Land-based and carrier aircraft can attack naval surface targets much more easily, at much less risk and all this while being able to identify targets at a longer distance than surface warships themselves can do. Fast attack craft with missiles are thus an anachronism, and anti-surface warfare capabilities have become an afterthought for the design of warships.
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| Land-based strike fighters could reach a ship anywhere in the North Atlantic with an anti-ship missile if supported by tanker aircraft. |
The last naval warfare campaign in which surface craft were important was the naval blockade of the Sri Lankan government against the Tamil rebels. They used mere patrol boats to intercept blockade-running boats used by the rebels to import supplies from nearby India.
Other than this the unimportant Battle of Latakia in 1973 between Syrian and Israeli missile-armed fast attack crafts was the most recent relevant sea battle. Air power could easily have substituted for either party, but the air forces were busy apparently.
The first serious people understood in the First World War that air power could wipe navies from the surface of the sea within its effective range. Some bombs used and the first aircraft-dropped torpedoes had been developed, and even some guided weapons had been tested.
Aircraft can synchronise attacks from multiple preferred angles with a well-timed application of anti-radar practically any anti-ship missile type (all of them are or could be adapted for air/sea use). They can do so while being a very fast and difficult-to-hit target, particularly at distances greater than about 40 nm. They can also provide standoff jamming and chase away or destroy AEW support.
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| 300 kg guided anti-ship glider, to be dropped from airships (1917) |
There are few legitimate scenarios in which frigates and destroyers might need to do ASuW in absence of any air support other than naval helicopters. Some of those are:
- Passing through a strait and encountering Q ships or small boats / wing in ground effect craft
- Engaging an auxiliary cruiser on an ocean after being attack with missiles, possibly from its helicopter(s)
- Ship battle after failure of either side's air power to sink the warships
- Surprise sea battle at the beginning of a conflict
- A sea battle including at least one poorly equipped navy (imagine a Western navy would escort humanitarian transports to a Biafra-like conflict zones and getting engaged by a desperate Third World navy that wouldn't be destroyed before it opened fire itself)
Non-scenarios
Still, I don't think the Taiwanese navy should for example equip warships to deter or sink a Chinese invasion fleet. It would be much more cost-efficient and thus much more effective to invest in land-based missile batteries instead. (Of course, their navy likes having toys at sea and thus they even have utterly pointless fast attack craft).
The extremely fashionable "Iranian speedboat threat" hype that appeared in 2002 during van Riper's use of simulated speedboats is ridiculous in my opinion. You won't have any trouble with Iranian speedboats if you don't attack Iran, and any powerful hostile country would be capable of much worse. The security of Kuwaiti and Saudi oil exports in the Persian Gulf is their problem. They can invest in a pipeline or two to the Red Sea for a few billion dollars. There's no reason why Western navies should prepare for war against Iran, and hardly any other scenario than another Gulf War/Blockade attempt for going that close to hostile shores in anything but a war of aggression. The last time the West escorted tankers against Iran was in support of Iraq waging its war of aggression against Iran - and Iranian oil exports were not protected, so it was at best a hypocritical Western campaign in support of an aggression.
As a rule of thumb NATO forces do not need to get close enough to hostile shores to fear speedboats in a defensive war. Such things might only happen in wars of aggression or stupid small wars.
As a rule of thumb NATO forces do not need to get close enough to hostile shores to fear speedboats in a defensive war. Such things might only happen in wars of aggression or stupid small wars.
Gap filler
ASuW by frigates and destroyers is thus nowadays a mere gap filler for when air power is not available. It was accordingly neglected by Western navies, which are still operating their 1970's generation of anti-ship missiles while the Russians kept innovating and refining their arsenal.
The typical armament of a Western warship for ASuW consists of 4 Exocets, 8 Harpoons or rarely 16 Harpoons and also a single or at most two guns of 57...127 mm calibre. There are a few other Western ship-launched missile types, especially Otomat (Italy) and RBS-15 (Sweden). The Otomat with its launcher is a bulky design similar to some Russian AShM launchers and to find or free up deck and roof areas for such launchers is difficult.
