MiG-31BM/Κ Interceptor/Attack aircraft: News

GarryB wrote:An interceptor needs to get to its intercept point as quickly as it can... the difference between Mach 2.84 and Mach 1.8 super cruise might be the difference between shooting down 10 B-1Bs, or having to take on 10 B-1Bs plus the 220 cruise missiles they just launched...

Who is talking about reducing speed of the plane?  

These are charactristics of the D-30F-6 engine:

Maximal thrust (H=0, M=0, t=15°C)                9500 kp (93,16 kN)
Full afterburner thrust (H=0, M=0)                15500 kp (152 kN)
Specific fuel consupmtion on maximal thrust 0,72 kg.kp-1.h-1
Specific fuel consumption with full afterburner 1,9 kg.kp-1.h-1
Maximal turbine inlet temperature                1387 °C
Air flow                                                150 kg.s-1
Pressure ratio on low pressure compressor 3
Pressure ratio on high pressure compressor 7,05
Overall pressure ratio                                21,15
Bypass ratio                                        0,57
Inlet diameter                                        1020 mm
Length                                                7040 mm
Dry mass                                                2416 kg
Maximal operation speed                        M=2,83

This is a huge engine with levels of thrust smaller products already reach (F119 indeed, AL-41F1 is close). It is even larger than the F135, which is not a supercruising engine and still produces ca. 128 kN mil. thrust and ca. 191 kN with AB. I don't think it is too risky to say that lower bypass or two stage VCE with today's technology could reach levels of thrust close to 150 kN in military settings. In fact the izd. 20 was tested on the MiG-25, supposedly 176 kN max thrust, I didn't manage to find dry thrust, but in any case it was an already designed supercruising engine with the right size, if you know what I mean...

Operation in afterburner has advantages at high altitudes because in mil settings the power of the turbine is being extracted at the same level while the thrust itself decreases with increasing altitude so in the end there is little left for propulsion. That creates an additional difficulty to reach AB thrust in mil settings, but even if it was not possible to cruise a 2.8 M but 2.3 or 2.5, it would be already a huge advantage in fuel consumption.

Look at the TSFC in dry vs. wet modes above, there is a 2.6 factor between them which would be translated almost directly into range. So you cannot fly 2.35 M to 700 km but to what, >1000 miles? And therefore allows to attack carriers even before they release long range missiles like AGM-158 JASSM-ER, or to substantially extend the range of Kinzhal attack missions too... it is a massive improvement, one that would put NATO again on their back foot, threatening their assets theatre-wide.

BTW another possible optimization of the MiG-31 could be to unify the K and BM versions, so it is not necessary to divert airframes from air defence to attack roles and vice-versa. Work on airframe + re-engining would make it possible, since the K got its radar removed and fuel increased due to the needs o the new mission, so a more powerful engine with lower fuel consumption is a big deal. They were not exaggerating when they said the modernization potential of the plane was far from exhausted...

For an interceptor the best propulsion would be a combined bypass turbofan with a ramjet or scramjet...

The YF-120 was modified in such way, since it was a VCE this was already implicitly possible in the original design. They said it could reach 4.1 M... which is shockingly similar to the speed announced for PAK-DP (4.2 M) and, to me, it makes clear what solutions the Russians are considering. Since izd. 20 was already done and probably izd. 30 is its continuation, an ABVCE based on it is only a logical following step...

The YF120 was also proposed as the basis for a more exotic engine, the Turbine-Based Combined Cycle (TBCC) engine that was to be used in demonstrator aircraft like the X-43B and future hypersonic aircraft. Specifically, the YF120 was to be the basis for the Revolutionary Turbine Accelerator (RTA-1). The variable cycle technology used in the YF120 would be extended to not only turn the engine into a turbojet but also into a ramjet. In that mode all airflow would bypass the core and be diverted into the afterburner-like "hyperburner" where it would be combusted like a ramjet. This proposed engine was to accelerate from 0 to Mach 4.1 (at 56,000 ft) in eight minutes.[11][12]

https://en.wikipedia.org/wiki/General_Electric_YF120



https://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/20050196667.pdf
https://www.slideshare.net/PraveenPratapSingh2/variable-cycle-engine-ppt-65048391

But you know they will...    

Sure, since Maidan was Putin's fault, the dementia of US politicians must be his fault too!!  

