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Armchair engineering. Rear firing AA missiles, two stage AA missiles


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Im pretty noobish when it comes to military aviation technology, so I dont pretend to know any better than the engineers actually making this stuff, but Im curious why we have never seen any of these, or maybe I just missed them?

 

- rear firing IR AA missiles. That seems like such an obvious "cheat" to win dogfights. Have one or two IR missiles that point backwards and instead of losing a dogfight you suddenly have at least a kinetic advantage over that plane on your 6. This does require all aspect IR missiles but we've had those since the 70s. And you could mount them to bombers and other non fighters to give them something to protect themselves against planes they have no chance of defeating in a dogfight. Arguably modern fighters have a similar ability with helmet mounted huds and all aspect rockets, but has no one ever tried a cruder version of this decades ago with the rockets already pointing backwards? One reason I can think off is airspeed will be negative initially and then be zero at some point. But given how fast these missiles accelerate, I doubt thats a big problem, or?

 

- two stage medium/long range AA missiles. Being educated by hollywood rather than anything else, I always imagined AA missiles burned their rocket motor from launch to impact. I was actually surprised to learn how they work, that they burn only for a few seconds and from then on are basically gliders with a very limited amount of kinetic energy to manoeuvre. That makes them "easy" to defeat if you know they have been launched at long range. Now imagine they worked differently, if they used just 80% of their fuel for launch and lofting to get close to the target, and then had a second burn once within a few miles, to be able to out-manoeuvre any plane and basically ensure a kill (if locked). I know there are 2 stage sams, but even they dont work like that AFAIK.


Edited by Vertigo72
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1/ it is simple pragmatic choice. why waste loadout station for a weapon which has little to no use for 99.99% of a time. It is the same reason why passenger planes do not have ejection seats...

 

2/ there are already such a2a missiles which can fire 2nd stage at terminal intercept. Why was that not used much in the past is related to the sensor tech which did not even allow for rangers where such config would had mattered.

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1/ it is simple pragmatic choice. why waste loadout station for a weapon which has little to no use for 99.99% of a time. It is the same reason why passenger planes do not have ejection seats...

 

hmm. yeah, but military planes do have ejection seats that arent used 99.99% of the time. Same goes for chaff and flares. Its not how often its used, its how effective it is at saving the plane or pilot when you need it.

 

AFAIK, strike aircraft are sometimes armed with AA missiles for self defense. Like the sidewinders on the A6 intruder and experiments with the FB-111. Those plane are not going to get on the 6 of an enemy fighter very often I imagine, so if pointing them backwards would work, that would actually make a lot more sense for self defense than pointing them forward.

 

2/ there are already such a2a missiles which can fire 2nd stage at terminal intercept.

 

Ah? Which ones?

 

Why was that not used much in the past is related to the sensor tech which did not even allow for rangers where such config would had mattered.

 

I dont know about that. Look at the phoenix or even amraam.

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1) Was experimented with off and on for a long time. In the 1990s there was speculation that the Su-27 and R-73 missile had that capability, complete with rearward facing radar, but I don't think it panned out in real life.

 

2) There's a long-range air-to-air missile in development for the US that has a two-stage design called the Long Range Engagement Weapon. (Which is different than the AIM-260 JATM.)

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1) Was experimented with off and on for a long time. In the 1990s there was speculation that the Su-27 and R-73 missile had that capability, complete with rearward facing radar, but I don't think it panned out in real life.

 

Cool. So the idea is not entirely crazy. Even if still too crazy even for the russians :) I can see the problem with trying to mount a rearward facing radar though, even a small short range one, which is why I assumed you'd want IR only.

 

2) There's a long-range air-to-air missile in development for the US that has a two-stage design called the Long Range Engagement Weapon. (Which is different than the AIM-260 JATM.)

 

Thanks, googled that, and then also stumbled upon this:

 

https://en.wikipedia.org/wiki/AIM-152_AAAM

 

Which was a planned replacement for the phoenix. I assume "Multiple-pulse solid-propellant rocket" achieves exactly what I had in mind. Weird that none seem to have made it off the drawing board so far. Its probably not quite as easy as it sounds.

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While not a long range missile, stingers are sort of two-stage. They have a launch motor to get the missile clear of the tube & operator, and a second motor in the missile

Launch motor can be seen trailing the missile in this image:

1-image-42.jpg

 

In general, two stage rockets are more complex, expensive and while they're more fuel efficient in the terminal stage, they're less efficient up front. In the end, it's a solution in search of a problem when single stage missiles get a sufficient PK as it is

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I understand that Vertgo72 is a "noobish" aviation enthusiaist...so lets go down into the rabot hole.

 

1: In order to fire a projectile to the opposite way of the lunch vechicles vector has numerous problems

-aqusition this needs a sensor that has a unrestrict 3d view to the rear of 90○ allaround

-projectile/missile has to effective in the same manner as the sensor and possible to lunch in that envelope without damaging the aircraft

-missile sensor has be able to see the enemy aircraft heat signature.

on top of all these basic phisics. the missile has to be stable after lunch effectivly flying backwards before transitoning to forward forward flight wich is opposite of the lunch aircrafts vector.

