PAK DP prospective long-range interceptor

Look,i'm not advocating to build others updated Mig-31 but to adopt a plane with about the same dimensions and general design but with the advantages that the natural evolution of techs have achieved.

calm down... I have no idea what design they are going to end up using, but the MiG-31 is already a lighter stronger more heat resistant redesign of the MiG-25 which was largely heavy stainless steel. Both aircraft are heavy but that is mostly fuel because flying fast burns lots of fuel.

I don't think new materials are going to give it the performance boost they are looking for in a new aircraft.

Certainly there is scope for improving the performance of the MiG-31 in areas like materials and engines, but I don't expect enormous changes... remember the MiG-31M upgrade was considered too expensive so they just have four R-37M missiles under its belly instead of 6 in the upgrade...

For rather higher speeds I think a new shape in addition with new materials and new engines will be required and I suspect internal weapon carriage to reduce drag will be considered too. The Mig-41 wont be a super multirole aircraft... heavy long range AAMs and rockets to sink ships or destroy satellites or incoming ballistic missiles should pretty much cover it all.

So, a lighter frames and way better engines , thanks to new materials and a wing and intake design that would give to it a better manoeuvrability in its designated speed ranges (i.e. something very different from the one in which Flankers/Fulcrum operate) instead to going into something like the YF-12 (that was an huge failure).

The SR-71 was not a failure... it was ridiculously expensive and they tried to cancel it several times and repeatedly retired it... but something would come up and it would come out of retirement...

The long nose meant it could not fly high, and they seem to want something that can operate at very high altitude as well as high speed.

Its interesting to note, the Mig 31 and its Mig-25 predecessor also look a bit like the Mig-29 fighter's predecessor ie the Mig-23. So I could imagine the Mig-41 as extremely fast, pretty stealthy but less manouverable than the Su-57.

Too much wing area is not good for high speed, and any MiG-41 is going to be in the air so it needs to be scanning continuously with its radar looking for low flying targets that ground based radar have missed.... so being stealthy is rather pointless too.

It needs to be able to operate from conventional air fields so while it needs to be able to fly fast it also has to take off and land on less than a 20km long airstrip.

Lifting body aircraft that you are talking about are not like the MiG-29 and Su-27 where the shaped fuselage generates lift at subsonic speeds and improves performance, I think you might be talking about hypersonic body lift a flying object gets above speeds of mach 5... normally only relevant for missiles and hypersonic gliders that can benefit from that by getting lift without the drag of wings.

Smart shaping of wings will help where the leading edge and the trailing edge can reshape to generate lift at low speeds, and retract or flatten out for very high speed use so a thin profile wing can generate lift but also drag for take off and landing, while for high speed flight flatten out and generate lift at very high speeds with minimal drag...

Over the decades they will have looked at an enormous range of shapes and layouts... each with good points and bad points.... they have supercomputers and new materials that might make some old designs that were discarded because they couldn't be made might be possible now... making physical prototypes is very slow and very expensive... with supercomputers they can test dozens of designs at a time and whittle tens of thousands of potential ideas down to a dozen or so that might be worth further exploration.

It is important to point out a design might be rubbish for an interceptor because its problems make it unusable... but that same shape could be used by a drone where the problems don't matter in its role as a drone...

It wont be a flying wing like a B-2, but it could be a flying wedge.... a sharply angled triangle shaped aircraft... it is going to be fun to see what they come up with...

For the MiG-41 I rather suspect the combination of rocket and scramjet would be a bit too volatile.

For very high speed flight then using slush hydrogen makes sense because you can pump it through the aircraft skin near leading edges for cooling, and also though various engine parts to cool those down too, but for an aircraft operating at only mach 4-4.5 or so a ramjet would actually be just fine.

A ramjet is the simplest jet design... a tube where air flows... it narrows which compresses the air which heats it up... fuel is added and burned and it blows out the rear of the engine at very high speed... no blades no turbine shafts or disks.... the only problem of course is that you need to be moving forward to start it and get useful thrust.

You don't have to be moving very fast... ramjet engines have been fitted to Biplanes to test to see if they boost performance.

But to operate as a fighter or interceptor and use conventional runways another jet engine is needed.

The most elegant solution was the SR-71. It had turbojet engines and bypass space around them... so the turbojets get you air borne and climbing, but turbojet engines can't get you to mach 3 because the rotational speed of the shafts and blades can't operate at that fight speed and they rip themselves apart.