I would say they are repeating what they did with the Blackjack... the difference is that while they only had 16 odd Blackjacks available so they had to restart production, with the MiG-31 what they were short of was the hot sections of the engines... which are the bits that wear out. Building new hot section bits should allow existing engines to be brought back to service and use meaning all those MiGs in storage can be used if needed... together with upgrades and overhauls to existing models they should be able to spend extra time getting the MiG-41 to where it needs to be... the US is funding hypersonic weapons... so clearly a good focus for the MiG-41 is to deal with such threats and also potentially launch weapons and satellites out of the atmosphere...

Exactly. New capabilities are needed no doubt, a very long range / very high speed performance on PAK-DP would benefit from a very big airframe capable of providing high performance weapons with additional launch energy, which is critical for operations against very high speed threats or in near space. That is not necessary for other roles the MiG-31 is covering now. The repair of the D-30F6 was already solved, and as said before, one of the main problems they found and that significantly delayed their capability to overhaul and airframes was de deviations from spec that they find in the planes. This forces them to rework the pieces before installing them, which is a very time consuming and very ineffective effort. With 3D printing they can tackle that problem much better.

https://www.ainonline.com/aviation-news/defense/2019-08-13/russia-relaunches-production-engine-cores-mig-31
https://zen.yandex.ru/media/id/5ddfbc8b9515ee00ac9e370a/3dprototip-dlia-miga-5dfb6c4e11691d00aeaac1e6

They could be the inner layer... the inner ring defence, with the faster likely longer ranged MiG-41 being an outer layer of defence.

That is a good idea, and one that is also reminiscent of the PAK-DA / Tu-160 case, with different performances that actually allow to think about parallel operation in complementary roles...

GarryB wrote:

Who is talking about reducing speed of the plane?

I understand what you are saying... going 5th gen supercruise engine technology on the MiG-31s engines should increase performance, but I am thinking it would be much easier to look at redesigning the engine to operate as a ramjet at higher flight speeds like the engines on the SR-71 does.

It would be easier to engineer and also I think taking it further and making the engine of the MiG-41 into something similar but with a 5th gen super cruising engine with a scramjet mode for higher flight speeds would be a natural progression...

For the MiG-31 the supercruising engine would keep the speed and reduce the consumption. I don't know what the airframe is ready to take in terms of dynamic pressure and temperatures, going beyond 3 M is pretty extreme. But why not. My point was that izd. 20 was already that very type of engine. I don't think they just destroyed the design documentation and I also doubt they don't realize the use it would have in the MiG-31, since they tested it precisely on the MiG-25. As said, by now the effort in the -31 simply means keeping it usable (BM modernization) and the airframes safe to fly for more years (newly announced project). Should they decide to go further, there are indeed interesting paths ahead...

BTW another possible optimization of the MiG-31 could be to unify the K and BM versions, so it is not necessary to divert airframes from air defence to attack roles and vice-versa. Work on airframe + re-engining would make it possible, since the K got its radar removed and fuel increased due to the needs o the new mission, so a more powerful engine with lower fuel consumption is a big deal. They were not exaggerating when they said the modernization potential of the plane was far from exhausted...

That is basically what the jet engines of the SR-71 did... at top speed almost no air went through the turbojet engines... which were idling... most of the air went around the outside of the engine as a ramjet...

Certainly, only new design and technology would allow to add 1 M to the speed. The J58 was a very exotic engine then, now VCEs are maturing and are going to turn into mainstream.

[/quote]

GarryB wrote:My understanding is that it was the engines and the rotational speed capacity of their blades that limited flight speed to mach 2.84.

I thought it was the max TIT being reached. Ram effect + compressor would overheat the air at the entrance of the combustion chamber, the faster you fly, the hotter it gets.

By running the engine as a ramjet and slowing the engine rpms down at high speed flight that speed limit is removed so then the speed limit is the heat limit and that high temperature aluminium and of course new ceramics and composites and titanium bits become more interesting.

Sure, that removes the temperature limitation of the turbomachinery and you use (almost) only the afterburner section. I am not sure this saves fuel in any significant way though

It might be the case that the new engines for the MiG-41 allow the MiG-31 to fly slightly faster than it does with the upgrades but also massively improve range and acceleration etc etc, which means you could get commonality of engines there too eventually.

