September 13, 2020

Missile Defense Through the Decades - A Worked Example

One subject that comes up a lot in discussions of modern naval warfare is missile defense, and I decided to try to get some reasonably hard data on the subject by using the amazing Command: Modern Operations game/simulation tool. This is a piece of software sold as a game, but also used by professional analysts. It's a fantastic resource for answering these kind of questions, and I used it to look at the period 1975-present.

The basics of the test were simple. I set up two bunkers, each armed with eight P-15 Styx (SS-N-2) anti-ship missiles in the Palos Verdes peninsula, near San Pedro, and stationed the target near Catalina Island, about 22 nm away. The bunkers would detect and engage the target immediately, firing off all of their missiles, while the target ship would shoot down as many as it could.

The first target was a 1972-spec Charles F Adams class destroyer, which I fired 16 missiles at. The Adams had a twin Mk 11 launcher for RIM-66A SM-1MR missiles, with 2 illuminators. Began engagement at around 10 nm, Ph 0.35.

RunSAMs FiredMissiles downedShip Sunk?
182Yes
282Yes
383Yes

After I had set up another few test runs, I realized that I had forgotten to turn on the target ship's radar, and modified the scenario to try it again.1 The first test after I fixed this was another Adams, this one in 1988 spec. The fire-control system looks to have been the same, but with RIM-66E missiles. Began engagement around 19 nm, Ph 0.54.

RunSAMs FiredMissiles downedShip Sunk?
1125Yes
2126/1 ChaffYes
3103Yes

At this point, it seemed worth going back and trying the 1972 Adams again. As before, it had a twin Mk 11 launcher for RIM-66A SM-1MR missiles, with 2 illuminators. Began engagement at around 17 nm this time, Ph 0.35.

RunSAMs FiredMissiles downedShip Sunk?
1103/1 JamYes
2103Yes
3102/1 JamYes

Certain trends are already becoming clear. The biggest limitation on the ships so far isn't illuminators, it's reload time on the launcher. Some of this is natural, particularly for the 1972 ship, but the 1988 version has SAMs capable of reaching out to where the launcher is. This problem is only going to get worse when I try ships with longer-range SAMs. So I do another run with the 1988 Adams, this time setting it 40 miles from the Styx battery. Things get interesting, as the missiles are detected on launch, then dive under the ship's radar horizon, being picked up about 25 nm out, right on the edge of missile range. Engagement starts at 22-23 nm, not much further than last time, but far enough that it looks like salvo 3 may have to wait a few seconds for salvo 1's illuminator to get clear.

RunSAMs FiredMissiles downedShip Sunk?
1145Yes
2146Yes
31482/2 chaffYes

OK. So I'm going to use the longer-range version going forward. Let's try another ship of the same era, but with more range, the DDG-37 Farragut class, starting with the 1975 model. One twin Mk 10 rail launcher with RIM-67A SM-1ER missiles, and two illuminators. Engagement began at 25 nm, and in this case it looks like launch rate is slow enough that the illuminators aren't a problem. Ph 0.44.

RunSAMs FiredMissiles downedShip Sunk?
1104Yes
2102Yes
3104Yes

One of the main reasons I've noticed that ships seem to be under-performing their stats in a lot of cases is that if the first missile hits, the second one is wasted. Fortunately, the USN was kind enough to give us a comparison here, in the form of the NTU (New Threat Upgrade), where ships got the Aegis-like ability to retarget missiles in flight. Sadly, the Farragut doesn't have this, but the follow-on Leahy class does. We'll start with the 1977 Leahy, with two twin Mk 10 rail launchers, four illuminators, and RIM-67A SM-1ER missiles. Engagement began at 25 nm, Ph 0.44 .

RunSAMs FiredMissiles downedShip Sunk?
1207/1 JamYes
2208Yes
3208/1 Jam 1 ChaffYes

Now, onto the 1987 NTU Leahy, equipped with RIM-67C SM-2ER BlkII missiles. The missiles are engaged at 26 nm, almost instantly upon coming over the horizon, and Ph is 0.55. Unfortunately, in-flight retargeting apparently doesn't work terribly well when the missiles are coming in this close together. But on the whole, it's a big improvement.

