Flagrum Posted October 6, 2014 Posted October 6, 2014 I was puzzled how dangerous the employment of the Kh-66 was: by the time it impacts you are already about to overfly the target as well. If you go with emerg. reheat, you "almost" overtake that damn thing! So I ran a few tests, shooting the Grom at different speeds of the launching aircraft. I also shot some S-24A for comparisation. All speeds are max speed taken from the F2 view. [TABLE].|A|B|delta B-A Aircraft|280 kts|680 kts|400 kts Kh-66|820 kts|820 kts| 0 kts S-24A|1300 kts|1700 kts|400 kts[/TABLE] The Kh-66 flies with a max speed of 820 kts, no matter how fast the launching platform was. Even if the missile can not keep up the total initial speed during the whole boost phase(s), the additional speed of the launching aircraft should make a significant difference, right?
kojdog Posted October 6, 2014 Posted October 6, 2014 Thought I'd add that this source: Friedman, Norman (1997), The Naval Institute Guide to World Naval Weapons Systems, Naval Institute Press, p. 235, ISBN 978-1-55750-268-1 According to wikipedia states the speed of the Kh-66 as 2,160–2,700 km/h. I don't have access to the actual document myself to verify.
WinterH Posted October 6, 2014 Posted October 6, 2014 No wonder we almost catch up to the missile when it hits during fast attack runs :). Can it be an aerodynamic limitation for 66 that limit it's potential top speed? Even then though, I would still expect to see some difference it missiles speed in accordance to it's initial velocity. Wishlist: F-4E Block 53 +, MiG-27K, Su-17M3 or M4, AH-1F or W circa 80s or early 90s, J35 Draken, Kfir C7, Mirage III/V DCS-Dismounts Script
Flagrum Posted November 6, 2014 Author Posted November 6, 2014 bug still present in 1.2.11.33866 OpenBeta
Dolphin887 Posted November 8, 2014 Posted November 8, 2014 Noted. Power through superb knowledge, training and teamwork. [sIGPIC][/sIGPIC]
iFoxRomeo Posted November 9, 2014 Posted November 9, 2014 (edited) ...the additional speed of the launching aircraft should make a significant difference, right? ...Can it be an aerodynamic limitation for 66 that limit it's potential top speed? Even then though, I would still expect to see some difference it missiles speed in accordance to it's initial velocity. What limits an object in its maximum airspeed? Right, it is drag that sets the limit. The rocket´s engine produces a certain amount of thrust to overcome drag. If the platform, that is shooting the rocket, flies slower than the rocket´s Vmax, the rocket will accelerate to its Vmax, but not faster. If the platform flies faster than the rocket´s Vmax, then the rocket will decelerate until it reaches it´s Vmax. The difference between shooting stationary or moving is the time the rocket needs to reach it´s Vmax, this leads to a different range it can fly. Fox Edited November 9, 2014 by iFoxRomeo spelling Spoiler PC Specs: Ryzen 9 5900X, 3080ti, 64GB RAM, Oculus Quest 3
ViFF Posted November 9, 2014 Posted November 9, 2014 Sources on the web point out that the Kh-66 terminal velocity is between 2160 to 2700 kph. Variance between 2160 to 2700 kph probably to account for variance in air density and angle of flight parameters. Assuming an extreme example of a launch occurring at near sea level with a very shallow angle of flight between launching platform and target: The Mig-21bis Vne is 1300 kph IAS and the Kh-66 should accelerate to at least 2160 kph by the time of rocket engine burn out. interesting find. thanks. IAF.ViFF http://www.preflight.us Israel's Combat Flight Sim Community Website
Flagrum Posted November 9, 2014 Author Posted November 9, 2014 What limits an object in its maximum airspeed? Right, it is drag that sets the limit. ... or max thrust, doesn't it?
Flagrum Posted November 9, 2014 Author Posted November 9, 2014 An other test shows that the missile does not decellerate at all. It starts right away with ~ 800 kts and keeps that speed. See attached .TRK and TacView (especially the 2nd launch).grom slow.trkgrom slow.acmi.txt
iFoxRomeo Posted November 9, 2014 Posted November 9, 2014 ... or max thrust, doesn't it? An other test shows that the missile does not decellerate at all. It starts right away with ~ 800 kts and keeps that speed. See attached .TRK and TacView (especially the 2nd launch). I´m not questioning your finding. The speed of the Kh-66 is obviously too slow. But you asked for the difference between a rocket fired from a moving platform vs. stationary platform. The Vmax is reached when sum of drag and sum of thrust are in equilibrium. The platform comes into play, when the rocket itself can not reach Vmax because it runs out of fuel before reaching it. Then the platform can make the difference. You wouldn´t expect the MiG-21Bis to reach a higher Mach number if it was launched from a Tu-160 at Mach 1.8, would you? Fox Spoiler PC Specs: Ryzen 9 5900X, 3080ti, 64GB RAM, Oculus Quest 3
Flagrum Posted November 10, 2014 Author Posted November 10, 2014 I´m not questioning your finding. The speed of the Kh-66 is obviously too slow. But you asked for the difference between a rocket fired from a moving platform vs. stationary platform. The Vmax is reached when sum of drag and sum of thrust are in equilibrium. The platform comes into play, when the rocket itself can not reach Vmax because it runs out of fuel before reaching it. Then the platform can make the difference. You wouldn´t expect the MiG-21Bis to reach a higher Mach number if it was launched from a Tu-160 at Mach 1.8, would you? Fox No, I wasn't assuming that you were questioning my findings. But I just wanted to make sure I understand all implications correctly so that I don't miss something obvious. ... aaaaand I still did miss something. Or made a silly mistake. I said, the missile does not decelerate after launch. Of course it does not, as the Vmax is higher than that of the launching platform. But anyways, yes, there is still something not right there - the missile should in fact accelerate from ~500 kts (launch platform) to Vmax = ~800 kts ... and that it does not either.
ViFF Posted November 10, 2014 Posted November 10, 2014 How do you know that the published speed of 2100 to 2700 kph is the maximum attainable speed while its rocket motor is still running or at the moment of rocket engine cut? Most air to ground weapons with propolsion constantly accelerate to the point of their rocket engine cut out and that is labeled their terminal velocity (what you wrote as vmax). In this and many other cases weapons' terminal velocity do benefit from the launching platform speed at moment of launch. Cheers IAF.ViFF http://www.preflight.us Israel's Combat Flight Sim Community Website
Flagrum Posted November 16, 2014 Author Posted November 16, 2014 Noted. Seems to be fixed with 1.2.11.34087.547 - thank you! At least someting drastically changed: the missile accellerates now and max TAS is now ~1100 kts (~2000 km/h). See attached tacview (and compare it to the previous data: http://forums.eagle.ru/showpost.php?p=2225854&postcount=9)
Aginor Posted November 16, 2014 Posted November 16, 2014 Jep, can confirm that. Much better now, thanks LN! :) DCSW weapons cheat sheet speed cheat sheet
TurboHog Posted November 16, 2014 Posted November 16, 2014 Another Phantom-fix will add to this list http://forums.eagle.ru/showpost.php?p=2233010&postcount=74 'Frett'
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