I’d really be happier if we can stick to a true manpad scenario. Of course one can use various vehicles, but there are certain benefits to my idea. Local mobility (urban areas, forests, mountains) as well as lower chances of detection – be it from the sky or various ground patrols. Of course one could always utilize a simple car to cross larger distances, loaded with missiles and all the equipment.

I assume 17,900 lbf thrust is uninstalled thrust at sea level? do you happen to know how much installed thrust were the engines producing at said contiondions – 73000 feet and mach 2? A ballpark figure would suffice.

thank you anatolij, finally the kind of answers in the form i was looking for. Same generation engine but greater mass due to the need of prolongued afterburner work sure does sound convincing, and it’d also a large enough drawback so it is logical not many other planes would want that ability, as it comes at a too great of a cost.

So, if i’m understanding you right, it comes down to f15s engines (or engines of most other fighters for that matter) not being able to withstand AB usage for a prolongued period of time, while mig31s engine/airframe can withstand it?

IF correct, then what is stopping other planes and engines to be remodelled so they can last longer in AB? I know there has to be a reason, so i’m just asking what is that reason. What would the planes lose by making themselves better at withstanding AB use for half an hour at a time?

Now we’re getting somewhere. Maybe. So EVERY plane could it it, with their existing engines (I didnt say anything about keeping the inlet system though), if they had enough fuel?

1500 km at mach 2.3 is some 36 minutes of flight time. But the amount of drag mig31 produces should be visibly more than f15, no? Even a f15 carrying CFTs, its still sleaker and thinner. Of course drag coefficient comes into play but i’m not willing to bet mig 31 has that sufficiently lower than f15. If somone can explain that it has, I’d be happy ro hear them. (lets also assume CFTs are specially made to be part of the plane and dont have structural speed limits) And such a f15, with internal fuel plus special cfts but no drop tanks still has some 13.500 kg of fuel. mig31 has 14200 kg of internal fuel plus 1.600 kg in a drop tank. So we’re talking about roughly equal values, if not better for the f15. Yet still no one ever said anything about f15 using afterburner at mach 2.3 for 30+ minutes, nor about any other similar fighter for that matter.

Are other manufacturers/users simply not saying what they can do, even if they can do it, or they cant do it? And if they cant do it – Why cant they do it? Then there has to be something that differentiates F15s and Mig31s AB fuel consumption at mach 2.3.

Thanks people for all the links, i have read them all, re read them, i do believe i understand everything they say. Yet it still does not answer my question. 🙁

The MiG-29 with the RD-33 is a medium ratio turbofan with a ratio of 0,47.

That does allow a sfc of 0,77 in military and a sfc of 2,0 in AB.
Lower that ratio and the sfc will rise in military, when it drops in AB, because less cold air has to be heated.
Rise that ratio and the sfc will drop in military, when in AB it does go up, because more cold air has to be heated.

What is said above is logical and goes well with all the texts people have given me. BUT. It does not mesh with mig 31 situation.
How on earth does d30f6’s bypass ratio of 0.56, which is a large ratio, which should have poor supersonic sfc, enable the same engine to have sfc of just 1.9 in AB??? It goes against what has been said up to this point.

I think I understand the bit about large intakes, ramps, oblique wave, keeping the pressure at bay, and how mig31 achieved enough thrust for its speed. I am okay with the amount of thrust, that doesn’t bother me. What bothers me is how did it manage to have such small fuel consumption while making so much thrust. And when that question is answered, I have another one: what disadvantages are there to it, so most other planes aren’t using whichever principle mig31 is using?

The following text sheds a bit of light on what i was inquiring about, though i’d like a detailed explanation, if possible.

“The R-15 is optimised for sustained supersonic flight, under which conditions it functions as a turboramjet, rather than turbojet. At high speeds, most of the intake air is compressed by the inlet, and therefore the low pressure ratio engine core adds little compression to it, essentially serving to feed the gargantuan afterburner with a flow of optimal temperature, density and oxygen content. Under these conditions most thrust is produced by the afterburner, and the SFC is as a result quite poor at 2.7. However, the engine can run under these conditions for as long as fuel and lubricant are available, unlike turbojets optimised for lower speeds which suffer excessive turbine inlet temperature rise resulting in hot end failures.

The penalty suffered by this powerplant configuration is abysmal subsonic and transonic SFC performance, resulting from the poor pressure ratio of the rudimentary compressor. An SFC of 1.25 in dry operation is 50% greater than it US contemporaries, such as the J79 at 1.9/0.84. An interesting comparison is the P&W J58 fitted to the SR-71A, which has an 8 stage compressor and 2 stage turbine, producing up to 34,000 lbf of thrust and exhibiting SFCs of 0.8 dry and 1.9 in reheat.

The D-30F has excellent SFC performance in dry setting at 0.72, and its afterburning SFC of 1.9 is also very good. These provide for excellent endurance in cruise and subject to fuel available, respectable endurance in afterburner.”

While i understand the D15 bit, i must confess i dont understand how d30f managed to keep sfc so low for both subsonic and supersonic flight. Am i right to assume that supersonic flight envelope changes a lot from, say, mach 1.5 to mach 3? Ram compression, or ram recovery is much, much higher at mach 3?

when an engine, any engine, does 100 amount of thrust, and it is said that dry thrust is 60 and 100 is thrust with AB, does that mean that all 100 of thrust can be gained by bypassing the already fully compressed air (as much compressed as it would be passing through the engine) around the engine core and just lighting the burner on it? And then, by not using the engine core we save fuel? I could live with such an explanation. Or is the engine core work essential part of 100 amount of thrust at very high speeds (mach 2, mach3) and without it the thrust would fall to a smaller amount?

That is all fine, but question remains: how come mig31 crossed such distances at high speeds (mach 2.3 often quoted) when it had afterburners on? What is the principle that enabled its afterburners to use less fuel than other planes used? Most other planes can not use afterburners for that long. Or someone is lying about something.