2016/01/29

Naval air defence of the 2020's

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Currently navies use ship-to-air (surface-to-air) missiles of greatly varying sizes, ranging from shoulder-launched man portable ones originally developed for ground forces to missiles weighing more than a ton. Extreme ranges of a hundred nautical miles or more had been achieved in the 1950's already, but only so against targets in line of sight (flying high).
NATO used Sea Sparrow, SM-1, SM-2MR and SM-2ER missiles and a few competing equivalents by the end of the Cold War, but nowadays the big commercial successes appear to be RAM, Evolved Sea Sparrow and Aster. All area air defence missiles are nowadays expected to be available in a vertical launch version that does away with unreliable mechanical launchers and allows for a quicker sequence of firing.
The trend goes towards much better guidance or specialised missiles against guided ballistic missiles, and as a consequence individual missiles can have appalling costs.

ESSM Block 1 launch
There is one outstanding program that may become a true standard: RIM-162 Evolved Sea Sparrow (ESSM) Block 2. The original ESSM already excelled with its compactness, allowing four missiles to be packed into a single versatile vertical launch silo cell, unlike the French competition (Aster) that uses a too wide booster stage and is usually coupled with a vertical launch silo type used for the two Aster versions only.

missiles in vertical launch silos

Block 2 adds additional range (seemingly up from about 40-50 to about 80 km, but such published figures are unreliable and tell little anyway), more manoeuvrability and more importantly, a vastly improved seeker (active radar mode, semi-active radar mode and as I understand it also a home-on-jam mode, but the hardware would also be capable of an automatic command control mode).

The active radar will no doubt cost a lot (the missile may easily cost € 2 million in today's money), but it adds the ability to engage targets that are not in line of sight, but were reported through datalink by other platforms (ships, AEW aircraft). It also allows smaller ships to use this missile, for no dedicated target illumination radar or powerful-enough multi-function radar has to be carried for the target illumination as with ESSM Block 1's semi-active radar terminal homing.
The increased range finally may bring ESSM Block 2 into the range class of an Aster 30, which is recognised as an area air defence missile. In the 2020's an area air defence missile may be quad-packed into standard vertical launch silos. This may change a lot.

For example, ships specialised on the anti-submarine warfare (ASW) mission could still be part in the task force's area air defence plan with a substantial footprint (against very low-flying targets comparable to what 1990's dedicated air defence destroyers achieved). Their most substantial shortcoming compared to dedicated anti-air warfare destroyers would be a weaker radar suite, but this might matter little in a networked task force with AEW support.

ESSM Block 2 could thus do no less than end the era of separation between ASW and AAW frigates and destroyers in Europe without requiring the expense of very large (8,000+ t) combined ASW+AAW destroyers (as preferred by the USN since the 80's at the latest). A frigate of 5,000 t with all the typical anti-submarine warfare specialisations might still double as a powerful area air defence asset. The two paths would be joined through the characteristics of a (by comparison to a ship) tiny missile.
GP (general purpose) frigates may become dominant European designs in the 2020's instead of jack-of-all-trades-master-of-none export warships as they have been so far.

A missile which requires no target illumination radar could also be fired from inside a container carried by a mere cargo ship, of course. This may particularly be used as a second missile defence layer. GP frigates surrounding a convoy could form the first layer, and the escorted cargo ships would be platforms for the second layer. The old layered defences with some extended range missiles such as SM-2ER as an outer layer in addition to medium range missiles never offered much depth against seaskimmer missiles. The "extended range" applied to high-flying targets only because their terminal semi-active radar homing required a line of sight between ship and target.

Important for the area air defence capability will be the actual engagement envelope. This is a very tricky story, even if we ignore the very tricky radar physics and poor reliability of published range figures. I take two graphs from here to illustrate this:

(note the waist: The smallest width of the dark brown area is the part of an air defence perimeter's circumference that the air defence system may cover well. This important metric is very different from the "range" figure and never published. It also depends a lot on the target, particularly its altitude, speed, changes of course and evasive manoeuvres capability.)

(this gap exists mostly for short range SAMs)

A missile with a published range of "80 km" may effectively protect other ships against missiles passing at a distance of 20 km at low altitude, but maybe the correct figure is "30 km", or "40 km". It won't be "80 km", though. At least the active radar seeker offers the possibility of engaging very low targets beyond the horizon (if the rocket engine offers enough energy for it).

The dual-mode seeker will likely retain the capability of Sea Sparrow and Block 1 ESSM to engage ships and boats. The damage done to a warship by the small warhead can be substantial and vastly degrade its ability to defend itself, as evidenced by two accidental hits of a cruiser by two Shrike missiles (which were closely related to Sea Sparrow) in 1968 and an accident with Sea Sparrow hitting a Turkish warship in 1992. ESSM has demonstrated its ability to hit small fast-moving boats and is no doubt difficult to defend against when employed to disable a warship in a surface engagement. Meanwhile, the Block 2 missile could with its passive radar homing capability be used to suppress a hostile ship's radars* for a crucial few seconds in a synchronised attack with anti-ship cruise missiles (substituting for an anti-radar missile) - if and only if the ship radar's frequency range is covered by the ESSM Blk 2 seeker.