 

2: Meteor air to air missile

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hmm. yeah, but military planes do have ejection seats that arent used 99.99% of the time.

practicality encompasses issues including maintenance and weight. ejection seats are explosives -- they need to be checked on and replaced if needed. in addition, while they may be negligible weight penalty in a 1-2 seat aircraft, when you start talking about 200 or so of them, that really adds up. so when we talk about the worth of the 0.01%, we're talking about it being balanced against these costs. nothing comes for free, and aerospace is especially unforgiving. even today as we try to sidestep physical limitations by shifting functionality from hardware to software, power and cooling issues still represent a tether to the tyranny of physics.

 

vQgBKtu.png

engineers are not uncreative, rearwards facing missiles are an obvious concept. but shooting off missiles is not as simple as just having a missile launcher, it needs its attendant targeting equipment and in the end adding it all together (ammunition, launch apparatus, support equipment) you are looking at weights that penalize both survivability (speed, maneuverability) and offensive capability (range, payload) and the net gain may even be negative!

 

nowadays the rearfiring missile problem is being solved by high-off-boresight (hobs) + lock-on-after-launch (loal) missiles that can orient themselves after launch towards any target. this is an elegant solution that minimizes weight penalty by not requiring a dedicated missile + launch complex for each hemisphere.

of course, as missiles miniaturize even further, we may yet see non-forward-pointing missiles become a reality; the msdm would be a tiny missile intended to intercept incoming missiles and possibly aircraft and they may be siloed not unlike chaff and flares.

 

weight is a significant, perennial issue in aerospace which is why 'fancy ideas dont fly'. by the time a technology matures enough to not pose a weight challenge, there are often advancements in other areas that obviate it altogether, but at the same time, there is never one 'eternal solution': what is a bad idea at one point in time may turn into an excellent idea at another point when proper conditions are met.

 

--------------

 

also at this point hollywood has become so detached from reality that one may well be able to consider it subversive and destructive. its vision of air warfare is forever mired in ww2 tropes, and only serves to disorient the expectations of the public towards their military. it is good that media such as dcs exist to provide insights on some of the complexities that accompany this field.


Edited by probad
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- rear firing IR AA missiles.

It's better to try to win, than to try to lose. The rear missiles would only be useful once you've messed up. And modern front facing IR missiles can do 180's already.

 

 

- two stage medium/long range AA missiles. Being educated by hollywood rather than anything else, I always imagined AA missiles burned their rocket motor from launch to impact. I was actually surprised to learn how they work, that they burn only for a few seconds and from then on are basically gliders with a very limited amount of kinetic energy to manoeuvre. That makes them "easy" to defeat if you know they have been launched at long range. Now imagine they worked differently, if they used just 80% of their fuel for launch and lofting to get close to the target, and then had a second burn once within a few miles, to be able to out-manoeuvre any plane and basically ensure a kill (if locked). I know there are 2 stage sams, but even they dont work like that AFAIK.

So the way you described them here, you could end up with slow and short range missiles that would be defeated by traditional missiles. They would be slow because they wouldn't burn all their fuel on launch and have lower top speed. The fuel weight would also make them less maneuverable and slow down faster. This will make their journey to the target longer. They'd also be less able to loft because again less fuel use means less climbing.

 

 

To really say what the merits and drawbacks of this idea are would take a deeper analysis, but on the surface level saving your fuel doesn't provide an immediate advantage over burning it all on launch.

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Most 'famous' are ASRAAM, Derby ER and PL15, PAC3 MSE... in works are MICA NG, Astra 2, etc.

 

I'd hesitate to call a Pac-3 mse a multistage rocket/missile.

 

Dual pulsed motors are a delay bulkhead placed in the fuel source using the same motor/nozzle assembly. A multi-stage system jettisons spent fuel/motor assemblies

 

6 in one, half a dozen in another I suppose

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Vertigo is correct, I'm wrong, as far as the stall speed, and with that in mind logically the pursuer would not have a kinetic advantage, or not much of one, as the missile would not necessarily be tumbling uncontrollably.


Edited by zhukov032186

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hmm.. a few things; first, about that falling out of the sky and flying backwards.. a sidewinder accelerates to mach 2.5 in just over 2 seconds. If you launched it backwards, it would initially even accelerate faster as air resistance would help it achieve positive airspeed. The time it would spend being aerodynamically uncontrollable (if any by the time it leaves the rail) would be just a fraction of a second and barely more than any ground launched missile who all launch with zero airspeed. But if even that is a problem, there is always thrust vectoring. And that doesnt have to be fancy gimbaling rocket motors, just putting control vanes behind the rocket exhaust would work. I guess I cant say that isnt rocket science, because it is, but its hardly a new idea or high tech, the V2 had that in the 1940s.

 

Im also unsure what kinetic advantages you think the pursuer has, when the defender has nearly twice the missile range and considerably shorter missile flight time, all other things being equal.


