This post includes pictures gleaned from various places on the internet. I will gladly remove any of them in response to copyright complaints.
International readers (he said, as if there were any) will notice that the scope here is limited to American weapons and systems. This is not to cast aspersions at Sea Dart, Sea Wolf, Sea Ceptor, Aster, SA-N-6 and so on. I simply lack the requisite in-depth knowledge to write about them.
Some of this piece is recycled from my earlier post on the future of the US Navy.
U.S. Naval Weapons and Systems Development: Surface-to-Air Missiles and the Aegis System
We tend to think of Russia when the topic of surface-to-air missiles comes up, but the U.S. Navy has been at the forefront of SAM technology since the 1940s, and remains there to this day. American warships were deploying fairly advanced SAM systems as early as the 1950s, the product of a research and development effort that was first perceived necessary even before the Second World War had ended. The initial impetus was provided by the German development of air-launched, guided anti-ship missiles, which had been used to attack U.S. warships from beyond the range of anti-aircraft guns. It was the Kamikazes, though, that fully convinced everyone that a better way needed to be found to counter air attacks.
“Kamikaze” was a word with great historic resonance to the Japanese, dating to the era when the Mongol Empire, under the great Kubla Khan, threatened to conquer Japan. Two attempts were made in the thirteenth century to conduct an over-ocean invasion of the Japanese islands, and according to Japanese legend, both times the invasion fleets were thwarted by severe storms, which the Japanese referred to as the “divine wind” – in their language, “Kamikaze”. Thus the suicide attacks on the US Navy at the end of WW II were given the same name; in sacrificing themselves, the pilots would become a divine wind that swept the American fleet aside as surely as was Kubla Khan’s, centuries before.
They first appeared in the naval battles during the campaign to re-take the Philippines, and swarmed in great numbers at the battle of Okinawa, attacking the invasion fleet stationed off shore. Probably nothing in the annals of warfare has been more unnerving than manning the gun batteries of those ships as human beings dove their planes at upwards of 400 MPH towards the deck, often almost impossible to stop – it didn’t necessarily do any good just to shoot them down, as being shot down didn’t really alter the mission plan. You had to shoot them down before their crashing trajectory would take them on a ballistic path to the target ship anyway. Despite the fighter sweeps, anti-aircraft guns of up to 5 inches in calibre, dense blankets of smaller calibre fire, despite all of it, between 10-15% of the Kamikazes, enough to wreak havoc, made it through.
From the modern perspective, the Kamikaze attacks were the first mass use of guided cruise missiles in naval warfare, which weapons employed the most sophisticated guidance package ever developed for combat use, far outstripping the technology of anything deployed today. The suicide attacks were so alien to the Western psyche that some U.S. gunners were driven literally insane – I’ll always remember a story recounted by a veteran in the BBC series The World at War, which I first saw when I was about 12. In the midst of a particularly intense wave of Kamikaze strikes, a gunner looked over at his friend, said “It’s a hot day today!”, and jumped right off the deck of his aircraft carrier.
It was the horror of this experience that accelerated the development of ship-mounted, guided surface-to-air missiles. Something had to be done to strike at such threats at longer ranges, in the zone between the fighter screen and the relatively small defensive hemisphere within reach of anti-aircraft guns. The aim was to shoot threats down at ranges measured in tens of miles, not thousands of yards. The program to create the new defensive systems was code-named “Project Bumblebee”.
Bumblebee was an amazing project, years ahead of its time. On the premise that the range required would preclude the exclusive use of rocket motors, the effort first concentrated on a ramjet powered design – this at a time when conventional jet engines were still in their infancy. Ramjets do away with the bulky compressors of ordinary turbojets, and rely on the sheer speed of the vehicle, accelerated at first by rocket booster, to cram air in the front at such volumes and velocities that the compression, in essence, takes care of itself. Essentially similar technology, in the form of “scramjets”, is the basis of current attempts to develop hypersonic cruise missiles. The result was the RIM-8 Talos, an 8.000 lb. (with booster) monster with a warhead of almost 500 lbs., a speed approaching Mach 3 – reportedly Mach 4 in later versions – and a range that eventually extended to as much as 140 miles. It first entered service in 1958.