RunSAMs FiredMissiles downedShip Sunk?
121310/2 CIWSYes
2206/1 Jam/1 CIWSYes
32211/2 CIWS/1 Jam/1 Chaff/1 MalfunctionNo

So that got us our first survival by the target ship. It was extremely lucky (neither chaff nor jamming is usually that reliable, and the malfunction was maybe a 25% chance) but none of the other ships could have even gotten close.

OK, it's time for another test. This time, I'm going to use USS California (CGN-36). She has RIM-66s instead of RIM-67s, and also was fitted with NTU later in her career. Also, Mk 13 single-rail launchers which fire rapidly and might let the illuminator limitations show up.

The first test is with the 1977 version with RIM-66B SM-1MR Blk Vs. Engaged at 23 nm, Ph 0.49. The illuminators limit salvo 5 somewhat, as each missile launcher fired two successive missiles at the same target, but it seems to work pretty well.

RunSAMs FiredMissiles downedShip Sunk?
12612Yes
22813/1 chaffNo4
32612/1 chaffYes

I then tested it with the 1991 NTU version of California. The big draw here is the wider spread between follow-up salvos, which should make NTU a lot more effective. The missiles are now RIM-66J SM-2MR Blk II. Engaged at 26 nm, Ph 0.54.

RunSAMs FiredMissiles downedShip Sunk?
13014/2 CIWSNo
23012/2 CIWS/1 JamNo5
33011/3 CIWS/1 Jam/1 MalfunctionNo

OK. So missile defense has now reached the point where a ship has a reasonable chance of surviving a pretty heavy missile attack, even without Aegis. But let's throw Aegis back into the mix and see what we get. We'll start with Ticonderoga herself, fresh from the builder's yards in 1983. She has two twin Mk 26 launchers, four illuminators, and RIM-66C SM-2MR Blk I missiles. Engagement begins at 25 nm, Ph 0.49.

RunSAMs FiredMissiles downedShip Sunk?
14216No
23616No
33416No

Because of the fast-firing twin launchers and the lack of illuminator limitations, 24 SM-2s were in the air before the first one reached its target. In-flight retargeting is also working pretty much seamlessly, and the closest any Styx got across the 3 tests was about 5 nm. Some of this performance is down to Aegis, but some is also down to the Mk 26 launcher, which fires about as fast as the single Mk 13s on California, but has two rails instead of one. So it's worth seeing how Virginia, a cruiser with a pre-Aegis system but Mk 26s, will do. I'm using the earliest (1977) version, with RIM-66B SM-1MR Blk Vs, and two illuminators.6 Engagement begins at 23 nm, Ph 0.49.

RunSAMs FiredMissiles downedShip Sunk?
12613Yes
22412/1 ChaffYes
3228Yes

This test didn't go as well as I'd hoped, due to illuminator limitations. Fortunately, this is a solvable problem. Command lets you edit units, so I added another pair of SPG-51Ds to the ship and turned it loose. Same missiles and launchers as last time.

RunSAMs FiredMissiles downedShip Sunk?
13616No
24015No7
33610/1 JamYes

That's better, but still not great. Illuminator restrictions aren't totally gone, and did hold up a few salvoes, but it's much better. Do note that the closest missile in the first test was at 1.3 nm instead of 5 nm for the Tico, while the other two let some missiles through.

But could something like NTU compensate for the illuminator limitations on the Virginia? To find out, I tested the 1991 version of that class, with RIM-66J SM-2MR Blk IIs, which is listed as Semi-NTU.

RunSAMs FiredMissiles downedShip Sunk?
13916No
23216No
33616No

Semi-NTU apparently means that it can handle two salvos in the air at once, so the performance is quite similar to that of the 4-illuminator ship, except that the missiles were significantly better. The nearest missile was killed at 1.4 nm, although on the other two runs it did significantly better.

But enough messing around. How would a modern ship do? Let's use one of my favorites, USS Wayne E Meyer (DDG-108), a Flight IIA Burke. She has three illuminators, 36 RIM-162A ESSM, and 16 RIM-174A ERAM SM-6s. Engagement begins as soon as the missiles cross the horizon, 26 nm out, Ph 0.77.