As the SR-71 gets faster and higher the huge nose cone in front of the engine moves and redirects the airflow so instead of flowing through the turbojet, at very high speed it flows around it.... making it bypass air. Now normally when we talk about bypass air we are talking about a turbofan where the turboshaft extends in front of the turbojet engine with huge blades that in the centre suck air through the turbojet, but the outer surface of the blades suck air through a bypass tube that goes outside the turbojet. You seen them on airliners they are called high bypass turbofans and they move a lot of heavy cold air which means they can only be used for subsonic flight. A low bypass turbofan has smaller front blades that blows cold air around the hot section, but at higher speed and when it gets to the AB section more fuel can be added and burned in the AB because it is cold and oxygen rich unlike the air that flowed through the hot section.

With the SR-71 the bypass air effectively works like a ramjet... no blades pulling the air through so at high speed you can shut the turbojet down and in the AB section add fuel there to power the ramjet... your flight speed is limited to the temperature your aircraft can take... which was about mach 3.4.

For the MiG-41 you don't need a powerful engine... reliability is much more valuable and would only be used during takeoff and climb and during landing.... when zipping around the place at high speed only the ramjet will be running... they could be clever and have two turbojet engines for takeoff and landing and have a bypass ramjet between the using the same exhaust, or each engine could each be their own ramjet too...

SABRE engine is nice idea but by now little more than that, mainly intended to extend the range of a rocket engine in order to achieve single stage access to orbit, though they are trying to extend it to hypersonic flight as a way to create a very light air breathing engine. In any case I see it more as a curiosity or a niche application, it would need cryogenic fuel instead of normal aviation kerosene and in general is a novel unproven technology and that is normally incompatible with military applications.That is my impression at least...

What I am trying to say is that the MiG-41 doesn't need rocket propulsion to achieve the speeds they want it to operate at.

Cryogenic fuel is generally hydrogen... with a scramjet engine you can scoop up oxygen in the air to burn the hydrogen fuel... no need to carry highly dangerous oxygen except for use outside the atmosphere and the MiG-41 wont be leaving the atmosphere.

Missiles like the SA-6 and Kh-31 and many other types of rocket ramjet missiles the Soviets and Russians have developed are single use weapons that need to be accelerated to make them more effective and efficient.

The design of a ramjet engine means lots of empty space down its core where the air flows through the ramjet to produce thrust.

Soviet and Russian designers filled that cavity with a solid rocket motor to accelerate the missile and allow it to climb a bit before the ramjet engine was started... once the rocket motor burned out the structure for it was ejected leaving space for the ramjet to start up and start propelling the missile instead.

This improved performance without making the missile bigger because instead of tacking a solid rocket booster on the end and effectively doubling the missiles length which is what the west did with the British Sea Dart naval SAM or the various American Naval missiles with ramjet propulsion and big solid rocket boosters, with the internal rocket the missiles were much more compact and lower drag.

The SA-4 had strap on side mounted solid rockets around the ramjet core and was a huge missile.... the SA-6 in comparison was tiny and much more elegant.

The point is that for an aircraft a normal turbojet or turbofan engine would make rather more sense and only needs to get the aircraft airborne and allow it to climb to altitude and moderate speed before propulsion could be transferred to ramjet and the speed really increase and climb to much higher altitudes.

A rocket would work but they are terribly dangerous with their liquid oxygen requirements... and most liquid rocket fuels are rather toxic.

For near orbital speeds then slush hydrogen rocket ramjets might make sense... as I said the super cool hydrogen could be used to cool the engine and heated parts of the skin surface at very high speeds but such things would not be needed if the speed is only going to be Mach 4.2 or so.

limb wrote:IIRC russian liquid fuel rockets use kerosene or hypergolics no? Those are not cryogenic. Only the liquid oxygen is gryogenic.

The fundamental principle of the SABRE engine is using the cryogenic fuel to cool the compressed air by some hundred degrees, without a heat sink at extremely low temperatures the cooling process would be much less effective.

Rocket/ramjet tech has been pioneered by the soviets with their air to surface missiles and continued with the zirkon.
Also VCEs,  PDEs, etc are even more unproven, and the SR-71 solution turned out to be highly impractical. PDEs havent produced a single flyworthy powerplant, seemingly eternally trapped in black project bench tests.  

I agree PDEs are further in the future, but the J58 engine of the SR-71 lies in fact at the root of the new RTA engines. It worked ok when it was operational.

Hell, the whole concept of a mach 4+ interceptor is unproven. Doesnt mean it isnt developed.

What do you mean? The faster the interceptor, the better. There is no big need to prove that. It does not exist in iron, agreed, but neither does the SABRE as a commercially mature solution.

Unlike the theoretical SABRE wielding space plane, the MiG-41 would only need enough rocket fuel+oxidizer to power for its SABRE engines to bring it to hypersonic speed, not to LOE.

