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Will we ever fly supersonically over land?

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Re: Will we ever fly supersonically over land?

#131

Post by perl4ever »

pessimizer wrote: post #96
quotemstr wrote: post #70

Earlier quoted context omitted.

If you think that we use too much fuel, increase the price of fuel. Don't just randomly oppose specific technologies that use fuel on the grounds that you, personally, yellow_led, don't feel those technologies are necessary.

So it's alright to increase the price of fuel because yellow_led, personally, thinks too much fuel is being used, but not alright to randomly oppose specific technologies on the grounds that yellow_led, personally, thinks they use too much fuel? I'm not following your logic. Also I don't know how you randomly oppose specific things.

>yellow_led, personally, thinks too much fuel is being used

>randomly oppose specific technologies on the grounds that yellow_led, personally, thinks they use too much fuel

I think the assumption is that we mostly agree on the first item, but the second one is supposed to be a means to the first. Which yellow_led and others think is a big mistake.

>I don't know how you randomly oppose specific things.

Random means arbitrary here, I think. Without sound logical reasoning.

Re: Will we ever fly supersonically over land?

#132

Post by hugh-avherald »

FridayoLeary wrote: post #73
dogma1138 wrote: post #63

Earlier quoted context omitted.

Europe banned supersonic commercial flights over the continent 2 years before the US did. Whilst this was political to some extent the politics were very much local, as in people don’t want to hear booms.

Also, shattered windows. A boom can easily smash windows.

Not that easily. Even with a fighter at 500 ft above, Mythbusters couldn't break windows. The Oklahoma tests had eight booms a day using very large aircraft. It took months before windows broke.

Re: Will we ever fly supersonically over land?

#133

Post by Zababa »

nostromo wrote: post #76
failwhaleshark wrote: post #61

Earlier quoted context omitted.

Flying, in-general, is inefficient unless it's a large, lifting body in ground effect.

Flying on a full or almost-full plane is more carbon efficient than driving solo. And that's not taking into account the cost of the road networks we build and maintain to allow high volumes of vehicular traffic. https://yaleclimateconnections.org/2015/09/evolving-climate-...

> Flying on a full or almost-full plane is more carbon efficient than driving solo.

But how do they fare against trains, especially since trains can run on electricity? The mpg quoted in your article (21.6) also seems really low.

Re: Will we ever fly supersonically over land?

#135

Post by lazide »

kortex wrote: post #99
nine_k wrote: post #95

Earlier quoted context omitted.

I don't see why the boom energy has anything to do with the size of the aircraft producing it. It should only depend on the speed of the spike that produces the boom; typically the entire aircraft fits within the sonic boom cone produced by the nose spike when flying straight. So I suppose an artillery shell, a jet fighter, and a Concorde should produce about the same amount of boom at the same speed of, say, 1.5 M,…

Why wouldn't size correlate with magnitude? A whip crack breaks the sound barrier, it doesn't shatter windows. Same with a bullet, which goes even faster. You need both pressure level (voltage) and momentum (current) in order to stay strong over distances (shock waves diffuse over time) to break windows. Small, super fast things create large pressure differentials, big jets create more momentum.

Because the Mach cone produced by the leading edge/cone keeps most of the air from interacting with the aircraft behind it. It’s in the ‘wake’ as it were, though there may be multiple Mach cones or non-‘cone’ shaped ones depending on the shape of the aircraft.

This does cause some stability or handling issues for the aircraft.

The analogy re: voltage or amperage are spurious and just don’t apply here.

Re: Will we ever fly supersonically over land?

#137

Post by Clewza313 »

beerandt wrote: post #109
jltsiren wrote: post #57

Earlier quoted context omitted.

That depends on passenger volume. Trains require massive initial investments, but the marginal cost per passenger is very low. Air travel is mostly about marginal costs, and it requires massive infrastructure at endpoints. For example, an aiport serving 50 million passengers/year is two orders of magnitude larger than a railway station with a similar passenger volume. And while the airport would be one of the 30-40 b…

Yea, which is why trains costs are so sensitive to distance- it's massive up front cost is a function of that distance. It's not the stations, it's the rails and right-of-way. The problem most people ignore is that train marginal-increases max-out at some number of trains per day, before you need an additional set of tracks. And that happens at a much lower number than most people assume, especially if you're plannin…

With dedicated track, though, those limits can be quite high. The Yamanote Line in Tokyo carries around 4 million passengers per day on two tracks.

Re: Will we ever fly supersonically over land?

#138

Post by boulos »

new_realist wrote: post #134

In a rapidly warming world, I don't see the need to spend all that energy on supersonic transport when Zoom will do just fine. There are sustainable fuels, but they use a ton of energy. It's an extravagance the world cannot afford.

People definitely shouldn't fly if they don't need to, but I think you're overestimating the warming effect from aviation. Estimates put it in the ~3% range overall [1]. Most of that (80%) was passenger travel [2] (pre-pandemic) and 20% cargo.

The EU's push for short-haul flight bans [3] makes a lot of sense though, especially when high-speed (and sometimes electrified) rail is an option.

[1] https://ourworldindata.org/co2-emissions-from-aviation

[2] https://ourworldindata.org/co2-emissions-from-transport

[3] https://en.wikipedia.org/wiki/Short-haul_flight_ban

Re: Will we ever fly supersonically over land?

#139

Post by dghughes »

cameronh90 wrote: post #64
dghughes wrote: post #42

I hope not mainly because where I live in south-eastern Canada we seem to be the tailpipe of North America. All aircraft heading east seem to go over my region. The summer in non-pandemic times) is a constant parade of large passenger jets flying over. The jets are high up and in the evening you hear the rumble as the aircraft highlighted by the sun fly over while the ground is in evening shadows. Even a dozen US mil…

Do you live in Nova Scotia or New Brunswick? That seems to be where flights from NE USA to Europe fly over generally. That said they should be at cruising altitude by there. If you can hear them at 36k feet, it must be fairly quiet where you live! I live close to the path of the Heathrow approach, and planes tend to fly over me at about 5k feet, and I have to say that it's pretty rare I even hear them.

You're close, I'm in Prince Edward Island. Yes it's pretty quiet here even in the largest town.

Often I can hear the jets at night from inside my house. That's if there isn't any wind.

Re: Will we ever fly supersonically over land?

#140

Post by variant »

new_realist wrote: post #134

In a rapidly warming world, I don't see the need to spend all that energy on supersonic transport when Zoom will do just fine. There are sustainable fuels, but they use a ton of energy. It's an extravagance the world cannot afford.

What's the "right" temperature for the world?

We'll be fine.

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