Talos missiles on the aft launcher of USS Long Beach
As part of Bumblebee, shorter range weapons were also developed to complement Talos. One of these evolved into the RIM-2 “Terrier”, which became operational about two years before Talos. The Terrier was a medium range missile, still fairly large, and was further developed into a short-range missile system for small ships, dubbed the RIM-24 Tartar, which began use in the mid 1960s. The three missiles that came out of Bumblebee, all given names starting with “t”, were thus known as the “3 T” series. They were revolutionary, extending the defensive envelope of warships to unheard-of distances, but as with all “first of kind” weapons, there were inevitable teething troubles, some of them inherent in the available technology of the 1950s and 60s. These were gradually overcome.
Of the Three T generation, Talos was the real star, with its long range, hitting power, and accuracy. It was one of the first NATO SAM systems to be used in combat, downing MiGs over North Viet Nam. However, Talos was a very bulky and expensive missile, and its associated radars were likewise big and expensive. No ship smaller than about 14,000 tons ever carried it (no cruiser in today’s fleet exceeds 10,000 tons), and as it worked out, this limited its deployment to only seven ships. Talos could not be put into widespread service.
USS Little Rock fires a Talos
Terrier and Tartar, meanwhile, were deployed on all sorts of cruisers and destroyers, but were also apparently somewhat disappointing in service, and not optimally reliable. Their electronics were a little touchy, and the rigours of ship stowage and handling were likely to do them damage.
Terrier missiles on a Mk.10 launcher
A Tarter missile on its Mk.13 launcher
This is not to say that the Three T missiles and their associated systems were anything less than amazing technological achievements. The real problem was that the anticipated adversary was up to some rather amazing technological advances of its own, and as powerful and sophisticated as weapon systems like Talos and Terrier were, they had limitations that needed to be addressed. Extraordinary efforts, and an unfathomable quantity of innovation and outright brilliance, were dedicated to that end, aiming to eliminate the issues that made the Three T generation less effective than soon seemed necessary.
The Initial Systems Were Too Easy to Overwhelm
Susceptibility to “saturation attack” was a major concern. While of course nobody expected hordes of actual Kamikazes, the new threat was not dissimilar, being air, surface and submarine launched cruise missiles, basically pilotless aircraft. The Soviets were fielding these missiles in increasing quantities. Almost all of their naval warfare platforms were designed for them. It was reckoned that a typical attack might involve dozens of such weapons inbound, and while the first versions were subsonic, it was not long before supersonic missiles appeared, capable of Mach 2 or more, and carrying warheads of terrifying size, something like a ton of high explosive in some cases. Thus a “saturation attack” would be upon the carrier very quickly, presenting the escorts with more targets than they could deal with, while if even one missile made it through, the impact would be very destructive.
The state of the existing technology created the saturation problem. Early on, the U.S SAMs were “beam riders”, meaning that they flew along a beam of radar energy trained by a ship-mounted director at the target. Before long, this guidance technology was replaced with “semi-active homing”, which meant that the missiles had their own radar receiving antennae – “semi-active”, because the missiles themselves could not emit radar signals, only receive them. The ship did the emitting with its own radar directors, shaped rather like satellite dishes, that were cued by the main search radar and pointed at the targets, thereby “painting” or “illuminating” them. The missiles would home on the reflection. So, once loaded up on the rails, the missiles would be pointed in the right direction, and after an unguided boost phase, begin homing on the radar energy reflecting off the target. This improved accuracy over the beam-riding method, since, as distance increased, a radar beam tended to become wider and more diffuse, “fan-shaped”, allowing an increasing margin of error to creep in. The signals chased by semi-active homers behave as if they are emanating from the target, and thus became narrower and more accurate as the missile approached its quarry.
