It's time once again for our regular Open Thread. Talk about whatever you want, so long as it isn't Culture War.
Apologies for getting this up late. This is what happens when I play Aurora.
Overhauls are Classes, Aerial Cruise Missiles, Modern Propulsion Part 1, and for 2022 Norway Part 10 and Victory Ships.
Comments
Did fleets often keep a straight course in battle because they were in too tight a formation to do much else without hitting each other?
It's been suggested here that ships avoided turning in battle, and sometimes even fired easily-dodged torpedoes to make the enemy turn, because early fire control systems couldn't correctly calculate where to aim from a turning ship. However, it seems to me that they'd be even worse at aiming at a turning ship, and hence that this would be a reason to turn more, as turning would hinder your enemy more than you. (At least if the problem is allowing for the ships' velocities. I've seen it suggested that heel/vibration/structural bending can also matter, and those are reasons you don't want to be the one turning.)
This suggests there may have been a different reason (or reasons) for not turning.
Early in its history, the line of battle (i.e. a fleet in single line astern, firing to the side) was typically longer than its effective fighting range. Hence, it was an advantage to have the line as tightly spaced as possible, because when a tighter (and hence shorter) line faced a longer and looser line, all of the shorter line was able to fire, while part of the longer line was out of range. (The explicit statements I've seen of this are from 1794 and c.1906. Both these sources note that this is also a reason to prefer fewer larger ships, because they fit in a shorter line than the same total number of guns on more smaller ships.)
A line that is as tight as possible for going straight, plausibly might be too tight for turning. (Particularly if the flagship was giving the order to turn via actual flags or similarly slow means.) Trying to turn anyway plausibly might mess up the formation enough that they have to stop shooting to avoid friendly fire, or even cause outright collisions.
This would be less of an issue in smaller battles, and later time periods (better fire control = longer effective ranges, and better communication). A fleet that is already short compared to the range appears to have little reason to make itself even shorter, and hence can instead choose to form a looser line that can maneuver aggressively.
However, I don't actually know that, and there could have been other reasons. (Including the simple one that if you're trying to get somewhere, a straight line is the shortest way there. This could be a physical place you're trying to attack or defend, or something like "closer so we can use our short-range weapons" or "away because if we stay in this battle we'll lose".)
This might be related to why intentionally choosing non-broadside angles for their increased armor effectiveness is a thing in games (small virtual fleets), and possibly for cruisers, but mostly not for real battleships.
Are you overlooking the keep-the-guns-pointed-at-the-enemy part of the problem?
If you mean the ship's roll and pitch (i.e. aiming accurately from a ship at sea was hard, until it became possible to automate that part), I don't think of that as much worse when you're intentionally turning than when you're going straight, but that sentence was in part intended as that I might be wrong about that.
(If you mean that turning too far from broadside-on will take some of your guns out of arc, I was probably thinking of that as too obvious to need to be said here. Sorry, I do tend to overdo that.)
I was talking about the even more obvious one. Turn the turret one arcsecond to the right every time the bow moves one arcsecond to the left. Good luck doing that with the information the turret crew has at its finger tips.
@muddywaters
I'm currently working through Rules of the Game, and it at least incidentally bears on this. One of the major reasons for a lack of maneuvering, at least among the British, was probably the limitations of their signalling setup. Their system was very powerful, but also very slow. George Tryon was the leading advocate for a simpler "follow the leader" system, but his death and subsequent personnel assignments killed that off. I doubt it was a safety measure, as fleets were executing more complicated maneuvers fairly safely (with one obvious exception) decades earlier. The important thing there was apparently that all maneuvers were made at a constant speed, which removed a major variable which had previously made close-range maneuvering too dangerous.
Re turning and fire-control solutions, I do think that's the correct answer. At least on the British side, the Dryer system would be completely messed up if either ship turned. Pollen's would handle things better, but it didn't see wide service and there were some technical limitations there. I suspect that it may also have been easier to do updates if the other ship maneuvered and you didn't, given that you have a stable baseline to work from in a way you wouldn't if you turned as well. Even during WWII, I believe only the USN could truly maneuver and just not care about the effects on its fire-control solutions. "But it will hinder the enemy more than us" isn't really how someone raised on a diet of scored practice firings is likely to think about tactics.