An engine using normal aviation fuel and engines derived from well understood ones seems more practical to me. Let us see what results of the program.

PapaDragon wrote:MiG-31 has engines that are capable of pushing it past it's max speed but it's limited due to canopy material not being able handle friction heat

AFAIK the 2.83 M limit is due to the engines both in the MiG-25 and -31. The faster you fly, the bigger the ram compression added to the operation of the turbomachinery, to the point the temperature limit of the engine is surpassed. Also a regular turbofan loses capability to propel the plane at increased speed, from 3 M onwards a ramjet is the proper thing.

Materials are no longer issues as well, if they have uber awesome materials that can deal with heat from Mach 20-27 on Avangard making some rock bottom variety that handles heat on Mach 4 or even 5 is nowhere near a problem

But it is a completely different problem... the Avangard can have smart ways of handling plasma or use ablative shields, while the mechanical demands and operational life of the engine is incomparably higher...

My guess is that they will be making aircraft with standard jet propulsion like MiG-31 only much more advanced and probably larger because it would need to carry it's weapons internally (as for bay size I would go for it being able to fit Kinzhal missile inside or larger)

I am not so sure about the engine as explained above, but we will see. Regarding the missiles, why not carrying them recessed? That is way cheaper and lighter, and it will allow the plane to carry very big and heavy weapons. A plane flying that fast and high will be seen from hundreds of km away regardless, I am not sure it makes any sense to give it internal bays either from aero or from detectability point of view. At least not for the bigger weapons.

Side by side seating with pressurized cockpit like Su-34 would also be very desirable

 

If the platform is very big it would be acceptable, if not it would increase drag a lot.

MiG-31 has engines that are capable of pushing it past it's max speed but it's limited due to canopy material not being able handle friction heat

Those engines are late 60s / early 70s technology, today they could easily make upgraded version (or design brand new ones if they aren't feeling frugal) which could deliver massively superior speed

My understanding is that at flight speeds above mach 3 the rotational speeds of the blades inside the turbojet or turbofan engines is such that they lose their shape and damage the engine beyond repair.

The solution in the SR-71 is to change the flow of air from going through the turbojet engine to bypassing the engine completely.

Those bit pointy nose cones sticking out of the front of each engine can move back and forward... when it is back the air can flow into the jet engine for takeoff and landing, but once it reaches speed and altitude it moves forward so the air can't go into the jet engine... it goes around it... and that bypass air is a ramjet with no moving parts or blades or disks... the only problem is being a ramjet and not a scramjet the fuel has to burn in a subsonic air flow so it would be limited to about mach 5 or 6 at most.

The point is that when the SR-71 is flying at Mach 3.2 there is no air flowing through the jet engines it used to take off with... the air flowing through the engines is bypassing the jet engines and going through tubes effectively operating as a ramjet.

The MiG-41 will likely do the same... if it is designed well and the aircraft can take the heating effect on the various parts of its airframe that will be subject to friction heating, then speeds of mach 4.2 wont require anything exotic like a scramjet.

There are lots of ways they could do it... they might have one jet engine for takeoff and landing and two ramjet engines running down either side so it might be a bit sluggish taking off and landing but at high speed it could be a rocket, or to reduce fuel burn they might have two smaller jet engines to get airborne and for landing and one ramjet for high speed cruise or supercruise at about mach 2 or so.

Ramjets don't need to be big... the scramjet they tested on an SA-5 surface to air missile looked about the size of a large coffee tin on the tip of the missiles nose and drew fuel from the place where the warhead would normally be located... the solid rocket boosters and main rocket motor helped the entire missile to climb to high altitude and about mach 5 flight speed, and then they started up the scramjet which operated for about 90 seconds and accelerated the missile from mach 5 to mach 6 and flew about 180km...

My guess is that they will be making aircraft with standard jet propulsion like MiG-31 only much more advanced and probably larger because it would need to carry it's weapons internally (as for bay size I would go for it being able to fit Kinzhal missile inside or larger)

Side by side seating with pressurized cockpit like Su-34 would also be very desirable

But that's just my guesstimate, we'll have to wait and see

It will be interesting... staying in the same size range will make large weapons difficult to carry internally and this aircraft will need to carry some anti ship and anti satellite weapons that could be very big, though they might be carried conformally perhaps.... they have had interceptors of all sizes and there was even a suggestion that the Blackjack could be used as a large interceptor... the Tu-160P but of course they only made about 30 so it wasn't really a viable option.

Now it is probably not fast enough, but a Tu-22M3M upgrade perhaps with huge AESA and much longer weapon bay...

I am sure they will come up with something cool.

