SwingKid

Ok, now that you've repeated this a couple of times, I would like to know your sources of info about AIM-120C. AFAIK, any software updates to the C can also theoretically be be programmed into the B - that was the whole point of the reprogrammable B, to prevent needing new hardware when new software came along. The C is only supposed to introduce clipped fins, but I can understand how this would require the flight control software to be reprogrammed with teh new lift coefficients of the reshaped control surfaces. That would be specific to the "C", and the new coefficients would certainly give the C "improved" performance over a C that was programmed with original B coefficients, but I don't know if I would call this a guidance section "upgrade" in capability over the B. The C-1, 2, .. 6 AFAIK are intended to introduce non-essentials like an improved fuze, and a new motor section that is designed to burn from both directions if accidentally ignited on board a ship, etc. Maybe some "patches" were made to the software along with these packages to fix some small bugs, but I don't remember reading about any major changes that would make the B in need of replacement. It's pretty easy to see whether the B is still in use with US forces, simply by looking for clipped or unclipped fins. If you wish to test this hypothesis, I would propose to conduct look-up attacks against a chaffing target with both missiles. This is the only way to remove the ground clutter, which plays a major role in Lock On, from the equation. AFAIK, you cannot get rid of ground clutter by range gating when using MPRF pulse-Doppler. MPRF and HPRF require integration of thousands of pulses in order to perform frequency filtering, and that will inevitably cause inter-mixing of reflections from distant and near reflectors, that can only be separated by frequency. I.e. if the target has a large enough RCS, the AIM-120 can see it at practically infinite range - like a heat-seeker locked onto the sun, that is billions of miles away. The ground clutter has the RCS of a planet and can only be filtered out by frequency, at virtually any look-down slant angle. Resistance to chaff is based entirely on Doppler shift, and resistance to ECM is based almost entirely on a monopulse antenna. As long as you have enough processing power and software to permit using these two ECCMs, then I don't see where programming can make any further significant contribution. The best I can imagine is to fix bugs to ensure basic functionality - although I wouldn't put it past a missile maker to name such bug-fixes, "improvements for better performance." ;) Generally, no. An aircraft reflects a smaller fraction of your radar energy the farther away it is. So, it has a constant RCS, and the reflected signal follows 1/R^4 rule. The ground's RCS actually increases the farther away you are, because it's larger than your radar beam - and so you simply illuminate a larger chunk of it the farther away you are, because your radar beam has spread wider at that distance. So, it doesn't obey the same R^4 rule and can be a serious problem at any range. ...AFAIK. -SK

I recently had a research paper accepted. Today I found a mistake in it. ;) -SK

This was not what was paid for. To qualify as a success, it needed to out-range R-27ER. They were? What was deficient in AIM-120C-5 software, and why is AIM-120B still being used then under the same name? I thought these changes were mostly to the fuze and rocket motor fire safety, allowing its safer storage aboard aircraft carriers. The whole "B->C" nomenclature change was over fin dimensions. It appears to be because in these tests, the AIM-120s are having targets illuminated look-down, while the AIM-7M targets are being illuminated look-up. Give the AIM-7M the same ground clutter problem, or shoot at higher-altitude targets with the AIM-120, and the AIM-120 should beat the AIM-7. With AIM-7 using loft, and AIM-120 not using loft? Odd, but ok, I didn't realize that. The loft trajectory is extremely dependent on knowing target range. The air up there is so thin the missile is flying ballistically and is unable to maneuver or generate lift until it descends back down to thicker air, by which time it already needs to be pointing at the target. So, I don't think we should separate the two. If "guidance" only means "terminal PN homing trajectory" - well that part was already working many decades ago. What does it do, pull lead better? How does it resolve a look-down target against the background of the earth, if not by pulse-Doppler that requires a Doppler shift? I don't think guidance computers are yet so advanced that they can change the laws of physics to own advantage. -SK

Have you read "Clashes"? -SK

This is entering the realm of things I'm probably not supposed to know about, but basically, "AFAIK" - the "loft" mode was basically not working on the early AIM-120A, making it almost a dud missile as a result, with a reduced range compared to AIM-7M. They tried to add a loft flight profile but it kept undershooting its targets. The trouble is that the AIM-120 is a dynamically unstable missile, allowing it to have lighter weight, smaller control surfaces, smaller power requirements and thus contain more fuel etc. instead of batteries and control surface actuators, but a dynamically unstable airframe requires a flight computer and advanced software to fly. The AIM-120B didn't introduce a new computer so much as it introduced re-programmability. The predicted, simulated flight trajectories were simply not matching what was happening in the tests, so the flight trajectory had to be constantly re-programmed and tailored bit-by-bit as a result of experimentation. The R-77, also a dynamically unstable missile, also required a reprogrammable computer. The new computer of the AIM-120B finally allowed the loft flight profile to be ironed out, and it started appearing in AMRAAM manuals somewhere in the late 90s. This finally gave the AMRAAM range performance that could compete, and even beat, the AIM-7M. The Lock On AIM-120 (and the Jane's F/A-18 AIM-120) was initially designed based on unclassified data from the earlier, loftless AIM-120A, and for this reason it had initially a shorter range than AIM-7 in these sims. So maybe this is splitting hairs, but I think all the new hardware and software has only just managed to let the AIM-120 "catch up" to (and ok, now finally surpass) the much better-matured technology that was already available in AIM-7M, that was able to optimize its own flight profile without such advanced equipment, simply by virtue of being dynamically stable. So, "yes and no" - those advanced computers and software make the AIM-120 a better missile, but they alone wouldn't help the AIM-7M at all. The main motivation for those advances was to compensate AIM-120-specific deficiencies, rather than to further advance a superior design. End "speculation." ;) -SK

