[HN Gopher] Rolling Airframe Missile
___________________________________________________________________
Rolling Airframe Missile
Author : cwillu
Score : 129 points
Date : 2024-02-04 15:24 UTC (7 hours ago)
(HTM) web link (www.navalgazing.net)
(TXT) w3m dump (www.navalgazing.net)
| isoprophlex wrote:
| I'll just comment that that is the most clever website name I
| came across in a long time!
| metadat wrote:
| So many great articles on this site. This rainy Sunday is in
| serious jeopardy of falling off the cliff and being sucked into
| the gravity well wormhole that is navalgazing.net.
|
| https://www.navalgazing.net/Phalanx
|
| I've always wondered how the Battleship guns with the white dome
| cylinder chamber above the gattling gun worked, but the
| background story is way more interesting than I expected.
| Apparently it's called a Phalanx, and no, a person doesn't sit in
| the white cylinder chamber*.
|
| * Despite Battlefield 2 leading me to believe a person occupied
| the cylinder, anyone remember Wake Island with the USMC carrier,
| F-35B, and J-10? haha, good times.
| thunderbird120 wrote:
| The article on VLS is also quite nice
|
| https://www.navalgazing.net/VLS
| poooogles wrote:
| >...only a handful of cases in which ships equipped with
| Phalanx have been the subject of missile fire, and none that
| have actually seen the system tested.
|
| Worth noting that this line is now out of date. Allegedly
| they've been tested in Yemen recently [1].
|
| 1. https://www.businessinsider.com/houthi-missile-close-us-
| wars...
| jhartwig wrote:
| I had thought it had been used during the gulf war in a
| friendly fire event.
| Simon_ORourke wrote:
| The Missouri got raked with it from its escort ship - not
| pleasant for anyone concerned I'd say.
|
| http://billgx.com/2019/10/autonomous-friendly-fire/
| jhartwig wrote:
| Yep that's the one
| thebruce87m wrote:
| tldr: the Missouri fired a chaff and the other ships CIWS
| was all "not in my airspace" and started shooting at it
| even though the Missouri was behind the target.
| Interesting, I wonder if the whole battlegroup has synced
| systems now to avoid such things, e.g. 1) I'm going to
| launch something, everyone else disregard it as a threat
| and 2) if a threat has a friendly behind it, don't shoot
| it.
|
| Maybe 2) is more of a judgement call since a few bullet
| holes is probably preferential to the alternative.
| ethbr1 wrote:
| IFF in any capacity on Phalanx seems like a poor match.
|
| At ranges that close... you really want a "deconstruct
| anything in the air" device, not a "consider what you're
| about to hit" device.
|
| Which I'd imagine has been designer pushback on
| complicating it and going that route.
|
| Safety through deciding what mode to set it in; not
| through leaving it alone and forgetting about it.
| thsksbd wrote:
| And the system failed, requiring the last line of defense
| machine guns to engage.
| aoki wrote:
| Phalanx is the US CIWS based on the 20mm Vulcan gun. in
| other words, Phalanx is the "last line of defense machine
| guns" to which you are referring.
|
| You may be thinking of Aegis, the integrated combat control
| system. We don't yet know why the Gravely was unable to
| intercept the missile further out. Could have been human
| error, could have been a sea skimmer getting too close
| before being detected. To date, Aegis has been extremely
| effective against ballistic missiles and old cruise
| missiles. But given enough time an enemy can test your
| potential weak spots.
| whartung wrote:
| It's a radar directed gun. The dome thing is the radar. Once, a
| sailor was on top of one and the radar turned on, and it cooked
| the sailor. That radar has some real power.
|
| The Phalanx motto is "it flies, it dies". It has an autonomous
| function. Turn it on, and it kills anything in its airspace.
| However, that's never turned on. WAY too dangerous, there's
| always a man in the loop.
|
| There's two primary challenges for the Phalanx, also known as
| the CIWS (though this often pronounced "see whiz").
