[Fuddh]

Supersonic flights over land is actually a fairly difficult problem to solve, as the noise levels are very high. This is a major reason behind why the Concorde only flew across the ocean.

Nonetheless I did not know Boeing was lobbying against it - that kind of protectionism does indeed hinder innovation.

[capilotractor]

When I was 13, we had a math class that was scheduled at the same time the Concorde flew over the school, 35 km away from the Roissy airport. The teacher had to stop talking for 10 seconds and wait for it to fly away. This thing was loud.

[caf]

Concorde did actually fly over land - Braniff Airways operated it between Washington DC and Dallas Fort Worth under a short-lived, strange 'tag flight' arrangement (where the aircraft would continue on from Washington to London / Paris under BA / AF crews).

This segment was sub-sonic, though.

[dingaling]

And for each US domestic rotation each individual aircraft was reregistered onto the US N-register, and then back onto the UK or French register for the Atlantic crossing.

At that time only N-reg aircraft were pemitted to operate internal commercial US flights.

To simplify the process the BA Concordes were allocated unique-for-the-UK alpha-numeric registrations which could have their 'G-' prefix hidden by speed-tape:

http://www.braniffpages.com/n94aa.jpg

[jrnichols]

Here's a link to an old Braniff schedule showing the Concorde as a route out of DFW...

http://www.departedflights.com/BN102879p52.html

[mabbo]

Apparently (can't find the article I read on it) the noise would be much less of a problem today.

The magnitude of the sonic boom is relative to mass, and modern planes are being built lighter and lighter (to save on fuel). Something like a 50-seat mostly-carbon-fiber super sonic aircraft at 50,000 ft might well be perfectly fine to fly over land at Mach 2. The smaller size might also help with the problem of empty seats. As well, ideas like wings that change shape/angle for different portions of the flight could also help.

Someone just needs to put down the R&D money and take the risk to build such a plane.

[brian_cloutier]

That doesn't sound reasonable. The sonic boom is caused by (I had thought) air being compressed at the front of the plane. That would mean the loudness is determined by speed and shape of the plane.

The only way mass would have an effect is if the exhaust (which heavier planes presumably generate more of) contributed to the sonic boom, which doesn't sound right.

I'll believe that modern planes might generate smaller sonic booms, being more efficient sounds like it's related to how you displace the air, which sounds very related to the size of the boom, but I don't believe you that mass is related.

[mcguire]

Not necessarily. The amount of air displaced is related to the mass of the aircraft. A heavier plane displaces more air, leading to a more energetic boom.

[nf05papsjfVbc]

Are you suggesting that if we have two planes of the same size and shape, the heavier one displaces more air?

I can understand that objects floating on water follow that principle but that's because they are floating. Once fully suspended in water, I think the amount of water they displace is just their volume. Shouldn't it be likewise for aircrafts in the atmosphere?

[mcguire]

To maintain level flight, a plane has to generate lift equal to its weight. It generates lift by forcing a mass of air down. More mass means more air disturbed.

[nf05papsjfVbc]

Interesting. I never thought of it this way. Thanks for helping me see the missing part of the picture.

[brian_cloutier]

Ah, you're right, thanks for clarifying. My comment now looks pretty dumb, wish it didn't get so many upvotes.

[mzs]

You are describing ground effect not lift.

[mabbo]

Ah, my mistake!

Someone else in the thread posted an article I may have read (or the author of the one I read, read, x levels of authors deep).

[LeifCarrotson]

The magnitude of the sonic boom is not relative to mass. It is relative to the altitude and to the speed of the aircraft, and the duration and maximum amplitude of the shock wave are dependent on the shape of the aircraft.

You may have misread an article describing pounds-per-square-foot as a measure of sonic boom intensity. This measurement is not about the mass or density of the aircraft relative to its area, this is the change in air pressure at the ground caused by the sound wave.

[ohitsdom]

NASA is working on quieter sonic booms.

http://arstechnica.com/science/2016/02/meet-nasas-new-x-plan...

[digi_owl]

I seem to recall that they did some testing with a fat nosed F-5 that showed such a configuration greatly reducing the shockwave.

[spitfire]

https://en.wikipedia.org/wiki/Shaped_Sonic_Boom_Demonstratio...

Pretty cool looking actually. Though it does dull the "fighter-planes-fighter-plane" look of the F-5 a bit.

[iainmerrick]

I disagree, it looks much better! It's like something right out of Flash Gordon or Dan Dare.

[Fuddh]

I did not know this - great point!

Actually being able to use simulations to a much larger extent than was possible back when Concorde was being developed must play a role in lowering the costs of building a new supersonic aircraft. I believe this is what Boom is trying to do! Let's hope they can spur more investments into this field - it would be very cool if we got to see supersonic travel again :)

[mabbo]

Apparently, I was wrong! While many organizations are working on reducing sonic booms, mass is not a factor.