IMHO the trouble is not with locking onto the Harpoon, but rather with not locking onto the launching aircraft that is also 3 nm away, flying at a similar speed and inbound direction, presents an even more appealing target, and may be using ECM. None of that co-bearing distraction exists when dealing with standoff ASMs, so parameters like minimum range resolution or bearing separation for detection don't affect the engagement. -SK

Try launching a Harpoon against the naval systems from 3 nm away. It won't get locked fast enough. Therein lies the difference. -SK

Whoa, missed this comment. Why by my logic? AIM-7M uses a monopulse seeker, AIM-7F conical scan. I would would say that IS huge. It also has command inertial, boost-sustain motor and other improvements that have little to do with processor speed. Take all those away, but let it keep the computer, and IMHO you have little difference from AIM-7F at all. -SK

Where does it say it can detect Mavericks along ECM bearings? -SK

Yes, in my opinion it should be removed or limited to small depression angles/short ranges, just like MiG-25PD that uses a similar radar. But, my opinion is just that. -SK

Like, not being LD/SD, for example? ;) LD/SD = coherent = pulse-Doppler The MiG-23MLD radar only has MTI envelope-detection technology. This allows it to occassionally see a very strong target against very weak background clutter, but there's no frequency filtering as in LD/SD. The word "improved" can be applied as debonnairely to a 1% improvement as to a 1000% improvement. -SK

Maybe this is the path to a solution - it should be possible to beam the SARH missile if EITHER the illuminating fighter radar is in a look-down situation, OR the missile itself is in a look down situation. And, a "look-up" situation where chaff is being employed by the target effectively counts as a "look-down" situation. That should give the AIM-7M a lower Pk than AIM-120, all things being equal... you have two different ways to beat the SARH shot, whereas only one for the AIM-120. Ok, I could get behind that. What do you think? Good, productive discussion. -SK

Was the AIM-120 doing this also? Or, it was diving on a beaming target from above? This is what I originally thought was the problem, your own fighter maneuvers were giving a more solid target than the AIM-120 radar could provide -SK

Hmm.. You have a good point here with chaff, I was thinking more about beaming. Chaff should be little different from ground clutter. Does the AIM-7M have real look-down, shoot-down capability? I thought that's what the "inverse processing" was for - clutter rejection by doppler shift. But come to think of it, that does sound like it could be unreliable. -SK

Terminal Active Radar Homing. i.e. before the "terminal" phase, it's understood to be using inertial guidance. -SK

Let me see if I can explain my position a little better. (1) Proportional navigation has not fundamentally changed since it was first used on the Sidewinder in the 1950s, and even will all the hardware and software advances in the last half-century, it is still in use today. There was nothing wrong with the algorithms, computing power or software in these early missiles that was preventing them from hitting their targets. Rather, if a missile didn't hit, very often it was because some part of the system failed. A failure is different from a miss. We don't have weapon failures in Lock On, so unreliable missiles will seem to be performing better than their real-world coutnerparts. This is where I think the AIM-120's greater Pk comes from in the real world - a drastically improved reliability over the AIM-7M and R-27R. But the reliability of all missiles in Lock On is 100%. We are only studying the hit/miss Pk of the missiles that work - that launch correctly, guide on the target, etc. When the failures are removed, even real-world results of working missiles from the 1950s were giving 90% or higher Pk. So, what difference will new software contribute? It is like, nobody disputes that the F-22 is a much more powerful fighter than the F-15, but - who cares? That extra power can't possibly contribute any improvement to the combat ratio, because the F-15 ratio was already without loss. Similarly, new hardware and software cannot contribute anything to the already perfected PN homing trajectory. (2) "Improved" ECCM. There is a quantum leap in improvement in ECCM when you go from a conical scanning antenna (like AIM-7F) to a monopulse antenna (like AIM-120, AIM-7M, R-27R and even R-23R). A monopulse antenna gives you bearing to the target regardless of signal amplitude changes, allowing your missile to fly a PN course in HOJ mode almost no matter what kind of ECM is being used. No amount of hardware or software improvement can compare this one powerful ECCM improvement, that it is already present on all missiles being discussed. Similarly, no improvement in hardware or software can now "burn through" the jamming to get any additional information, like range. Any further "improvement" in ECCM, beyond having a monopulse antenna, must be practically trivial, like pilot testimonials about the F-15 "Sniff" mode, and only worth mentioning in an elusive, non-quantitative way, just to sell missiles. There was nothing wrong with AIM-7M ECCM. When were they being duped by ECM? In ODS?? Nonsense. So on what grounds should AIM-7M now be "more dupable" in our sim? Monopulse is monopulse, there is no half-way. You either have HOJ capability or you don't, and ALL of AIM-7M, AIM-120, R-27R and R-77, together with all modern fighter radars since MiG-23, have this monopulse ability. (3) The AIM-7M lacks an active radar, but the active radar on a TARH missile is no match for the active radar on the launching fighter, no matter how much hardware and software you give it. This is what's causing the Pk discrepancy in Lock On. In the real world, AIM-7Ms fail. In Lock On, you're never fighting the AIM-7M. You're fighting the AIM-120 radar lock, or... the F-15 radar lock. And the F-15 is harder to beat. So, if we discount failures, and we start using ECM and hard maneuvering in the real world the way we do in our sim, then I don't see any way for AIM-120 software improvements to give it a significantly better Pk than AIM-7M. The question is whether we want to be adding failures to the sim, so that many of our SARH missiles simply don't work. That all said, I admit that I'm not sure, in D-Scythe's testing, why the AIM-120 was missing. I'm assuming that the targetted fighter was successfully breaking the AIM-120 radar lock, but for whatever reason was unable to break the launching fighter's lock in the case of the AIM-7M. But maybe D-Scythe can answer better, what was going on, and under what circumstances the AIM-120 was missing. Were AIM-7Ms hitting, even without a guiding radar lock? Bugs like this have happened before, in which case all the above argument is academic. Just MHO, thanks for interest, -SK