It could be the case, if they where VCE enabling the -31 to supercruise as argued above. If it is only a hypercombustor, then it would not necessarily help with range. Of course the technological difference would be substantial, it may provide much more thrust and a more efficient design in general. A change to a ramjet engine in general is considered necessary to go above 3 M, if the air vehicle itself is not designed for that, the advantage of using the same engine may not be justified.

It might be fairly easy to get it up to mach 3.2 or faster without much more effort, which would make it useful in designing the MiG-41 too.

+

I would presume the shape of the MiG-41 will mean if flys faster than they could make the MiG-31 fly and likely with an internal payload so drag is not an issue with full weapons loads either for the 41.

Why do you think they designed it for a speed higher than what they knew it would be operated at? That would mean to assume many compromises in other areas. For instance, the wing sweep is not very marked for a plane which is almost 3 M, but it provides more lift so, in the end the thing needs to take off and land too. Dynamic loads at those speeds are huge, temperature becomes a significant problem from 3 M onwards... maybe with new materials they manage to do that, I (personally) just think it was not designed to fly significantly faster than it does.

magnumcromagnon wrote:The talk about what powerplant/engine should be powering MiG-31's, completely neglects FPI's successful efforts in creating test benchmarks in spin-detonating ramjets, and completely electric engines.

I just think PDE is way too far in the future for an update to MiG-31 that should be done within next 10 years and not be massively expensive, as to electric engines... what would they offer here? We talk about levels of energy density that electric propulsion is nowhere close to reaching, and BTW how do you use them to create a highly supersonic gas flow that propels a Mach 3 plane?

GarryB wrote:Alcohol injection cools the intake...

I know about that trick in the MiG-25, does it apply to the MiG-31 too?

It wouldn't need extra after burner, it just needs airflow bypassing the jet engine... so essentially you fly faster without dramatically increasing the fuel burn rate...

You use the already existing afterburner but the air comes bypassing the core... I would need to check about what the fuel consumption would be in that regime, because maybe you are right. The compression is done by the speed itself so the combustion should be more efficient than conventional afterburner...

It really does not matter whether you have to use AB for a few seconds or even minutes to achieve supersonic flight, if you can continue in dry thrust the result is essentially the same, so I discount the US requirement to achieve supersonic speed without using AB because it is simply childish.

I would agree, in fact it makes sense to engage AB to go through the transonic region as fast as possible, no point in staying for a long time blocked in a region of specially high drag...

Being able to fly a supersonic speeds in dry thrust even if it can't super cruise is good enough in my opinion.

Where I agree with the US criteria (the original one) is that supercruising should not be >1 M but >1.5 M. There are and were many planes capable of flying faster than Mach 1 on mil power. 1.5 M sets  specially designed platforms apart. It is not the same to fly 1.1 M than 1.8 M... in the case of a very low drag platform like the MiG-31, maybe >2 M would be possible. And the flight altitude for platforms with such high wing load depends on flying very fast. Based on the diagram I already attached few days ago, MiG-25 with 28 t weight can fly at 15,000 m @ 1.5 M, 21,000 m @ 2.5 M.

I am not suggesting more than Mach 3.5 or so...

It is not unthinkable, but I don't know how much margin there may be.

Indeed right now they are working on a new replacement for the R-37M, the Item 810, which is described as having between three and 9 times more range than the R-37M depending on the launch profile... AFAIK it is a rocket powered missile.

Special for internal carriage, with 1.5 times more range from what I read. 360 sec. operation (ca. 500 km @ 5 M), 40 km altitude.

This piece is about the PAK-DP but it deals also with the same topics we were discussing about MiG-31

http://www.aviationunion.ru/news_second.php?new=18338

Honored military pilot of Russia Vladimir Popov believes that the main task of the promising aircraft, as well as its predecessor, will be to patrol and defend the Northern territories of Russia.

"The designers have the possibility of deep modernization of the MiG-31 fighter at the expense of new engines," says Popov. — The interceptor will be able to fly at supersonic speed for a long time without an afterburner. It will barrage in economy mode at a high altitude in the waiting area. Such vehicles will help very quickly repel the attack of any means of air attack — cruise, ballistic or tactical missiles, drones and bombers."

Mig-31BM2 Super Irbis-E wrote:Why was there no Mig31BM in Syria for testing?

What would they do there?

The filthy wahabbi goat-rapers don't have any aircraft that require high speed/altitude interception, and MiG-31s aren't exactly configured as bomb trucks for moving mud...