A little water-navy story

I was inspired by Pournelle’s “littoral navy” story to whip up a short story of mil-fic for a somewhat nearer water-navy story. A new type of ship. It’s been long enough since I read modern navy fiction I’m forgetting the terminology, and there are likely some minor problems with protocol. Any former squids / bubble-heads out there want to take a gander and offer feedback?

56 thoughts on “A little water-navy story

    1. Very good. The idea isn’t amphib, but transformable. And reviving an old sub concept, the deck gun.

      Some major related thoughts. “surface presence” is a part of the force continuum – you look out and see the guy floating there, large caliber deck guns pointing at you, and you have a visceral understanding that things are serious in a way that an invisible sub or supersonic plane unseen high above can’t give. So, deck guns mounted under a water-tight streamlining clam shell arrangement.

      Next is relatively small size, small crew, aimed at being used in littoral waters. What’s the smallest practical size for a nuke boat?

      Third is for surface speed. Hydrofoils are faster / steadier than displacement hulls, but suck up a lot of power. So, is there an intersection on size/mass/power for a nuke hydrofoil sub, as long as the dive depth isn’t too great (which would require thick steel).

      Idea being – sneek along away from lasers and radar underwater, pup up, uncover an array of guns and other weapons, board and inspect (or whatever), then slip away. Torpedoes are sort of an “all or nothing, sink your ship or watch twiddling our thumbs” proposition, but if you have a 5″ gun, missiles, torps, RC machine guns, 20mm CIWS, etc, your available options for making an opponents life problematic are rather greater.

      Thoughts or obvious problems?

      1. Guns: Not in a clam shell. Mount them on a retractable platform. When not in use, they drop below decks or other retract inside the skin of the ship.

        Reactors – pretty damn small, depending on your requirements
        http://www.ted.com/talks/taylor_wilson_my_radical_plan_for_small_nuclear_fission_reactors

        If all your weapons are electrical (e.g. rail guns), you’d need a big reactor, or a large capacitor bank, or you won’t be cruising at flank speed while shooting.

        Hydrofoils need LESS power than a displacement hull, once you are on the foils. The trick is having enough power to get up on the foils. Remember that a hydrofoil is not a ski, it’s a wing. Water is 1000 times as dense as air, so it can provide 1000 times the lift, and 1000 times the drag. Of course, the drag from a hydrofoil is still <<<< than the drag of a wetted hull at the same speed. So once you are up on the foil, your power requirement goes way down, or conversely, your top speed goes way up. Remember that the old Pegasus boats the Navy once used had a top speed hull borne of 12 knots, but on foils, they could hit 48 knots. (of course, my LCAC could clear 100 knots, but we were on a cushion of air). Being overpowered bets you up on your foils fast, but leaves you overpowered (which is not a bad thing for a warship). You could implement a bubble sheath around the hull when trying to get up on foils to cut down on the water drag, but that adds complexity.

        Of course, a submarine with hydrofoils sticking out into the water will not be very stealthy unless it is barely moving (the foils will create turbulence, turbulence creates noise, hydrophones will hear it coming), so the foils would have to be able to retract into the hull, which adds complexity & eats up hull volume.

        And before you think about trying to use an air cushion instead of foils, keep in mind that a hovercraft is a flying barge, which will be utter crap as a submarine.

        1. The thinking was (relative) stealth when underwater, fast and highly visible when above water. Not both at the same time. Sneak in, appear blazing fast out of nowhere, look flashy and hit hard, disappear into the night.
          A 5″ gun has considerable recoil; I was thinking a low-profile turret with a streamlined clamshell (only closed when the barrel was aimed straight forward, offering a very narrow profile). That was it doesn’t mess with pressure hull integrity contours. But retracting might work too, depending on geometry. The smaller systems (CIWS / machine guns / missile tubes) I was thinking fold-away with water-tight covers to avoid the whole deep-submersion-in-seawater problem. While vertical-launch Harpoons would likely work, they don’t look quite as scary, and part of the goal is to have something that just looks like wicked-bad juju to mess with; I figure lots of pop-up guns and launchers would meet that requirement.

          Hmm… bubbeler up front to reduce friction via a small air layer to get up on the foils. Might work.