RunSAMs FiredMissiles downedShip Sunk?
136 ESSM16No
232 ESSM16No
334 ESSM16No

One thing immediately jumped out at me from this. The retargeting isn't working great because of how close together the missiles are, and I wouldn't be surprised if the actual software staggered launches to compensate. I run a test with the ROE set to only fire 1v1, and see what happens. Instead of shooting off 30+ ESSMs, it fires only 20. I don't see much need to do repeated tests. We know that all the missiles will die. It's just a question of when.

Right. So we've looked at air defenses from the mid-70s to the present, but what about the future? Command doesn't just do missiles, and I decide to test the USS Ponce, a former amphibious ship equipped with a laser. The result is astonishing. All of the missiles are destroyed almost instantly upon entering laser range. Aegis made it look easy, but this is something else. The caveat is that I'm a lot less certain of Command's model for lasers than I am for missiles. For one thing, they don't have a sharply-defined range, and tend to require some dwell time towards the edges of their effectiveness.

I doubt this is the end of my work on this problem in Command. The biggest gap is that I've only looked at a single type of weapon, and an old and relatively high-flying one at that. But it's also only been American vessels, and one at a time in good weather. We'll see what comes next.


1 Actually, I did a fair bit of fine-tuning between the first run described above and getting everything nailed down, but there was no point in keeping records of those tests.

2 The last two SAMs were fired when the ASMs were at very close range, and the first one killed the target before the second was launched, so the second was fired at a different ASM, which it also killed.

3 The last salvo was interrupted by the arrival of a Styx.

4 It looks like one of the two surviving missiles hit, and the other just barely missed, so the ship survived.

5 Ship was hit by one missile, badly damaged.

6 Friedman doesn't say so explicitly, but this appears to be because the Virginias originated as a single-ended (one launcher) ship, and got the second launcher in place of their ASROC box. But while this gave two launchers, they still only got two illuminators.

7 One missile hit, ship damaged.

Comments

  1. September 14, 2020inc said...

    How do gun-based anti-missile systems like the Phalanx compare?

  2. September 14, 2020bean said...

    They don't, really. Phalanx is very much a last-ditch "everything else failed" system. Several of the ships here had them, and it's noted where they knocked down missiles, but it was usually shooting down 2 or 3 missiles, not 16. If they miss, there's no second chance, and the Pk isn't good enough to make me confident in that system. It's very useful for raising the bar on how many missiles it takes to kill something, and it did save the ship several times, but it's not anywhere close to SAMs in terms of effectiveness.

  3. September 14, 2020AlexT said...

    If I understand correctly, the ASMs were in a tightly-grouped salvo - the worse-case scenario for CIWS, right? Maybe if more guns were added - a point-defense battery of say a dozen guns per side, each side controlled by a single radar and fire control computer. Or are they too large/heavy/expensive?

    Also, there was a recent test where a ground-fired HVP shot down a drone simulating a cruise missile. If I understand correctly they can be fired out of 127mm and 155mm naval guns as well, and reach far beyond 5km.

  4. September 14, 2020bean said...

    Yes. I had two 8-round launchers dumping their missiles as fast as the game would fire. I'm not sure how much sense your super-CIWS makes. The big advantage of CIWS is that it's a small and relatively light way of raising the number of missiles it takes for your ship to be in serious trouble. There's a lot of cases where that's very valuable (Stark and Sheffield spring to mind, although Stark's problem was that the system was off) but that doesn't mean you want to try to do all of the defenses that way. You're into diminishing returns, and as you point out, it would probably be too heavy.

    (Also, props for noticing the radar problem. AIUI, you can't fit more than 4 Phalanx on a ship or they start interfering with each other.)

    Which isn't to say that the idea of a heavier gun-type CIWS is a bad one. A lot of nations use 30mm systems, and the Italians have long used a 40mm CIWS. These days, they hook the CIWS radar up to OTO 76mm Super Rapid guns instead to try to kill the target as far away as possible. And HVP offers even more options there, although guidance is still an open question. (All of the HVPs I've seen use GPS, which isn't really great for shooting at cruise missiles.)

  5. September 14, 2020Jade Nekotenshi said...

    Italy has guided shells for both the 76mm and the 127mm (DART). I'm not sure if they're LOSBR or SARH, though. I'm curious how well those add up, and whether the Russian "lots of 30mm with off-mount FC" works as well as Phalanx.

