What Does It Take to Sink a Ship, another Illustration

We only have a limited sample of the effects of modern weapon systems, so I think they are worthy of consideration.

gCaptain has a report on the recent test launch of a Naval Strike Missile from LCS-4, USS Coronado, I would like to point out the video that shows the result of a hit by this type missile in an earlier test that is included in gCaptain’s report and posted above, and talk about not the damage that was done, but the damage that was not done.

The result, is shown on the video at time 0:55. The target of this earlier test was a decommissioned Norwegian Oslo class frigate. These are relatively small ships, 317 feet long and 2,100 tons full load, only a little larger than a Bear class cutter and considerably smaller than the average merchant ship.

The Naval Strike Missile has a 125 kG warhead, smaller than that of a Harpoon (just under 500 pounds), but still respectable. The explosion and the resulting smoke are impressive. The damage would almost certainly have caused a mission kill, wiping out critical command and control, sensor, and fire control systems.

On the other hand, it appears the hull is largely intact. In fact, the target did not sink, it was subsequently towed back into port. I have observed that sea-skimming anti-ship cruise missiles always seem to strike about 20 feet or more above the waterline. This may be necessary to ensure they do not strike waves as they make their final approach, but it also seems to limit hull damage. This kind of hit might not have damaged the propulsion or steering gear, particularly on a larger ship.

If the Coast Guard is required to stop a medium to large ship, bent on doing some mischief, I don’t think even a cruise missile like NSM, could assure immobilization of the threat.

30 thoughts on “What Does It Take to Sink a Ship, another Illustration

  1. Isn’t a mission kill enough? If you want “one shot, one kill”, then a MK 48 ADCAP torpedo is needed. I would argue that in most cases a mission kill is sufficient.

    • Mission kill might be enough in the case of a normal naval engagement, but in the case of the Coast Guard attempting to stop a medium to large ship being used for a terrorist attack, we need a mobility kill. (In that case, I suppose a mobility kill would also be a mission kill.) A heavy weight torpedo like a Mk48 would certainly be the surest way to achieve that, but at over $1M a piece it is unlikely the CG is going to get enough Mk48s to go around to all the vessels that might find itself in a position to need the weapon, not to mention its large footprint and maintenance requirements. That is why have been saying we need a light weight torpedo that can target the propeller(s) of a larger ship.

    • Nicky, I am sure you could have looked this up. But, the Brahmos and the Naval Strike Missile approach the problem of an anti-ship cruise missile by completely different paths. The Brahmos is much larger, faster, longer ranged, and with a bigger warhead. On the other hand, in order to get that range, the Brahmos cruises at a higher altitude where it is easier to detect (it is a sea skimmer on its final approach), and is not as stealthy as the NSM. I also understand the NSM has a very intelligent targeting system.

      Potentially the same weight of weapons could be spread over many more NSMs making them more likely to swamp the target’s defenses, but so far no one is using that many missiles, while it appears as many as 16 Brahmos may arm some Indian ships.

  2. I would point out a couple things, with the caveat that I didn’t look up the video source or test description:

    1) The NSM has two terminal manuever modes. One is straight in. The other is a countermeasures avoidance pop-up manuever. It appears this video shows the straight-in sea-skimming mode. The pop-up mode would definitely give a different angle to the destruction due to warhead orientation, but I doubt the fusing would make the damage go deeper. Not to say the fuse couldn’t be adjusted though…

    2) My best wild guess about this test is that it was to show the seeker’s ability to discerne and not be distracted by “hot” alternatives to the target. Note the low angle of the sun – right on the horizon, and that the angle between the sun and target was minimal from the launch point (maybe 20 degrees?). I’d say “straight-in” mode was selected more as a demonstration of the seeker’s ability to not get distracted by the sun…

    This system impresses me more and more.