This goes way beyond what utility the Aster appears to promise (assuming the Block 2 missile will be completed and be effective at all, of course).

One of ESSM's known strengths is its spectacularly small minimum engagement range. This is apparently a few hundred metres (possibly only in easy scenarios), while Aster 30 with its booster had such issues with short range that the Aster 15 version with shorter range and shorter minimum range had to be developed.

A very short minimum range may make dedicated short range missiles unnecessary, which affects the RIM-116 Rolling Airframe Missile. This missile has racked up an impressive reliability and hit record in test firings, but it has a possibly fatal flaw: It (almost certainly) cannot reliably defend against an infrared guided anti-ship missiles such as NSM. Its passive radar seeker capability is useless against it, and its own infrared seeker almost certainly cannot sense a missile incoming from the direction of a dawning sun.


The ESSM Block 2 may thus become an all-in-one answer to naval needs for defence against aircraft and air-breathing missiles for the 2020's.


Meanwhile, dedicated, very large and very expensive missiles such as SM-3 may be used to provide a defence against guided ballistic missiles and an engagement capability against low orbit satellites. Even a  10,000 ton warship struggles with the mass, volume, topweight and electrical power hunger of a long-range ballistic missile defence radar, though. Dedicated BMD warships resembling more a LPD-type ship than the more slim frigates or destroyers.
A convoy escort group could have one such BMD ship that also serves as replenishment ship and helicopter carrier (AEW helicopter) as its core among the escorted ships, and general purpose frigates surrounding the convoy with gapless overlapping low frequency active sonar search and area air defence zones. That's but a possibility, of course.


There will likely still be an interest in some short-range weapon, and I suspect the classic 76 mm naval guns with their extreme rate of fire (for a short time) would still fit this bill without the expense of developing and deploying some gold-plated short-range missile or a range of specialised short range missiles. Nowadays these guns can even employ guided projectiles.



SM-3 / ESSM Blk 2 / STRALES - a possible AAW trio for a well-funded navy of the 2020's. It could greatly change some warship categories as they were known since the 70's (and thus the face of European navies).

I didn't cover fighters / interceptors yet, though they will also be relevant to naval air defence. A task force of frigates protecting a convoy may have a flight of potentially helpful fighters nearby, but even four fighters would carry anything ranging from two dozen to three dozen relevant missiles, while a frigate flotilla may have two hundred or more relevant missiles. The fighters' utility could be larger than these figures suggest because they could by virtue of their speed engage the missile launch platforms (combat aircraft) instead of the munitions (anti-ship missiles), of course.

related:
2009-04 SAMs with active radar homing
2013-01 Naval and air warfare; the problem with technology assessment (see the final part of this!)

S O

P.S.: In case you wondered: No, I still don't think surface warships are relevant for alliance defence in the Baltic Sea and I don't think they're very important in the Mediterranean Sea either. Russian air power could wipe the Eastern Baltic Sea surface clean no matter what air defences the ships have. 

*: If and only if it uses the right frequency band!
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10 comments:

  1. In http://csbaonline.org/publications/2014/11/commanding-the-seas-a-plan-to-reinvigorate-u-s-navy-surface-warfare/ there is an "economic explanation" to include laser cannons/Electromagnetic railguns (EMRG) in surface military ships to improve their anti-air defenses: their ammunition will be "very cheap" (but with high hit probability thanks to its speed) and their ammo magazines will require fewer space than missiles or classic artillery... but those new defenses will require a lot of electrical power.
    NOTE: That document, all of it, is a good reading (at least for me).

    Perhaps those technologies will not be mastered in the 2020's, but new surface ship designs probably should think about how to install them in the future.

    One more thing: I think that specialized frigates/destroyers can not be merged in just one design of 5.000 tons. I think that always we will see AWD (Air Warfare Destroyers) with big tonnage (probably at least 6.000 tons, like Spanish F-100) to get a very powerful radar in order to operate in the worst jamming environments... and those AWD are dirty expensive, so countries will need "specialized" ASW ships (cheaper frigates) and "Patrol ships" (corvettes or even less armed ships) to get enough number of ships to do all their navy's missions.

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    1. They always make up some supposed cost-saving effect for the new toys they want. I remember almost no examples of such projected cost savings having become real during the last 30 years in any NATO country.

      You appear to largely ignore (or underestimate) the importance of AEW and I already dealt with the OPV issue before.

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    2. You are right that most cost-saving claims are only made to get money to develope something new that finally is not as cheap as promised. Probably laser cannon could became one of those (I don't know if it will work in a foggy day).

      But research is fine, and perhaps electromagnetic rail gun could be a good investment (because it's basically a gun with very high muzzle speed).
      By the way: One cost-saving effect in NATO navies -> automation, so less crew.