@bean
Speaking of reading, can you make an amazon-wishlist for us, so we can buy you books?
Isn't it possible that they didn't develop turning FC tools/techniques because there wasn't a real need for them? The idea being that it was vastly more valuable in combat to maintain a fast, cohesive formation.
Considering battleships had enough firepower to inflict crippling damage to each other in a few salvos (at the right range), actual time under dangerous fire wouldn't be that long, so there would be little time for fancy sailing tricks to dodge shots. But maneuvering would bleed speed and formation integrity, so the fleet would become less able to bring max firepower to bear at the right time (crossing the enemy T etc).
Thinking here mostly about the big North Sea battles in WW1, but maybe valid later too. Does this make sense?
@ike: battleship guns do have sights (often visible on the side or top of the turret, though remote sights (directors) were the primary method after c.1915). However, the aiming controls could be awkward.
As noted above, I think of the aiming part as hard but not much different whether you're intentionally turning or not. However, it's possible that this is where I'm wrong: I've heard that one British director would skip steps at high train rates, and it would explain why the 1940s USN (with RPC) didn't have a problem while others still did.
It should be possible to distinguish those: do we know whether it was "keep straight" or "keep the enemy on the same relative bearing"? Those are different things if you're on non-parallel courses, even if the enemy doesn't turn.
@bean: the version I've seen (from Dreadnought Gunnery, which does hint that it might not be generally accepted) is that both the Pollen and the Dreyer started off unable to handle turns, and both gained that ability at around the same time, possibly going through a phase where they could do it in theory but not in practice. (Operators who are (reasonably) afraid for their lives aren't likely to be at their best.)
That's basically what I'm suggesting.
It never even occurred to me that ships in the "put rams on everything" era were fighting at ranges closer to those of the age of sail than Jutland. That helps explain that one disaster.
@bean how's the new Aurora version? DLed, didn't open yet. I hear you can give dark eldar swirlies for dressing like a hot topic catalog now, so automatic GOTY.
Sort of. AIUI, the "put rams on everything" era ran right up until the start of the Dreadnought era. And while long-range heavy gun were too slow-firing to be effective sole primary armaments for most of that period, the 6" quick-firing guns of the pre-dreadnought era had a theoretical effective range of several miles. The big limiting factors were gunnery and fire control, which were limited partially for technological reasons and partly because of doctrine.
And doctrine bring us back to your comment: a lot of the doctrine up until the latter part of the Pre-Dreadnought era still assumed that major fleet engagements would be decided at close range, even though in hindsight we see that with good gunnery battles could have been fought and won at significantly longer ranges (not nearly Jutland ranges, but at least a couple thousand yards). As our esteemed host has discussed in the context of ship design, there was rather an extreme lack of major combat experience to inform warship design during the Ironclad and Pre-Dreadnought eras: up until the Spanish-American War and the Russo-Japanese War, the main significant major combat between iron warships apart from the American Civil War was the Battle of Lissa (1866). Both Lissa and the ACW were right at the beginning of the Ironclad era, before longer-ranged guns were available, and both were largely fought in littoral waters which forced closer ranges independently of gunnery. Ramming was used effectively in some ACW naval engagements and was decisive at Lissa, which naval designers and doctrine theorists overgeneralized for far too long for want of other real-world data.
@ike
That's a really good idea. I will try to get to that this weekend.
@AlexT (first)
I think it was mostly technical limitations. We live in a world of cheap, accurate gyros. They very much did not.
As for not needing firepower for very long, that is not the case. Battleships proved themselves to be very durable things, so long as they weren't British battlecruisers. (Hood was unlucky, the others stupid.)
@muddywaters
It has been more years than I like to think about since I read deeply on that stuff. Pollen seems like it should be able to handle both types of turns about equally well, while I would expect Dryer to be more disrupted by an ownship turn. But that's based on high-level reasoning, not experience.
@Bernd
Battle ranges grew significantly starting in around 1890. I should probably quantify that at some point.