It's not forgotten. This is included in definition of "TARH". -SK

Define "much". How much expendable on-board processing power does a missile need, to follow a dot? What's it doing, running a flight simulator? ;) As above. What software? The dot goes left. How much AI is required to decide that the missile should also go left? Is the AIM-7M guided by ED's AI? ;) Personally, I think the ability to carry it on an AIM-9 pylon, or the ability to maintain it using parts that are now still being produced, are far more relevant than any vaguely-defined "software improvements." Which had a better dynamic campaign, Lock On or Falcon 3.0? Newer is not inherently better. That all said, the Pk results do indicate a superior missile. I just don't agree this is proof of any AIM-7M processor or software disadvantage. -SK

I meant at the same target. Two simultaneous shots against the same target would require multi-channel capability on the part of the missile, to distinguish its own inertial updates from those intended for other AIM-7M missiles in flight. We know the AIM-120 has this. I think "firing attempts" includes cases where the missile didn't leave the rail. -SK

All things being equal, I don't think there's any time I would rather have a SARH missile than a TARH missile. That's a huge advantage (a) that has nothing to do with: (b) Pk © range (d) maneuverability (e) ECCM On points (b), ©, (d) and (e), I haven't seen any believeable argument yet why one or the other missile should have a significant advantage. Why? If (b) through (e) are equal, the "USAF (and everybody else) likes AMRAAM better" can be easily explained by (a) alone. So, this is not a solid proof of advantage on any of points (b) through (e). -SK

Is it possible to guide more than one AIM-7M at a time? -SK

I remember reading, "the Yugoslav air force was able to continue operations throughout the duration of the bombing," but since I don't have a cite, that could be mistaken memory. It sounded a lot more serious than a few SAM vehicles hiding in a garage, and we know that a lot of MiG-21s were at least flyable by the end. And of course there were corroborating reports from refugees who insisted they could tell the difference between NATO and Yugoslav a/c, and that it was the latter that was still attacking them as the campaign dragged on. Otherwise, your data is excellent, no argument against 60%. What did you mean by "80% of kills were made by a single AIM-120"? -SK

Look what I found -SK

I stand corrected. Checking a more reliable source, it seems to be 23-25 kills for 71 "firing attempts". :confused: F-15s were returning from missions in 1999 with AMRAAMs expended in greater numbers than the kills achieved, and unlike AIM-7M accomplishments in ODS, NATO never claimed to have achieved air superiority with AIM-120 over Yugoslavia. Perhaps for the first time that I'm aware of in air combat, published Serb pilot testimonials tended to match pretty well with NATO pilot testimonials (contrary to their respective official government testimonials), and included several AMRAAM misses. Without a missile physics model that is able to distinguish between a draggy PN HOJ shot and a inertially-guided lofted shot, I think that nitpicking over the differences between AIM-120 and AIM-7M is unproductive. Both missiles are IMHO too simplified to model true BVR tactics in a modern, ECM-equipped environmant. The real-world performance of one is probably much closer to that of the other, than either is to its Lock On counterpart. So, I'm waiting for the new weapon physics to be integrated before I get really interested in this. Lots else to look at in the meantime. That's just my opinion. Regardless, some parts of the discussion can be interesting... :) -SK

Really? I somehow thought the -7M in ODS had a better Pk record (around 70% IIRC) than all the AIM-120s fired since (around 50% IIRC). My sources on this may not be 100% reliable though. -SK