The R-77 is not much larger than the AMRAAM in terms of size, the caliber goes up to 200mm from 178mm…
The AMRAAM has less than a 2s booster with approximately 5-6s sustainer with significantly less thrust. The R-77 has a 4.5-6s booster only, which is similar to what they do later with the AMRAAM.
Grid fins have significantly higher drag at transonic speeds due to shock waves forming within the lattice of the fins. The drag is known as “wave drag” (for others reading who want to look this up further). At speeds above mach, the grid fins have lower drag and provide greater maneuverability than conventional tail sections like seen on the AMRAAM. At subsonic speeds they have equal drag and greater effective control than conventional fins due to their much higher angle of attack before a stall occurs. They can maneuver better at slower speeds when attempting to hit targets near the end of their flight envelope.
Another important aerodynamic characteristic of grid fins concerns drag, although it can be an advantage or a disadvantage depending on the speed of the airflow. In general, the thin shape of the lattice walls creates very little disturbance in the flow of air passing through, so drag is often no higher than a conventional fin. At low subsonic speeds, for example, grid fins perform comparably to a planar fin. Both the drag and control effectiveness of the lattice fin are about the same as a conventional fin in this speed regime.
The comment “The R-77 is a significantly draggier missile in every way over the AMRAAM” is simply not true, it can maintain high speeds for longer due to reduced drag from the grid fins at high supersonic speeds. The way of maximizing it’s kinematic range is to simply launch it above mach 1.3 where it will not suffer the transsonic wave drag from the grid fins.
In short:
A 4.5-6s boost will help the missile go faster than the AIM-120 and the grid fins will help it keep that speed for longer if launched above mach 1.3. Further, the AIM-120 will not be able to maneuver as well as an R-77 when attempting to reach a target at maximum ranges because the grid fins allowing almost double the maximum AoA can help to maneuver the missile better towards the end of its’ kinematic range.
Something we should also note, the R-77 is larger and has more room for batteries. It’s been said that it has 8-9 batteries in the base after the rocket motor and before the control actuator section. The control actuator requires less power to move the servos than on the AIM-120 because the grid fins require far less torque. The maximum guidance time could be far longer than the AIM-120 allowing it to coast into targets. This is also assisted by the fin design on the mid-body of the R-77.
Considering the statee missile dimensions (200mm diameter, 3.6m long R-77 vs 178mm diameter, 3.65m long AMRAAM) the math puts the R-77 frontal area at 0.031m^2 vs 0.025m^2 which is almost 20% larger. The overall surface areas of the missiles are closer, with the R-77 at roughly (assuming a cylinder and ommiting the rear surface) 2.289m^2 vs 2.065m^2 which is just about 10% more surface area (ommiting fins for both).
Considering the rest of the drag equation to be roughly equivalent, and therefore canceling itself out, the R-77 are roughly 10-20% draggier than the AMRAAM, and as stated before, thats ommiting control surfaces and ignoring the effect of base drag that the AMRAAM gains an advantage in due to the longer sustainer.
You YOURSELF state they reach similar speeds after launch from their boost phase. Considering all known factors, its pretty simple to figure out the any advantage in propellant the R-77 may have is negligeable simply due to the drastricly increased drag.
Can you make a similar in-depth research into both AIM-7F and R-27ER? Ignore Warthunders implementation of the missiles or their performance charts. Could you take a look at their airframe and mass sections? I’d be interested in hearing your conclusions.
The R-77 has approximately 63.03 inches long area wherein propellant is stored if we do not go off the seams, and rather off the possible area filled with propellant casing.
Using the formula for cylinders to calculate total area used for propellant yields approx. 88.998m2
After revising my look at the AIM-120A propellant it seems the area where propellant is stored has around 56 inches of motor. The total area used for propellant comes out to around 74.703m2.
The R-77 could yield somewhere between 10 to 19% more propellant, reaches a similar or higher speed than the AIM-120A despite a larger caliber (albeit with reduced drag from the control surfaces).
You were not accounting for the radome shape much in the same way I do not account for the fact that the propellant casings are not perfect cylinders, but
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Essentially,
The R-77
More body drag from caliber (12.36% increase in caliber).
Significantly less drag at high supersonic speeds from grid fin design.
10 to 19% more propellant.
Significantly more thrust / acceleration. (Similar or higher top speed with less burn time).
Better maneuvering capacity near end of kinematic flight range due to higher CAS AoA.
Significantly hampered by launches below 1.3 mach.
The AIM-120
Better drag (initially) due to slightly longer burn time. (~1-2s more).
Significantly worse acceleration and top speed as altitude decreases (2s boost, 5-6s sustain).
Publicly known to use lofting.
My conclusion:
The R-77 may have slightly better straight line performances, but to my knowledge did not (at least initially) have any kind of lofting profile. The all-boost motor lends itself to reaching significantly higher speeds from launch at lower altitudes in comparison to something like the AMRAAM, provided it can be launched at or near mach 1.3.
At high altitude where drag matters very little, the R-77 will likely outperform the AIM-120 due to the better acceleration, better speed retention at high supersonic, and having obviously more space for more batteries.
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As a comparison, the AIM-54A (according to this sheet) has 1224.86 m/s deltaV. The AIM-7F has 955.54. This means the AIM-54A has 28.2% more deltaV than the AIM-7F. The AIM-54A has a caliber of 380mm, whereas the AIM-7F is 200mm. This is a 90% increase in caliber. In my testing (see chart below) the AIM-54A can travel a distance of 54.97km before it can no longer chase an 1100 m/s target at 10,000m. That is the furthest it can go and remain within lethal warhead radius and successfully kill the target. Likewise, the AIM-7F can only go 37.26km in the same scenario. This is a 47.5% increase in overall distance traveled and 48.4% increase in separation distance from target where the missile was able to successfully hit it with just 28.2% more deltaV and 90% larger caliber.