As for Aurora, 2.2 isn't out yet, I just got back into 2.1.
Actually, it looks like 2.2 is going to have some major changes to missile combat. This could get very interesting.
Pursuing this tangent, has a battleship ever been hit by more than say a dozen heavy caliber rounds (similar to its main battery) without taking serious damage? I.e. not necessarily sunk, but with significantly reduced combat power and structural damage.
Like, Warspite at Jutland was combat-ineffective from some 15 hits, and on the other side Konig was lucky to escape after a dozen or so, ish? And while Hood at Denmark Strait was bad luck, what happened wasn't inconceivable. And then in her final battle, Bismarck's main battery was effectively disabled in the first 15 minutes. The pattern I'm seing is that BBs were extremely survivable, except against each other.
@AlexT: most sunk battleships were sunk by something other than shells, but it's plausible that shells were better at disabling ships than at actually sinking them. You previously mentioned an estimate of 10 hits.
(Note that those 10 hits would often be from many more shots: ~5% hits seems to have been roughly typical.)
@AlexT, "extremely survivable except against each other" is pretty much why you build battleships in the first place. From the age of sail on the idea of a battleship is that if one shows up, everything smaller has to run away. If you can't send your own battleship in response, you lose control over that patch of sea.
If you haven't already seen it, YouTube Drachinifel has a nice video "The Architecture of Dreadnoughts" and others which include discussion of the necessary trade-offs. Build your battleship so well armoured that it is largely invulnerable to all enemies? It will be either (or both) so slow that it takes too long to get where it is needed, or so undergunned that it can't damage an enemy battleship of similar size.
As for examples of surviving, the British battlecruiser Tiger took a lot of heavy hits at Jutland but didn't lose any main guns or speed. While Warspite wasn't in great shape by the end of Jutland, she kept shooting her main guns throughout, quite effectively.
What is the advantage of having very large AWACS planes instead of a bunch of smaller ones (Drones!!) that offer much less of a juicy target?
Bigger radars are significantly better than small ones, so you can't easily replace it with a bunch of smaller platforms.
OTOH more radars could give you multi-static capability.
@Fxbdm, @Anonymous the laws of physics say that the more power you send out, the further away you can detect things. The bigger your antenna, the further away you can detect things. (The radar range equation for energy transmitted vs energy received, even for non-stealthy targets, is brutal.)
A big AWACS plane can cover say a 200km radius circle. (Yeah it's in 3 dimensions, but the altitude range for aircraft is very limited compared to distances.) If your drones have say 20km radius radar range due to being small, you need 100 to cover the same area.
And the big plane can stay in the air for hours. Drones can't , so you need another 100 to take their places after a while.
@Anonymous, by multi-static do you mean multi-spectrum radar? Or passive radar? If so, the big plane with a big modern antenna can still detect multiple frequencies at much longer ranges.
There are three main considerations.
1) Power and antenna gain.
To have a decent range, particularly in a context where adversaries are trying to jam it, radars both need to put out quite a lot of power, and need highly directional ("high-gain") antennas. Assuming no gross errors are made, the latter is a straightforward question of the antenna's size (actually as a multiple of the wavelength used).
2) The information gained being of moderate usefulness.
The ideal effect would be to have the radar drones fly immediately next to each other, dish-tip to dish-tip. That improves the antenna gain in the obvious way. If they fly farther apart (even wingtip to wingtip, but the wingspan is larger than the dish) then even in the theoretical best case of signal processing (problem 3.) what you get from a "sparse array" is mostly an interference pattern. You go from "the enemy is on a number between 25 and 35" to "they are on an even number between 26 and 34".
3) The physical infrastructure of the signal processing.
The precision requirements on everything are ridiculous if you are trying to treat it as a single dish. As in, millimeter errors in positioning and nanosecond errors in synchronizing turn into ~1° angular errors. Which is not a problem for a solid structure, but is simply not how aircraft fly.
There are two practical use cases that I know of for radar drones.
- Near-range radar "escort" for a stealthy aircraft. Have your radar picture and eat it too, as in, not eat an ARM.