    Not that either is a replacement for SAMs, but I'm curious how they stack up as a supplement, and/or whether having Phalanx (or another gun CIWS) as a backstop for missile CIWS like RAM or SA-N-19 makes any sense.

  6. September 14, 2020Jade Nekotenshi said...

    Should have specified radar-guided shells. Apparently there's also VULCANO, which, depending on what I read, uses GPS but might also have terminal IR and/or SALH? That's not completely clear to me.

  7. September 14, 2020Blackshoe said...

    @AlexT

    Maybe if more guns were added - a point-defense battery of say a dozen guns per side, each side controlled by a single radar and fire control computer. Or are they too large/heavy/expensive?

    Jade already alluded to it, but yeah, this was basically how the Soviets treated point-defense systems (except each mount got its own radar, and a plucky-little konscriptniki to manually back it up, as well).

  8. September 14, 2020Jade Nekotenshi said...

    Also, the fundamental issue with guns is range. Unless each gun can engage a separate missile, adding more of them doesn't do a whole lot more than marginally increase the Pk for each missile engaged. If they can engage separate missiles, that buys you a bit more, and I'd think something like Aegis can do that (or could be easily modified to do it), but guns still don't reach out very far. That means each gun - even if it can target independently - does poorly against a dense salvo, and can probably only engage 1-2 missiles before needing to be reloaded. To boot, you have the issue of a cloud of (potentially supersonic) fragments still having enough hangtime to hit the ship anyway. That's probably better than eating an intact missile, but might still shred radars, radios, weapon mounts, etc, or maybe even golden-BB your entire combat system if you get unlucky.

    That might make a case for light armor - the US seems to think it does, which is the point of the kevlar splinter protection on the Burkes - but there are still things you can't armor like radars, that won't take kindly to a few kilos of supersonic aluminum scrap.

  9. September 14, 2020DampOctopus said...

    Thanks for doing these simulations. It looks like a more thorough version of your answer to some of my questions about missile defence a while back.

    It's really a shame that CIWS (low reliability, low per-shot cost) has shorter range than SAMs (high reliability, high per-shot cost). If it were the other way around, you could use expensive SAMs only on the missiles that leaked past the CIWS. Maybe lasers will change this, depending on their effective range.

    As it is, though, the Wayne E Meyer in your last test used up most of her SAMs. A second, similar attack could finish her. How expensive are those low-tech, 1960s-era ASMs?

  10. September 14, 2020AlexT said...

    HVP offers even more options there, although guidance is still an open question

    How difficult would it be to make the PD shells remote-controlled from the ship that fired them? No guidance, just a rear-facing radio receiver in the tail, with the ship constantly monitoring the shells and the target and providing guidance commands. AIUI, they're not really meant to intercept beyond the horizon, and in our day and age there should be computing power to spare, both for the ship and for the shells.

    @Jade Nekotenshi

    Unless each gun can engage a separate missile, adding more of them doesn’t do a whole lot more than marginally increase the Pk for each missile engaged

    I'm thinking, if the whole battery fires against a single missile, and if the gun emplacements are spread out along the ship, there's a higher likelihood that, no matter how the missile jinks, it'll be CBDR towards some gun, which should increase that gun's chance to hit. More so up close.

    Against multiple incoming, more guns means a bigger salvo must arrive simultaneously, which AIUI makes the attacker's coordination and fire control problem exponentially more difficult.

    Also, many guns spread all around the ship means that attacks from all bearings are actually the best-case scenario for the defender. To defeat the PD battery, all the incoming should arrive on the same bearing, which simplifies interception with missiles, I think?

  11. September 14, 2020bean said...

    As it is, though, the Wayne E Meyer in your last test used up most of her SAMs. A second, similar attack could finish her. How expensive are those low-tech, 1960s-era ASMs?

    They aren't hugely expensive, but economic warfare isn't a great plan for several reasons. First, note that if you're just dueling the missiles, you're doing it wrong. Meyer's first line of defense would be her Tomahawks, which could quite probably take out quite a few of the missiles before they were fired. Second, note that Aegis is smarter than CMO, and I was able to cut it from 32-36 ESSMs down to 20 by switching from 2 missiles/incoming to 1 missile/incoming. There's also the issue of needing to support and transport a bunch of big missiles.