|
| The first is finding the target in the first place, notably a
| sea skimming missile, picking it out of the surface clutter.
| The second is that, once identified, determining that its
| actually destroyed the target in a timely fashion so as to not
| keep pumping bullets into a flying debris field.
|
| The system uses the radar to track both the target and the
| stream of bullets. So, to the radar system, all of the bullets
| are "tracers" to help the system direct the fire into the
| target.
|
| Another issue with the Phalanx is that it's not armored, and
| the possibility of it getting hit by the shrapnel of the
| missile it took out, is not zero. Unlikely, depending on
| trajectories, but not zero. The missile may not explode, but
| it's still a bunch of metal hurtling at several hundred miles
| per hour.
|
| While designed for the naval environment, the machines have
| also been deployed, and used in combat, mounted on trailers to
| be used in forward land positions as point defense against
| missiles, low flying aircraft, and even artillery shells.
|
| The CIWS was recently used to down a Houthi missile in the
| conflict currently happening in the Red Sea.
| chasil wrote:
| Would the Phalanx have stopped a barrage of Neptune missiles,
| which were reported to have sunk the Moskva?
|
| Was the defensive weaponry on the Moskva unable to defend
| against the Neptune, or did the crew make mistakes in
| operating it?
| dilyevsky wrote:
| It should've had a ciws system. Probably older kashtan--m
| (there's a newer panstir-m system). My guess it was either
| inoperable or switched off
| actionfromafar wrote:
| IIRC Moskva was partly broken.
| WalterBright wrote:
| I've wondered many times why a radar-directed machine gun isn't
| used to protect against drone attacks. The drones the
| terrorists used are rather slow moving, so the gun doesn't have
| to be that sophisticated. And it should be relatively cheap.
| icegreentea2 wrote:
| They are to some extent?
|
| One issue of radar-directed machine guns in the context of
| the Red Sea is that machine gun range is limited, so they can
| only provide point defense. This means that a warship can
| only protect itself, and any commercial ships that are -very-
| nearby.
|
| Yes, you could probably figure out a way to rig up a lot of
| these onto smaller ships to escort individual ships/convoys
| through, but hey you go to war with the navy you have.
|
| Unironically, the LCS's might be useful in this role.
|
| More generally, you see stuff like the army's new M-SHORAD
| having missiles (Stinger+Hellfire) and 30mm + 7.62mm guns.
| WalterBright wrote:
| I was thinking of the recent drone attack on a military
| base, where three soldiers were killed.
| icegreentea2 wrote:
| Oh. Yeah, I mean there's nothing preventing such a system
| - land based Phalanx is a thing. We also don't know what
| air defenses were even at the base (maybe they already
| had land based Phalanx...).
|
| Sounds like the base was caught by surprise.
| swagasaurus-rex wrote:
| There was a friendly drone returning to base, so their
| defensive systems were turned off.
| giantrobot wrote:
| There is such a system, it's called C-RAM and is
| basically a Phallanx mounted on a trailer. You can find
| videos of them working at bases in Iraq recently. There's
| also smaller systems in development like M-SHORAD and
| MADIS (Army and Marines respectively if I remember
| right).
|
| Whether stuff like that is deployed to a particular base
| is a question of them being available and the particular
| location being well supplied enough to use them. The
| M-SHORAD and MADIS systems are designed to mount on light
| vehicles so they can be deployed more readily and to
| smaller forward positions.
| wolverine876 wrote:
| Isn't it the same problem - you need complete sensor and
| shooter coverage of the entire perimeter. Bases are
| pretty large - much larger than ships.
|
| Also, as Hamas did, an attacker can try to overwhelm one
| point of defense, which means your sensors, targeting
| computers, and shooters need lots of extra availability
| (extra equipment and soldiers) everywhere.
|
| I don't think you'd want the perimeter of a base covered
| with auto-targeting/firing guns. And also, on what does
| all that metal (bullets) land?