Edited by Vertigo72
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- two stage medium/long range AA missiles. Being educated by hollywood rather than anything else, I always imagined AA missiles burned their rocket motor from launch to impact. I was actually surprised to learn how they work, that they burn only for a few seconds and from then on are basically gliders with a very limited amount of kinetic energy to manoeuvre. That makes them "easy" to defeat if you know they have been launched at long range. Now imagine they worked differently, if they used just 80% of their fuel for launch and lofting to get close to the target, and then had a second burn once within a few miles, to be able to out-manoeuvre any plane and basically ensure a kill (if locked). I know there are 2 stage sams, but even they dont work like that AFAIK.

Take a look at the Meteor missile. It uses a rocket booster to get to speed quickly and then switches to a variable ramjet to cruise along at mach speeds, which means that unlike classic rocket propulsion missiles, it retains its speed.

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Take a look at the Meteor missile. It uses a rocket booster to get to speed quickly and then switches to a variable ramjet to cruise along at mach speeds, which means that unlike classic rocket propulsion missiles, it retains its speed.

 

yeah I saw that. But thats really "next gen", if you can have mach 4 and propulsion from launch to impact 100+Km away thats obviously even better than what I proposed. And btw, if that missile ever makes it in to DCS, we may have a problem.

 

My thinking was using traditional rocket motors, how do you get the most bang (literally) for your oomph. You need thrust initially to get up to speed and altitude. But then having a coast phase, even if it slows you down, really is not a bad thing to maximize your range for a given amount of thrust/fuel (Im biased, Im a glider pilot, gliding is efficient ;). Especially when the missiles fly almost in the stratosphere. Its only a bad thing in the terminal phase, especially at lower altitude, where not having propulsion on a missile, you lose most maneuverability right when you need it most. Hence my idea to have another "stage" or pulse at the end. Apparently that does exist, but its not as widespread as I would have imagined it to be.

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  • ED Team
Im pretty noobish when it comes to military aviation technology, so I dont pretend to know any better than the engineers actually making this stuff, but Im curious why we have never seen any of these, or maybe I just missed them?

 

- rear firing IR AA missiles. That seems like such an obvious "cheat" to win dogfights. Have one or two IR missiles that point backwards and instead of losing a dogfight you suddenly have at least a kinetic advantage over that plane on your 6. This does require all aspect IR missiles but we've had those since the 70s. And you could mount them to bombers and other non fighters to give them something to protect themselves against planes they have no chance of defeating in a dogfight. Arguably modern fighters have a similar ability with helmet mounted huds and all aspect rockets, but has no one ever tried a cruder version of this decades ago with the rockets already pointing backwards? One reason I can think off is airspeed will be negative initially and then be zero at some point. But given how fast these missiles accelerate, I doubt thats a big problem, or?

 

- two stage medium/long range AA missiles. Being educated by hollywood rather than anything else, I always imagined AA missiles burned their rocket motor from launch to impact. I was actually surprised to learn how they work, that they burn only for a few seconds and from then on are basically gliders with a very limited amount of kinetic energy to manoeuvre. That makes them "easy" to defeat if you know they have been launched at long range. Now imagine they worked differently, if they used just 80% of their fuel for launch and lofting to get close to the target, and then had a second burn once within a few miles, to be able to out-manoeuvre any plane and basically ensure a kill (if locked). I know there are 2 stage sams, but even they dont work like that AFAIK.

 

 

The main problem of reversed missiles is their stability at the initial part of the way. This is the same problem as to fire them from "Cobra" maneuver.

 

As the missile can not accelerate instantly, some time after launching it will fly reversed as it has plane's velocity. Due to its directional stability it will tend to rotate along the plane. This angle can break the head lock on target.

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The main problem of reversed missiles is their stability at the initial part of the way. This is the same problem as to fire them from "Cobra" maneuver.

 

As the missile can not accelerate instantly, some time after launching it will fly reversed as it has plane's velocity. Due to its directional stability it will tend to rotate along the plane. This angle can break the head lock on target.

 

I understand these are challenges, but they dont seem particularly hard to overcome to me? you could fairly easily maintain attitude control by putting control vanes behind the rocket exhaust. The exhaust velocity is far far higher than the airspeed of the plane that launches it, so even if the rocket as a whole is flying backwards, those controls still work as they do flying forward and with plenty of authority. As mentioned earlier, even the V2 did that (well, usually not for flying backwards, but the idea is the same).

 

Alternatively, you could have some disposable fins at the front of the rocket, a bit like Falcon 9 grid fins, that stabilize the rocket while flying negative airspeeds, but are ditched the moment it achieves positive airspeed. That should be super easy to do, even just mechanically have air pressure release them. Heck, maybe even a drag chute would work.

 

And even if that flight phase is too violent and thus challenging to maintain a steady attitude and target lock, how much difference does it make if you where to lose lock for like half a second, in a stage of flight where you barely have any airspeed yet? A $2 accelerometer is all it takes for my drones to be able to return to a previous attitude after having been flipped upside down.


Edited by Vertigo72
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On Rafale, Mica can make a 180° turn after firing to shoot down a target at 06 o'clock.

Demonstrated twice with live firing against target drones.

 

I think it should also be possible with latest AIM-9X (Lock On After Launch).

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