- Medium-range passive (non-emitting) RDF. A modern adaptation of artillery observation balloons looking for muzzle flashes and triangulating.
I'm disappointed the "very large drone array" won't be a thing. Thought that was a clever idea.
And once more this community comes through with flying colours. I knew I could count on you guys explaining it clearly. Cheers!
Hugh Fisher:
Global Hawks are very much capable of staying in the air for hours.
Hugh Fisher:
No, multi-static means something else in radars.
The idea would be to have the transmitter and receiver on different aircraft which could be widely separated so as to still be able to pick up signals reflected at a different angle than straight back.
@Anonymous a Global Hawk isn't that much smaller than a Hawkeye, and in fact has a significantly larger wingspan. I think that's more a point in favour of the 'one large AEW aircraft' plan rather than the 'more smaller drones' option, even if the RQ-4 is actually unmanned. Smaller AEW drones might still have their place though, as most navies have nothing that can get an E-2 into the air, and even the USN won't always have a carrier nearby.
One thing I like to think about is whether fire control had to happen when it did, or whether there are fun-to-imagine ways it could have gone differently.
Available precision of manufacturing probably mattered, as is common in the history of technology generally. Precisely made cams etc, as analog computing accumulates error. Rifled guns (known since c.1500, but then impractical), because fire control can only be as good as the weapon's intrinsic precision. For central control systems and particularly directors, having the sights and mount axes aligned to give a tight pattern. (This one was noticed at the time: Fiske invented an electrical-transmission director in 1890, but didn't try to get it adopted because of the alignment issue. Percy Scott, in adopting centralized spotting in 1904, first had to deal with inaccurate sights.)
I don't know how much of the proto-networking that went into central fire control was invented within the military and how much was pre-existing technology.
Dreadnought Gunnery does mention gyro error as a limiting factor, and you've previously suggested that the Dreyer was initially better because plotting range vs time works without a gyro. (The range axis probably needs a plot and rate fit more than the bearing axis does, because optical rangefinders and spotting are noisier than sights. Hence, it's more accurate (if neither ship turns) to average down that noise over some time rather than just using the current rangefinder reading + expected motion during the time of flight. Which raises the possibility that the 1940s USN's special ingredient might be radar??)
Using a gyro to automatically fire when the ship's roll crosses the target was initially rejected, presumably because it was then worse than doing it manually, but became standard around 1917.
Alexander:
It appears to have a bit more than half the mass.
Though the Reaper is significantly smaller and manages to stay airborne for more than a half a day, the even smaller Predator can do that too but with much less load and at lower altitude.
Alexander:
Not needing to fit on a carrier does have its advantages.
Alexander:
The AW101 can do the job for anything big enough to operate it.
The bigger problem with a Global Hawk/Reaper based AWACS is that it isn't organic to the carrier, and anything which isn't organic can't really be counted on. You can't send one up quickly if you get warning of an incoming raid. It's either there or it isn't.
As for the AW101, it's good, but it has neither the payload nor the endurance of the E-2.
It does seem to me that there might be some utility in having AW101s, or something like them, distributed around on amphibs and maybe even surface combatants.
bean:
Neither is an E-3 yet the US has a lot of them (for the moment anyway).
bean:
Then use the Stingray (related engine to the Global Hawk so should have similar payload capability).
Jade Nekotenshi:
The average surface combatant probably can't handle it along with the other helicopters it needs, though with Trimarans it might make some sense.
Though the flattops the crayon eaters get really should have a few.
Yes, we have E-3s, but there's a reason we also have the E-2. One is for operation from land bases, the other from carriers.
I don't think the MQ-25 is big enough to make a good AWACS platform.
As often as not right now, Ticos and Burkes deploy with one helo despite having two hangars. I'd think at least one or two could ship out with both a 60R and an AEW helo, though there is the slight problem of the US not currently having an AEW helo in service.
