We don’t “know” as it is not included in the video however given that it is a test of the missile’s performance, would it not be more logical to assume the planes are maintaining a set speed so as to exclude that variable from the test?
1 Like
This reply is talking about the IRL (in real life) footage of Tomcat launching Aim-54 I posted above: The AIM-54 Phoenix missile - Technology, History and Performance - #1106 by SE_8749236
The bottom line is, for testing purpose, the Tomcat IRL is either accelerating or maintaining current speed.
So let’s evaluate each case.
- Tomcat in IRL footage is accelerating, and the Aim-54 is not falling behind by significant amount after launch but before ignition.
This means Aim-54 has vastly superior drag coefficient to the point that it is not losing any speed before ignition.
Conclusion: Aim54 in game has too much drag - Tomcat in IRL footage is maintaining speed,and the Aim-54 is not falling behind by significant amount after launch but before ignition.
This means Aim-54 has some drag but not enough to cause it fall behind by 10 meters during its ignition delay.
Conclusion: Aim54 in game has too much drag
So it doesn’t matter, Aim-54 in game has too much drag either way.
2 Likes
This reply is talking about the in game footage of Tomcat launching Aim-54 I posted above: The AIM-54 Phoenix missile - Technology, History and Performance - #1106 by SE_8749236
TL;DR: The Aim-54 in game is estimated to have a drag coefficient of ~4.25, a typical amateur rocket IRL has drag coefficient of 1 or less.
Using in game footage and kinematics, we can estimate the drag force that the Aim54 is receiving.
With aircraft as reference frame, Aim-54 starts at 0m/s and displacement of 0.
After launch and it starts fall behind, when ignition, it was displaced backwards by ~10 meters.
I’ll calculate 5 meters displacement as well in case I’m over estimating the distance it moved backwards.
10m:
Using d = v1t + 0.5at^2, you get:
10m = 00.5s + 0.5*(a*(0.5s)^2
10m = 0.5*(a*(0.25s^2)
a = 10m / 0.5 / 0.25s^2 = 10 * 2 * 4
a = 80m/s^2
F=ma, and let’s use the lighter Aim54A, m=443kg.
F = 443 * 80 = 35440N of force.
This is clearly an overestimation, since this is more than twice the thrust of Aim-54.
5m:
Using d = v1t + 0.5at^2, you get:
5m = 00.5s + 0.5*(a*(0.5s)^2
5m = 0.5*(a*(0.25s^2)
a = 5m / 0.5 / 0.25s^2 = 5 * 2 * 4
a = 40m/s^2
F=ma, and let’s use the lighter Aim54A, m=443kg.
F = 443 * 40 = 17720N of force.
This is still more than the thrust of rocket motor.
Perhaps base drag reduction is already implemented.
I did calculation wth 4m, since it can’t possibly have displacement less than 4 meters since the missile clearly moved at least its body length after launch but before ignition.
4m:
Using d = v1t + 0.5at^2, you get:
4m = 00.5s + 0.5*(a*(0.5s)^2
4m = 0.5*(a*(0.25s^2)
a = 4m / 0.5 / 0.25s^2 = 4 * 2 * 4
a = 32m/s^2
F=ma, and let’s use the lighter Aim54A, m=443kg.
F = 443 * 32 = 14176N of force.
For comparison, Aim54’s rocket motor in game has 14350N of force.
This yield a net force of 174N, which translates to ~0.4m/s^2 of acceleration, or 1.44km/h per second.
If base drag reduction is not modeled b=ub gane, Aim-54 in game shouldn’t accelerate noticeably at all. Thus base drag reduction is likely modeled.
However, the drag is still way too big and it significantly negatively affects Aim-54 after its burn ends.
If we use drag equation we can estimate the drag coefficient of Aim-54:
Launch speed = 337 knots = ~624km/h = ~173m/s
Launch altitude = 31841ft = ~9705m ==> air density = less than 0.4671.
Missile cross section area when nose first (using 0.39m diameter to compensate for fins): ~0.477m^2
Equation: drag = CA0.5pv^2, C = drag coefficient
Assuming drag = 14176N
14176 = C * 0.477 * 0.5 * 0.4671 * 173^2
C = 14176 / (0.477 * 0.5 * 0.4671 * 173^2) = 14176 / 3334
C = ~4.25
That’s a drag coefficient of whopping 4.25, even worse than a bowl with concave side facing towards the air stream.
This doesn’t make sense for a streamlined missile.
Even if you play with the number and get the estimated drag coefficient down to 2, it is still way worse than IRL. Since typical amateur rockets has drag coefficient of 1 or less when not burning.
This means either CxK is not drag coefficient for missiles and it needs to be lowered, or CxK is drag coefficient but War Thunder has bug where missile’s drag coefficient is 4 times (or more) than it was supposed to be.
Early launch tests might have been on low throttle (decelerating) to avoid engine issues due to smoke intake. Can’t rule this out. We do know the drag is too high, but the exact altitudes and speeds and whether accelerating or not is not known.
Doing the equation, V=a.t
10m – 80m/s^230s=2400m/s
5m — 4030= 1200m/s
But the drag reduses the speed, how to calculated how much reduses?
When the changes are live, anybody want to try em out?
probably tomorrow
Maneuverability buff?
Yes
1 Like
80% ish Fin AoA buff
Aaaand, reverted back?
all changes were reverted, something broke and they panicked
Almost, the sensors were not changed back.
You are assuming missile booster or drag is performing constant acceleration, but that assumption is not true.
Also 32, 40 and 80m/s^2 are estimated acceleraton due to drag force before rocket motor ignites, they are not the thrust of rocket motor.
If the change in Fins AoA goes through, will this primarily influence the low speed turning ability and not so much high speeds? Does fins AoA mean how much the fins deflect from the missile or how much AoA they can pull on the air?
Small question, could AIM-54 be launched at long range without range/velocity data?
There was a test where AIM-54 was launched against a BQM-34E using noise jammer from 110 nm. There is no way AWG-9 achieve sufficient S/N ratio from such distance to burn through jamming, but it is such an extreme distance that I don’t get why it possible to launch without knowing target speed and range
Why would it need to burn though the jamming? Both the AWG-9 and AIM-54 have HOJ capabilities and it is still potentially within range of auxiliary sensors(IRSTS, TCS IRST).
Yes, I do know that AWG-9 have ability to track the angular direction of the jammer (JAT) and AIM-54 can home on the jamming source. But if I recall correctly, isn’t both JAT and HOJ only give angular direction and no information about distance to target or velocity of target?. And it is also the same case for the TCS and IRST. That what confuse me, I thought extremely long range shot required you to know distance and target speed, otherwise it can’t be done.
But on the otherhand, if very long range shot can be done without knowing distance to target and target speed. Then wouldn’t something like F-16CJ with ASQ-239 be a very good counter against any stealth fighter?