  12. September 14, 2020Jade Nekotenshi said...

    Also, a Burke/Tico probably has more than 36 ESSM + 16 SM6. Can't say how many we actually carried on deployment when I was in, but it was more than that, and we had SM3, Tomahawk, SM2-MR and VL-ASROC too. 36+16 doesn't even take up the whole forward launcher on a Burke since ESSMs are quadpacked. That said, that's a reasonable loadout for the new frigates, and 24+ Termits to skag a frigate looks like a pretty expensive way to fight a war.

  13. September 14, 2020bean said...

    The loadout was decided by CMO, not me, and it included quite a few Tomahawks and some VL-ASROC. I just didn't list them because they weren't relevant.

  14. September 14, 2020Alexander said...

    I'd be interested in hearing more about the advantages of different modern air defence systems, and why a ship like the Burke (or a Kirov) has so many. There are very large and long range missiles such as Standard or Aster, smaller (but still very capable) missiles like ESSM and Sea Ceptor, Missile CIWS (e.g. RAM) and a whole range of gun systems. Evidently having ESSM doesn't make RAM redundant, and you probably also want a gun CIWS (or at least an autocannon for defence against small boats, which might as well double up as CIWS). What is the overlap between ESSM and RAM, or Phalanx and a Mk110 (or a 76mm Super Rapido with DART, since MAD-FIRES is still in the future)? Are the smaller, non deck penetrating systems only competitive because they can be squeezed in on an existing ship where another weapon wouldn't fit?

  15. September 14, 2020Placid Platypus said...

    What does the "Ph" signify?

  16. September 14, 2020Alexander said...

    The probability of the ships SAMs scoring a hit (Probability hit).

  17. September 14, 2020bean said...

    I’d be interested in hearing more about the advantages of different modern air defence systems, and why a ship like the Burke (or a Kirov) has so many.

    I plan to talk more about this at some point. I believe there's some stuff being published later in the year which will be quite helpful, and which I'm holding out for. The short version is that you want rings to deal with a serious attack. SM-6s are very capable, but also very expensive. ESSM is probably cheaper and takes up less space in a VLS. There's some debate over the utility of gun CIWS against modern supersonic anti-ship missiles, which is why the Flight IIA Burkes originally lost their CIWS in favor of ESSM. ESSM got delayed, and they decided they wanted the CIWS anyway because of boat concerns. The niche for RAM seems to be in the ships that don't have full VLS/Aegis air defense systems, probably because it provides a good balance of capability and number of rounds. Just for fun, I threw an LCS-2 into the scenario I set up here, and it took out 9 of the missiles with its 11 RAM.

    Are the smaller, non deck penetrating systems only competitive because they can be squeezed in on an existing ship where another weapon wouldn’t fit?

    Not necessarily. One of the big advantages of PD weapons is a low minimum range. Bigger missiles take longer to get on target (one of the downsides of VLS, although less so for ESSM) and something like CIWS doesn't have to worry about that. That said, the low footprint definitely helps.

    What does the “Ph” signify?

    Probability of hit, according to Command.

  18. September 14, 2020Alexander said...

    You do see RAM and ESSM together on some ships, which suggests that either they are complementary, or there would have preferred more ESSM, but didn't have the space/weight. With gun CIWS, presumably not all are equal. I think of 20mm as being too short ranged for comfort, though possibly because I am conflating their performance with WWII 20mm AA. Obviously a Phalanx would be more than adequate against Japanese kamikaze attacks Ü. Would a 30mm Goalkeeper, or 35mm Millennium do better than Phalanx against supersonic ASMs? How about even larger guns like the OTO Melara 76mm? If you had the tonnage (and the budget) would you just fit a big VLS and some Mk110s like the Zumwalt (setting aside its issues) and abandon RAM and Phalanx?

  19. September 14, 2020DampOctopus said...

    I was able to cut it from 32-36 ESSMs down to 20 by switching from 2 missiles/incoming to 1 missile/incoming

    I noticed that part, too. Framing it a different way: launching the missiles more rapidly (two at a time instead of one at a time) doesn't let you overwhelm an AEGIS ship, but may force it to use its SAMs less efficiently.