  3. The photo of the video appears to show a Swedish RBS 15, NOT a Norwegian NSM.

    A missile with a blunt (no-skip) nose and enough structural strength could be aimed to enter the sea in front of the ship, travel a short distance underwater and detonate there.
    The Second World War’s (dumb munitions) Bombentorpedos were meant to do this, and some 5″ rockets used against submarines as well. This could also be aimed at the screws/rudder area.

    Even torpedoes would not necessarily stop a ship within minutes.

    The only really reliable way to force a change of course without massive expenditure of ordnance is probably to tug the target.

    • the problem with this story is that its kind of misleading. Its better than the first generation of Harpoons, but what about Block 2s.

      • Have to remember that while the US has sold Block 2 to allies, the USN does not have them. Harpoon does have a larger warhead, but the NSM has a smaller radar cross section and a smarter guidance system.

      • More importantly, there are tactical considerations more than range and warhead size. NSM being an IR Guided missile, will avoid most threat – detection systems. It’s terminal profile and ECCM software make hits more likely and lower countermeasures ability to defeat it.

        While the test on ex-Ogden shows the smaller warhead on NSM certainly can sink a large vessel (as opposed to the concern expressed by Chuck above), I would point out that neither the Ogden, nor the Norwegian target ship had ECM, chaff/flares, point defense, nor a damage control crew working to protect and save the ship.

        Clearly though, the NSM warhead is no slouch and the guidance is excellent. It’s lighter weight, smaller size, and sharp deck mounting system make NSM an ideal system for LCS, OPC, NSC, & future frigate- or corvette-sized designs.

    • No clear description for this video. I’ve seen some say it is the NSM, while others say it’s 1 Harpoon & 1 NSM. Clearly there are 2 separate hits. Appears to me to be NSM on the starboard hull hit, and flooding from that eventually rolls her over and sinks her.

      • The fact that we could deal with a large ship with repeated missile strikes does not change my reservation regarding the best weapon system for the Coast Guard to field for the purpose of stopping medium and large ships that might be used as a terrorist weapon.

        Cruise missiles would at best be added only to the largest cutters. Those large cutters are not likely to be available when a terrorist attack is recognized to be underway.

        Light weight torpedoes that target the propellers (and probably also simultaneously damage the rudder) are the cheapest, lightest, least impactful way to give our smaller cutters the ability to immobilize a ship.

  4. The target recognition ability of the missile to distinguish between the actual target and decoys is particularly important. I have -seen some figures and while only one anti-ship cruise missile has ever been defeated by hard kill systems, over 50 have been defeated by soft kill systems like chaff.

    Getting the first hit is particularly important, because it will probably destroy the ship’s ability to defend against additional attacks. Once the first hit is made it should be much easier to make additional hits that will destroy the target.

    It appears that considering only weight (NSM launch weight=407 kg/Harpoon=691 kg) a ship should be able to carry about 70% more NSMs than Harpoons. That is not likely to work out in real life, but 50% missiles is probably doable and that could make a huge difference. It would more than make up for the difference in warhead size and significantly complicate the target’s problem by giving him more threats to deal with.

    • I look at it the other way around. Once adding up the weights for the missiles, box launchers, and fire control systems, the NSM will be deployable in similar or slightly smaller numbers on much smaller vessels than Harpoon, such as the OPC, NSC, perhaps even the FRC.

      Can Harpoons be put on very low displacement vessels (such as the PHM class of the 1980s)? Absolutely, but if a 70% lighter system were available, there might be some design-weight left to have other mission equipment, which is a must for CG cutters. Realistically, short of a full war scenario, all the weapons bigger than 25mm are a waste of weight on a Cutter’s hull. The NSM could give a “full capability” (because it is foolhardy to have platforms an enemy would target, with no weapons, because we have them in “peacetime” configuration) missile while saving weight and space for peacetime missions.

