Bisnovat/Molniya R-40 (AA-6 ACRID) AAM

[Ronny]

Well it’s true. ER has more powerful motor and less drag. Much less drag. It does go faster and twice as far. The top speed of R-40 is Mach 5.27. This is close to average speed of R-27ER across its flight time at high altitude. On the deck, R-40 is doing no more then Mach 2.8.

To be fair, I agree that the R-40 likely experiences more drag than the R-27 at the same altitude. However, the Mig-25 operates at significantly higher speeds and altitudes than the Su-27, especially when carrying missiles so drag unlikely a limiting factor near their respective service ceilings.
At lower altitudes, drag would certainly become more problematic for R-40. But at height around 27 km, it’s difficult to believe that drag alone would prevent an R-40 from catching a Mach 2.27 target from behind, particularly when launched from a Mig-25 traveling at approximately Mach 3.2.
For comparison, earlier we noted that an R-27ER launched from a Su-27 at about 18 km altitude could successfully intercept a retreating target flying at Mach 2.5 from up to 45 km away
Btw, what is their respective thrust and motor burn time though?

Its 540-720 m/s added velocity depending on altitude.

Do we also have manual or something source stating that?.

I’m sure R-40 can intercept that fast 2500+ kmh if you’re close and high, but you would have to very close and high, extenuating circumstances. It’s not a hard limit but more of a “recommendation” and “if you intercept someone faster you better know what you’re doing.”

They said the maximum speed of target that can be intercepted to 2400 km/h, so it is a hard limit I think otherwise they would have use the word "recommended or something similar. This is extremely strange to me. Mig-25 top speed is already 600 km/h faster than that.

 

[NMaude]

particularly when launched from a Mig-25 traveling at approximately Mach 3.2

The SR-71 cruised at M3.2, the MiG-25 could fly at M3.0 in a clean condition but only M2.8 if carrying its' complement of four AA-6 Acrids.

 

[Ronny]

The SR-71 cruised at m3.2, the MiG-25 could fly at M3.0 in a clean condition but only M2.8 if carrying its' complement of four AA-6 Acrids.

Still much faster and higher than Su-27 though

 

[Aeria Gloria]

, what is their respective thrust and motor burn time though?

Impulse almost 250. 118 kg fuel. 4-6.7s burn. It is what the CFD is made with. You can see that regardless of “drag,” it de-accelerates at a faster rate then R-27, AIM-7, etc according to CFD. The thrust to weight is very equal for R-27R vs R-40 which makes sense but 27ER has basically 50% more thrust to weight. As far as deltav, for R-40 it is 540-720 m/s which is very equal to R-27R but for ER it is 800-1100 m/s. R-40 has 118 kg fuel but ER has 142 kg fuel with smaller lighter less draggier body.

Do we also have manual or something source stating that?.

MiG-25 manual that I believe I have linked

recommended or something similar. This is extremely strange to me. Mig-25 top speed is already 600 km/h faster than that.

This is explained on the part of the page you underlined where it says the interceptor in rear aspect attack should have 20% speed advantage. Remember it shows target speed is “1”/interceptor speed “1.2”. So it’s just the assumption they are going with for a successful intercept.

 

[Squirrel]

small question, given that R-40 were designed to intercept SR-71, how come the maximum target speed limited to around 2400 km/h (Mach 2.26)?

First this context ,max possible launch parameters for R-40R and R-27ER :

Max possible speed of MiG-25P and Su-27P ( launch speed /first speed of the AAM plus max speed increase of the AAM compared to the fighter , max possible values ) ...

For R-40R =900m/s +720m/s =1620m/s for launch height 20+km ( above Armstrong's line)

For R-27ER=700m/s +1000m/s=1700m/s for launch height 18km ( below Armstrong's line)

Second one ... 'story' about that possibility for engaging high speed targaet like SR-71 in the tail-on aspect.
I think there was a catch with the radar ,not with the AAM itself. RP-25/N005 were LPRF only ,pulse only radars. If we compare that with e.g N001 than we have this result ,as we knoew it is dual-mode MPRF/HPRF radar.

''И хотя не все задумки конструкторов в конечном итоге удалось реализовать, РЛС Н001 вполне отвечала современным требованиям. Впервые в отечественной авиационной радиолокации при создании этой РЛС были решены задачи обеспечения режима средней частоты повторения импульсов для обнаружения и сопровождения цели со стороны задней полусферы на малых высотах, режима радиокоррекции для управления на первом этапе наведения ракет типа Р-27ЭР (Р), применения единого передатчика для работы РЛС и подсвета цели для наводимой ракеты, функционирующего последовательно в режиме импульсного и непрерывного излучения. ''

''Although not all of the designers’ ideas were ultimately realized, the N001 radar fully met modern requirements.For the first time in domestic aviation radar, the development of this radar solved the problems of providing a medium pulse repetition frequency mode for detecting and tracking a target from the rear hemisphere at low altitudes, a radio correction mode for control at the first stage of guiding R-27ER (R) missiles, the use of a single transmitter for radar operation and target illumination for the guided missile, functioning sequentially in pulsed and continuous radiation modes.''

Maybe that LPRF mode only was limiting factor for engaging faster targets in the rear hemisphere ?

 

[Aeria Gloria]

They said the maximum speed of target that can be intercepted to 2400 km/h, so it is a hard limit I think otherwise they would have use the word "recommended or something similar. This is extremely strange to me. Mig-25 top speed is already 600 km/h faster than that.

Maybe that LPRF mode only was limiting factor for engaging faster targets in the rear hemisphere ?

As I have been trying to say, it says right here on the page quoted that a speed advantage of 20% is needed!

Read, velocity of target must be no higher then your velocity divided by 1.2. If it flew 4,000 kmh this limit would be 3,333 kmh.

It is about the MiG-25 top speed and its ability to chase and catch a target. Not the missile or LPRF or anything else

 

[Squirrel]

It is about the MiG-25 top speed and its ability to chase and catch a target. Not the missile or LPRF or anything else

Do you know that navigation system in the MiG-25P was fully functional at speed of 3.25 Mach ?

 

[Aeria Gloria]

Yes I do. It is a simple dead reckoning system corrected by either RSBN or RSDN. Easy enough to add speed and heading change over time according to pitot tube and heading gyro/magnetic flux meter/magnetic heading correction and co-sign of elevation angle. Then you displace it by the amount of RSBN/RSDN calculation.

 

[Squirrel]

Again ,as colleague Ronny stated ,max speed of the target engaged in the rear aspect/hemisphere ( tail-on ) ,can be 2400km/h. As we know ,max oper. speed of the MiG-25P/PD with two/four R-40R/RD (TD) was 2.8 Mach or 3000km/h at 20+km.

 

[Aeria Gloria]

Maybe optical fuse has some dust

 

[Squirrel]

^

On the photo is R-40TD-1 with 'Bekas' combined radio-optical proximity fuse.

https://reviews.ipmsusa.org/review/r-40td-med-range-aa-missile-wpassive-ir-hh