          But at least it’s not an idea that you just laughed at and said “yeah….. riiiiiiight……” πŸ™‚

          1. I’ll read it this weekend if that’s soon enough (I’m pushing a release today)?

            Recoil? Not that much (hydraulic damper system), see: https://en.wikipedia.org/wiki/5%22/38_caliber_gun

            You’ll want a boat that is semi-submersible, something that won’t dive, but will sit very low in the water, with a very low visual & radar profile, when it wants to be sneaky. You’d think that on open water, spotting a ship would be easy, but if radar misses them, it’s actually very easy to miss a ship until it’s right on top of you. Ships are spotted by their wake as often as not. Also, if the ship can come right up on foils , it’ll run down anything short of a cigarette boat or hydroplane racer (and that is what .50-cals are for, one shot to the engine and she is dead in the water). Sure, it’d be scary to have a boat surface right next to you, but having one run you down has it’s own flavor of terror.

          2. That would be fine. I just had a thought about it… would a torpedo taking the hydrofoil off a large hydrofoil-type craft also be 100% likely to hole the hull (even the pressure hull of a shallow-dive sub) when it’s high above the water, or just “most likely”? or would the stand-off distance be sufficient to prevent holing and it would just get a big dent?

          3. Depends on the warhead. Torpedoes can be straight HE or HE Shaped Charges. A shaped charge that hits the foil will trash the foil, but the hull would probably be fine (maybe dented), since the surrounding water would absorb the energy of any of the remaining warhead (kind of like shooting a bullet into water, if the bullet was superheated copper or tungsten). A shaped charge that makes direct contact with the hull is gonna punch through it like a supersonic nail.

            The HE charge, on the other hand, can be very nasty depending on depth. Near the surface (i.e. the boat is surfaced, if not on foils) and HE charge would mess up the foil, but the hull would handle it. At depth, however, your boat is well and truly screwed. The overpressure that would result from the shock of the HE detonation would be like having that part of the boat suddenly find itself many hundreds of feet deeper, causing massive localized stress and popping rivets and welds all over.

            MK48s (IIRC) have simple HE warheads that can detonate on contact or proximity, and they add insult to injury by making sure to not only detonate the warhead, but any remaining fuel as well. Near the surface, they tend to detonate right under the keel of a ship, where the explosion not only lifts the center of the ship up out of the water a bit, it also causes a hole to form in the water, so when the ship comes down, it falls a bit more (no water to support it) and it snaps the keel. At depth, they just blow up close enough to the sub to let the overpressure do the job.

          4. OK…. So it would not be totally unreasonable for a hydrofoil craft to get up above the water and run away from a torp at speed, and have it still manage to catch up but only mangle a foil rather than sinking it. That would add a bit of tension to the story, and add to the survivability of the craft. Might have to add that in.

          5. Yeah, the chase speed would also carry your wounded boat past the hole that should break her back. But make no mistake, a full sized torp catches the STAG and blows on a foil, she’s gonna be limping home & spending time in a barn, and there’ll be casualties. They pack a whallop.

  1. Smallest nuke to date was the NR-1 but that was an electric drive boat that could only do about 4 knots.. It takes a 360′ boat to hold a reactor that can get it going over 20 knots submerged (less on the surface because we can’t cool the reactor as well.

    For your application I’d think a hybrid of an Air Independent Power plant for submerged operation, diesels for cruising on the surface or awash, and gas turbines to get/stay foil-borne would give you the power levels you need. Note that we can’t cool a nuke plant in the air without huge heat exchangers…

    I’m a Navy Nuc. I spent four years on the USS Omaha SSN-692 as a Mechinist Mate and ELT and got out as an MM1(SS).

    I loved TSCB (especially how Rockwell’s most famous product makes an appearance) and would be happy to give feedback.

    1. Re running away from a Mk48… Even foil-borne you might not make it, the estimated top speed is over 50 knots, so it could run down a 45 knot hydrofoil.

      Plus, we have stories of ASW helos nearly pulled into the water when a torpedo locked on to the noise of the bird, broached, and got fouled in the cable for the dipping hydrophone. Between the noise from the supercavitating propellors and the foils you have something screaming “Shoot Me” to a submarine torpedo.