Well and good, but such a system still has limitations:
- There were hard limits on engagement range (though, for the time, both Talos and Terrier performed quite well on this score). If a missile has to be able to start homing on a target quite soon after it’s fired, this means that the radar signal must travel all the way to the target and then all the way back to the missile, where the missile must receive it before it can guide. This is known as “home all the way” guidance. This creates no major slowdown, since radar waves travel at the speed of light, but it does mean that the radar signal coming back must be strong enough to be seen by the missile’s comparatively tiny receiver before the missile can track properly. The main radar on the ship, with its much bigger antenna, therefore sees the target much sooner – and the smaller illuminator radars can start “painting” the target much sooner – than the missile, with its little receiving dish, can see it – thus at longer ranges the radar return, still strong enough to be seen by the big antennae on the ship, is too small to be seen by the little antenna in the missile. The missile, whatever its rocket strength and aerodynamic capabilities, is therefore limited in range. It may be aerodynamically capable of flying 100 miles, but if its little antenna can’t see the target until it is 20 miles away, all that potential range is wasted. This issue can be mitigated through the use of large and powerful illuminator radars – the ones that guided Talos were huge – but achieving Talos-like ranges with smaller missiles and radars, the sort that could plausibly be deployed on regular cruisers and destroyers, was highly desirable.
AN/SPG-49 missile illuminators on the USS Oklahoma City, part of the Talos system
USS Dale, a “double-ended” cruiser of the Leahy class, with Terrier missiles (actually, inert practice rounds, as indicated by their blue paint) loaded up on its Mk. 10 launchers. Note the twin AN/SPG-55 illuminators atop the bridge.
- There were limits on the number of missiles that could be kept in the air. If each missile has to home all the way to the target, then the illuminator radar (the ones like satellite dishes) must dwell on a target and bounce radar off of it from the second the missile goes into homing mode until that target is hit. Thus the number of targets you can engage at once is limited by the number of radar “illuminators” that the ship could carry, and no ship carried more than eight; the damn things were expensive! The vast majority of cruisers had four illuminators, and a destroyer typically had only two, meaning, for example, that a destroyer was limited to engaging two targets at a time.
- There were limits on rate of fire imposed by the launching systems. A pure semi-active homing missile apparently worked best when it was pointed in the direction of the target before firing, perhaps because otherwise, it might fail to acquire the target and simply blast into the stratosphere. Whatever the reason, the first naval SAM systems were designed on the assumption that some sort of rotating rail launcher was needed, and the missiles, which must of course be stowed below deck, had to be loaded onto the launchers, after which the launchers needed to traverse in azimuth. Meanwhile, with the early missile variants, sailors below decks were part of the system, attaching fins to the boosters to prepare them for launch. This slowed rate of fire, at least in theory. Early on, the bottleneck produced by the shortage of illuminators meant that even the slowest rail-arm launcher mechanism could load up rounds faster than the guidance system could use them. For the future, though, any increase in the number of missiles that could be guided would have to be pursued in concert with a faster method of loading and launching the missiles.
- It all happens too fast for the original radar and guidance systems to react. The main search radars tied into the early SAM systems were themselves a problem. Like most radars, the units on U.S. cruisers and destroyers of the sixties rotated. Typically, it takes a few sweeps of the radar before an accurate target plot can be created giving speed, direction and altitude, all of which you need to know before the main search radar can cue the illuminators to point at, and dwell upon, the target. This is no big deal if it’s 1945, and the incoming hostile is approaching at 250 MPH. In 1965, the incoming might be approaching at 1,800 MPH. At that speed, it would chew up too many miles in its flight in the time between radar sweeps. This is another factor tending to limit the range at which targets could be engaged, and in any case, the incomplete picture provided by a rotating antenna seemed inadequate in an era in which supersonic missiles might be coming at you simultaneously from all points of the compass.