Materials are no longer issues as well, if they have uber awesome materials that can deal with heat from Mach 20-27 on Avangard making some rock bottom variety that handles heat on Mach 4 or even 5 is nowhere near a problem

They might only be able to stand it for a few hours and then need replacing like heat tiles on the space shuttle...

I am not so sure about the engine as explained above, but we will see. Regarding the missiles, why not carrying them recessed? That is way cheaper and lighter, and it will allow the plane to carry very big and heavy weapons. A plane flying that fast and high will be seen from hundreds of km away regardless, I am not sure it makes any sense to give it internal bays either from aero or from detectability point of view. At least not for the bigger weapons.

Of course internal weapons carriage raises the question of can it open its weapon doors at mach 4.2 and release those weapons?

The MiG-31 solves the problem of weapon separation by using weapon hard points with pnuematic rams that throw the missile down when they are launched so they clear the aircraft cleanly before starting their motors even at mach 2.83...

Those patent drawings of missiles stored vertically and fired upwards in flight could be a clue to how weapons could be released... perhaps released backwards, or up and back to start a steep climb to altitude to start their long range flights...

Will be interesting.

This will actually work to it's advantage as it'll be able to launch larger and more capable weapons from within the weapon bays.

Fully internal weapon bays might be problematic... and getting a really big aircraft to fly at mach 4.2 will be harder than getting a smaller aircraft to do the same, though I suppose it doesn't need huge engines for takeoff and landing... once it is airborne if can climb and accelerate and engage a few ramjet engines that would be more than up to the task of getting even a very large aircraft to very high speeds...

Just check out Tu-28 Fiddler, it was huge and was in service for very long time:

It was an interesting aircraft, that was focused more on range than on speed, but both can be important...

Being able to make a Tu-128 faster than MiG-25 while still retain long range and heavy payload will make it rather cool...

The production facilities to produce new Tu-160s means they can make very large aircraft of titanium and other difficult to weld materials and the swing wing box structure needed to have a fast low drag design with the ability to take off and land at lower safer speeds... so it does not need 20km long runways...

The Tu-22M was supposed to be a mach 3 bomber, but fortunately Tupolev managed to make them realise that it would be an enormous waste of fuel and payload capacity and would not be much safer against a modern air defence. For an interceptor however speed has advantages... especially when covering a lot of territory.

magnumcromagnon wrote:I can almost guarantee you that the next gen interceptor will be a large aircraft. The MiG-31 is a large aircraft, and PAK-DP will probably be even larger. PAK-DP will likely be between the Tu-22M3M and the Tu-160M in absolute dimensions. This will actually work to it's advantage as it'll be able to launch larger and more capable weapons from within the weapon bays. The speed and drag would be such that traditional weapon bays would be replaced with revolving door weapon bays that I've previously advocated for.

I assume it will be bigger than the MiG-31, because it makes sense for range and payload mainly. The fineness ratio of a longer plane is also normally better, that helps at high speed. I don't think it will be as big as you say though, but who knows. I think the role of the plane against space based assets is going to be crucial to define it size. US seems completely invested in militarizing space, therefore Russia needs a very capable tool against both surveillance means deployed en masse and eventual agile, weapons-carrying platforms of the X-37B type. Very capable interceptors against low orbit targets are needed and they will be probably BIG!

GarryB wrote:There are lots of ways they could do it... they might have one jet engine for takeoff and landing and two ramjet engines running down either side so it might be a bit sluggish taking off and landing but at high speed it could be a rocket, or to reduce fuel burn they might have two smaller jet engines to get airborne and for landing and one ramjet for high speed cruise or supercruise at about mach 2 or so.

No need for that, we see there are engines that can take care of all flight required regimes...

Of course internal weapons carriage raises the question of can it open its weapon doors at mach 4.2 and release those weapons?

The MiG-31 solves the problem of weapon separation by using weapon hard points with pnuematic rams that throw the missile down when they are launched so they clear the aircraft cleanly before starting their motors even at mach 2.83...

Those patent drawings of missiles stored vertically and fired upwards in flight could be a clue to how weapons could be released... perhaps released backwards, or up and back to start a steep climb to altitude to start their long range flights...

In the Su-57 the weapons bay profile has a special shape to allow for supersonic release. For much higher speeds I admit I don't know if the idea is still feasible. Vertical release makes sense for lower speeds IMHO, otherwise there would be a big lateral moment as the missile's body is launched into the wind, in fact for supersonic speeds this sounds pretty crazy due to the shock.

As for launching missiles from internal bay there's always simplest option of slowing down to standard supersonic speed while launching

Speed and height of the aircraft means extra speed and range for any missiles they launch... slowing down to launch missiles would reduce missile performance...