      1. Well, the gunboat wouldn’t have to outrun a Mk 48, only the Russian / Chinese / NorK equivalent, and if she’s running away she’d just need enough distance to get it to run out of fuel. 5 kts of speed differential with a 3 mile lead means a fifteen mile run, and the Russian Type 53 torpedo only has a ~12 mile range. That could make for an exciting chase scene. Have to work that in…. And if it turns out there are two torps, it outruns the first one, loses a foil to the second, but still can do her thing. have to think about that a little bit.

    2. I was only a turbine tech, so I’m gonna defer to the bubble head with the healthy green glow regarding navy reactors.

      I do think you could use a smaller reactor, but only if you got away from the style of reactors the navy has historically been comfortable with. I’ll also agree that a turbine for foilborne ops makes sense, even though it eats up volume for the machinery & fuel.

    3. Glad you liked TSCB – I figured the number of people that would get the Encabulator joke would be small, but it would be the sort of thing that is worthy of cleaning the keyboard for those that do.

      Yes, I’d be happy to get feedback from someone who’s been there, done that. Every additional detail of authenticity I can add helps (and I learn stuff, too).

      Bummer on the nuke plan. I was figuring on having a lot of water coming up a foil strut, scream through the power plant, then get squirted out as an additional water jet propulsion assist. downside to that, of course, is if you lose the foil strut you lose your intake… but then, you’d also be hull-in-the-water at that point, and can use the normal cooling water intakes. Currently thinking of making it a ~65m boat/ship/thing.

      Hmmm…. OTOH, I could have this early one be a hybrid (AIP / diesel / turbine) but mention plans for a nuclear powered variant with a newer experimental design, and leave the details out. That would make for a much nearer-term deployment. I’ll do a quick re-write with those ideas – mind if I send you a copy, see what you think?

      1. Instead of hydrofoils what about it being a GEV (ekranoplan)?

        Mission profile would be cruise to near the op area on the surface, submerge on AIP to in close then pop up and engage with a railgun, CIWS, or missles (whatever fits in the retractable fairing) then either going under to sneak back out or hitting the turbojets for an air sprint out of area if it gets too hot. With that design you could have turboshaft engines for primary cruise with turbojet units outboard.

        Mad Rocket Scientist, how long does it take to cool down a turbine after you shut down? Are we talking minutes or hours to get to ambient with a little forced air cooling?

  2. Mr. Tengdin made a comment and it appears to have evaporated.

    A GEV/WIG/Ekranoplan is intriguing (& piques my interest since I’ve done quite a lot of research and design on them in college – I’m a ground effect geek, what can I say). It would make a crap submarine (it could be designed to submerge, but would be extremely limited in speed and maneuverability), but as a rapid response littoral gun boat, it could be quite effective. If you want me to list out the pros & cons of one, let me know.

    As for turbine cooling, when a turbine is shut down, it is usually kept spinning via the starter motor (usually powered by electricity or bleed air) until the temperature comes down a bit and all the exhaust gases are blown clear. Takes a couple of minutes to do this for the big turbines (LM-2500 or equivalent). One thing the turbine stacks also have is a waste heat boiler, basically a small coil of tubing in the stack that takes advantage of the exhaust heat to boil water for whatever you need hot water for. For a rapid dive, you could line the length of the stack with such tubing, and in a crash dive, vent the turbine just long enough to clear the exhaust gas, then use the waste heat boiler to do the rest, shedding heat throughout the interior of the boat via water jacket and just letting the ship HVAC move the cooling air around (since the stacks would be sealed, the cooling air would have to come from and vent to the interior) until the heat bleeds out through the hull. Depending on the hull volume, it shouldn’t heat the boat more than a few degrees.

  3. Guys, what are your thoughts on manning Rolf’s STAG, especially with battle damage…. Once you have the number of bodies to man all stations (engineering, bridge/conn, weapons) add about 50% to allow for damage control teams and/or replacing wounded sailors I’m not sure 48 guys is enough unless it is 48 plus the 18 Marines….