Guns of 57...127 mm calibres are not really ship killers, but they can disable and set afire ships with enough hits at the right places. The 57 and 76 mm calibres are rather boat killers than serious against ship targets, though.
The gap filler role of ASuW for frigates and destroyers means that relatively little money, volume, deck/roof area and weight should be allocated for ASuW. It's also quite important that weights mounted high on a ship are much more troublesome than weights located rather low - this is about top-heaviness (rolling) of ships and about metacentric height.
Some navies appear interested in joining the ASuW and land attack mission into one type of missile and one type of gun (the latter usually 127...155 mm), which would make some sense if land attack as a mission made sense. It doesn't make much or any sense in deterrence and defence, but it's a favourite child of great power gaming fans.
Basic tactics
There are formulas from operational research that are too far from realism to be of relevance - the Lanchester equations, for example. The insight that those who shoot first may hit before the others launch their missiles helped the Syrians very little in 1973. Their initial salvo was an utter failure, the Israeli return salvo a success.
To avoid being surprised seems to be the most important rule for naval combat if not combat in general.
Modern ship-to-ship combat may actually place a 100% emphasis on dealing with the naval helicopters. These can carry AShM, but more importantly they are the forward eye in the sky for their surface allies. To take out these helicopters could thus be the most important part of a modern sea/sea battle. Long-range area air defences would be expected to take them out if neither naval nor land-based fighters were available. That's a point in favour of carrying a few SM-6, for its effective range may be about 250 nm against helicopters according to published info.
A towed, tethered aerial sensor (project TALONS or a similar autogyro approach) could have a much farther horizon at altitude than mast-mounted sensors, but this would still not be a replacement for a helicopter. Moreover, I expect such tethered systems to be used at a much lower altitude for a simple reason; targets can be detected best on the horizon, when there's no sea in the background. Most sensors that could be lifted to 400+ m would have a much smaller effective range than the horizon distance at such altitudes (almost 50 nm at 450 m altitude). Infrared sensors that do not betray the ship's location with radio emissions might have their effective range against missiles matched with the horizon at about 50 m altitude already, for example. 450 m towed altitude might be useful for ESM (passive direction finder for radio/radar emissions), though.
A towed, tethered aerial sensor (project TALONS or a similar autogyro approach) could have a much farther horizon at altitude than mast-mounted sensors, but this would still not be a replacement for a helicopter. Moreover, I expect such tethered systems to be used at a much lower altitude for a simple reason; targets can be detected best on the horizon, when there's no sea in the background. Most sensors that could be lifted to 400+ m would have a much smaller effective range than the horizon distance at such altitudes (almost 50 nm at 450 m altitude). Infrared sensors that do not betray the ship's location with radio emissions might have their effective range against missiles matched with the horizon at about 50 m altitude already, for example. 450 m towed altitude might be useful for ESM (passive direction finder for radio/radar emissions), though.
Another very important issue is to detect and identify early, and to make decisions without unduly long lags. This means especially that the tactical commander has to have sufficient confidence in a positive identification of a target. He couldn't simply unleash firepower of great destructiveness on what might be cruise ships or fishing boats. Even an utterly amoral commander wouldn't want to do so because wasting munitions on false targets might be the doom of friendly forces later. You got to get a positive identification of high confidence.
Anti-ship missiles with two-way HF datalink and imaging sensors might help with this if their radio connection wasn't cut, and relatively cheap drones with HF datalink could help a lot as well. They would either be shot down/jammed (confirming hostile presence) or report back.
No such drone is known to me as being in naval service. There were some projects, but none competed successfully with naval helicopters. Too bad killing those helicopters might be rule #1 in sea battles. In the end, sea battles are so unlikely that hardly any modern surface warship is really well-equipped for one. The Russians have some heavily armed (for ship killing) cruisers and destroyers, and that's about the most extreme there is.
