Air-to-Air Missile Discussion

[Kuky]

80nm for 120? That just can't be :) Maye if you shot it from 30000ft 45° nose up (with no lock as you can't lock anything at that range to begin with) and that would be ballistic range... then ok, I could believe that. After all it's an

 

Advanced

Medium

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The ER has inertial part of flight also, do you have reliable info that ER never flies loft?

Edited November 5, 2013 by Kuky

[lunaticfringe]

... the AIM-54 is heavier and had more drag (according to you) but it somehow has lot more range then 120?

 

Have you seen the size of the sustainer on a Phoenix? Do you have any idea how long it fires for? Compare it to an R-27, and you'll have your answer.

 

These factors do not exist, nor do they operate, in a vacuum. R-27ER is not only a heavier weapon than the AIM-120C, it incurs a much higher drag penalty. Thus, while inertia is on your side, net drag is negating it.

 

Byproduct of this being that all control surface inputs affect the Alamo at a higher rate than AMRAAM; this is the one area that, if the missiles are tuned to air density and control surface induced drag, which the intercept logic is going to involve. Weapons with better logic (see: having the built-in programming to loft and generate better intercept profiles) are going to induce fewer control inputs, which means that their overall energy state is degraded thus at a lower rate over time.

 

Further, the AIM-120C, being a lighter weapon than the R-27/ER, requires a smaller net impulse to make both a given maximum velocity AND sustain that velocity. Thus, a missile *can* slow down while the sustainer is in effect based on the above factors of intercept logic and net drag, generating you a smaller range for that heavier (raw "better inertia") weapon.

[GGTharos]

M2+ Launch at 70000' 80nm with terminal target maneuver of about 5g. The last part is my guess, but I know that this is guided range :)

 

80nm for 120? That just can't be :) Maye if you shot it from 30000ft 45° nose up (with no lock as you can't lock anything at that range to begin with) and that would be ballistic range... then ok, I could believe that. After all it's an

 

 

The ER has inertial part of flight also, do you have reliable info that ER never flies loft?

 

Yep. Think about it this way ... AIM-120's design specs were to be faster and longer ranged than the AIM-7. The AIM-7 is very comparable to the R-27R (actually I think it may be sitting somewhere between the 27R and 27ER, but I could be wrong). There's also a reason why the R-77 was designed as replacement for the R-27 series instead of just buying R-27EA. The R-27 is outdated aerodynamically and electronically.

[Kuky]

At high altitude drag is much less ... inertia due to mass is the same... so at high altitude (much less air, much less drag) mass favors ;)

[Kuky]

Yep.

 

can you show this?

[GGTharos]

No, ask Chizh :)

 

(Actually I could somewhat show it with math ... but it's complex enough that I don't want to).

 

can you show this?

[lunaticfringe]

At high altitude drag is much less ... inertia due to mass is the same... so at high altitude (much less air, much less drag) mass favors ;)

 

The fact you're winking acknowledges the fact that you don't grasp the effect of induced turn drag.

 

Form drag- that of the missile itself, is less at altitude. It's more true to state that the missile is able to convert to a higher energy state at less airform drag in a straight line than it is at lower altitude. However, this dynamic changes when the weapon *turns*.

 

A body at the same calibrated airspeed at two grossly divergent altitudes have the same effective Q (energy state). The primary difference is that the two objects, when turning at a given G load, induce the same amount of energy loss per second, while making significantly different rates of turn.

 

So take a missile with enough Q to generate 30G; that weapon will not only turn tighter, but will spend *less energy* to change 30 degrees of net heading at an altitude of 15K versus 50K. What you're left with is a weapon that's faster, but loses energy through the requirements of generating a successful intercept profile over time at a higher rate because of the time it takes to successfully turn.

 

Thus, for every interval of time of your choosing that it takes the higher missile to turn the same course change, given the same applied G and base calibrated air speed at those two altitudes, the higher weapon will lose more energy. Same KIAS, if it takes the lower missile 1 second at 30G to make the needed intercept turn, and the higher missile 2 seconds at 30G to make the same turn, the higher missile has lost twice the energy. Lower missile has lost more energy from the higher density air against its aerodynamic shape, but the induced penalty for maneuver is greater for the higher weapon.