I don't think this is a huge issue right now, but could be if fighting a near-peer: suppose the carrier temporarily loses the ability to launch its Hawkeyes due to a catapult casualty, damage to the flight deck, lack of parts or something like that - or maybe even due to the Hawkeyes in the air having to divert to a land base due to the carrier coming under attack. It seems to me that having some kind of over-the-horizon air search and direction would be better than none. Though I suppose if F-35B can do some of this, then at least LHDs can contribute to that mission somewhat.
But an enemy ought to be able to detect when a CSG doesn't have AWACS up, and that would certainly be one of the better times to attack, if someone were going to.
The AW101 is also used as an ASW and cargo helicopter, but I don't know if the same individual helicopter can do both. (The AEW system is referred to as a pod, but I don't know if it's actually removable, and it's probably more weight and drag than you want when not using it.) It's also physically larger than the MH-60R, so might not fit even as the ship's only helicopter.
Why do Tico's and Burk's deploy with only one helicopter? Seems odd to me.
bean:
Big enough to be an inflight refueling tanker.
Jade Nekotenshi:
Modern fighter radars are good enough to function as mini-AWACS in a pinch.
Jade Nekotenshi:
Probably better to spend the money preventing that from happening and in the event it does use fighter radar.
The use case would be to give the crayon eaters AEW capability when their flattops are operating alone.
muddywaters:
I'd be surprised, at the very least the AEW and ASW versions need crew inside the cabin to operate the equipment so don't expect much cargo capacity to be left (though the AEW system might be able to pick up a surfaced sub).
muddywaters:
LCS-2 is about the only US surface warship I'd have confidence of being able to fit it.
Re alternate AEW options - a V-22 with a phased array like that on the wedgetail seems like it would achieve a lot of capability without requiring a full CATOBAR setup, while avoiding the issues of a true helicopter mounted system around range, endurance, and altitude.
(You would need some engineering for hangar clearance as well as the additional interference from the antenna, both aerodynamic and signals wise, but those seem surmountable for a sufficient budget)
Drones seem like the value is coming up with new concepts for them - if you try to replace an E-2 or E-3 with a UAV, you likely end up with something that's basically similar. But persistent cheap drones seem like they invite different use cases that augment traditional platform - instead of having a single platform providing overhead coverage of a battlegroup, you deploy a few of them far out to be basically aerial mines or whatever.
Not that it's a perfect comparison, but I think you also see this with unmanned surface / subsurface vessels - we're not going to replace DDGs or SSNs with UUVs, because by the time you have equivalent performance in terms of speed and sensors and so on, you have a 10k ton platform that you might as well make manned (or at least is comparable to manned platforms in terms of size, cost, and so on). There are no free lunches.
But for persistent slow speed surveillance or low intensity operations where quantity/presence is more important than quality, they're a better fit. (Or if you have a disposable platform, but naval warfare seems less amenable to that than ground warfare for various reasons)
Also, re the AW101 and the DDG - it was designed as a Sea King replacement, and the RN uses them on their various surface combatants. If you poke around enough in the Navy documentation you can find landing envelopes for the H-3 on DDGs and CGs, though interestingly the H-3 had a wider envelope on the FFGs, not sure what drove that.
Yeah, Sea Kings can certainly /land/ on a DDG, but I don't think they can fit in the hangar. The CGs have a bigger, or at least taller, hangar, so they might fit there, and I think there were still Sea Kings in the fleet when the CG-47 class was built.
My thought on the helo-based AEW is in addition to Hawkeye, though, not instead of. Also, as something to provide an eye in the sky for a surface combatant operating alone or as a SAG, with no flattop in sight.
I think it is useful to distinguish between AWACS the aircraft type and AWACS the role. I don't see small drones (or helicopters) replacing the AWACS aircraft type, but they can do the role.
The big AWACS aircraft need to be that size for the antenna and power supply. (And multistatic doesn't help: if you want to detect the reflection of someone else's radar signal at range, you still need a big antenna.) The long radar range means that such aircraft can be not fast, not agile, not stealthy, not covered in defensive gun turrets and countermeasures. A dedicated AWACS aircraft is meant to stay well away from the actual fighting. In the future we may have drone AWACS replacements, but as noted above they still won't be small and cheap.