Long range anti-ship fires offer a particular problem; the subsonic missiles may travel for 300 nm or even a thousand nm if built for it, but the targets would have moved by several nm and a convoy may have changed its formation. Targeting data input from before launch would often be obsolete, leaving the missile's computer all alone in its attempt to figure out which contact to engage. It might even hit some neutral ship that's in the wrong place at the wrong time. The answer to this is straightforward; a datalink by radio. The missile could at very least receive targeting updates, if not even send back processed sensor data. Datalinks aren't necessarily reliable even in peacetime and whatever eye in the sky was tasked to provide data for updates might be gone by the time the missile needs the updates. A higher average speed (supersonic missiles) and a limitation to shorter engagement distances can be used to make do without targeting updates by datalink. Alternatively, one might put neutral ships at risk and simply launch more missiles to make up for those that hit decoys and already wrecked or otherwise unimportant ships.
The supposed speedboat threat is similar to the heavyweight torpedo threat in that one might try to run away at 30+ kts even though the speedboats are faster. This buys more time for countermeasures, though mostly fast ships (running away wouldn't help 15...25 kts cargo ships as much). The installation of the gun on the forecastle of the LCS classes was thus plain stupid and regarding ASuW at best explainable with aesthetics. (The forecastle location makes a bit more sense for CIWS purposes). A ship that runs away from speedboats would want to be able to fire to the rear 30°, or else the last several knots of its top speed that were purchased at great expense of other ship characteristics would be wasted. The ship would not be able to move straight away from the threat and shoot at it with a forecastle gun at the same time.
What does it take to sink a ship?
Chuck covered this in several blog posts, so I'll simply link to him:
https://chuckhillscgblog.net/2011/03/14/what-does-it-take-to-sink-a-ship/
https://chuckhillscgblog.net/2012/04/06/what-does-it-take-to-sink-a-ship-illustrated/
https://chuckhillscgblog.net/2014/10/02/what-does-it-take-to-sink-a-ship-another-illustration/
https://chuckhillscgblog.net/2016/09/16/what-does-it-take-to-sink-a-ship-the-ex-uss-rentz-sinkex/
What does it take to sink a ship?
Chuck covered this in several blog posts, so I'll simply link to him:
https://chuckhillscgblog.net/2011/03/14/what-does-it-take-to-sink-a-ship/
https://chuckhillscgblog.net/2012/04/06/what-does-it-take-to-sink-a-ship-illustrated/
https://chuckhillscgblog.net/2014/10/02/what-does-it-take-to-sink-a-ship-another-illustration/
https://chuckhillscgblog.net/2016/09/16/what-does-it-take-to-sink-a-ship-the-ex-uss-rentz-sinkex/
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| a heavyweight torpedo hit on a rather small warship |
In the end, shells and missile warheads damage ships very much and often set them on fire, while torpedoes go to work opening the hull to seawater with often much more decisive effect regarding the question of whether a ship is floating or not.
ASuW with missiles
Area air defence missiles can be used to damage warships, and surface-to-air missiles have indeed damaged warships in accidents already. A firepower kill is feasible even with the small fragmentation warheads of such missiles, and a salvo of SM-6 (64 kg warhead, very long range against ships, up to Mach 3.5) missiles could weaken the defences of a targeted warship to such a degree that obsolete Harpoon follow-on missiles could score hits even without the element of surprise.
Some modern air defence missiles (with CIWS/short range and area air defence types) have demonstrated the ability to destroy tiny boats, even within well less than a nm distance. That's a nice to have backup, but warships shouldn't really come into contact with speedboat threats anyway.
Some AShM types are claimed to be able to fly evasive manoeuvres in the terminal approach to the target to improve survivability especially against gunfire, but it's unknown to me if any missile does so in response to actual targeting (or just as a matter of autopilot behaviour) and it's unclear just how effective this is. I suppose it would reduce the distance at which gunfire can intercept the missile, and thus increases the chance of missile wreckage or explosion fragments hitting the ship target.
There are no publicly known dedicated anti-radar missiles in shipboard use nor any publicly known anti-ship missiles with ARMs as submunitions. ship-to-ship missile combat thus lacks the ARM element that air/sea combat may have.