 

So, if you want to say that the higher missile copes with a lessened drag effect, it's not actually true, unless you're simply launching it in a straight line like an Estes rocket. And I don't know about you, but I want my weapons to hit things.

 

Lofting is a trade; it's trading acceleration performance for turn performance, same as it is for the launching aircraft. Acceleration begets energy, energy begets range *or* turn performance, but not both. Better net turn performance, based on both the aerodynamics of the weapon and its logic, lessens the penalty incurred from absolute range.

[GGTharos]

It'll actually get both against your intended target because the missile will maintain more energy at range and will be in a dive when terminal.

 

Lofting is a trade; it's trading acceleration performance for turn performance, same as it is for the launching aircraft. Acceleration begets energy, energy begets range *or* turn performance, but not both. Better net turn performance, based on both the aerodynamics of the weapon and its logic, lessens the penalty incurred from absolute range.

[lunaticfringe]

It will, but I'm also trying not to throw the entire kitchen sink out there of equations. Clearly, there's issues with overall conceptual understanding, else the conversation wouldn't jump around like an excited puppy-

 

BALL (inertia)!!!... HUBCAP (impulse)!!!... SQUIRRELL (drag)!!!

[Kuky]

That was funny (the last comment) :lol:

 

Now seriously, I know what you mean lunatic ;) (see I winked, but it doesn't mean I don't know what I'm talking about, and on same note, GG winks in his posts/statements all the time.. does that make him not have a clue what he's talking about?)... anyway... as GG points out Chizh should know/have docs/info that ER's never loft... I doubt that (because Russians surely know this would help with range and reduce drag when missile is gliding without rocket power, why would Americans be only ones to know/use this???)... so I have asked him to show this info (that ER's never loft)... I'd like to see what he has to say.

[GGTharos]

AIM-7's of the same era don't loft either. 7Ps do, but 7Ps are a very modern AIM-7 development. The USAF had switched to 120's and never got them, only the USN uses them. By comparison, the R-27 is not known to have received such upgrades, instead they intended to replace it with the 77 and then the wall came down.

 

And he'll tell you this: The manuals say that the R-27 uses APN all the way to target, including during mid-course. They even have the ECCM circuit logic diagrams...whether they can share all this or just tell you that they have it, they have it.

[lunaticfringe]

I doubt that (because Russians surely know this would help with range and reduce drag when missile is gliding without rocket power, why would Americans be only ones to know/use this???)...

 

Different philosophy, and contrary to what you may believe, different levels of understanding; these conspire to underline much of the differences (as much as, if not more, than technological access) of design for respective systems between the two primary sides- NATO and Warsaw Pact.

 

Look at the difference between what amounts to comparable systems in the R-27 versus the AIM-7. Sparrow III's control surfaces look positively dimunitive compared to the Alamo, yet its turn performance in close quarters is superior; launched in lag, the AIM-7F/M can destroy targets at ranges inside of a mile. Alamo ain't making that turn.

 

Move forward to AIM-120 versus R-77, and hear where the Russians put their emphasis on the potato smasher- end game maneuverability. Yet that mesh assembly is an incredibly draggy affair.

 

There's also an old rule about the implication of ego on such things: "not made here". Doesn't sound sensible, but it exists.

[volk]

Sparrow III's control surfaces look positively dimunitive compared to the Alamo, yet its turn performance in close quarters is superior; launched in lag, the AIM-7F/M can destroy targets at ranges inside of a mile. Alamo ain't making that turn.

It's difficult to say without exactly known some specific data - can turn, can't turn, but both missiles have ability to intercept targets, maneuvering at 8g. Compared to this, R-24 intercepts 7g target.

[Alfa]

That was funny (the last comment) :lol:

 

... as GG points out Chizh should know/have docs/info that ER's never loft... I doubt that (because Russians surely know this would help with range and reduce drag when missile is gliding without rocket power, why would Americans be only ones to know/use this

 

The concept of lofting must be incorporated into the missile guidance system in order to work. Remember that the R-27 is a modular concept, where the R-27R and R-27ER shares the same guidance and autopilot sections - IIRC the two-stage motor was a later addition to the system and it might well be that lofting logic wasn't considered when the guidance section was developed.