Setting the Stage for Aegis
Now, you’re thinking to yourself, the best defence is a good offence, right? So the way to prevent our ships from being overwhelmed by incoming missiles is to destroy the enemy platforms before the missiles are launched – no? Of course that’s right, and every effort was made in that direction. In particular, the F-4 Phantom, which was then doing a damn fine job at dropping bombs and chasing MiGs over Hanoi, simply had to be replaced in its primary role as defender of the carrier. It had plenty of speed, climb rate and range, but its radar wasn’t big enough, and it could only fire one missile at a time at closing targets no more than about 15-20 miles away at the moment of launch.
The answer was the F-14 Tomcat, which could fire 6 missiles at a time at closing targets 110 miles distant. That did much to redress the air-launched missile problem. In a pinch, the mighty Phoenix missiles carried by the Tomcats, which had a velocity of Mach 5 and boasted a 135 lb. warhead, even had a fair shot at destroying the incoming missiles themselves, a partial solution to the surface and submarine-launched missile problem. (If you want to see an aviation enthusiast blubber inconsolably, bring up the premature retirement of the F-14).
An F-14 fires an AIM-54 Phoenix missile
Yet, with so many Russian platforms capable of launching so many missiles at the battle group, you had to figure that some – maybe a lot – would leak through even the Tomcat’s potent shield. The only thing was to improve the capabilities of the ships and the air defence weapons they carried.
By the late 1960s, one part of the answer was being tested, the Phalanx “Close-In Weapon System”. This was an autonomous, self-contained, radar-equipped, computer-aimed 20mm Vulcan rotary cannon. It was literally “plug and play”, all you needed on an existing ship was somewhere to put it, and you could have a weapon that had a fair chance of destroying an incoming missile. However, it was very much a “last ditch” weapon, and if it hit the incoming missile at all, it was likely to be scorchingly close, maybe only a mile away, maybe even less. A big missile going 1800 MPH will, even if Phalanx detonates its warhead, spray the target with supersonic shrapnel that will do serious damage. More was needed.
So, a second part of the answer was improvements in the missiles. New motors made them far, far less likely to “poop off the rails” owing to rocket failure. New solid state electronics made them far more robust, and meant that the missiles didn’t need lengthy warm-up time. Better batteries made them less needy of servicing.
All these improvements were incorporated into a new version of the Tartar missile, which quickly became the basis of a whole new family of SAMs, given a rather unimaginative name, “Standard Missile”, which rather understated what superlative weapons they were. The first version, the SM-1, was very reliable, and Standard missiles came to be referred to as “wooden rounds”, meaning they needed no more upkeep, and were no more delicate, than if they were pine four-by-fours, rather than sophisticated missiles. You stowed them and forgot about them until you needed to fire them, at which point they would almost certainly fire properly.
What really set the stage for Aegis, though, was the second generation of Standard missile, the SM-2. SM-2 featured a programmable auto-pilot and the capacity to receive mid-course guidance updates from the launching ship. Thus, while the SM-2, like its predecessors, was still a semi-active homing missile, it didn’t need to home all the way to the target; it would guide itself most of the way there, with the aid of updates from the launching ship, and only started homing on the radar reflected off the target when it was quite near to it.
This was a huge improvement. Because it didn’t have to be guided all the way in, the SM-2 could be fired while the illuminator radar was dwelling on a different target for a different missile. An illuminator was thus no longer dedicated to a missile throughout its flight, but could concentrate only on those missiles that were closest to their targets, and after those hit or missed, switch to guiding the next ones, one after another, as they arrived. An existing ship could thus share its illuminators between rounds, and have many more missiles in the air at once. Even for ships that had the traditional rotating radars and older computer systems this implied a huge increase in firepower, and initially, the Navy’s existing fleet went through a “New Threat Upgrade” that took advantage of SM-2s guidance capabilities.