If you don't have the really big antenna, your radar detection range comes down and you have to worry about being shot at. It seems to me that this is where AWACS becomes a role that a general purpose combat aircraft can perform, rather than having a dedicated aircraft type. The aircraft with the best radar, or in the best position, concentrates on keeping situational awareness for everyone else up to date. I believe the Iranians often used their F-14s for this in the 1980s, and today it's likely to be the F-35 in a mixed force. In the future I can imagine an R2-D2 style conversation within a drone squadron about who goes active on their radar and datalink transmitter while the others stay passive.
Re airborne radar, how expensive/complicated would a radar-illuminator drone have to be? The concept being to launch it in the general direction of (suspected) enemy forces, and after travelling a set time it starts turning and emitting. Friendlies stay back and pick up reflections. Hopefully the enemy shoots it down with something 10x more expensive. Essentially, a cheap expendable way to increase (quadruple?) the range of a radar of a given size, and keep the precious receiver with all the cool electronics and people passive and far away.
The other design that it suggests is the ultra-stealthy-long-range-pop-gun-intecptor for anti-AWACS duty.
@AlexT I feel the power requirements for the illuminator would drive up the size & cost too much.
Basil and Hugh have made the important point, about requiring a big antenna to detect a radar reflection at range. To state it a bit more formally: to have the same radar detection range as a single big AWACS, a group of smaller radar aircraft needs to have the same total antenna area and transmission power.
Using multiple smaller radars has a few advantages, though. It has better resolution, so you can tell the bearing to your target more precisely, making it easier for you to determine the number of aircraft in a close formation, or to spot targets in your Doppler notch by tracking their lateral movement. And a lot of stealth design is about ensuring radar reflections don't go straight back to the transmitter, so if the receiver and transmitter are separated (e.g. there are several of each), stealth is less effective.
@Basil, the above means that I agree with your first counterargument to the viability of a group of smaller radars, but I disagree with your remaining two points. Contra your second point: the information from a sparse array can be difficult to interpret, but the ambiguity goes away rapidly as you add extra aircraft to the array. To illustrate this by extending your example: you start with "the enemy is on a number between 25 and 35"; with two aircraft you have "the enemy is on an even number between 26 and 34"; and with three aircraft you have "the enemy is on a number between 25 and 35 that is a multiple of 2, 3 and 5" ... which pins it down precisely.
@Basil, contra your third point, the precision requirements don't seem unreasonable to me. You don't need to keep your aircraft in perfect formation to millimetre-level precision: you just need to keep track of how much they deviate from that formation. Similar problems have already been solved, with suitable calibration: VLBI arrays maintain coherence to about the same precision when one element is halfway to the moon; adaptive optics maintains coherence only across a ~10m telescope mirror, but to sub-micron precision.
The real killer, I think, is the signal-processing requirements. The required processing has components that scale linearly with the number of elements, quadratically with the number of elements, linearly with the number of elements you could fit in the gaps in your sparse array, and quadratically and possibly cubically with this last number. If you have, say, 1m antennas flying in a formation 1km across, that's a billion-fold increase in the amount of computing you need to do.
@AlexT Not at all, but such a "radar starshell" would be mostly useless, because in military radar, basically the emission side is difficult and you get the reception side almost for free.
If you were trying to detect civilian aircraft (or WW2 bombers), the idea would make complete sense, because ...you have gain on both sides. You can use a good telescope and a wimpy light source just as well as the reverse.
The problem is that the enemy can (and does) put jammers onto potentially every aircraft. Now whatever you use for illumination has to put more power onto a/the target aircraft than its jammer can produce, otherwise you'll be seeing the jammer, not the actual echo. (If your reception side is good you'll be seeing the jammer very clearly, but that's not exactly useful for most purposes.) And it turns out that generally it's more practical to increase power density by using a larger antenna to concentrate the emitted power into a narrower beam than it is to emit more power.
Given that, the least unviable idea is to put an EMP warhead on a missile. For the next step up, producing several seconds of illumination, most of the payload mass goes into a rocket-turbine-alternator. The electronics are open-cycle cooled i.e. are boiling off a bath of water. For this to not have terrible range, the initial idea I have is to go for a "wide strake" aerodynamic surface (<1 aspect ratio wing), put the fixed antenna array into the bottom surface, and have the program be: roll 90°, emit while pitching "up", thus sweeping the fan-shaped beam.