| envalid wrote:
| If a target is moving slow enough it can be difficult to
| track. Similar to how you can defend against radar missiles
| by 'notching' aka flying perpendicular so the relative
| velocity of the target is near zero. Radar typically relies
| on the dopplar shift caused by the target moving to eliminate
| clutter.
| WalterBright wrote:
| The solution then would be to have two radars a distance
| apart, so they can triangulate.
| jcrawfordor wrote:
| Locating the target isn't the problem, you don't need a
| Doppler shift to calculate range by time of flight. The
| problem is detecting the target at all. Radar in these
| sorts of defense environments will pick up an enormous
| number of returns off of the carrying vessel and sea
| surf, which is actually a rather difficult problem for
| radar because it reflects in myriad directions, it moves,
| etc. By far the easiest way to select an "interesting"
| radar return is to use Doppler shift to find something
| that is moving very quickly. That can't be just a wave,
| it has to be a missile.
|
| The problem is that rotary wing drones are very slow
| (compared to missiles) and so they don't present an
| obviously different shift from the background. A lot of
| R&D is going on right now into better ways to select
| slow-moving, low-cross-section objects like drones from
| the background.
|
| This sort of thing is much more difficult for missile
| defense than the more conventional radar application of
| airspace surveillance, because for several reasons
| (including the fact that this makes radar detection hard)
| missiles tend to come at you from close to or below the
| horizon. This means you're getting a huge amount of
| clutter (radar returns from the environment) around them.
| icegreentea2 wrote:
| Not to minimize the challenges, but I think it's worth
| pointing out that a lot of the drones of topical interest
| are -not- quadcopters.
|
| The Houthis (for example) have been using UAVs (Samad and
| Qasef) are prop driven fixed wing drones with total mass
| in the 50kg+ class (and warheads in the ~20kg class).
| They have max speeds of 200+ kph, wingspans in the 2-5m
| range. The Samad has ranges in the 1000km+ range.
| Obviously, they could slow down in terminal stages of
| attack, and I have no idea what their stall speed would
| be like.
|
| These are more akin to the Shahed class drones that
| Russia has been deploying in Ukraine (though still much
| smaller), than the FPV drones we see attacking
| tanks/trenches.
| WalterBright wrote:
| The British used radar guided artillery to knock down
| wave after wave of V1s, which flew at around 400mph.
| Surely we could do better today.
| icegreentea2 wrote:
| Totally. I just guess the US didn't
| procure/deploy/use/turn-on the appropriate systems.
| Plenty of other posts in the comments identifying
| potential modern (and modern-ish) solutions that match
| your parameters.
| robbiep wrote:
| Really? I had heard that sometimes pilots would nudge
| them off course or shoot them down but nothing about
| artillery, I thought radar came along a bit too late to
| use it for targeting with regard to the V1
| actionfromafar wrote:
| I thought so too, but lately I have heard and read
| accounts akin to a lot of what happened in late WW2 with
| regards to radar technology was _highly_ classified and
| much didn 't enter the history books.
|
| Pilots shooting and nudging definitely happened but
| likely other, more advanced stuff happened too. The
| germans had fully automatic radar controlled flak guns.
| lupusreal wrote:
| > _Automatic gunlaying (using, among others, the SCR-584
| radar) and the proximity fuze played an important part in
| Operation Diver, (the British operation to counter the V1
| flying bombs). Both of these had been requested by AA
| Command and arrived in numbers, starting in June 1944,
| just as the guns reached their free-firing positions on
| the south eastern coast of England. Seventeen per cent of
| all flying bombs entering the coastal 'gun belt' were
| destroyed by guns in the first week on the coast. This
| rose to 60 per cent by 23 August and 74 per cent in the
| last week of the month, when on one extraordinary day 82
| per cent were shot down. The rate increased from one V-1
| for every 2,500 shells fired to one for every hundred._
|
| https://en.wikipedia.org/wiki/SCR-584_radar#Operational_u
| se
|
| > _90mm anti-aircraft guns were normally operated in
| groups of four, utilizing the SCR-584 microwave computer
| and being controlled by the M9 Director. The SCR-584 was
| accurate to about 0.06 degrees (1 mil) and also provided
| automatic tracking. Direction and range information was
| sent directly to the M3 Gun Data Computer, and M9
| Director, which directed and laid the guns automatically.