Additionally, because the SM-2 navigated most of the way to the target based on updates provided by the ship, rather than by homing all the way, it didn’t need to fly an essentially flat trajectory all the way to impact. It could travel along a far more efficient ballistic arc, climbing high before the rocket motor burned out, then trading altitude for speed after that – this more or less doubled the aerodynamic range of each missile.
Moreover, this range increase could be exploited, because the SM-2, not needing to see the target for itself from quite soon after it was launched, was able to exploit much weaker radar returns. The target might be too distant for the SM-2 seeker head to see it just after launch, but no matter; since the missile would get target coordinates from the big ship’s radar and then navigate itself most of the way there, the signal only had to be strong enough for the missile seeker to see when it was very near the target. As a result, the effective range of the missile was limited only by how far it could fly.
Finally, because the missile was able to navigate without “seeing” the target for itself until it was very close, it no longer needed to be pointed at the target like a gun barrel when it was fired. This meant that you really didn’t need the rotating rail launchers anymore. Folding fins obviated the need for sailors to prepare the missiles for loading. Therefore the SM-2s could be stowed vertically under hatches in the deck, like coke bottles; you could fire off as many as you could guide, as fast as you liked. No more cumbersome missile loading! This vastly increased potential rate of fire. If a way could be found to guide them, a vertical launch system could easily put 20 missiles into the air in 20 seconds.
An SM-2 loaded on to a Mk.13 launcher. Externally, the SM-2 was virtually identical to Tartar.
The groundwork was thus prepared for a system that could deal with saturation attacks. What was needed was a radar that did away with the slow reaction time inherent in rotating antennae. Also required were computers powerful enough to track very large numbers of targets at once, so that the illuminators could be switched rapidly from one to another as missiles became available in the target areas, without losing track of any of the incoming.
A first stab at this was attempted in the 1960s with a system called “Typhon”. Rather than a rotating search radar, the Typhon system featured a large, conical and rather bizarre looking radiating element that sat on top of the superstructure. It contained transmitters and receivers that pointed in all directions at once – no more sweeping radar signal, but an uninterrupted 360-degree view at all times. This was a fabulous advance, but with the technology available, Typhon needed enormous power supplies, and was terribly heavy. It advanced to prototype stage, and was tested on a large navy missile test ship (the USS Norton Sound, for all you trivia buffs), but it was so big and heavy that only quite large ships could carry it and ship enough armament to be useful at the same time. Its associated missile was a much-modified version of Talos, and the missiles were thus huge, heavy and costly. A ship with the firepower of a frigate would need to be bigger than a cruiser. It was too bulky, too expensive, and couldn’t survive.
USS Norton Sound with the Typhon SPG-59 guidance radar
The RIM-50 Typhon missile
Research continued, and by the 1970s the USS Norton Sound was testing out a new approach. Rather than one large central array, the method adopted was to fix four smaller flat arrays to the corners of the superstructure. Each stop sign-like octagonal array was a cluster of fixed radiating elements scanning a quarter of the sky, known as “phased arrays” or “Passive Electronically Scanned Arrays”. The new phased arrays were much smaller, lighter, and less hungry for power than the Typhon system, but provided the same 360-degree view. Though expensive, it was now practical to mount them on destroyer-sized ships (albeit large destroyer hulls in the 9,000 ton class) that could also carry substantial armament, and the new Standard missile, far less bulky than Talos, but with equal range, was just the ticket.