      Now, this all presumes the smartest thing to do with CG Cutters during a war is put them where they need a surface-to-surface missile capability. I’d argue CG Cutters would be better utilized as frigates/escorts in the lower threat environments, where their primary need would be ASW. (So, again, back to a torpedo, plus add on a TAS.) However, with the current state of affairs of small surface combatants in the USN, that may be a luxurious plan; hence the good reason to look at a lightweight anti-ship missile.

      • I am coming around to the idea that for a peacetime outfit, a cutter’s weapons should be a 25mm Mk38 mod2, eight SeaGriffins (or Hellfire or Brimstone), and two light weight anti-surface torpedoes.

        The gun would primarily be a signaling device for firing warning shots. The mount does also have a very useful electro-optic package as well that can be used without pointing the weapon.

        The torpedoes should be able to stop medium to large vessels and would likely sink ships of under 1,000 tons.

        The missiles could deal with targets too small and fast for the torpedoes and if engaging a larger target could be used against them as well.

        This outfit would probably also serve for enforcing a blockade in a relatively low threat area like Operation Markettime.

        Plus it would fit on smaller cutters, including the Webber Class and possibly the next generation WPBs, which we should start thinking about fairly soon. The oldest are already 16 years old.

      • Chuck said:
        “I am coming around to the idea that for a peacetime outfit, a cutter’s weapons should be a 25mm Mk38 mod2, eight SeaGriffins (or Hellfire or Brimstone), and two light weight anti-surface torpedoes.”

        I think you are really on to something there Chuck! I would tweak it a little bit.

        First, I’d say, especially against boats and small vessels (up to 300t?), the Mk.38 is more useful than just warning shots, but I know you are thinking about the more innovative but distinctly plausible threats from larger merchants.

        Second, I’d say the easiest/cheapest way into the torpedo is getting the USN to supply a single SVTT mount. Basing your anti-surface torpedo on the Mk.54 torpedo should save some money and make development easier. Best of all, if full war-footing were needed, Mk.54 torpedoes could be put in the tubes for ASW. The “only” addition needed would be a sensor and weapon control station.

        My biggest reservation is the guided small missile. With as small as it is, it is no more decisive in impact than, let’s say, a burst of 5-10 rounds from a 57mm. Range isn’t a whopping big difference either. I’m just not sufficiently sold there is a big enough performance difference to justify the cost. I think a precision-guided small missile can be an asset, but for the cost difference (vs. a dozen small cannon rounds), it should be able to be targeted in all weather & day/night, and for the larger targets, the operator should be able to pick the impact area on the target. So, I’m thinking a thermal or imaging IR sight. Maybe something based on the US Army’s Javelin missile’s seeker and controller?

      • Bill, I would certainly agree that the 25mm might be useful for more than warning shots, but the other two weapons are more certain to take out the target quickly making the 25mm’s capability secondary, while it should be very effective in the warning shot role.

        There are three arguments against the choice of a 57mm over the small guided missile.

        1. While the cost of the missile may be more than the cost of the 57mm ammunition you really have to consider the cost of the weapon as well. The 57mm gun, its maintenance, its ammunition allowance, the training of personnel etc. certainly cost more than the comparable cost of a few SeaGriffin, Hellfire, or Brimstone.

        2. The 57mm like all guns, is more likely to cause collateral damage, which was the original reason I began to see a need for the precision of the guided weapons.

        3. The Coast Guard is unlikely to put a 57mmm on anything but the largest cutters, so it is not likely to be available when needed. We need weapons that can be deployed on small ships (I know the 57mm has been used on ships than the Webber class, but I don’t expect the Coast Guard to do this).

        My impression is that the small guided missiles, at least in the semi-active laser guided mode, can be selective regarding the where to target larger vessels.

        Regarding the torpedo, my first thought was to rework now obsolete Mk46 or even Mk44 torpedoes, but I’m not sure there are any left. I understand the Mk54s are being built by reworking Mk46 torpedoes. Certainly there is good reason to stick to the current size parameters and fire them from Mk32 torpedo tubes. While the Coast Guard has only used the triple Mk32 tubes, they are also available as single and twin tubes. An installation on a patrol boat might be two single tubes tucked into the corners of the fantail with the muzzles pointed aft under the taffrail. The torpedoes propulsion could be the same as current ASW torpedoes or they might be battery powered electric. They would not need extremely high performance in terms of speed and range.