| All the crews had to do was load the guns._
|
| https://en.wikipedia.org/wiki/M9_Gun_Director
| WalterBright wrote:
| I'm talking about a land based system to defend military
| bases from drone attack, not sea borne vessels.
| wolverine876 wrote:
| If they can't see the target, how do they shoot missiles at
| it?
|
| I've wondered the same as the GP: Why not just send a wall
| of metal at the drone from one of these things?
|
| If not that, why not traditional anti-aircraft fire, with
| projectiles that explode in shrapnel clouds?
| ethbr1 wrote:
| > _Why not just send a wall of metal at the drone from
| one of these things? If not that, why not traditional
| anti-aircraft fire, with projectiles that explode in
| shrapnel clouds?_
|
| If this had been the 1950s or early 60s, every advanced
| military on the planet would have been able to do exactly
| that.
|
| However, both aircraft (MiG-19+) and missiles were
| speeding up.
|
| At some speed, it becomes impractical to solve a high-
| speed aircraft or missile problem with a gun. [0]
|
| Consequently, development from the 70s on turned to
| missiles capable of dealing with these threats.
|
| Which left the only remaining systems mostly consequences
| of failure to upgrade (e.g. the German Gepard).
|
| As the saying goes, history doesn't repeat itself, but it
| rhymes...
|
| [0] See: M19 (1945) > M42 (1953) > MIM-46 (1960-63,
| cancelled) > M-163 (1965) > MIM-72 (1967) https://en.m.wi
| kipedia.org/wiki/M19_Multiple_Gun_Motor_Carri...
| https://en.m.wikipedia.org/wiki/M42_Duster
| https://en.m.wikipedia.org/wiki/MIM-46_Mauler
| https://en.m.wikipedia.org/wiki/M163_VADS
| https://en.m.wikipedia.org/wiki/MIM-72_Chaparral
| WalterBright wrote:
| The drones used by terrorists are homemade and slow
| moving.
| ethbr1 wrote:
| But those weren't the primary threat military defense of
| ~1965-2020 was designed against. (Higher then) Lower,
| faster, and/or stealthier were the worries.
|
| And aside from the economically-mobilized war that
| Ukraine is fighting (and Russia is gradually shifting
| to), it's unclear if capability or cost need to be
| optimized. For every conflict economically less than
| that, capability wins.
|
| I expect the FPV quadcopter grenade-on-a-drone solution
| will be looked back on like the Toyota Hilux tactical --
| effective when introduced, but superceded and dominated
| by specialized systems produced by military industry.
| tyingq wrote:
| Maybe hard to sort out small drones from large birds?
| antoniojtorres wrote:
| That space is currently littered with all kinds of new
| projects given the urgency. One that has stuck with me is the
| German Rheinmetall Skynex which works the way you are
| describing. It's like a really high tech flak cannon. There
| are neat videos of it on youtube.
| ranger207 wrote:
| Radar is essentially a searchlight shining up into the night
| sky. If you have a radar-directed machine gun pointing into
| the sky, it's relatively easy to triangulate where the
| emitter is and direct artillery to take it out.
| ianburrell wrote:
| The US has Mk38 canon on lots of ships. The Mod3 added radar.
| Its primary focus is against small boats and could probably
| work against USV that Ukraine has been using against Russia.
| I hope the Navy is working in modifying to work against small
| and medium drones.
|
| The other thing that might help against drones are the
| automated weapons stations hat are on lots of vehicles. I
| think I read about project to add radar and automated
| targeting of drones.
