Lee-Gardner Amendment would reduce supersonic fuel burn

It's fine to be suspicious, but one should at least read carefully while in that state. TFA is about "amendment -> more noise on takeoff -> narrower engine -> fuel savings -> lower costs". Literally one paragraph mentions the sonic boom restriction, while the rest is about fuel savings. Lots of comments here are skipping that entirely, which indicates some confusion. Perhaps Boom will publish something else with more detail about flying jackhammers?

To address that issue, ISTM we trust FAA to get many things right, but previously the thoughtful regulation of supersonic civil aviation was not one of those things. If this amendment passes, it will become one of those things. Is there a particular reason not to trust FAA thoughtfully to regulate this sort of flight?

Thank you for the link to the stackexchange discussion. I read it and the Wikipedia and NASA pages it links to. Based on the Wikipedia link the calculated second table by the stackexchange author is incorrect. The Wikipedia article points out that the path of the N-wave will generally be curved upwards due to the temperature gradient from altitude to the ground making the distance longer. The path of the N-wave is not going to be the cone normally depicted. But, there are two things not discussed in the Wikipedia article that I think will also play a role in the magnitude of the sonic boom. 1) As altitude increases, air density decreases; meaning that for a given speed a smaller number of air molecules will be displaced thus reducing the magnitude of the sonic boom at the ground. 2) The sharp N-wave close to the supersonic source is not a soliton and will undergo dispersion reducing the over pressure. That is, as altitude increases and the distance to the ground increases, the N-wave is going to spread out into more of a layed-over-S wave reducing the magnitude of the sonic boom.

With regard to the SR-71 making record setting flights and flying at the limits of its flight envelope to do so(100,000+ feet or "the edge of space"), I think the sonic boom at that altitude may not be noticeable to human hearing.

I know the that the SR-71 and the Space Shuttle have produced very noticeable sonic booms, but what isn't answered is at what altitude did the sonic booms become noticeable or annoying. It seems to me that with all the things that reduce the the magnitude of a sonic boom that it may be possible to fly supersonic without being annoying and slow down to subsonic to takeoff and land. It might also be possible to design the aircraft body to promote dispersion of the N-wave.

Typo edit

> The article asserts that the problem fixed by the legislation is noise regulations that end up requiring wider supersonic engines to meet, which increase drag and cost of operation.

> To the extent the costs result from legislative mandates, and are not inherent in building supersonic aircraft, you obviously can

The problems with cost are real, but it's more from flight restrictions than drag (subsonic flight over mainland to final destination using a supersonic-optimized engine is going to be very inefficient).

We can just look at the Concord as a prime example. Barred from supersonic flight over mainland, it became economically infeasible to continue to operate only trans-oceanic flights (I believe all 3 operators ran it as a loss-leader, of sorts, due to the novelty). Even then, when approaching the destination, the Concord had to revert to subsonic speeds, and ditch the shock wave while still out at sea. Unless there's some magical way to generate only minute shock waves from large passenger aircraft (I'm highly skeptical here), you're going to break people's windows etc, or you're going to burn up a bunch of fuel and wind up with the same issues all over again.

The other lesson learned from the Concord is, there's very few cases where people need to be somewhere that quickly, and are willing to pay the high ticket prices to do so. One can almost always book an earlier flight, for a substantial savings (I'm also highly skeptical there's any fuel cost savings with supersonic flight as the article seems to claim).

Can somebody explain this please?

Sonic booms are very loud and disruptive. NASA has done some research into mitigation by using blunt-nosed aircraft, but none of that applies to Boom's more conventional design.

Here's what the Concorde sounded like at altitude, from the ground: https://www.youtube.com/watch?v=cbPh2llw0-M

Engine noise is understood well enough that you can choose the level you want and develop an engine that is as good as possible that reaches that level.

TL;DR This is legislation Boom wants enacted to allow for more relaxed noise emission levels.

"Current engine noise rules for new supersonic aircraft are more stringent than those for the existing subsonic fleet. By setting our engine noise to the same levels as existing subsonic airplanes, we could make our engines produce so much less drag that we would save 20–40 percent on fuel, depending on whether you use this year’s or next year’s rules as a baseline."

Curious if they've hit a wall in their aerodynamic design and need this to move forward.

> What I don't understand is the engine size rule.

It's not a size rule, it's an engine noise rule which ends up (per the article, I don't know enough about the relevant fields to confirm this) requiring wider engines which end up producing more drag.

I am delighted by the idea of a little anthropomorphic chunk of air shouting "Move, there's a plane coming!" and then face palming upon realizing too late that it is using sound to warn other bits of air about something moving at supersonic speeds.