[Alfa]

Move forward to AIM-120 versus R-77, and hear where the Russians put their emphasis on the potato smasher- end game maneuverability. Yet that mesh assembly is an incredibly draggy affair.

 

The question is to what extend the AIM-120 and R-77 really are directly comparable - looking at their designs it appears to me that the two missiles were designed for different purposes.

 

The AIM-120 as a dual purpose weapon for medium range fighter-to-fighter engagements while owing to its two-stage motor, lofting and an aerodynamical config allowing it to double as longer range intercept weapon against "non-manouvering" targets.

 

The R-77 as a dual purpose weapon for medium range fighter-to-fighter engagements while owing to a larger boost-only motor and the aerodynamical config allowing it to overlap with the dedicated "dog-fighting" weapons and remain effective for close-in encounters - in this connection it should also be noted that the radars the R-77 initially was "designed around" had scan limits in azimuth of some +/- 85 deg.

[GGTharos]

That depends on which version you're comparing.

 

AIM-120B is the 77's contemporary. The motor is the same as the A, but it certainly wasn't a weapon lacking in maneuverability. It's range is obtained via lofting, it has nothing to do with the rocket motor propulsion.

 

In terms of pure range capability, there is strong suspicion that the 77 doesn't do as well as the 120B - there are many reasons why this might be the case, but one way or the other, for now we consider them to be more or less 'on par'.

 

The 120C5 and later use an all-boost engine since it's a more efficient use of rocket fuel than dual-thrust arrangements, and has more range. I don't think it really matters what type of target it is intercepting. The type of target dictates the shape of the missile usually, not the rocket motor (think AIM-7 vs AIM-54).

 

As far as high off-bore capability goes, perhaps the 77 had better close-in ability if it has very wide gimbals and higher AoA ability. I don't know how you'd use it though since there doesn't seem to be any accompanying HOBS hardware to designate with - BUT, it would also serve to decrease the min range in head-on and tail-on situations where other missiles couldn't make the turn.

 

The new 120's have high off-bore capability also, and are supposedly integrated with the various helmet mounted displays.

[pepin1234]

In terms of pure range capability, there is strong suspicion that the 77 doesn't do as well as the 120B - there are many reasons why this might be the case, but one way or the other, for now we consider them to be more or less 'on par'.

 

Well in our "Simulator" this dont seem to happen. The R-77 in our game right now have a poor range. This missile is not a middle range in our Sim, seem to be a short range missile with the new AFM.

 

So while the AFM missile development go ahead, we must see how the US counterpart have dopple range than the R-77.

 

A lot of Mig-29 pilots simply have to stop fly this aircraft because this Situation. Even when the FC3 is already paid and have an important part still in development. The problematic AFM for the Missiles have made enough damage to the Mig and Su pilots.

 

While ED have the excuse of the to AFM development. Lot of pilots have to see how they are easyly downed.

 

Some new F-15 pilots could feel so pride to see how capable is the F-15 of ED. I say this is not a Simulator any more.

 

 

 

perhaps the 77 had better close-in ability if it has very wide gimbals and higher AoA ability.

 

Close combat with the actual R-77!! you are amazing. Right now if the Migs Pilots have not some R-73 they can eject before the splash.

 

Enjoy the unrealistic stage of our game.:thumbup:

Edited November 7, 2013 by pepin1234

[Alfa]

That depends on which version you're comparing.

 

AIM-120B is the 77's contemporary.

 

Yes and I was comparing design philosophies - i.e. what the developers initially wanted their weapons to do and why they chose the specific designs they did.

 

The motor is the same as the A, but it certainly wasn't a weapon lacking in maneuverability.

 

No one said it did - the question is how it compares with the R-77 in this regard and in particular "last ditch" end-game manouvrability for a close-in "knife-fight".

 

It's range is obtained via lofting

 

Which the R-77 doesn't have.

 

...it has nothing to do with the rocket motor propulsion.

 

Range has nothing to do with rocket motor propulsion?