  20. September 14, 2020bean said...

    I think you're misinterpreting what happened. I went from 2 ESSM/incoming ASM to 1 ESSM/incoming ASM. All I did was tweak the ROE the game was using. The ASMs were still coming in at the same pace. I figured that actual Aegis isn't dumb enough to dump the ESSMs the way it did during the test, and tweaked it to simulate a more realistic engagement scenario.

  21. September 14, 2020bean said...

    You do see RAM and ESSM together on some ships, which suggests that either they are complementary, or there would have preferred more ESSM, but didn’t have the space/weight.

    I suspect it's more the later. The only ships with Aegis and RAM are the missile defense Burkes of the 6th fleet, and that's because they have very limited air defense capability while doing BMD. RAM gives you a lot more weapons than ESSM in a given weight/space, which can be important. (RAM is primarily used on the CVNs and amphibs.)

  22. September 15, 2020Philistine said...

    @AlexT: "How difficult would it be to make the PD shells remote-controlled from the ship that fired them? No guidance, just a rear-facing radio receiver in the tail, with the ship constantly monitoring the shells and the target and providing guidance commands. AIUI, they’re not really meant to intercept beyond the horizon, and in our day and age there should be computing power to spare, both for the ship and for the shells." It sounds like you'd be back to needing a separate transmitter aboard the ship to guide each individual piece of ammunition in flight.

  23. September 15, 2020bean said...

    I don't think you'd need a separate transmitter for each shell. The proposal is similar to the updated autopilot Aegis uses, and it's easy to just update each missile/shell in turn.

  24. September 15, 2020Alexander said...

    "The only ships with Aegis and RAM are the missile defense Burkes of the 6th fleet, and that’s because they have very limited air defense capability while doing BMD. RAM gives you a lot more weapons than ESSM in a given weight/space, which can be important. (RAM is primarily used on the CVNs and amphibs.)"

    The carriers have ESSM too, but presumably the requirement for space for their primary mission of supporting aircraft makes the more compact RAM more practical. Might it even be worth pushing ESSM off onto the carriers escorts?

    How about the heavier gun CIWS? I'd think that more sophisticated ammunition makes heavier guns more viable despite a lower rate of fire than revolver/rotary cannon. I quite like the idea of a small 3" DP battery like the Italians use on their Horizons.

  25. September 15, 2020bean said...

    I'm not quite sure what the story is. A lot of me suspects that the ESSMs remain because pulling them for RAM looks bad, but I can't be sure. The big issue is that the carriers and big-deck phibs usually have 8 or 16 ESSM, which just isn't that much. It might be useful to help deal with leakers (remember that the ships are talking to each other) or to cover some gap in RAM's performance that we don't know about. In a lot of ways, RAM is where the early Sea Sparrow was in terms of performance, while ESSM is where Tartar/SM-1MR was back in the old days.

  26. September 15, 2020Jade Nekotenshi said...

    Could the capability of ESSM (and NSSM before it) to engage surface targets have anything to do with it? I'm having a hard time imagining any scenario where a CVN ever gets an LOS shot at any kind of surface anything where the cost of a missile makes any kind of sense, but I could just about see it for a phib. Maybe torpedo boats coming out of a sheltered cove or something while they're doing well-deck ops, and you want to make sure they get blasted apart before they can launch? (This is probably less of an issue now with CEC - you could have a DDG fire an SM6 - but before that, it might have made a little sense.)

    It's a reach, to be sure, but I wonder.

    The other thought is that the higher power available to a shipboard illuminator might be able to burn through some kinds of jamming that could fox RAM's passive seeker, and the larger warhead might give better odds of neutralizing something more durable like a fighter or one of the big Russian missiles.

  27. September 15, 2020Jade Nekotenshi said...

    @AlexT - that's basically what DART's guidance is. Well, it's beam-riding instead of command, which is more limited but also simplifies the job the ship's systems need to do. It does have one transmitter per gun, though, mounted on the gun. (I've seen sources saying that newer DART also has semi-active radar homing using the same transmitter, though.)

  28. September 15, 2020bean said...

    RAM has capability against surface targets these days, although I'm not exactly sure how good it is, and the warhead is probably a bit small. Also, a good point about non-missile targets, which RAM can attack, but it's not optimized for. (I'm now remembering the issues Sea Wolf had shooting at Skyhawks in the Falklands.) As for jamming, note that RAM's main sensor is IR, not RF, so it's operating in a completely different band.