USS Norton Sound again, this time with an Aegis SPY-1 phased array
Concurrent strides were made in computer capacity, and the uniting of the new computers, radars, and Standard missiles became the Aegis system. Aegis was spectacularly effective, as much a quantum leap in its field as jets were over props and nuclear subs were over diesels. Ships outfitted with Aegis could track, at very long ranges (hundreds of miles, nobody in the public knows for sure), literally hundreds of targets. In one early test, an Aegis vessel was able to track all of the civilian air traffic off the US Eastern seaboard, I think it was something like all aircraft from NY down to Philadelphia. Fixed, non-rotating radar meant no more accumulation of information from time-consuming radar sweeps in order to build up a good target track. Each target within range was continuously lit up by the radar. This alone cut reaction time drastically.
All of a sudden, a battle group with even one Aegis vessel had access to more data, and had a better overall picture of the theatre of combat, than had ever been available – and the powerful computers were able to share and amalgamate information from other platforms, like AWACS aircraft. The Aegis ship thus becomes the battle group’s information organizer, gathering together through secure datalinks everything available, coordinating it, and then dispensing it around the fleet. An AEGIS ship can control aircraft, track surface vessels (and engage them) and can even guide the Standard missiles of other, non-Aegis vessels, so other ships can fire at targets they cannot themselves detect or illuminate.
In the Gulf War of 1991, AEGIS proved it could detect and track Iraqi SCUD missiles for most of their flight, including the parts of the trajectory that took them into space. This has prompted development of the next version of the Standard missile, SM-3, which will be discussed further below.
New Russian anti-ship missiles have become more and more potent, but Aegis can engage even small targets closing at Mach 3 speeds. New versions of the phased array radars deployed over the years – we’ve progressed from the SPY-1A to SPY-1D – and upgraded variants of the Standard missile have kept the system at the forefront. So potent is Aegis, and so meagre other systems by comparison, that the Americans decided it made sense to retire all air defence warships – even the nuclear cruisers – that didn’t mount the system. As a result, most of the vessels I grew up thinking of as modern – the guided missile cruisers of the Leahy, Belknap, California and Virginia classes (as well as the “one off” nuclear cruisers Long Beach, Bainbridge and Truxtun), and all of the guided missile destroyers of the Coontz, Charles F. Adams and Kidd classes, were decommissioned.
In their place were the 22 Ticonderoga class cruisers and the expanding ranks of the highly successful Arleigh Burke class destroyers, of which there will be more than 75 within the next few years. The former cost a billion each, when built, and the latter about two billion in today’s dollars, but they were worth every penny. Aegis was a true revolution in naval warfare, and the battle groups of the US Navy simply could not swagger all over the world’s oceans the way they do without it.
Newer Threats, Greater Challenges, Better Systems
The SPY-1 radars, even in their most advanced form, are “passive” arrays, so-called “PESA” radars. This means that a single element is used to generate the intial radar pulse, but its output is then split among dozens of individual modules in the phased array. These modules are “passive” because they do not themselves generate the emissions.
An SPY-1 radar array on the cruiser USS Lake Erie
At the same time, all versions of SM-2, however advanced, remain semi-active radar homers, though the latest also carry infra-red guidance systems as a supplement to help overcome electronic countermeasures that may spoof or jam radar.
There are now better ways to skin both of those cats.
AESA, Active Guidance, and Cooperative Engagement
The Aegis system and its associated SPY-1 radars have been continually updated over the years, culminating in Baseline 9, and the SPY-1D phased array. It’s an incredibly potent system, yet soon to be pushed to an even higher level by the introduction of more advanced radars, software, and data sharing capabilities. First, Aegis warships are gaining an enhanced cooperative engagement capability under the rubric of “NIFC-CA” (for “Naval Integrated Fire Control – Counter-Air”). This allows warships to guide each others’ missiles, or share targeting data, so that a given shooter can exploit not only its own on-board sensors, but the sensors of other warships and airborne platforms like the new advanced E-2D AWACS aircraft. This vastly increases the potential reach of each vessel’s interception capability.
Cooperative engagement is what strategists call a “force multiplier”, and it’s going to be crucial in blunting the saturation missile attacks that will assail future battle groups. No one is as advanced in this, on land or sea, as the USN.