    By my counts, in control you have 8:
    CO
    Officer Of the Deck
    Navigator/plotter
    Helmsman
    Radar Operator (general overview)
    Chief of the Watch (Ballast Control Panel operator) who manages the trim of the ship.
    Radio Operator/Communications
    3 Weapons techs (main gun, missiles, torpedos, all different consoles)

    In Sonar room 3: (in a separate compartment now since they use displays show the angle to contacts, not a rotating hydrophone):
    Sonar Supervisor
    2 Sonar Operators

    In Engineering: 7
    Engineering Office of the Watch
    AIP Operator
    2 Diesel Operators
    2 Gas Turbine Techs?
    Aux Machine operator

    Weapons: 12?
    2 Fire Control Techs for main gun, possibly 3
    2 for each retractable launcher
    1 for each CIWS
    1 for each remote controlled MG or Grenade Launcher

    That leaves the XO, 2 Cooks, mess cook, Corpsman, and Yeoman as non-assigned bodies but the Corpsman will be doing his own version of Damage Control :-)…

    1. Marines can double up as junior gunners mates/cooks/machinist mates (during deployments, the Marines would often have a handful of guys working in the galley, and some would help out in gunnery, aux gang, etc. – jarheads get bored when no one is shooting at them, and most aren’t just useless riflemen). Cross train your turbine techs & engine men.

      I do think 48 is probably good if the Marines are helping, take a look at the PHM boats, they had 4 officers & 17 enlisted.

      1. 4 Officers is about right, with the CO and XO as LCDRs, Ops and Engineer as LTs..

        17 for a two power plants, only air-side sensors, and non-guided weapons is probably OK, but we have another power plant that is*very* different, water-side sensors and systems, and multiple guided weapons (main gun, torps, Harpoons, Surface missles) not to mention the CIWS..

        The Marines can man most of the remote-controlled weapons during approach then hand off to sailors during boarding, so that helps..

        I’m still concerned about having men available for Damage Control and still be able to fight the ship.

        1. I’m not entirely sure the STAG would need the diesels. Frigates have a pair of LM-2500s and do OK on those.

          Use the LM-2500 (or a pair if you want) to spin a big ass generator that charges batteries & provides power to the motors for the screws and water jets. Now I just need GSMs, GSEs & some EMs for the AIP.

  4. How fuel-efficient are the LM2500s a low(er) load? The Pegasus was a hybrid plant and we are talking about something only about 50% bigger than the PGH, and a fraction of the tonnage of a Burke-class DDG for tankage.

    1. At constant speed, constant load, turbines can be extremely efficient (i.e. what a turbine would experience when spinning a generator). There is a reason co-gen power plants mount turbines and not piston engines.

      Turbine efficiency suffers when load and speed change rapidly, which, again, is another reason to have it turn a generator instead of a screw/jet. Batteries can act as a buffer against rapid changes.

  5. I’m familiar with Combustion Turbine Combined Cycle power plants, my brother was an Instrument Tech at Moss Landing when they put in their units to replace the supercritical steam plants. Now there was a scary power plant.

    We are talking about a propulsion load here, so it would be varying all over map but mostly 25-30% power level for a Full bell, and that is where I’m concerned about fuel efficiency.

    1. Well, this wouldn’t be combined cycle. Just a straight connection. Generators are spun at constant speeds, with little variation allowed. The load can change, but the speed has to hold very constant. If our turbine is spinning a generator, it could produce considerable power (shaft output of 35 MW for the latest gen4 sets). Couple that to the battery pack and the battery pack evens out the load requirements so short duration changes don’t alter the efficiency too much. A long term hard run (like, say, running from a torpedo) would change that and the turbine would have to experience more loading, but that would (hopefully) be the exception, not the rule.

      If you are thinking that going up on foils would cause the efficiency to drop drastically, you’d be right, kinda. Much like a jet taking off, you’ll suffer during the acceleration part of the curve, but once on foil and cruising, the power requirements will again level off and the efficiency will return.

      The question to ask isn’t the efficiency, it’s power & power to weight requirements. A well tuned piston engine will always be more efficient than a turbine, but piston engines scale up poorly. If I have a ship that is tight on internal volume, it may make more sense to just use the turbine(s) and eat the lower overall efficiency rather than try to cram a turbine and some diesels in there just because the diesels are better at low speeds(also, the LM2500 might actually be more turbine than the ship needs, although I doubt it).

      Depending on the systems and the numbers, it might make sense to run the ship primarily on the electric drives and batteries, with the turbine coming online every so often to top off the batteries, or just turning at a low idle to keep the generator turning (maybe with a gearbox to keep the generator speed constant), then, if at GQs on the surface, the turbine is running so whatever power needs there are can be met.

