Max speed is not what matters in air combat. It’s only used when you’re trying to escape a combat space or avoid a missile. You can’t even attain those speeds meaningfully given heating effects on the engine that will reduce their efficacy and speed at which you’re guzzling fuel. Acceleration is a far more important performance metric.
Chinese Engine Development
- Thread starter jackbh
- Start date
That would depend on the pressure recovery of the J-20's air inlet. Shock geometry changes with the Mach number. So an aircraft needs variable geometry inlets for having good performance over a wide range. Otherwise thrust scales in a bad way.
It could be used to boost the range of your AAM.
Yes, pressure recovery is also a factor of course. But realistically you’re going to hit a limit on that based on your engine’s overall pressure ratio too. You can toggle the parameters but the fundamental principles of attainable airspeed limits are still the same. The limit isn’t defined by max thrust alone (especially not the max thrust in ideal conditions figure that engines are reported with).
And to go after objectives or targets that are extremely time-sensitive, i.e. intercepting enemy fighters and/or bombers that are enterring key battlespace and/or targetting crucial allied platforms and installations.
Otherwise, fighter jets usually operate below their maximum speeds most of the time.
You need to more than basic Newtonian thrust=drag logic if you want to understand how air breathing engines work.
The frame of reference the reaction mass of a rocket engine works against is the object expelling the propellant. The frame of reference an air breathing engine works against is the velocity of its free stream. These are not the same physics problems.
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Yes, but you need at least that. When you say something like
I immediately discount everything you have to say about how air breathing engines work because I'm not sure you've made it as far as Newtonian thrust=drag logic.
Static or take-off speed thrust is what is reported usually. Both are quite irrelevant in supersonic aircraft. Look at the comparison of the F-100 on the F-15 vs Al-31 on the Su-27. Different designs like different altitudes and speeds.
No. Because your attainable thrust is a variable, not static, factor based on a number of relationships with the engine’s ability to extract work relative to the air stream it’s ingesting.
Before you try to insult people based on what you think they understand about physics maybe you should double check your own comprehension of the physics behind air breathing engines.
Before this conversation goes any further, I'd like you to answer three questions:
1. What are the forces acting on an aircraft in flight?
2. What are the conditions under which an aircraft attains its maximum speed in level flight?
3. In your model of the forces acting on an aircraft in level flight, explain how
I'm not trying to insult anyone. When people call out my very simplified model to illustrate why @manqiangrexue is not seeing the performance improvements he expects from the WS-15, I'm going to make sure I check those people's understanding of middle school physics.
The laws of physics don't change because the working principles of the engines involved changes.
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