Allied to this will be a new radar christened AMDR (“Air and Missile Defence Radar”), a scalable, module-based Active Electronically Scanned Array system. AESA arrays are composed of hundreds of small individual active radiating modules, each in effect a little radar antenna in its own right, thus “active” rather than “passive”. An AESA offers many advantages over a PESA, and the new AMDR, designated SPY-6, is said to be 30 times as sensitive as the latest version of SPY-1. What this means exactly isn’t in the public realm, but some indication can be gleaned from what’s known about the anti-missile system on the new UK Type 45 destroyers, whose SAMPSON radars can keep tabs on hundreds of targets simultaneously out to a range of 240 miles. It’s claimed that SAMPSON can track as many as 1,000 objects no larger than cricket balls, each travelling at three times the speed of sound, which implies an ability to engage high performance stealth targets. Surely, AMDR will be at least as good. Being an AESA, AMDR comprises a multitude of individual radiating modules, each of which can provide independent target illumination. This greatly increases the number of threats that can be engaged simultaneously with semi-active homing missiles like the SM-2 Blk.III (the current USN mainstay), which were previously reliant on separate dish-shaped illuminator radars.
A prototype SPY-6 array – “AMDR”
New missiles also contribute to a step change in capabilities. The Evolved Sea Sparrow Missile has proved itself fast, agile and reliable, supplying “short range” defence against air and missile targets out to about 30 miles (a distance that would once have been characterized as “long range”). ESSM is also compact, and can be “quad-packed” into single cells of the standard Mk.41 Vertical Launch System, meaning a ship could be armed with, say, 32 of these rounds while absorbing only 8 of its missile tubes (out of a total of 96 for a Burke class destroyer, and 122 for a Ticonderoga class cruiser). The initial variants of the ESSM were semi-active homers, like SM-2. A new variant, Block II, will have an active seeker head.
An “active homing” missile is one that doesn’t merely receive reflected emissions, but generates its own radar pulses. Each missile, then, has its own little radar set, analogous to those found in the noses of fighter jets. This was a technology that first appeared in air-launched missiles, most notably the mighty AIM-54 Phoenix, and the later AIM-120 AMRAAM. Active missiles don’t need to home in on radar emitted by their launching ships, and thus don’t need the support of ship-mounted illuminators. This greatly increases the number that can be in the air at once, even over the prior Aegis system of shared illuminators. A missile gathers in mid-course guidance from the ship until it gets close enough to home on its own emissions.
Taking advantage of this better guidance technology is the latest member of the Standard family, the SM-6 Extended Range Active Missile, or “ERAM”. The ERAM has an active seeker head – a larger version of the active seeker of the AMRAAM – which makes this version of Standard a sort of deck-launched Phoenix missile. By sharing targeting data, ERAM can engage targets up to 200 miles away, and has proven equally adept at intercepting sea-skimming threats and ballistic missile targets in their terminal, endo-atmospheric phase. ERAM will not replace SM-2, but will be a potent supplement. A major buy of several hundred units has just been announced.
An SM-6 ERAM
On to Ballistic Missile Defence
At first blush, BMD is an unlikely function for destroyers and cruisers, but with China deploying ballistic missiles for targeting aircraft carriers, and North Korea throwing proto-ICBMs into space, it’s become a priority, and indeed, an established capability. The combination of recent baseline Aegis systems (culminating in the new Baseline 9) and the Standard SM-3 missile – another member of the Standard family, and by far the most expensive – has been a great success, proving itself capable of engaging ballistic missile targets at the apogee of their trajectories, outside the atmosphere.