 

In terms of pure range capability, there is strong suspicion that the 77 doesn't do as well as the 120B - there are many reasons why this might be the case, but one way or the other, for now we consider them to be more or less 'on par'.

 

Heh well I would subscribe to that suspicion - how can an R-77 possibly "do as well" as an AIM-120B in terms of pure range....no lofting, more draggy and no second-stage sustainer to compensate.

 

The 120C5 and later use an all-boost engine since it's a more efficient use of rocket fuel than dual-thrust arrangements, and has more range.

 

Why then did both the AIM-7 and initial AIM-120 versions have dual-stage motors.......designers didn't know any better at the time or because new types of propellant changed the situation?

 

I don't think it really matters what type of target it is intercepting. The type of target dictates the shape of the missile usually, not the rocket motor (think AIM-7 vs AIM-54).

 

The type of target dictates the range you can hope to intercept it at - a Tu-95 can be locked at a much longer range than a MiG-21, so it makes sense to have a missile that can cover the distance. I don't know where you are going with the AIM-7 vs. AIM-54.....surely you don't mean to say that they only differ in "shape"? :D . But for what its worth the AIM-120 was supposed to take over for both the AIM-7 and AIM-54, so if anything it would seem to support my initial impression that the AIM-120 was designed to cover the tasks of both these missiles - i.e. fighter-to-fighter and longer range intercept respectively, while there is nothing to suggest that the R-77 was expected to take over for the R-33 :) .

 

As far as high off-bore capability goes, perhaps the 77 had better close-in ability if it has very wide gimbals and higher AoA ability.

 

It might have - I cannot remember the stats for the 9B1340 seeker off hand though and I don't know what they are for the AMRAAM. But then...

 

.. I don't know how you'd use it though since there doesn't seem to be any accompanying HOBS hardware to designate with....

 

....I think you misunderstood:

 

...in this connection it should also be noted that the radars the R-77 initially was "designed around" had scan limits in azimuth of some +/- 85 deg.

 

The "radars the R-77 initially was designed around" meaning the aircraft radars meant to employ it - N010 and N011. So the "HOBS hardware" being those aircraft radars and more in terms of being less likely to loose an off-boresight target.

 

The new 120's have high off-bore capability also, and are supposedly integrated with the various helmet mounted displays.

 

Again I was talking about the initial AIM-120 design(A, B) not newer variants that were practially redesigned.

[GGTharos]

Which the R-77 doesn't have.

 

I was only vaguely aware of this, but is there a good source?

 

Range has nothing to do with rocket motor propulsion?

 

I should clarify: The difference between a boost-sustain and all-boost motor in terms of range will be there. I haven't done the math, but I suspect that the sustainer will allow higher average speed in some cases and may increase the range a little.

However, lofting will flat out get you scary range increase, probably with some caveats.

A sustainer also tends to burn longer than a booster, so it may have advantages in terms of a loft climb, but ... what if you could get your booster to run as long as you boost+sustain configuration?

 

Heh well I would subscribe to that suspicion - how can an R-77 possibly "do as well" as an AIM-120B in terms of pure range....no lofting, more draggy and no second-stage sustainer to compensate.

 

Yep ... but really, the difference in propulsion between the two isn't a huge deal. The sustainer makes little difference IMHO. The loft does the entirety of the heavy lifting.

 

Why then did both the AIM-7 and initial AIM-120 versions have dual-stage motors.......designers didn't know any better at the time or because new types of propellant changed the situation?

 

Wish I knew. All I know is that right now, they have switched to all-boost designs. It's a similar story to missile control surfaces: We had canards and mid-body wings, and now it's canards (Sometimes) and tail-control.

 

The type of target dictates the range you can hope to intercept it at - a Tu-95 can be locked at a much longer range than a MiG-21, so it makes sense to have a missile that can cover the distance. I don't know where you are going with the AIM-7 vs. AIM-54.....surely you don't mean to say that they only differ in "shape"? :D . But for what its worth the AIM-120 was supposed to take over for both the AIM-7 and AIM-54, so if anything it would seem to support my initial impression that the AIM-120 was designed to cover the tasks of both these missiles - i.e. fighter-to-fighter and longer range intercept respectively, while there is nothing to suggest that the R-77 was expected to take over for the R-33 :) .