  29. September 15, 2020AlexT said...

    @Jade Nekotenshi

    that’s basically what DART’s guidance is

    I think it's a different principle. This is supposed to be a cheap, dumb projectile, unpowered after leaving the muzzle. Ship-side, there's one big, accurate radar, one FC computer and one guidance transmitter, and an arbitrary number of computer-controlled guns.

    The calculations shouldn't be a problem - I'm pretty sure for the cost of one SM-6, enough CPU can be bought to handle a few dozen guns and a couple hundred projectiles at a time without breaking a sweat.

    The ship's radar does need to be pretty accurate, though, to guide the shells to intercept. Maybe the projectile could burst into shrapnel before impact (the ship's FC computer also sends the burst commands) so maybe actual collision isn't necessary?

  30. September 15, 2020Jade Nekotenshi said...

    If the ship is sending commands, the projectile needs power to move control surfaces and run a radio receiver. That's not a lot simpler (if at all) than a basic circuit that keeps the shell centered in an RF beam. It's simpler than SARH, sure, but even then, not a lot simpler. There might be a small win here if you don't have to track each projectile, but that needs the projectiles to be smart enough to know where they are (inertial guidance). Command guidance - which is what you're describing - requires the launch platform to track both the target and the projectile, and if there are multiple projectiles, you need a way to send commands to each one individually, which needs more smarts on the projectile than a simple bang-bang beam-rider needs. (Enough extra smarts that you're competing with things like IR homing or semi-active laser/radar homing, where you don't need to track the projectiles.)

    As for non-impact, sure - proximity fuzes have been doing that since the 40s, and AFAIK, DART rounds are proximity-fuzed. You could do something like Bofors 3P or AHEAD too, it's not hard once you've got the bits to add any kind of guidance.

  31. September 15, 2020bean said...

    which needs more smarts on the projectile than a simple bang-bang beam-rider needs. (Enough extra smarts that you’re competing with things like IR homing or semi-active laser/radar homing, where you don’t need to track the projectiles.)

    I don't think this is necessarily the case. All you need is the ability to tell "this command is for me" from "this command is not for me", and that's not going to add very much at all to the cost of the shell if you've already got guidance. Making sure the shell and ship agree on the shell's identity is a bit tricky, but I can think of several ways to do it offhand. The rest is just stuff that's been done since the 80s, scaled up a bit. Which isn't a big problem these days.

  32. September 15, 2020DampOctopus said...

    How about a completely dumb projectile with an ablative base, and a laser to guide it? Aim the laser at the edge of the projectile, and the differential ablation will steer it in the opposite direction. Or if your laser's not quite that accurate, have a spinning projectile with an asymmetric ablation layer, and pulse the laser at the spin frequency: the phase of the pulses will determine which way you steer. Slew the laser fast enough, and you can guide several projectiles at once.

    Pros: no expensive electronics in the projectile; probably packs more punch than just hitting the target directly with the laser. Cons: a bit Rube Goldberg; probably well outside the realm of practicality. Depends on just how magical lasers turn out to be.

  33. September 15, 2020quanticle said...

    I’d be interested in hearing more about the advantages of different modern air defence systems, and why a ship like the Burke (or a Kirov) has so many. There are very large and long range missiles such as Standard or Aster, smaller (but still very capable) missiles like ESSM and Sea Ceptor, Missile CIWS (e.g. RAM) and a whole range of gun systems.

    There's also the fact that larger, longer ranged missiles tend to be less maneuverable. The Arms Control Wonk podcast's May 27th episode focused on the S-400 air defense system and one of the points that Rob Lee (the analyst who studied this system) made is that the S-400 can fire a variety of missiles, with a tradeoff between range and maneuverability. The 40N6E missile, can engage targets at up to 400km away, but by the time it gets there, it's not going to have much energy left to cope with a maneuvering target. The 9M96, on the other hand, has an engagement radius of only 120km, but is designed to achieve high hit probabilities against fast, maneuvering targets.

  34. September 15, 2020AlexT said...

    @DampOctopus

    Re Rube Goldberg, how about an explosive as the ablative layer? The laser causes a small localized deflagration that pushes the shell. This gives more thrust than just the laser's beam power, and whatever "propellant" isn't used during flight, blows up at impact. At which point, maybe just do away with the warhead entirely.