What are the challenges involved in powering a phased-array radar? Could you run a jet engine with a big honking alternator for power and regeneratively cool the electronics with JP-5? Since you're not lugging around delicate meatbags and their life-support systems, a UAV could devote a higher mass fraction to heavy-duty cables and antennas.
The phase-shifters are expensive (one for each row/column, whichever there are more of).
Separately, what airframe-relative plane is the antenna in?
Other than that, more or less yes. Alternator->rectifier->pulse forming network->emitter->antenna. (And I expect more cooling is needed.)
Lambert:
Like the Nimrod AEW.3?
No, that's a bad idea.
Basil Marte More power isn't the only solution to jamming these days. When I did a (non-classified) introduction to radar short course a couple of years ago, that was one of the key points the instructor wanted us to take away. Modern electronics and phased arrays do tricksy things with the outgoing signal so you can extract the reflection even from massive amounts of jamming noise.
(This does however make multistatic radar harder, because you need precise knowledge about the outgoing signal which is obviously a heck of a lot easier when you sent it.)
In some ways though this is just moving the power requirement from the transmitter to the ultra high speed parallel processing chips in the receiver. The same course instructor described a typical phased array radar as a massive air conditioner with an antenna attached.
Re the various 'radar starshell' options - one option seems to be decoupling the emitter from the receiver. This is obviously disadvantageous in some (many?) ways, but it also seems like it creates a few benefits: 1. Emitter is not co-located with receiver/processing equipment (making HARM missiles less HARMful) 2. Multiple emitters can be used by one reciever 3. Emitters may (or may not!) be closer to the targets, which provides a significant benefit in terms of power delivered to the target and breaks the 1/x^4 rule of generalized radars into (1/(emitter distance)^2 * 1/(receiver distance)^2)
The emitter drone would not have the power and processing problems required for a full phased array, as you could use traditional beam forming equipment and steer the azimuth by pointing the antenna and/or platform so that the reflections would hit the receiver platform.
The signal coordination between the receiver and transmitter would be non-trivial, but I think you could probably find some way to bounce it off a satellite or use a low-power direct radio link (or even encode position and timing data in the radar pulses somehow).
Also, on the jamming front - even a relatively unsophisticated antenna system should be able to provide the bearing of the jammer, right?
"Signal coordination between the receiver and transmitter"
In general, basically this is the reason for putting the emitter and receiver into the same vehicle -- so that you can coordinate the physical location by "this is the same vehicle, what do you mean" and coordinate the information by a cable, which is not subject to the enemy reading from and writing to it.
If you use a separate channel (satellite or direct radio), I'll bring a centralized jammer. (It might eat an ARM.)
If you use in-band signaling, I have some analysis to do and may have to upgrade the jammer module in every aircraft I have, but now they can spoof this signal until burnthrough. (And if you have the ability to keep K out of N operating modes secret before the war breaks out, you have K-ish time-windows in which you can fly strikes with this system free of spoofing until I can analyse this opmode.)
Which context is why the above discussion mostly assumed the "old-fashioned" situation where the emitted signal carries negligible information to be monkeyed around with by either party. Thus we can assume that any target aircraft can carry a jammer module that "knows" the signal, and the emitter has to burn through with power density. Which implies a mixture of antenna gain (and hence antenna size) and peak power that either ends up expensive enough that we might as well make it a "normal" monostatic radar and gain all the capabilities offered by monkeying with the signal, or which implies an extremely short operating time.
Jammers: yes, but they only need to emit when your system "targets" them (for individual jammer module) or any friendly in the vicinity (for central jammer).
But how much of the cost and sensitivity is a function of receiving and signal processing, and how much is signal generation and emission?
