air.
    If all of a sudden, all of them suddenly stop showing up, or disappear, its one hell of an obvious sign that war is imminent..

    If they dont hide in advance and telegraph that wars coming, they cant run after the fact, 3knots is slow, really slow,


    I'm explaining this really badly, there are just massive logistical problems.

    ReplyDelete
  7. New ASW technology...

    http://www.janes.com/article/56146/raytheon-delivers-sonar-for-darpa-s-unmanned-asw-vehicle-programme

    ReplyDelete