| avar wrote:
| I'd think the primary defense against drones on a naval
| vessel would be that the ship's made of metal, and doesn't
| have squishy humans wandering around (unless it's a carrier).
|
| IOW a very small drone also means a very small payload.
| windexh8er wrote:
| The size of the payload is still a significant problem if
| your enemy is close with many drones. This video [0] shows
| a Russian missile cruiser being sunk by Ukrainian drones
| recently in the Black Sea. The problem these boats have
| with drones is that they are slow all around compared to a
| rather nimble drone which can react to its operations. As
| can be seen in the video multiple drones are used to sink
| the large ship.
|
| Edit: A better article around the situation and
| effectiveness of the drones is at [1].
|
| [0] Video Russian missile cruiser "Ivanovets" destroyed by
| sea drones at January 31/February 1 in Black Sea -
| https://v.redd.it/hevs3v05hyfc1
|
| [1] https://www.theguardian.com/world/2024/feb/01/ukraine-
| sea-dr...
| lazide wrote:
| I think they were referring to aerial drones, which tend
| to have limited capacities for cheap ones.
|
| Those were seaborne (naval) drones carrying about 1000 kg
| of explosives each if I remember correctly.
| foofie wrote:
| > I've wondered many times why a radar-directed machine gun
| isn't used to protect against drone attacks.
|
| You mean something like Germany's Gepard?
|
| https://en.wikipedia.org/wiki/Flakpanzer_Gepard
| saiya-jin wrote:
| Went for Phalanx article immediately too when I saw the link, I
| guess there is just something about that 20mm beast throwing
| massive tungsten slugs at even crazier speeds that no missile
| can compete with (for attracting readers).
|
| These things require super quick reactions, operator is
| optional (and thats why no real usage in combat, USN ends up
| turning it off often in situations where they don't want to
| risk absolutely destructive friendly fire.
|
| Now if everything will be eventually 'ai'-infused, well, fuck.
| Navy apparently doesn't trust automation with their lives much,
| and fancier neural network with unpredictable decision paths
| ain't gonna improve things.
| hef19898 wrote:
| You always want a human in the loop. FDS sometimes drives
| into trucks or disengages randomly. Automated defence systems
| shoot at stuff they consider to be a threat, and that can be
| anything from non-combatants to friendlies. Or just the
| enemy, but the particular attack might be a diversion, hence
| a human might hold the defence back. Also just for stealth,
| radar is a giant beacon leading right to back to you. As is a
| rapid fire 20 mm cannon.
|
| Unless we have General AI, in which case, well, you'd still
| want a human in the loop, just at different level.
| paulmd wrote:
| Phalanx: "is it for me???"
|
| https://www.reddit.com/r/NonCredibleDefense/comments/13kd6m0...
| CafeRacer wrote:
| I wish you could control with arrows or `wasd`. Or if at least it
| showed a message explaining how controls work. Took me a bit to
| figure out controls on a laptop.
| qwertox wrote:
| Did my adblocker block out a game on that page or did we read
| different articles?
| throwanem wrote:
| I believe that was meant for
| https://news.ycombinator.com/item?id=39189285, "Missile
| Game".
| droro wrote:
| I had always wondered whether there was a missile that was spin
| stabilized with minimal control surfaces like this one. They
| mentioned it only had two control fins, but not whether they are
| independent. It seems possible to steer a spinning missile using
| a single actuator if the control pulses are precise enough.
| icegreentea2 wrote:
| From
| https://secwww.jhuapl.edu/techdigest/Content/techdigest/pdf/...
| it seems that the two control fins are driven off a single
| shaft/motor - so they are not independent.
|
| The RAM uses single plane tracking - basically imaging that
| it's only ever steering in pitch. But because it's constantly
| rolling, "pitch" will sweep over both axes and control to zero.