      1. Batteries have two classes of problems:
        Lead-acid cells are HEAVY…. Not what you want to get foil-borne…
        LiPo cells are an explosion hazard if they are breached in a casualty…

        Rolf, this is where the Engineer’s Secret Weapon comes in: Hand-wavium….

        Turbine & AIP is probably fine for your story, we can worry about optimizing range later πŸ™‚

      2. Constant speed yet, but the power level will change based on the speed of the ship.. I wonder where the throttleman sat on the PGHs, I assume they were on the bridge not buried down in the Engineroom… No real reason to keep him there once the plant is ready for maneuvering..

        We are back to Hand-wavium and Hammer Space for Rolf to make everything fit…

  6. What’s interesting to me (getting back to manning) is the new LCS trimaran has 11 officers and 32 enlisted… I’ve never heard of command that is 1/4 officers! Makes having a wardroom and crews mess kind of meaningless. At least on LA class we are 90-odd enlisted and 13 officers.

        1. new topic: op range and support… Suppose the STAGs are run as local raiders, 7-14 day operating endurance away from a support tender that stays out in International waters, probably part of the Carrier Group. That gives the airdales an excuse to be on call and reduces the spares/tankage/etc. space required. It also allows for the tender to provide higher levels of maintenance than Ship’s force can provide. Sort of like being a submarine AC-130 gunship…

          If the tender was based on an LSD or similar they might be able to lift a STAG clear of the water to replace blown-off foils and other below the waterline repairs more quickly..

          Admin note: Rolf, we are getting emails of new comments before they show up on site. MRS didn’t see one of mine yesterday, and I can’t see one of his today…

          1. Send me an email to madrocketsci at gmail dot com & I’ll forward you what I wrote to Rolf this morning.

  7. Rolf, given the mission profile of a STAG I’m not sure a nuke power plant would be a good option for a number of reasons:
    – Cost, first and foremost. Lots more expensive than an AIP….
    – Risk of widespread contamination if a STAG is destroyed.
    – Risk of bad actors getting their hands on state of the art tech if a STAG is captured.

    Unless the hydrofoils are retractable you won’t get 20 knots submerged without too much flow noise no mattter how much power you can generate underwater.

    The place a nuke *might* factor in is to use a newer class fast attack or SSGN as a mothership carrying the STAG docked on her back with umbilicals to feed power to the STAG for atmosphere control and sensors. Cruise in, undock to go topside to kick ass, then submerge, redock/repower, and sneak out…

    If the STAGs operate from a mothership like I and Mad Rocket Scientist have suggested the nuke’s long endurance is less of an advantage…

  8. Oh yeah. Rolf, thank you for the offer to help build your playground!

    I hope we aren’t getting too far into the weeds with some of these discussions.

    1. Holy crap, guys! I go off to do a little actual job-type work, and I come back to a post with 41 messages on it!

      Jeeze.

      No, not at all. I like weeds. My garden is full of them. lots of room to play in them. πŸ™‚

      I’m learning all sorts of good things. I generally don’t like the idea of a tender because it’s a big “raiders in the area” flag, and a big obvious target. OTOH, it solves some practical problems assuming something like current tech in a very practical way. One tender per four or five STAGs, offer space for crew rotations, repairs, keeps tankage reasonable, all sorts of things. If a mother-ship is good enough for Somali pirates, it must have something going for it.

      Hmmmm… a light, relatively shallow-dive attack sub with a couple of STAGs piggy-backed, and umbilicals. Neat. Make the whole things smaller, lighter, shorter-range, designed to work together like a carrier fleet and her air-wing. Maybe mix that with the tender idea above: one tender, a sub, four or five STAGs. But that changes the power/size numbers a fair bit. Maybe for a future version of the story, developed to a full novel, after a few more beers, er I mean, R & D here.

      Handwavium on batteries? Nah, if I gotta use that it’ll be on nuke power, maybe something based on this. It’s been pretty slow progress on that front compared to everything else electronic/electrical for a long time.