    @Jade Nekotenshi

    the projectile needs power to move control surfaces and run a radio receiver

    Yeah, by unpowered, I meant it's in unpowered flight, ie it's not self-propelled.

    a basic circuit that keeps the shell centered in an RF beam

    The problem I see with beam riding, is that you need one beam per gun, per target, right? Also, if the target is distant, the projectile trajectories will have to arc, which is awkward for beam riding, and you end up needing one beam per in-flight projectile.

    Re proximity fusing, I'm thinking it adds complexity to the projectile, and it relies on radio bounces from the target, therefore is vulnerable to EW. Instead of putting little, expendable, lightweight radars in each shell, I'd just put a really big, powerful, sensitive one on the ship, and keep the shells as dumb as possible.

  35. September 15, 2020Alexander said...

    @quanticle Is there a version of the Standard optimised for dealing with maneuvering targets? Or are they more 'Standard'ised than the Russian land based systems? I can imagine that even with a significant number of VLS cells you don't want over specialised missiles. Hence the secondary surface to surface role mode.

    Regarding a laser powered point defence projectile, I would think that a sufficiently powerful laser would render the projectile unnecessary. Just target the incoming missiles directly.

  36. September 15, 2020bean said...

    Re proximity fusing, I’m thinking it adds complexity to the projectile, and it relies on radio bounces from the target, therefore is vulnerable to EW.

    Note that most modern proximity fuzes are laser-based instead of radio, probably for precisely this reason.

    Is there a version of the Standard optimised for dealing with maneuvering targets? Or are they more ’Standard’ised than the Russian land based systems? I can imagine that even with a significant number of VLS cells you don’t want over specialised missiles. Hence the secondary surface to surface role mode.

    I don't believe so. Some of that is probably standardization, and the USN not wanting to build too many types. Do note that SSM modes for naval SAMs go way back to the first SAMs.

  37. September 16, 2020John Schilling said...

    One problem with a beam-riding system, whether for guns or missiles, is accuracy. A two-meter X-band (NATO I-band) radar will have a beam width of about one degree, corresponding to a 17-meter spot at 1000m range. 40mm proximity-fuzed shells have a lethal radius of ~2 meters against missiles, so you're talking 30-40 shells for a ~90% Pk, which is 6-8 seconds of firing time - and even a subsonic antiship missile will cover 1000 meters in 3-4 seconds. The math isn't much better for medium-caliber guns with larger shells but lower rates of fire.

    Radar beam riding works best for missiles with large fragmentation warheads, and against aicraft that can be mission-killed with less damage than it takes to put down a kamikaze robot.

    Laser beam riding with an electro-optical (or LIDAR) tracker would be a much better proposition, but the United States Navy at least seems reluctant to trust optical fire control.

  38. September 16, 2020bean said...

    Even for missiles, radar beam riding didn't last all that long. Tartar entered service in 1962 with SARH, which is about the same time Terrier switched over. (Except the nuclear versions, because of concerns about positive control.) I know that laser beam riding has been done a few times for land-based SAMs, but even missiles benefit a lot from SARH.

  39. September 16, 2020Jade Nekotenshi said...

    Hmm, this Wikipedia article seems to think DART uses CLOS guidance, which is pretty much exactly what AlexT is describing except that the transmitter is on the gun. I was pretty sure it was a beam-rider, but I might well be wrong about that.

  40. September 16, 2020bean said...

    Navweaps suggests that DART is beam-riding, and Jane's (which I can't link) confirms.

    @John

    There are ways to do beam-riding which offer better accuracy now that I think about it. DART seems to use a four-lobed beam, which should let you get better precision than the antenna itself is capable of.

  41. September 16, 2020bean said...

    Just for fun, I decided to run a version of this test with the Bergami (Italian FREMM). The Sea Vipers took out 12 of the 16 incoming missiles (reported Ph .85, retargeting worked well). It turns out that the game models DART as a missile, and gives each salvo a .25 Ph. Two of the remaining missiles fell to DART, one to jamming and one to a malfunction.

  42. September 28, 2020Aaron said...

    Really interesting topic and discussion. Would love to see more of these experiments in the future.

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