3 ms·
The key thing is that the absolute pressure rise through the shock wave isn't very high - it's just perceived as a loud boom when it is reached in a very short
by bernulli 6y ago
The key thing is that the absolute pressure rise through the shock wave isn't very high - it's just perceived as a loud boom when it is reached in a very short time.
The pressure wave is ultimately caused by displacement because of the volume of the aircraft, lift, and engines. We cannot really get rid of any of these. Given enough time, a strong enough pressure pulse will steepen into the double-shock 'N-wave' (because the pressure signal is N-shaped) the sonic boom.
Sonic boom mitigation then means to prevent the pressure waves from steepening into a boom before it hits the ground, e.g. by a long nose, lift distribution over a large part of the aircraft length, putting the engines on top so that their pressure wave radiates upwards, etc.
- Tossrock 6y agoUninformed speculation: I wonder if you could mitigate via a precisely out-of-phase second boom which destructively interfered with the first one? Kind of like noise cancelling headphones. Schlieren photography shows us that there are actually multiple waves being produced over the body based on where the geometry experiences sharp changes, so maybe if those were designed juuust right?
- bernulli 6y agoUnfortunately, it turns out that (for ideal gases, such as our atmosphere) a 'negative shock', i.e. a rarefaction shock, is impossible. It would violate the 2nd law of thermodynamics! And if you have multiple, subsequent shocks (one at the aircraft tip, another at the engine inlet, another at the wing, etc), the later ones will eventually catch up to the first one, resulting in the N wave we would want to avoid.