Like, if you just have a large but only moderately sophisticated signal generator feeding a single antenna at fairly low PRF but high Peak Power, how much does that actually cost compared to a full phased array set-up? Also, being able to fly the drone closer to danger helps ameliorate some of the power and gain problems (i.e. the E-2D has a quoted radar range of 345 miles, so if you can fly the drone 50 miles in front, you only need 70% of the power for an equivalent return strength, and 100 miles out it's down to 50%) I'm not sure how much the potential for off-axis transmission/reception factor would increase/decrease effectiveness, probably depends on the target.
Gain is obviously a function of antenna size, but at radar wavelengths a single antenna element would be relatively small, either for a parabolic antenna or some sort of stacked dipole.
Adding reception capability obviously makes it more useful in some ways, but then you rapidly end up going back to a fully capable E-2/E-3 equivalent.
Can't tell about cost, but you lose most functionality.
If you have a parabola (or an electrically fixed dipole array), then basically you can scan or closely track one-ish contact, but not both, simply because you can't illuminate in different directions. The main point for literal phased-array radars is that they can change "which way the dish points" at the speed of electricity, thus they can allocate their pulses in basically arbitrary ways; pinging multiple widely-separated tracked contacts (some more often than others) while still searching, which need not be a simple sweep.
Unrelated to literal phased-array tech, modern radars also e.g. modulate the transmission with the output of a random number generator, which allows the receiver to do a huge amount of pulse compression if and only if the receiver knows the random numbers. This is straightforwardly equivalent to increased power (e.g. if the pulse is 50 bits long, that's exactly as good as 50 times as much power, as long as the target doesn't know the 50-bit modulation code for the next pulse before the pulse hits it, and thus cannot get its jammer-emission-power to also be stacked up 50-fold by the receiver doing a convolution on the signal with the code).
Higher-end stuff can also connect multiple emitters, working on slightly different frequencies, pointing into different directions, to a shared antenna array.
By "antenna size", I don't mean the size of an individual antenna element. (That's basically not subject to discussion; the operating frequency sets that.) By antenna size, I mean the size of the parabola dish, or the number of dipoles packed next to each other, or the size of any other device you are using to focus the energy (RF lenses do exist, but are rarely used).
Sure, but the whole point of what’s essentially a remote transmit only drone would be that you’re illuminating those parts of the sky where the opponent is coming from, and offloading the HARM risk to a relatively low cost platform. The receiver would still be a full featured phased array on an E-2 type platform.
Also, while physical antennas can’t match the speed or performance of a phased array antenna, for long distance work it doesn’t seem like pointing would be prohibitive.
Understood, but I believe airborne radars are 10cm or less wavelength, often closer to 1cm, so even many wavelength antennas are comparatively small. Power dissipation is probably an issue, but workable.
@Basil Marte
The radar starshell drone would not be expected to generate and maintain targeting-quality tracks, just to briefly (and cheaply) reveal what's in an area. Then, more capable/expensive assets would be required to actually engage whatever the starshell illuminated. But to go from zero knowledge to a workable picture of contested airspace risking only an unmanned platform that costs $100K, sounds like a good deal (in a real war).
As long as it can plausibly be done with a $100K drone, that is, which is what I'm asking.
Yes, there are some proposed solutions upthread. Basically a missile with either an EMP warhead, or with a setup to sweep a beam across the area once, in a few seconds. The problem is that these solutions don't come out looking like what the word "drone" and the other things said about e.g. ARMs imply.
$100k (or any other budget where it's reasonably expendable and we won't care if it eats an ARM) puts a size (/performance) limit on the overall size of the thing. It will never be able to independently cruise above the speed of sound, accompanying a strike as a separate vehicle, not even with zero payload. It won't have a propulsion-fuel tank large enough. Hence "missile", carried on a hardpoint for most of the way (and definitely expendable). What else does the airframe size limit imply? 1) "radar fuel" tank size (i.e. total emittable energy aboard), 2) antenna size. Oops. Small antenna = bad gain = for the same power density maximum, we need more power (since the rest is spilled into places we have already looked at, or will look at later, or are unlikely to contain hostile aircraft) -> well, energy/power=time, we'll run through that carried store of energy in a very short time. It turns out, the ARMs never mattered, the starshell won't emit long enough for an ARM to make its way to it.