3 ms·

Surely the air is still interacting with the airplane. The shockwave generated by a body shaped like an acute cone is a (somewhat less acute) cone with the sam

Surely the air is still interacting with the airplane. The shockwave generated by a body shaped like an acute cone is a (somewhat less acute) cone with the same apex. Inside the shock wave, the air gradually turns around to move parallel to the body, like so [0]. Each streamline that enters the shock structure keeps turning around, so each bit of air keeps feeling a force even after it passes through the original cone-shaped shock. In the case of a cone-shaped body, the interaction happens to create a single "straight" wave, but it's still generated by the entire surface of the cone, not just the sharp point of it. As a rule of thumb, the magnitude of the sonic boom is proportional to the weight of the plane. That is because most of the interaction between the plane and the air is from the wing, it needs to continuously deflect down enough air to generate a lifting force. So the total boom has one contribution from the cross-section of the fuselage, and another from the wings, and the latter is determined by the weight. [0] https://www.researchgate.net/profile/Richard-Benay/publication/238189753/figure/fig3/AS:668946889977857@1536500775189/Streamlines-of-a-conical-flowfield-Taylor-Maccoll-method.pbm https://www.researchgate.net/profile/Richard-Benay/publicati...

lazide 5y ago
sub-sonic, trans-sonic, and supersonic aerodynamics are fundamentally different. You’re calling out some differences, but not covering others. They are wildly, fundamentally different in behavior. You’ll notice that supersonic aircraft have different airfoil shapes, different airframe shapes, and wildly different engine configurations because they don’t work the same way. There is of course air behind the Mach cone, but it is much lower pressure, will often completely separate (airflow wise) from the airfoil shape in ways you would not expect, and the shockwaves/speed of propagation can cause bizarre pressure, lift, and drag issues. You can end up with massive vacuum where you previously had pressure, or pressure where you preciously had vacuum. Transonic flight or high angle of attack flight at supersonic speeds of course produces rapidly changing variations of all these effects. [https://arc.aiaa.org/doi/abs/10.2514/8.1394?journalCode=jans https://arc.aiaa.org/doi/abs/10.2514/8.1394?journalCode=jans] Unlike subsonic flight, the air can’t “get out of the way” in time, leading to potentially catastrophic issues without careful design. Supersonic flight is better categorized as ‘shoving through slow air’ than flight. What you’re referring to is not wrong - just doesn’t reflect the magnitude of the actual differences

lazide 5y ago

sub-sonic, trans-sonic, and supersonic aerodynamics are fundamentally different. You’re calling out some differences, but not covering others. They are wildly, fundamentally different in behavior. You’ll notice that supersonic aircraft have different airfoil shapes, different airframe shapes, and wildly different engine configurations because they don’t work the same way. There is of course air behind the Mach cone, but it is much lower pressure, will often completely separate (airflow wise) from the airfoil shape in ways you would not expect, and the shockwaves/speed of propagation can cause bizarre pressure, lift, and drag issues. You can end up with massive vacuum where you previously had pressure, or pressure where you preciously had vacuum. Transonic flight or high angle of attack flight at supersonic speeds of course produces rapidly changing variations of all these effects. [https://arc.aiaa.org/doi/abs/10.2514/8.1394?journalCode=jans https://arc.aiaa.org/doi/abs/10.2514/8.1394?journalCode=jans] Unlike subsonic flight, the air can’t “get out of the way” in time, leading to potentially catastrophic issues without careful design. Supersonic flight is better categorized as ‘shoving through slow air’ than flight. What you’re referring to is not wrong - just doesn’t reflect the magnitude of the actual differences