To be honest if the weapons are carried in an internal weapon bay they could have their control surfaces deflected slightly down so when they are thrown down into the slipstream on launch they would naturally continue to fly away from the launch aircraft as they light up their rocket motor and fly away.

Certainly there were plans to launch satellites and anti satellite missiles from the MiG-31, and I think a MiG-41 that is faster and higher flying would be even more interesting in terms of launching small things into space so as high and fast as possible is best.

Carrying weapons externally simply isn't feasible or economical at those speeds (and there's also issue of stealth to take into account)

Any RCS advantage would be ruined by significant and constant bold IR signature... and the fact that being an interceptor it will likely have an enormous AESA radar of some sort blazing away scanning for small stealthy targets and targets at very long range including low earth orbit...

I think internal carriage for low drag makes sense but the doors will need to open in a way that it does not act like an airbrake...

MiG-31 was like two Su-27s taped together, I expect MiG-41 to be like two MiG-31s taped together

With this it's go big or go home, jet interceptors have always been big

A point is that ramjet are very good propulsion systems for aircraft in those flight ranges... the technology is mature and reliable and new materials should allow ramjets that can operate for long periods and maintain high speeds even with large heavy aircraft...

No need for that, we see there are engines that can take care of all flight required regimes...

Even new technology turbo (jet and fan) will struggle at rotational speeds to operate a big aircraft at mach 4.2... in comparison a ramjet should be fine... no problem at all... no blades or disks or blisks having to deal with enormous rotational speeds and trying to resist shattering and destroying the engines.

The engine needed to get the aircraft airborne could be the engines currently used on the MiG-31... the ramjet component can be the new part that allows the high speed high altitude flight at efficient fuel burn rates to get decent range without a drop tank the size the space shuttle used...

Save the super engines for the mach 7, 6th gen fighter or as upgrades for the Flanker family and Su-57.

After they have made the next few scramjet powered long range missiles then hybrid scramjet/turbofan engines can become a thing...

PapaDragon wrote:As for launching missiles from internal bay there's always simplest option of slowing down to standard supersonic speed while launching

In order to give range to their missiles, altitude and speed of the carrier have a massive effect. If they intend to use the plane against targets in near space or against hypersonic missiles, then launching interceptors as fast and high as possible is indeed one of the cardinal requirements and in fact the very reason such a plane would need to be developed

GarryB wrote:Even new technology turbo (jet and fan) will struggle at rotational speeds to operate a big aircraft at mach 4.2... in comparison a ramjet should be fine... no problem at all... no blades or disks or blisks having to deal with enormous rotational speeds and trying to resist shattering and destroying the engines.

This is what we have been discussing, ABVCE can cope with this task and they are based on relatively well known technology. Having one type of engine instead of several of them is a huge advantage.

The engine needed to get the aircraft airborne could be the engines currently used on the MiG-31... the ramjet component can be the new part that allows the high speed high altitude flight at efficient fuel burn rates to get decent range without a drop tank the size the space shuttle used...

It can be the same engine, once if is variable bypass the only big change needed is to extend the operational regimes into ramjet mode by allowing the core just to idle at high speed and bypassing the airflow to the afterbuner. This is a perfectly feasible and best of all, it allows a progressive transition from high bypass mode for takeoff to turbojet mode for low supersonic flight into ramjet for high supersonic flight. This allows to optimize thrust and fuel consumption in all flight regimes.

Save the super engines for the mach 7, 6th gen fighter or as upgrades for the Flanker family and Su-57.

Hell, the ABVCE is a super engine!

The point is that the MiG-41 will be operating in two different operational modes... takeoff and landing for which enormous speed and enormous acceleration is neither wanted nor desired and even the current MiG-31 engines would do the job, though if the MiG-41 is a lot bigger... like Tu-22M3 size then perhaps two NK-32s might be better, but operating at mach 4.2 no conventional existing turbojet or turbofan could get them to that speed and maintain that speed efficiently, but a ramjet or two certainly could do it.

No need for 5th gen engine technology or any super turbine performance or materials... just a standard ramjet... that could, over time be upgraded to scramjet which would in the future offer potential speed increases no jet engine with blades or disks or blisks could match... ie mach 10 plus...

Bucaneers,

Buccs were naval strike weren't they?

Ironically the plane that eventually evolved into the F-111 was designed as a carrier based interceptor... the engines of the F-14A and the radar are developed from the early model carrier based F-111s... but it was too heavy to safely operate from carriers so it was adapted to land based strike, while its engines and missiles and radar were adapted to be used by the F-14A...