 

To clarify what I was saying then - the aerodynamic design of the 54 is very very different. It is a fat missile with huge lifting and control surfaces, meant to loft through very thin air in order to get its range. Both its aerodynamics and trajectory are vastly different from the AIM-7 (but like the 120, it has tail control!).

I don't think the 120 can loft as high, but other factors like lower drag allow it to have phoenix-like (but still less) performance up high when we're talking about the newest motor for the 120D. The 120B isn't even close.

 

It might have - I cannot remember the stats for the 9B1340 seeker off hand though and I don't know what they are for the AMRAAM. But then...

 

I believe it was a 55 degree gimbal for the 120.

 

The "radars the R-77 initially was designed around" meaning the aircraft radars meant to employ it - N010 and N011. So the "HOBS hardware" being those aircraft radars and more in terms of being less likely to loose an off-boresight target.

 

Makes sense :D

[blkspade]

Its pretty obvious to me where the different principles of thought are in the design differences are between the R-27 and AIM-120. The R-27ER is faster to at altitude since it based on the principle that the shortest distance between two points is a straight line. The loft profile of the 120 would be a drawback in this respect (excluding the fact that both parties should be maneuvering). It makes up for it by not requiring terminal guidance, along with better sustained energy.

 

To the point Kuky was trying to make about the benefit of the R-27's mass. Since gravity is a constant variable which acts on the mass, it only helps it in a dive but then drag would be increasing. I don't know the math to determine if one factor is enough to negate the other, but if the target starts to climb after a brief dive then the missile and its mass are working against gravity. Counter that with a long range shot with a loft profile like the AIM-54 or AIM-120, what ever mass it has is coming down on you the entire time in the terminal phase and has a chance to actually further accelerate after the motor has burned out.

[GGTharos]

The R-27 and AIM-120 aren't being compared. The contemporary to the R-27 is the AIM-7.

 

AIM-54's shed mach like crazy on their way down once they re-enter thick atmosphere. Yes, in the dive. Even powered, a shot from 50000' to 0' on a relatively steep angle severely limits the top mach because of atmosphere so the dive plays a huge role in preserving speed, but there is a limit when the speeding demon it's a comet out to crush the planet.

 

No one has presented an actual physics-based argument (and by physics based, I mean doing the math) as to how an R-27ER is superior to an AIM-120 and under what circumstances. All I've seen so far is pure speculation, with some physics sprinkled in for fun.

 

This isn't a case where we can relatively easily say 'bigger surface, more drag', this is a case with additional factors that no one has bothered to compute, and I suspect that once there is proper modeling of those factors (if such a thing can happen, because I know some missiles are either missing data or data for them cannot be used) they'd be rather surprised and dismayed at how an R-27 any version compares to a 120B, in almost every single circumstance.

Edited November 7, 2013 by GGTharos

[Teknetinium]

Its pretty obvious to me where the different principles of thought are in the design differences are between the R-27 and AIM-120. The R-27ER is faster to at altitude since it based on the principle that the shortest distance between two points is a straight line. The loft profile of the 120 would be a drawback in this respect (excluding the fact that both parties should be maneuvering). It makes up for it by not requiring terminal guidance, along with better sustained energy.

 

To the point Kuky was trying to make about the benefit of the R-27's mass. Since gravity is a constant variable which acts on the mass, it only helps it in a dive but then drag would be increasing. I don't know the math to determine if one factor is enough to negate the other, but if the target starts to climb after a brief dive then the missile and its mass are working against gravity. Counter that with a long range shot with a loft profile like the AIM-54 or AIM-120, what ever mass it has is coming down on you the entire time in the terminal phase and has a chance to actually further accelerate after the motor has burned out.

 

 

Exactly, bigger mass of ER-27 dose

not work against it in at all situations.

 

When the missile is diving down, it should sustain velocity better then lighter one, drag is playing a big roll I this as well in witch we have little info.

Edited November 7, 2013 by Teknetinium

[blkspade]

There are lots cross conversations going on about all the missiles. Obviously I know what should be compared to what, but from the in game perspective that is the most frequent match up. The RL physics of it all is an actual factor due to the AFM.