| 13of40 wrote:
| Yeah (and apologies if I get this wrong after 30 years) with
| a rolling airframe, you can have two fins on the same axis
| that "wiggle" back and forth at the same frequency as the
| rotation of the missile. Direction control comes from the
| phase of the movement, so the fins are pushed in the
| direction you want to go when it rotates to that point.
| amenhotep wrote:
| Vikhr also does this, and Starstreak and M1156 both use a
| clutch to transfer force from a freely spinning fin assembly at
| the nose to the rest of the projectile when appropriate,
| achieving guidance without _any_ movable control surfaces!
| Missile designers are very clever.
| lazyeye wrote:
| Just curious....what else have you always wondered about?
| saiya-jin wrote:
| newer versions have 4 fins... better read the actual article,
| pretty good stuff there
| Fatalist_ma wrote:
| BTW That's a pretty common control scheme for Soviet and
| Soviet-derived ATGMs.
| https://thesovietarmourblog.blogspot.com/2021/07/soviet-atgm...
| LispSporks22 wrote:
| I don't think these systems will work against cheap, tiny drones
| or swarms of drones. eg. Russian ships vs Ukrainian boat drones.
| ranger207 wrote:
| Probably not. They were designed to take out multi-ton
| supersonic cruise missiles so they need a larger warhead than
| would be required against drone swarms. Of course, since
| they're so large and capable they certainly could take down _a_
| drone, and then it becomes a question of how large the incoming
| swarm is.
|
| Now, if the incoming swarm is large enough, then either each
| drone carries a tiny amount of explosives, or each drone is
| large and expensive. The US Navy has been building ships to
| protect against mass swarms of incoming cruise missiles since
| about the 60s or so, so if the incoming drones are large enough
| then you could also use larger missiles against them and rely
| on the RAM only for whatever leaks through.
| cgearhart wrote:
| That's what the lasers are for.
| https://www.nationaldefensemagazine.org/articles/2022/10/19/...
| wolverine876 wrote:
| Always important to look critically at the person speaking (I
| mean to imply nothing about them, just sharing what I found):
|
| _It [the blog] grew out of my time as a tour guide on the
| battleship Iowa (BB-61) in Los Angeles, and although I now live
| halfway across the country, Iowa is still one of the mainstays of
| this blog. It also came from my frustration with existing
| sources, which tended to be either way too high-level or too
| technical, with very little to bring an interested general
| audience up to speed. ..._
|
| _I 've been a military geek since I was in grade school,
| although my affections didn't settle on matters naval until after
| I graduated college with a degree in aerospace engineering. ...
| Unfortunately, I didn't like my actual job, and ended up getting
| another job in Oklahoma, doing work on military aircraft._
|
| https://www.navalgazing.net/About
|
| Certainly they should understand how flying machines work. I
| dunno about their history. :)
| lapsed_pacifist wrote:
| bean used to post long and in depth posts into the
| SlateStarCodex Open Threads, then someone helped him set up his
| own site, and here we are. He organizes meetups at Naval
| History sites too.
| wolverine876 wrote:
| > The use of a gun limited effective range to no more than 1500
| yards
|
| Aren't sniper rifles effective at that distance (if they hit)? A
| weapon not constrained to human limits in dynamic movement, heat,
| sound, pressure, size, etc, isn't effective at a much greater
| distance?
| unwind wrote:
| I am no expert but I imagine one important tradeoff is between
| cartridge power (necessary for long range with sufficient
| energy) and cartridge size/mass, these systems have high rates
| of fire (because trying to hit very fast-moving targets) and
| that can't be easy with a giant cartridge.
|
| What happened to "Metal storm"?
| laverya wrote:
| How long does it take for a bullet to reach 1500 yards? Around
| 2 seconds. How confident do you have to be in the movement of
| your target to hit them with a 2 second lead? Very. (Or you can
| follow the CIWS methodology and throw quite a few bullets at
| once)
|
| The effective range isn't limited by the ballistics of the
| weapon (The 20 mm shells it fires will easily go 5+km), it's
| limited by actually hitting the damn thing you're aiming at.