  5. Chuck, lightweight torpedoes aren’t going to fare well in very shallow and congested waters.

    There are two other (relatively cheap and low maintenance) options for stopping a ship violently close to or in a harbour:
    (1) Depth charge thrower (smaller RBU-6000), aimed to detonate charges very close to where you would like to place a LWT. Blunt noses allow entry into water without bouncing off, and fuze can delay long enough that the projectile reaches the screws area.
    (2) Ramming bow (not meant to cut, but to push without sinking the cutter itself), and then push the ship off its course, tug-style. This works long after hitting the screws would have been too late due to momentum.

    LWTs are expensive, and their employment in tricky waters is unreliable. There are so many issues. Old sunk ships trigger fuze, freshwater/saltwater borders, rocky bottom a few dozen feet under the surface, yachts and other surface units you don’t want to hit, metallic tethers of buoys…it would take a multi-billion program to adapt a LWT to this mission in this kind of environment and equip all cutters with three LWT. All for the remote possibility of one ship running amok sometime. That’s wasteful.

    • Lastdingo, I think we are going to have to disagree on this. Of course you have to use some intelligence in the employment of a torpedo in a complex environment, but it is always going to be a whole lot easier than successfully stopping a medium to large ship by ramming, particularly if your own ship is much smaller.

      If the water is deep enough for a target that justifies a torpedo, then it is deep enough for a torpedo.

      As to the RBU-6000, it is hardly a trivial add on. http://en.wikipedia.org/wiki/RBU-6000 The launcher weighs 3,100 Kilos (6,820 pounds) and requires a below deck magazine. You are not going to put them on a WPC. These are unguided rockets, and not particularly accurate. They are designed to saturate a relatively large area to cover uncertainties in targeting and the inaccuracies of the projectiles.

      The light weight torpedoes need not be particularly expensive or sophisticated. They don’t have to dive to any great depths. They don’t have to be particularly fast. They don’t have to have great range, They don’t have to be quiet or wakeless. It is all pretty much 70 year old technology made easier by the digital revolution and, if electric, by much better batteries.

      Even over 100 year old torpedo tech has proven effective: https://chuckhillscgblog.net/2011/02/06/a-tale-of-two-harbor-defense-organizations-part-two-2/

      • Rocket dispersion at LWT combat ranges is measured in metres only. It’s not much of a problem at these ranges, at least not if the FCS takes the temperature into account.

        You can forget about a limited capability LWT. The bureaucracy will inevitably go for one that gives the CG some share of the ASW mission. That’s how bureaucracies roll.
        LWT development is very expensive, and the environment is different from the preferred environment for normal LWTs. Look at the MU90 or Mk.50/54 program costs.
        MU90: USD 2 million per LWT and half a billion for development.

        Best you could hope for is a program which costs a million per modified Mk.54, and you would need three per cutter due to insufficient reliability of effect with only one or two.

        Hundreds of millions for the unlikely case of a ship
        * about to ram or release something relevant in a harbour area
        * while CG is aware that something is wrong
        * in time
        * with a cutter instead of a mere smaller harbour boat present
        * able to intercept
        * again, in time
        * somebody actually musters the guts to shoot at the ship
        * again, in time
        * maintenance and training actually suffice for the action
        * said shooting has NOT an undesired effect
        * said shooting has the desired effect
        * the situation cannot be resolved without the particular torpedo

        In short; it would never be employed for its niche purpose.

      • Lastdingo, Sven, I would be happy to see the Coast Guard once again embrace the ASW mission. That might put torpedoes on our largest ships, but again, I don’t think any US ASW torpedoes have an anti-surface capability, and it is unlikely these larger cutters are going to be in the right place at the right time.

