We’re talking about the AIM-120A/B.
Do you have source saying the those early AMRAAM have a lot more range that what the Harier manual stated?
Did the harrier manual give a range or was that the Rmax indicators top line.
i don’t remember sorry, i’ll have to find the doc again.
Someone posted it on the forum, i only know it was 40nm (40nautical miles)
Iirc that was the max indicator on the HUD, a decent estimate for normal use but not really indicative of the max capability.
I’m not going to waste another 100 comments, I’ll just state the following and be done with this constant nonsense.
The R-77’s alleged 12km ground launched range comes from dubious sources not listing the conditions for launch against a target. It could be that it intercepted the target at 12km, was limited by seeker to 12km maximum launch range, or simply isn’t a true statement.
The data for R-77 that we have suggests that the first or last statement are true. People are welcome to share sources and information but until better data is available we will have to go off what we’ve got.
What we can best assume is that according to rosoboronexport the range of R-77 is 80km in the same conditions the R-27ER reaches 100km. We know the maximum range for R-27ER is actually 170km, likewise the range of R-77 can be said to exceed 100km.
For the AIM-120 to reach 80km would require a very very hight alt 0.9 mach launch (14km+) or a supersonic launch from 10-12km alt. Even so, it reaches those ranges by lofting unlike the R-77.
So you are using the specific impulse of the ER? 281 s? When the calculations on the r77 give 236s( for both 4.5s-30.4kN and 6s-22.8kN), only way its higher is with the 6s-30.4kN giving 315s or lower with 4.5s-22.8kN for 177s
Different rocket. 77 is 200mm in diameter while 27series is 230mm. Its also 2x lighter than the ER and 70% of the 27Rs weight. Its 22% shorter than ER and 8% shorter than R.
All this give a much lower ballistic coefficient at end of burn. To get the same Bcoef would be for drag on the ER to be 1.83x higher than that of the R77. Or 1.22x higher on the R.
Looks like you did a VERY optimist calculation imo.
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I just have them both blocked along with Ziggy lmao
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They certainly are some of the forum posters of all time…
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The R-27ER is more around 260mm diameter as the new rocket motor is thicker iirc
I used a standard of around 250s impulse for the R-77, which is nominal for a 1990’s missile from the East. The AIM-7F by comparison is ~262s. The achievement of 280s was possible only for the West at this time, I am not certain where you got that figure for the R-27R/ER.
Of course all of the available information for the missiles is different. I am solely using the specific impulse. Weight of the R-77 and burn time along with all other measures are entirely different. The R-27R and R-77 are only likely similar in propellant type and efficiency.
I don’t know how you sit here and constantly talk about other people in such a negative manner while adding precisely nothing to the conversation. Please contribute or don’t say anything at all.
@MaMoran20 the following site is used for determining specific impulse of R-77… the data can be considered a primary source but unfortunately the source itself is not usable for the forum. If you want more data on it - you can join the site and contact the people who posted the information.
It is stated the following information:
175 kg launch weight
118 kg burn-out weight
Burn time of 4.5-6s
So we can do some simple math;
Burn time (4.5s) * force exerted (assuming ~22854.96 - 30473.28 (Newtons), for this we will use same as R-27R at (25,125 N) and divide by 9.81*(launch weight - empty weight which would equate to 57kg).
The result is ~269s for the 4.5s burn time. For the 6s burn time the math comes out around 202s. The intermediate result is 235s which means thrust is either a bit higher, or burn time is a bit lower than 5.25s. If the 235s impulse is correct, we are close to the expected performance of the motor.
If anything, the results show a 235s impulse and this is a bit on the low end. I’ve gone with this 5.25s burn time and 235s impulse for my in-game model. Do you think this is fair or should I change it up?
Made up
Datamine and did the simple specific impulse math. Force/[dm/dt].
Ingame I have (booster + sustainer) 328s+310s but irl is 311s+221s.
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I used the values you made on your R77 thread.
These are the 7 average mass flow rates for the 2 different burns.
And these are the 4 specific impulse(s) iterations. You see on 2 cases it falls on 236s. Total impulse of 137,126 Ns. Then you have 1 optimist case and pessimist case. The low end really is 178s for specific impulse, not 236s.
236 is the fair value
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The values in the OP aren’t up-to-date, simple mistake there. The data provided in my post above is more accurate.
The low end for specific impulse is 178s? What is this the 1950’s? That is lower than all previous Soviet missiles that we have in-game…?
That is the value that has been used in my testing. Here is the data, perhaps you want to see changes.
Info I’ve found is the same Diameter(which varies really) but the ER is 70cm longer to accommodate the rocket motor
Why don’t you just try both iterations? 6s for 22,854N and 4.5s for 30473N. Can’t say much for drag really but test with a chart for rear aspect at 1100kph and 900kph TAS.
I don’t have rear aspect data for comparison to the AMRAAM
I’ve tried both of the other burn times and adjusted drag a bunch but ultimately I think that increasing specific impulse above 260 isn’t correct, nor is reducing it to 200. As you said, 235s or so seems about right.
I actually think the drag is currently WAYYYYY too high, but it still has the energy to reach the target at 80km provided battery life limit is extended beyond 80s. I realize I forgot to change the drag coefficient back down to a more reasonable 2.6-2.8 in that screenshot. Tests were with too high of a drag coefficient.
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@MaMoran20 What do you estimate for the performance of the AIM-120A’s specific impulse and deltaV? I seem to be getting 10-20% higher deltaV for the R-77 with the impulse numbers we went over.
I’d say its very low.
I put them together. 80km at 10km alt at Mach 1 (R27 charts are given with 1100kph TAS and 900 kph)its a bit excessive don’t you think. When in both cases its half that range.
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Dunno, on the old forum I saw from 240s to 260s. Not sure really but thrust values are given
26,689N (6000lbf) for 1.5sec
And 13,344N (3000 lbf) for 5.5 sec