I’d make it if I had a vested interest but in this case, I do not. It’s obvious they’re trolling at a glance and from the brief look at Su-57 sources available… But there is no reason to entertain it on this thread.
I’d rather discuss the underperformance of the R-77. Currently thrust 1:1 matches the real world values, it should be higher to account for reduction in drag during burn time and loft should be removed. If it doesn’t still meet the performance metrics without loft, thrust should be increased further or drag slightly reduced.
ANALYSIS OF GRID FINS AS EFFICIENT CONTROL
SURFACE IN COMPARISON TO CONVENTIONAL
PLANAR FINS
Even if you do some napkin maths(which would yield lower Mach number) with the fin dimension, 35mm chord and ~35mm between each parallel plate (0mm for plate thickness), the required velocity for supersonic airflow to pass unobstructed is mach 3.3. Faster than it and shockwave will have a small angle letting supersonic air to pass freely, mass flow rate rises with the velocity increase eventually approaching the exterior mass flow rate. Under it and the air interferes with the shockwave from the other plate but still passes(parasitic drag), mass flow rate isn’t that high. Mach 0.9- Mach 1.4, the shockwave reaches the trailing edge of the other side, basically chocking and restricting airflow considerably.
Many who wrote here and who do not like the R-77 are initially mistaken in thinking that the R-77 is an analog of the AIM-120 and created the BVR radar concept like the AIM-120…
In fact, no …
The missile was created by order of the Air Force for the MiG-29M/Su-27 M…as a universal highly maneuverable missile for short- and medium-range combat at an altitude of 3-5 km.(the main battle zone based on the experience of local conflicts)…The minimum height of the lesion is 20 meters…The minimum launch range is 300 meters…The angle of the target is 90 degrees…High-speed high-speed target’-12G…Maneuvering a missile with an angle of attack of 40 degrees…
Long-range missiles were created for the air defense forces-R-33S/R-37…
Now the Su-35S is armed with both universal missiles and long-range missiles…The same concept in China … and as far as I know, the United States has returned to this concept and is creating a long-range missile …
P.S.-The design of the R-77 from the very beginning provided for a variant with folding rudders-For the self-defense of the Tu-160…
Are you salty that the R-77 has worse performance than the AIM-120A below 15km 0.9/0.9 launch in the test server? Even though it has loft when IRL it shouldn’t, so its performance is likely to drop further? I doubt that R-77 will get a major motor improvement that the other missiles don’t, given that it has approximately the same Isp as they do(230-240 seconds).
ISP has never been accurate to real life in-game, it is also missing some thrust to account for reduction in drag during motor burn time as stated and doesn’t meet certain data points. This is the first iteration of these missiles… I would not be on the side of wagering they are final either… But I wouldn’t say it is due for a nerf either.
The red part. The proportions are the same as previous post, thickness of vanes varies but I’m going with 0 thickness( If there’s thickness drag coef will be higher).
Eitherway, the gap-chord ratio is ~1:1.
For drag to be low, there must be no to little interference between the shock waves early on.
Using the ratio I mentioned. The first shockwaves can be deduced. The minimum is when the shockwaves meet at the midpoint of the gap. That is a 45° angle which corresponds to a Mach number of 2.24. The Faster we go, the smaller the angle of the shock wave is. At M4.13 there is a gap at the end which is half of the gap. Here the supersonic air flows without issue and it meets the weaker shockwave of the trailing edge at 2x the chord length. The faster we go, the smaller the angle and less is the effect from other shockwaves. The mass flow rate increases.
At M1.4, the angle of the shockwave is 45° and its meets the other shockwave at 1/2 the chord length. The shockwaves meet and there’s interference, Mach number drops and pressure increases. The slower the go, the angle rises, velocity decreases and pressure increases.
Below you can see this part.
When the shockwaves meet the MAch number is slower. This translates to a higher pressure
When velocity decreases even more to the transonic region, the pressure inside the vanes is considerably higher. What happens whe we have a high pressure? We got a a wall. It’s “easier” for the air to go around the fins than through the higher pressure. Remember the higher pressure pushes “out”. You can aswell put an airbrake…
Also, as you saw above, the pressure behind the fins is high. That’s ALLLLL the parasitic drag. It decreases considerably at high (>M5) mach numbers as the supersonic flow just passes through.
Look at the shockwave, created. The MAch number of it. The pressure is high, all that makes the air to just spill around it as there’s less resistances. Same way if there’s an airbrake, there’s less resistance to move around it.
That was on 2d.
Go 3d and the case at Mach 4.13 and Mach 2.24.
This is the area which the air will flow by the trailing edge of the chord. At Mach 2.24 that is zero and meets it just at the end. At M4.13, the area where the air will cross will be 25% of the total area.
You also got the strong interference at the diagonal lines. Increasing pressure and all that even at high Mach numbers.
The calculations I did were at thin plates where the thickness is négligeable. Once you actually add a thickness to them, the imaginary tip of the shockwave will be ahead of the tip of the object and the shockwaves will meet earlier.
You can see below. The shockwave intersection is closer to the thin plate. If both were thicker, the intersection would ahead than that of a reallly really thin plate. AS shockwaves meet earlier, drag is higher.
The point being, that whole above Mach 1.3 grid fins superior less drag and everything is not true at all. That would be around Mach 5, which the missile doesn’t go.
Just imagine trying to push your plane around from Mach 0.8 to M1.4 with 32 airbrakes…
We stated it benefits greatly from launches above 1.3 mach and has superior energy retention at high supersonic regions. This is still absolutely true, to pretend the grid fin (which needs far less deflection for sharp maneuver) will not benefit more so than a planar fin in these regions is interesting. You’ve gone and made a lot of good points but it seems you are being intentionally misleading.
Especially with the comment I quoted, there aren’t 32 ‘airbrakes’. There are 4 maneuvering surfaces. Are the JAS-39s canards airbrakes?
In any case, the missile is only ever briefly at this region of speed and we have already discussed and covered the fact that it has relatively low impact on the performance of the missile overall. Planar fins have advantages, but the grid fins are more useful for the design goals of the R-77. You won’t see a missile like the Phoenix or AMRAAM above 25° AoA irl, the instability is too high. The grid fins are clearly superior for accuracy, control, and strike a fantastic balance for their use as a medium range missile.
The deltaV of the R-77 is already higher than the AMRAAM, and as I’ve discussed… They hadn’t given it the missing ~15% thrust to account for reduction in drag during motor burn time and the drag must be reduced when loft is removed so that it still meets the performance criteria.
Your discussion of grid fins is entertaining, but unless you have performance charts for the missile I’m not sure you’ll be able to change the in-game model based solely on hand drawn models of supersonic grid fin wave drag.