 

The R-27 and AIM-120 aren't being compared. The contemporary to the R-27 is the AIM-7.

Edited November 7, 2013 by blkspade

[Alfa]

I was only vaguely aware of this, but is there a good source?

 

Not off hand - I will have to look around . But on the other hand I have never seen any credible source(manufactures or otherwise) claiming that it does have lofting. I think we might just have assumed that it did based on the IMO bogus notion that the R-77 is some sort of Russian version of the AMRAAM("amraamski") based on some superficial comparison regarding overall size, guidance system and being contempory.

 

But I think you will agree that there are many things about the R-77 design that seems to suggest otherwise and also quite a few differences in overall philosophy. As mentioned earlier the AMRAAM was supposed to replace(at least to some extend) both the AIM-7 and AIM-54 - i.e. sort of an all-in-one "multirole weapon, wheras there is nothing to suggest that the R-77 was meant to replace anything but the R-27R.....not even the R-27ER since there were alternate design proposals(involving either a larger two-staged motor and even a ramjet version) for that.

 

I should clarify: The difference between a boost-sustain and all-boost motor in terms of range will be there. I haven't done the math, but I suspect that the sustainer will allow higher average speed in some cases and may increase the range a little.

 

However, lofting will flat out get you scary range increase, probably with some caveats.

 

A sustainer also tends to burn longer than a booster, so it may have advantages in terms of a loft climb..

 

Ok I agree - the point I was trying to make was that, as far as I can see, a slower burning second sustainer stage would benefit the missile when coasting(level flight) over longer distances and help to compensate for drag and that since the R-77 doesn't have it while being more draggy, that chances are such an engagement type wasn't envisioned for the missile.

 

..., but ... what if you could get your booster to run as long as you boost+sustain configuration?

 

Indeed and with the miniturization of components, recent versions of the AMRAAM have "room" for more(and possibly more effecient) propellant, so I am quite prepared to believe they can be "all-boost" and still have better range than an earlier boost-sustain variant, but again I think this is down to technical evolution rather than a change in philosophy - i.e. that the reason why the initial variant had boost-sustain configuration was that at the time this, in combination with lofting, was the best option range-wise.

 

Yep ... but really, the difference in propulsion between the two isn't a huge deal. The sustainer makes little difference IMHO. The loft does the entirety of the heavy lifting.

 

Possibly GG - but again the point was that they(AIM-120 designers) must have had a reason for choosing a dual stage motor, while the designers of the R-77 must have had a reason not to :)

 

 

Wish I knew. All I know is that right now, they have switched to all-boost designs. It's a similar story to missile control surfaces: We had canards and mid-body wings, and now it's canards (Sometimes) and tail-control.

 

Thats because a big "potato-masher" at the tail has recently been determined to be aerodynamically superiour :angel:.

 

To clarify what I was saying then - the aerodynamic design of the 54 is very very different. It is a fat missile with huge lifting and control surfaces, meant to loft through very thin air in order to get its range. Both its aerodynamics and trajectory are vastly different from the AIM-7 (but like the 120, it has tail control!).

 

I don't think the 120 can loft as high, but other factors like lower drag allow it to have phoenix-like (but still less) performance up high when we're talking about the newest motor for the 120D. The 120B isn't even close.

 

Ok.

 

I believe it was a 55 degree gimbal for the 120.

 

Ok thanks - I will see if I can find the specs for the R-77 seeker for comparision(although I doubt that there is much difference) .

[blkspade]

I guess I'm the only person that does 'dumb' stuff in single player, just to observe the effects. Like flying at 40k'+ at mach 1.5 just to pull up and fire a missile straight up and watching it in F6 view. There was actually point early in the FC3 release that would crash the game every time you'd try this. Once they fixed that, there an obvious point where the missile no longer has the speed for continued lift arcs and begins to fall back to the ground. There is a good amount of time that the missile is actually accelerating before the atmosphere starts slowing it down again. I haven't done it in a while, and if I could track myself in reference to the missile position I'd like to see if I could kill myself with a 120. Yes for sh!ts and giggles.