Naval helicopters can launch anti-ship missiles, but they don't have much payload, so the heavy missile types are de facto unavailable. Two lightweight torpedoes is a typical payload for such a naval helicopter - that's twice about 250-300 kg. Almost all AShM weigh more than 400 kg, save for rare lightweights such as the Marte. NSM is rather light at 410 kg. The typical Western anti-ship missiles such as Exocet and Harpoon are rather associated with medium and heavy helicopters, while the lighter end of medium helicopters tends to employ lightweight missiles such as Marte, Sea Skua, Penguin. The latter ones were still highly regarded as missiles against fast attack crafts (boats smaller than 400 tons), as those lack area air defences. To launch an anti-ship missile from the sensor platform itself is less of a technical challenge than a networked engagement (helicopter detecting, ship firing a missile).
Helicopters can switch between being in the radar horizon and being below it quicker than area air defence missiles with semi-active radar homing can exploit this for a kill. This allows for a quick radar scan and then hiding again, just as the Super Étendard pilot did who sank the HMS Sheffield with a single AM39 Exocet missile.
Anti-ship missiles of all categories mentioned in the AAW article may be launched by warships even though some missile types have no version for shipboard use (Sea Eagle, Kormoran and Kormoran 2 had none, for example).
ASuW with missiles is of course very much under influence of what was written in the part about AAW, as a sea battle between capable warships would be about attack and defence.
ASuW with guns
Some post-WW2 warships were built without any guns. They didn't seem to need any, but this was later corrected and at least one gun (57 mm or bigger) is accepted as minimum backup to missiles today. The Falklands War and especially the air attack as San Carlos bay helped to dispel the reputation of in particular the British air defence missiles which were much less useful than their public reputation up to the Falklands War. Short range defences gained a lot of attention due to the Falklands War.
The 105 mm calibre was ridiculed as being of little value in ship-to-ship combat as early as the beginning of the 20th century, even as a deterrent or defence against the torpedo boats then in use. The explosive power of such a shell is too small. Modern 100 mm shells pack a better punch and proximity fusing makes it easier to achieve some effect on small targets (shell exploding above a boat and showering it with fragments), but the fundamental problem remains. Even 127 mm shells are of little sinking power unless they hit at the waterline. Submarines of the world wars sank scores of ships with 88 mm and bigger guns by getting very close and piercing the ship hull at the waterline. A blunt instead of rounded shell nose may actually help with penetrating the water on the final meter without ricochetting. Still, there's little ship-sinking potential in all naval gun in use world-wide unless the target is already utterly defenceless and needs nothing more than scuttling.
This fits to widespread opinions from the 20's to 40's which saw the lower limit for effective ship-to-ship combat guns at 150...155 mm, possibly 139 mm (the French view). 139 mm may thus be the lower limit of satisfactory ship-killing power with modern shell technology (better steel for thinner shell walls, more volume for better explosives). Attempts to install new guns heavier than 130 mm calibre in post-1960's warships were not really successful. Neither the navies nor the developers were able to resist automatic loading, which makes the whole thing much more expensive and heavy than necessary. One could employ a manually loaded 140 mm naval gun from the 1910's and mate it with a 100 or 127 mm turret's automated elevation and traverse control and would end up having the best if not only truly ship-killing (and naval gunfire fire support) naval gun system in service world-wide. Nobody seems to see a need for this, though. The last Western cruiser class with really good ship-killing gunfire capability was the Tiger class. The Zumwalt class "destroyers" have 155 mm guns, but those have munitions issues and are meant for land attack.
The typical guns on warships are thus of 76, 100, 127 and 130 mm calibre or smaller. A well-proportioned gun looks really good on a forecastle, but two 76 mm guns (mostly for AAW) or a single aft and low-mounted 127 mm gun seem to be the rather sensible choices. The latter would have little air defence capability (especially the American 127mm turrets that are lighter but halve a much lower rate of fire than Italian 127 mm turret designs), so a separate CIWS for the AAW role would be advisable.
76 mm L/62 Super Rapid turret (120 rpm) without munitions (and without optional STRALES): 7.9 t weight
127 mm L/54 Mk 45 Mod 2 turret (16-20 rpm) without munitions: 22.2 t weight
127 mm L/64 turret (33 rpm) without munitions: 33 t weight
ASuW with torpedoes
Torpedoes used to be important in surface actions, but their short range and slowness eliminated them from being serious ASuW munitions for surface warships and boats. Their success depends too much on the element of surprise. Torpedoes could still be of use in scuttling crippled ships, but even lightweight torpedoes could do this. Only the latter can be carried in satisfactory quantities for ASW, so adding heavyweight torpedoes for ASuW and ASW in addition to ASuW missiles and ASW lightweight torpedoes is an unnecessary expense and adds unnecessary weight and manpower/training needs. The torpedo designs are available (the submarines' torpedo designs could be used), but it simply makes no sense to use them on surface warships.