        Is it a threat worth countering? It might be not much more than the attack on Mumbai, it might damage or even destroy a aircraft carrier or SSBN. It might be introducing a nuclear device.

        It is a mission the Coast Guard has, and we need to address it seriously.

        The US Mk 54 is not as expensive as the cost you quote for the MU-90. Wiki has a notation at the bottom of the entry that “Senate Report 113-044 – NATIONAL DEFENSE AUTHORIZATION ACT FOR FISCAL YEAR 2014”. Library of Congress. 20 June 2013. Retrieved 2013-11-07. 150 Mk 54 cost $125.898m in financial year 2014. http://en.wikipedia.org/wiki/Mark_54_MAKO_Lightweight_Torpedo
        There is also a report that in 2011 there was a $42.6M contract to provide 100 Mk54s. http://www.defenseindustrydaily.com/team-torpedo-raytheo-partners-to-support-mk48-and-mk54-requirements-02533/ A simple, single purpose anti-surface torpedo would certainly cost less.

        On the other hand, if you thought of the Coast Guard as simply a place to store war reserve torpedoes in peacetime, that the country was going to buy anyway, the price of adding the capability to cutters would be negligible.

        Let us assume that the cost to add two torpedoes and tubes to a Webber class cutter is about $3M (two torpedoes at $1M each and $1M for tubes and launch controls), that is only 5% of the cutter’s acquisition costs. We only add four ships a year for a marginal cost of only $12M per year. Adding them to all 58 planned Webber class would only cost $174M. Not a lot even by Coast Guard standards. Even at twice the price, spread over several years, it is cheap.

        Defense expenditures are mostly made as a hedge against unlikely events. But they are still made because they may be unlikely, but they are high impact events.

        How much would it cost to reprogram the Mk54s to take on surface targets? Unknown, but I don’t think it would be a lot since they share software with the heavy weight Mk48 which can be used against surface targets. It might require only changes to the range of minimum and maximum search depths.

      • Of course, the US Navy pays for the weapons on Coast Guard Cutters, and the cost of torpedoes for the Webber class would be lost in the rounding error of their budget, so why are we not asking for this capability?

      • I highly disagree with the cost issue which lastdingo raises. The USN is in the process of phasing out hundreds of perfectly good Mk. 46s at this moment. The warhead, motor and structure (frame and body to use automotive vernacular) are all 100% re-usable and capable for this CG need. What would cost money is a new guidance system which is not ASW-centric.

        This would still not cost much, because it is technology older than WWII. The ideal guidance would be wake-nibbling. This would require the Cutter to position itself behind the target vessel to some degree, but being precisely astern of the target (in its wake) is unnecessary. Wake-nibbling guidance will cause the torpedo to attack the very spot desired as well. The cost of removing the ASW guidance package and replacing it with an anti-surface wake-nibbling package (and that package itself) would be the only costs.

        Now, the water depth issue lastdingo brings up may be an issue. The only open-source documentation I could find regarding required depths for surface launch of a 12.75″ LWT was 25m (yes, meters), here: http://en.dcnsgroup.com/naval/products/mu90/

        Also interesting at the MU90 website shown, is that they have given it a surface-attack secondary capability. So, someone other than Chuck has this idea on their radar. 🙂

      • The Russians, Chinese, and Europeans all make light weight torpedoes with an anti-surface capability.

        Re the required depth, I suspect it is partly a function of how high it is dropped from.

        I also see European ASW torpedoes launched with a drag shoot attached, apparently to retard their speed entering the water. That might also reduce the initial dive.

  6. Test of the NSM against a land target. Story here–http://www.navyrecognition.com/index.php/news/defence-news/2016/june-2016-navy-naval-forces-defense-industry-technology-maritime-security-global-news/4049-video-royal-norwegian-navy-skjold-class-corvette-fires-nsm-against-coastal-land-target.html

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