      AEW radars can be good, but ship radars can be far better (more and better size antenna, power, stuff to process signals,...). For me that's the logical of AWD (and the logical of "ASW frigates" and OPVs).
      By the way: I know about your economic case against OPV, but for me it's like thinking that in "COIN scenarios" you must employ jet fighters instead of cheaper aircraft. Well, it's a possibility, but I think that France choosed well her aircrafts in some relevant post WWII conflicts (but to fight probably was not the best option, and bomb civillians was the worst). A reference about those aircrafts: http://worldatwar.net/chandelle/v3/v3n1/frcoin.html

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    3. An AEW aircraft can patrol in the direction of greatest threat, which may easily add 100-300 km to its range relative to ship radars. Its radar power actually can be applied fully, and isn't limited by a close horizon (horizon for aircraft is hundreds of km distant). Even an AEGIS warship has less than 30 km range against even 1970's seaskimmer missiles, whereas an AEW aircraft (helicopter) may have 100 + km range against them (though not as much against stealthy ones, of course).

      The dedicated powerful ship radars are really superfluous if AEW support is available. Some smaller AESA multi-function radars would easily suffice for AAW then, and a few dedicated BMD radars on specialised ships would be necessary for BMD defence against precision guided (quasi)ballistic missiles of 1,500+ km range anyway.

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    4. I know that ship's radar is limited by the horizon. AEW is always a good thing to have, but it can't substitute an AWD, both are complementary. Would you safely operate OPV's/amphibious ships/tenders/... in the most dangerous scenario just because you have AEW? I don't think so (and in USA, France,... seem to have the same thougt).
      By the way: modern anti ship missiles can follow choosed routes before they try to engage an enemy, so sending your AEW 300 km away could be a risky option if the enemy has long, long range missiles... or sub-launched missiles.

      An AWD forces enemies to fly low and protects your own aircraft, so your pilots take "low risks" if they fly high... which gives range advantage to their ammunitions. An AWD gives a better "umbrella of protection" against air threads to all other ships of your fleet in the zone. For instance a "cheaper frigate" can do sub-hubting or an helicopter operated from an OPV can launch an attack with "more security"... My conclusion: An AWD, like some SAMs (modern S-300 or S-400), gives sophisticated anti-access/area denial (A2/AD) capabilities.

      About BMD radars... I suppose that they can do a good service trying to detect enemy mini-satellites in low orbit, or those quasi ballistic missiles. But if they are really needed I suppose that we will be fighting China or other country with atomic weapons, so the nuclear missiles will follow soon. Game over!

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    5. I have to correct myself. You're not only ignoring AEW, but also the fact that GP or ASW frigates very well have a radar that can spot sea skimmers about as well as a SPY-1 can do.

      Maybe that's why you don't understand why I assert that the dedicated AAW ships' advantage is diminished greatly nowadays. Their powerful radars used to be fine against large, high-flying supersonic Soviet anti-ship missiles. That's not all that important any more. Even Yakhont can employ a sea skimmer mode.

      And there's no A2/AD offered by SPY-1 like radars if the opposing force has enough of a brain to fly very low. Meanwhile, AEW can still detect them at low altitude and useful ranges.

      Any scenario in which you cannot maintain AEW support is likely a scenario in which even the most gold-plated AAW escorts won't be much of much use any more.

      Last but not least; AEW support can and has been provided by helicopters. You need no aircraft carrier for this.

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  2. "... without requiring the expense of very large (8,000+ t) combined ASW+AAW destroyers..."

    In short, building a large warship generally makes good sense unless there is a very specific reason to limit hull size.

    Hull size has little effect on the procurement cost of a warship, and almost no effect on the total cost of warship ownership. In fact the major cost of ownership is the crew, and automation has enabled quite modest sized crews to operate truly massive ships.

    On the other hand, a larger warship almost always has better sea keeping characteristics which directly impacts own sensor effectiveness. Bigger ships also have better reserve buoyancy margins, size facilitates machinery quieting and thermal emission limitations. Large warships have a proven history of operating close to shore – so the draft argument against large hulls has little merit.

    Modern radars are now so effective that there is very little benefit to being smaller. Stealth technology arguably shows no promise for use on hulls larger than a few hundred tons.

    GAB

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    1. The lack of self-discipline makes it very difficult for navies to not make use of a large hull by adding many expensive pieces of equipment into it, though. So in the end a larger ship is much more expensive. "Steel is cheap" isn't particularly true in naval shipbuilding anyway.
      http://navy-matters.blogspot.de/2013/07/steel-is-cheap-and-air-is-free.html

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  3. Do you foresee an European missile developing the same capabilities? Couldn't a CAMM-ER or Iris-T SL SAM achieve similar perfomance? At least the CAMM / Sea Ceptor seems to be even more compact than the ESSM with the 4x3 ExLS and soft lanuch. For sure with less range but maybe more suited to smaller navies with less money to invest in VLS.

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    1. CAMM-ER is similar, though some features of ESSM Blk 2 were not published for CAMM-ER as far as I know; SARH mode, anti-surface capability, quad pack in Mk 41 (only claimed for normal CAMM), and the range claim is ">45 km" rather than 70 or 80 km.
      CAMM/CAMM-ER may end up being limited to ground and Sylver VLS applications (though ESSM Blk 2 may be adapted for those as well).

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