        1. It would get known pretty soon, much like the Russian “trawlers.” But that would be for the “big players” that can keep track of things, like the Russians. Maybe disguised as a tanker – lots of them floating about in the ME not doing much. Lots of room. And it could double as a tanker πŸ™‚

          1. Yep, having a tanker or freighter that actually acts like one would help the disguise, as would simple things like changing the profile with bolt on fairings (wouldn’t fool a close inspection, but from a few miles out…) so the ship would have a habit of “disappearing” after it left port. The chief failing of the Russian trawlers was that they were trawlers that had been repurposed as spy ships, rather than purpose built as spy ships that look like trawlers. That and the Russians just didn’t care enough to make them hard to ID.

            But you are right that the big players would have the assets and resources to try and track the tender, which wouldn’t be a big issue unless they decided to share that tracking data with smaller players.

            Operationally, the tender would have not only her fleet of STAGs, but a couple of attack subs nearby as well, or perhaps a carrier group close enough the planes could be on hand in a hurry. It wouldn’t be perfect, but it would make the STAGs much more flexible.

  9. If the tender is an LHD/LSD or similar large Gator Freighter they might blend in better with the carrier group. The missions for STAGs can’t be out in BFE away from any US assets, the support logistics for a medium craft get crazy…

    Otherwise you need forward support bases like we did for the PT boats..

    1. A set of STAGs attached to a moon-pool tender, with the “partner” of a modified nuke attack sub for longer-range stealth deliveries. Tender tags along with various fleets and task forces. Tender also hauls a bit of fuel and ammo reserve for the other ships, occasionally delivers SEALs.

      Small-ish diesel generator to feed the electric motors/screws that AIP pushed and to provide efficient power when loitering around awash and just poking around; located in a different compartment than the main engine it also provides redundancy. One “latest generation” LM2500 for main power and hydrofoils. Cut down the length a bit, make her skinny to lighten her up a bit. A tight fit for the crew, but with relatively short deployments before going back to the main ship, and the expectation of regular time on deck, very manageable.

      Crew of 48, plus a dozen marines to cross-train as assistants and provide labor. Marines specialize in ship-boarding actions rather than amphibious landings.

      Hmmm… Could make a whole series of stories πŸ™‚

      Unrelated – the name. I’m calling the STAG Hammerhead right now, but with the hydrofoils a sister ship is the Flying Fish. But the navy likes to name things in a given class on a theme: states, cities, fallen heros, etc. What’s a good common theme, or should the just be fish? Or something else entirely? Others I was thinking about was Thresher and Pike (a double meaning name) for two others, but…. Thoughts?

        1. Other predator fish names that come to mind:
          Barracuda
          +1 for Swordfish
          Moray
          Albacore
          Salmon
          Shark
          Sea Devil

          What about predatory sea bird names too?
          Skua
          Osprey

  10. A power plant solution comes to mind, if it’s ok to be a bit more SF-ish.

    What if it were a Bussard “Polywell” reactor? Those are compact fusion reactors, and in fact the contracts that funded Bussard’s original work were from the U.S. Navy I believe. One version generates electricity directly, though it seems likely that it would be a bit big for a STAG. (That’s the B11+H1 fusion reaction — it takes more energy and therefore a larger machine.)

    1. re: Fusion power…. IMO it would have to be COTS to be acceptable for a STAG, you don’t want to put state of the art (or better) tech in an alley brawler, the risk of giving the Opposition access to your best tech when (not if) one is captured is too high. Maybe for the mother sub that brings the STAG closer to station.

      On a similar thought: since most of the tech in a STAG is COTS the real brains will be in the software. Question is, how to secure it? My thought is the master copy of all code is kept in a destruct container (tamper and it wipes the storage) so only volatile copies are kept on the respective systems. If you blow the main brain box the ship becomes a buoy as all systems shut down. Once you retrieve the ship you replace the main brain systems come back to life…

      1. Good point on the risk of the wrong people getting a state of the art power plant.

        On software: keeping the boot copy — the persistent copy — of the software in a self-destruct box makes sense. A small container with thermite would do nicely. Make it heavy as a backup — sort of like the classic lead-covered codebooks.

        It would be possible to have the code, even at execution time, encrypted by a key that’s kept within the CPU chip. I don’t know if people have done this but it would be easy enough. Then the plaintext of the software doesn’t exist anywhere.

    1. Now there is your AIP powerplant after it is scaled up to 5-6 MW output. Big question is what is the ‘recharge’ time after a long run. Add the second set of bottles to store the O2 for undwater ops and we are there.

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