Other remarks
ASuW missiles could be programmed to include an anti-helicopter mode, and be a little cheaper than long range area air defence missiles such as SM-6 in this role.
Helicopters have a theoretical ability to drop bombs and unguided PGMs, but I suppose that might at most be a niche with tiny PGMs or smoke munitions in support of boarding (fast rapelling/fast roping) actions. Doorgunners with machineguns are more relevant for this.
AShMs with two-way datalink could cooperate (fashionably: "as a swarm") and use their different perspectives to triangulate targets with IIR or passive radar, to report identified decoys as well as to synchronise their attacks to locally saturate defences.
Imaging infrared sensors (mounted on missiles) may be able to detect the muzzle flash of guns and the hot gases of air defence missiles. This could inform them about necessary evasive actions.
Imaging infrared sensors may also have the ability to tell already burning or sinking targets (pattern recognition showing the ship is already broken apart et cetera) from unscathed targets, informing the missile's decisionmaking in regard to target selection.
Supersonic missiles will likely not use IIR sensors because the friction at supersonic speed in the dense very low atmosphere would heat up the sensor's window. Good IIR sensor windows would also be aerodynamically inefficient.
Both the UV and the visible spectrum are dependent on daylight and even more weather-dependent than IR, and thus practically irrelevant for AShMs.
Conclusions
Again - as with AAW - an eye in the sky is most important and necessary for beyond/below the horizon fires (unless some other surface unit is more close to the target). Naval helicopters can detect, identify and even engage surface targets up to sea state 5 or 6. Long-range AAW missiles such as SM-6 might be useful in blinding the opposing force by taking out or suppressing their eye in the sky.
Area air defence missiles are relevant in ASuW even in an offensive role, especially to disable the air defence capability of the target. They may also be crucial keeping fixed and rotary wing aircraft from providing a positive target identification and targeting data for missile attacks.
Shipborne cruise missiles used to be installed in dedicated launchers on deck or on superstructures, but AShMs really should be loaded into vertical launch silos. This offers the advantage that opposing forces don't know the quantity of AShM that a warship has and that loadout can (in theory) be changed as estimates regarding ASuW threats and needs change. It also helps with radar echo reductions and generally frees areas and volume up for other purposes. Missiles in a silo are furthermore less of a secondary explosion hazard than relatively exposed missiles protected but by a tube. An effective hit on an otherwise loaded VLS would be catastrophic even without the presence of AShMs anyway.
The long range of modern AShMs suffices and seems to make the armament of helicopters with AShMs unnecessary at least when a HF datalink to the AShM can be maintained by either the helicopter or the warship itself.
A combination of multiple anti-ship missiles seems unnecessary for a warship albeit it would be a nice to have for air power. A stealthy subsonic sea skimmer with great target identification abilities and the ability to aim at particularly important parts of a ship would be well-justified in moderate quantities. The total reliance on a IR-dependent missile may be inappropriate given the weather dependence of its sensor. A missile with both radar and IIR might be more reliable and adaptable. A mix of two different AShM missile concepts (stealthy IIR seeker sea skimmer and supersonic active+passive radar seeker sea skimmer) might make sense due to its desirable redundancy.
The range of AShMs does not need to be greater than 200 km and at least a datalink for the upload of new waypoints and target locations to the missile would be promising, while a two-way datalink to a helicopter and other AShMs would be even better.
The weight advantage clearly favours two 76 mm guns or even but one 76 mm gun as a warship's gun armament, and this should continue to be the standard for Western frigate designs and possibly warships in general (in my opinion). These guns do little ship-killing in ASuW, but they can cause a mission kill on a nearby warship or boat just as much as heavier calibre guns can do and they are lightweight and relevant as CIWS.
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