| ranger207 wrote:
| Sniper rifles are firing a single shot, the bullet is smaller,
| and snipers can take significant time to prepare. I've heard of
| snipers firing a few hundred yards away from their target first
| to see exactly how their shot will be affected by drop and wind
| and only then aiming at their target. Sniper rifles have much
| less stress on them imposed by firing the cartridge than a
| Phalanx; a 12.7x99mm cartridge is nothing compared to 20x102mm.
| Finally, a sniper is firing a single carefully aimed shot; a
| Phalanx is firing 75 rounds a second from six rotating barrels.
| wolverine876 wrote:
| How does that reduce effectiveness of a Phalanx against a
| drone? With all that metal flying, the pinpoint accuracy
| problem seems solved.
| icegreentea2 wrote:
| The M61 (the gun the Phalanx is built around) apparently
| has a 80% dispersion of ~5 milliradians (see this amazing
| reddit post complaining about DCS - note that the evidence
| points to a range of values - I think 5 milliradians is a
| fair summary https://old.reddit.com/r/hoggit/comments/eyddn
| 3/m61_and_gau8... ). At 1500m that works out to a 75cm
| radius (I'm pretty sure its radius...) disc.
|
| Assuming your firing at a missile flying right at you, and
| assuming a Cold War era threat (so say a Kh-22 fired from a
| Tu-22M), you're talking about a 92cm diameter target (46cm
| radius) that you're trying to hit.
|
| In reality, things are worse because in addition to
| dispersion, your actual point of aim of your stream of
| bullets will be effected by external factors (like wind).
|
| You can see how in the scenario layed out above, you do
| actually have what seems to be a reasonable chance of
| landing a few hits when you're spewing out hundreds of
| rounds within seconds. But you can also see how quickly the
| odds go to crap as you push the range further and further.
|
| I think that gets to the reality of what the "effective
| range" value is. It is a rule of thumb designed to help
| weapons officers quickly determine how best to react in a
| scenario.
|
| Remember that CIWS was envisioned to be deployed in a
| scenario where USN ships would be subject to saturation
| attacks by supersonic anti-ship missiles from multiple
| bearings and sources. Phalanx itself only has a magazine of
| ~1000 rounds, which is good for maybe only 10s of firing,
| so you really do need to conserve ammo.
| jabl wrote:
| The shell itself flies considerably longer, although 20mm
| shells start to slow down and drop much more quickly than even
| slightly bigger shells like 30mm (see e.g. the Goalkeeper CIWS
| for a similar concept using the same 30mm gun as the A-10
| aircraft).
|
| It's a question of hitting the target with a usefully high
| probability. At longer ranges dispersion is higher, so even if
| the aim is correct there's a chance it won't hit. And think of
| how it works; it shoots out a stream of shells, and tracks the
| target and the shells with radar. But what if the target is
| doing some evasive maneuvers, which AFAIU many anti-ship
| missiles do in their final phases? The shells fly out at about
| 900 m/s, and a subsonic missile flies at maybe 300 m/s. So by
| the time the shells whizz by the missile it has moved a quite
| considerable distance, and while the radar tracking can apply
| the correct amount of lead (with a Kalman filter or similar to
| take into account measurement noise), if the missile is doing
| some unpredictable maneuvers that might not help. With the
| missile closing at 300 m/s, you don't have very many cycles of
| shoot-see-where-the-shell-goes-adjust-aim before the missile
| slams into the ship.
|
| And to make matters worse, there are also supersonic anti-ship
| missiles. Now evasive maneuvers in the high-density air at the
| surface isn't really a concept that works out for Mach 3
| missiles, but, well, the missile compensates by flying as fast
| as the cannon shells.
|
| Hence stuff like this RAM thingy is seen as a better system
| against high-end anti-ship missiles.
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