Another comparison that can be made is the R-27ER and the AIM-7F. The R-27ER has 1195.38 m/s DeltaV, the AIM-7F remains at 955.54. This is a 25.1% increase in DeltaV but only a 14.7% increase in overall distance traveled (albeit limited by guidance duration). The missile had a lot of velocity leftover to hit this target, but failed to at further ranges because it self destructed. This shows how important it is to accelerate quickly and maintain a higher speed, which the R-77 can likely do.
Gaijin does not implement different “drag” stages for missiles, like subsonic, transonic and supersonic. If they are about to add R-77, they have to create it and so far it seems difficult (like modeling lowered drag when the motor is burning). I think we will need a lot of bug reports for new FOX 3 missiles when they come.
I don’t think they model the drag from post-burn when there is no gas behind the motor section either, the R-77 will be favored in all of these simplifications. As long as the missile under certain conditions has the correct kinematic range and average time to target it will be considered good to go.
Favors all missiles equally, but alright. The R-77 will still have it’s drag and ranges optimized for altitudes 1-5k meters as Gaijin does with all other missiles so it won’t get much of an advantage in comparison to the AMRAAM in that regard.
0.8s after it is ejected from the frame it starts guidance, and 0.2s after ejection from frame does it start motor… interesting. I know that on the F-16 wingtips it is fired off the rail, I wonder how they will model these differences. Perhaps two separate missile files with changes in the guidance delay and such?
I doubt anyone wants to report it for the planes they play. Youd be hurting your own plane you main if your missile took an extra second to turn on motor when it could have used that one second to already be traveling towards whoever you’re locking onto.
Range estimates seem to vary wildly for the AIM-120A, and the above image doesn’t state an exact range either, but the above image indicates it exceeds that of the AIM-7M using command inertial guidance at least which is stated as a maximum of 70km.
I also haven’t really seen any official sources regarding motor burn times for either the AIM-120A or R-77, so I’m confused as to where all the previous motor burn times discussed as arguments for range of each missile came from. I’ve seen range estimates all over the internet ranging from >20 nautical miles (~37km) to >35NM (~65km) for the AIM-120A, but never any official sources with numbers regarding range or motor burn.
Also, id like to add that many sources online claim the R-77 has a 100km range. Thats an outright fabrication as evident by the official brochure regarding the missile, and considering its very similar dimensions to the AIM-7M I think its pretty reasonable to assume its motor doesnt particularly exceed the capabilities seen on the 7M by much. Id even ventute a guess that at any launch below supersonic speeds, the missile likely underperforms compared to the 7M rather significantly due to the drag from the waffle fins.
The range of the AIM-7F/M is limited by the receiver, not kinematics. The extension in range is generally referred to as something made possible by the mid-course inertial guidance methodology of the AMRAAM. This is also what allows the R-27R/ER to travel as far as they do despite not actually being able to track the target (yet). The only time the R-77 would be able to achieve 100km kill is in an insanely high altitude and high speed scenario. The target would basically need to just unwittingly fly himself into the missile. https://cdn.discordapp.com/attachments/398367636213334018/1141922952741396490/R-77.png
Obviously this chart is questionable at best, but highlights my point. No one is claiming 100km distance against a target below ~17km altitude and presumably at very high closure rate. 80km is a more practical distance for fighter sized targets as it is possible only at a altitude (per this chart) of around 15km.
At lower altitudes it seems the maximum practical range is less than 20km. The R-27ER will be the dominant Russian missile regardless of the fact that the R-77 is a fox-3 or has sufficient performance to out-range the AIM-120A/B.
Thats weird, you seemed to have missed the part where the Russian goverment doesnt claim 100km range at all, seeing as they claim an 80km max range on their official export brochure for the missile.
Not 80km+, not ~80km. Up to 80km. 80km max.
Considering they also have other “maximum” figures in their export document, such as max altitude of 25km, max target speed of 3600km/h I’m inclined to believe that what they mean by “up to 80km” for range is, yanno, up to 80km range against a non maneuvering target flying the optimal flight profile for it to intercept.
I think itd be a BIT weird if the official Russian export document got the max tange wrong by a whopping 25%… I’m sure your questionnable chart is a more reliable source tho
That’s not the “Russian government”. It’s the Russian export industry’ Rosoboronexport. A secondary source at best, they only take procured weapons from the defense industry and export them elsewhere. The stated range of 80km is as meaningless as the Air Force saying the AMRAAM is “20+ miles” range.
NAVAIR doesn’t even have the correct weight for the AIM-120A/B. It’s all classified, so the public numbers may be over or understated.
Hughes themselves show a weight of 326 pounds for the AIM-120A. This is a primary source, and one that is backed up by other secondary sources for various places. We don’t have this kind of accurate information for the R-77 (yet). If Gaijin wants to use restricted Russian documents in the background to model the R-77 they’ll likely get a missile with a maximum range stated as 100km. Doesn’t mean it will reach there, same as the AIM-7F.
The sole state intermediary for Russian arms import/export. A state corporation. They have no reason to undersell their weapons max range. Seeing as its an export item, they are more likely inclined to overclaim, not underclaim. There’s no reason to believe the missile can exceed its publicly stated max range by a whopping 25%.
Trying to compare this to AMRAAM claimed range is idiotic as well. 20+ miles is highly ambiguous, and considering the previously shown procurement papers, as well as just basic logic, the idea that the AIM-120A cannot match, or more likely exceed the AIM-7M’s range is dubious at best. The R-77 on the other hand has a stated max range, along with other stated max figures (alt and target speed). Those are not ambiguous figures, they are stated maximums.