SM-3 is truly a remarkable weapon. The Block IIA variant has an amazing range of over 1300 miles, and launches at an initial hypersonic velocity of something around Mach 15. That’s not a typo – Mach 15. It costs something like 12-15 million dollars a round, and has the ability to reach into space, where it deploys an amazingly sophisticated “exo-atmospheric kill vehicle”, a guided warhead that kills incoming ballistic missiles by kinetic force, that is, it collides with them. In one famous test an SM-3 was used to destroy an obsolete satellite flying at 17,000 MPH in low earth orbit. So potent and reliable is the system that it’s being adapted to land-based installations in the “Aegis Ashore” program. It is believed that SM-3 can handle the supposed “carrier killer” DF21 ballistic missile being fielded by the Chinese, even supposing the People’s Liberation Army is able to accurately target a task force moving at over 30 MPH at thousand mile ranges. Improved versions may be able to intercept the ICBMs North Korea seems certain to deploy – stress “may” at this point.
There’s no denying that SM-3 has proved impressive, and actually, it’s sometimes still a little difficult to believe that something small enough to be fired from a standard Mk. 41 missile cell on a destroyer can reach 250 km up into space and hit something going 8 times as fast as a high velocity rifle bullet.
SM-3 at launch
The Threat Becomes Still More Dire
A new weapon may be in the offing that could change the balance of power at sea and have a dramatic effect upon the viability of large surface combatants: the hypersonic cruise missile. It will soon be within the technological grasp of Russia, China, America, and heaven knows how many others to field guided anti-ship missiles that operate within the atmosphere at speeds above Mach 5, that is, at a clip at or exceeding a mile per second. These may be air-launched, or even strapped to the top of ballistic missiles, in a “boost-glide” package that takes the weapons to high altitude, on the edge of the atmosphere, before releasing them to plunge at ungodly speeds toward their targets. Artists’ concepts generally portray these missiles thusly:
Artist’s concept of Zircon missile (apparently based on the American X-51 Wave Rider test vehicle – little is actually known about Zircon)
The Russians claim to have one such weapon on the cusp of deployment, the “Tsirkon” (Westernized as “Zircon”), for which speeds as high as Mach 8 have been reported (dubiously); supposedly, these will be operational as early as 2018 on board a pair of refitted battlecruisers of the Kirov Class. Of course, the Russians claim a lot of things, touting over the years the construction of 20,000 ton nuclear powered super-cruisers, super-carriers akin to American CVNs, and so on. The fact is, they simply haven’t got the money to realize many of their ambitions (it bears remembering that Russian GDP is at present smaller than Canada’s), yet it would be dangerous to assume that their boasts of progress on advanced missiles like Zircon is nothing but hot air. We may not see such weapons by 2018, but we will see them some time soon, if not from Russia then China, and it’s an open question whether any good defence can be mounted against them.
Aegis and AMDR could certainly detect them, but could SM-6 intercept them? SM-3 (it would seem not, since the “kill vehicle” on these rounds is designed to be used in the “exo-atmospheric” environment – space)? Will the answer lie in directed energy weapons, electronic jamming and spoofing, guided rail gun rounds – or what? It’s hard to say, at this point. Recent commentary has them sweeping surface navies from the seas, never to return, which seems a tad alarmist, but hypersonic cruise missiles definitely pose problems that will be extremely difficult to solve. It isn’t so simple, though, as comparing the speed of a hypothetical hypersonic attacker (say Mach 6) with that of an interceptor missile like SM-6 (about Mach 3.5) – as many breathless “analysts” have been wont to do, recently – and conclude that the SAM has no chance of intercepting the incoming attacker. It isn’t a tail chase. The defensive SAM simply has to get itself to a point in space that will intersect with the target, harder, to be sure, if the incoming is going at Mach 6, but still possible. I’m not aware that any test has yet been run to see what SM-6 might be able to do in this regard, nor have I heard whether the speed of SM-6 could be boosted further, though no matter how fast it goes, the problem of colliding with a hypersonic weapon is a difficult one, especially within the atmosphere, where, unlike the kill vehicles deployed by SM-3, the terminal maneuvering will have to contend with extreme aerodynamic forces.