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Will we ever fly supersonically over land?

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Re: Will we ever fly supersonically over land?

#171

Post by ant6n »

cortesoft wrote: post #122
ant6n wrote: post #67

Earlier quoted context omitted.

Well, if there was no air travel, rail lines everywhere would likely be practical... again. If trains could go 250km/h on average, that 5000km trip would take 20 hours - that's plausible for an overnight trip, leave 6pm, arrive 10am. A flight over this is distance is probably a much more stressful red eye. Sure this is quite speculative, but perhaps less so than hyperloop dreams, or supersonic aircraft that somehow h…

That seems a strange argument… yes, if we didn’t have planes, trains would be our best option… but it would be a much worse experience. 20 hours is a lot longer than the 5 it takes me to fly to New York. If there was no air travel, I would just travel a lot less. If you want to argue that the environmental cost of air travel is too great to allow it to happen is one thing, but done act like it wouldn’t make the trave…

It’s not a strange argument. Read the discussion again, which starts with the thesis

> All overland passenger transport should be rail.

Then it was claimed that this is impossible. My argument is saying it’s possible to have rail replace rail, for example if air travel was severely restricted.

Re: Will we ever fly supersonically over land?

#172

Post by pyrale »

fastball wrote: post #106
pyrale wrote: post #105

Earlier quoted context omitted.

While producing clean energy would be great, a significant share of our travel issues is related to land use.

Ok, but... airplanes use the least land?

Much like the difference in land use with or without cars is not simply roads and parkings, but also the horizontal development of cities rather than vertical, the land use involved by planes is not simply the airstrips. Among others, it is also all the land developed specifically for vacation in remote places. If you look at [1] for instance, this area would simply not be developed if planes were not a thing.

[1]: https://www.google.com/maps/@21.1715988,-86.8077681,1041m/da...

Re: Will we ever fly supersonically over land?

#173

Post by blunte »

stouset wrote: post #130
blunte wrote: post #101

Sound is one thing, but there are other more significant obstacles. The benefits of faster travel really show on longer distances (London to Sydney for example). But over land, there just aren’t many common routes where the several hour savings would be worth it. The big challenges relate to risk. What happens to the vehicle when a major failure happens at high speed? What about sudden pressure loss at high altitude?…

> What happens to the vehicle when a major failure happens at high speed? What about sudden pressure loss at high altitude? Or mechanical failure… The same thing that happens in any other plane. > … or weather which causes a diversion (how much ground do you cover just turning around?). This is an extremely weird concern. There’s so much wrong with it I’m not even sure where to start: planes can slow down, sharp turn…

> The same thing that happens in any other plane.

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

The faster you are traveling (which really matters as a factor of the drag you are experiencing), the more serious any event is which changes the shape of your vehicle. Even non structural failures, such as an engine cowling coming off mid-flight can strike other parts of the aircraft, resulting in damage and changes to the structure.

Tolerances for these events are much lower the faster you're going, meaning the outcome is more likely to be severe if you're traveling much faster than we currently do with passenger aircraft.

Military fighters are built with higher tolerances and structural strength (and come in heavier, requiring more fuel and reducing range). Commercial aircraft are just impractical to operate safely at such high speeds.

With respect to diversions and changes of route, you have to consider several things.

Faster, heavier aircraft need longer runways to land. That limits your alternate landing choices. Diversions may cost you more fuel since they may be much greater distances away.

And you cannot simply make a "sharp turn" at high speed. Your passengers (and the airframe on a large craft) are not prepared for 4G turns. They aren't even designed for 2G turns.

Ask yourself this, can you turn your car as sharply at highway speed as you can in the parking lot? Sure you can slow down and then turn, but that takes time. That would not be considered "sharp". So while you're decelerating and turning, you are eating up great distances. It would be easy to overshoot a nearby location; thus you would need to plan ahead, take big slow turns, etc. Do you have enough extra fuel for that? Are you able/allowed to pass through all airspaces conveniently, or will that require extra planning and maneuvering?

The complexity of flying larger and/or faster aircraft is much more than one might think.

Re: Will we ever fly supersonically over land?

#174

Post by pyuser583 »

hugh-avherald wrote: post #132
FridayoLeary wrote: post #73

Earlier quoted context omitted.

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.

Long term wear and tear is a legitimate concern.

I’d be pisses if jets flying overheard broke my windows once every five years.

Re: Will we ever fly supersonically over land?

#175

Post by pyuser583 »

_Microft wrote: post #18
t0mas88 wrote: post #8

Earlier quoted context omitted.

Air travel has a big PR problem, because somehow a lot of people think it's the absolute worst for the environment. While on many routes a car is worse in terms of CO2 emission per trip than a small to mid sized airliner if there are less than 3 people in the car. Similar for your suggestion that we should take ships over the ocean, because cruise ships are much more polluting per passenger mile than modern airliners…

Air travel is not a problem because the emissions per kilometer are that bad but because one can easily travel one or two orders of magnitude farther than one usually would.

Why is further travel, per se, the problem?

Re: Will we ever fly supersonically over land?

#176

Post by pyuser583 »

throw0101a wrote: post #168
cortesoft wrote: post #38

Earlier quoted context omitted.

I live in Southern California, with family in Kansas, Wisconsin, and New York. The closest one is 2500kms away. The longest is almost 5000kms A train would take a lot longer than a plane. Even more than just the distance, though, is the fact that there would be no practical way to have direct rail lines to every major city in the US. Trains are useful, but there is no way they could replace air travel in the US.

> I live in Southern California, with family in Kansas, Wisconsin, and New York. The closest one is 2500kms away. The longest is almost 5000kms A train would take a lot longer than a plane. Perhaps people/families have spread themselves all over the continent because in the past energy has been 'too cheap' (i.e., didn't price in externalities). With carbon pricing people may make different decisions in how far they w…

Travel is extremely economically important, especially for the poor.

Living in a poor, rural county with poor schools and few jobs can really mess things up.

Someone I know is getting divorced.

She was a very high earner who moved to a low-cost of living, low wage area to be with her husbands family.

She had previously earned very high wages, but took a significant pay cut to live with in-laws.

As the divorce is concluding, she realizing that the terms of the divorce prohibit her from taking the kids out of state.

Which means until her kids are 18, she’s effectively trapped in a market where her MS in Engineering gets her a job at Walmart.

She had previously worked for a major firm in New York, and then worked for a the local government until she had to resign.

So she’s basically screwed.

Plenty of people have skills and credentials that can only be used with relocation. A MA in Journalism isn’t very helpful outside big cities.

Re: Will we ever fly supersonically over land?

#177

Post by lazide »

vilhelm_s wrote: post #151
lazide wrote: post #135

Earlier quoted context omitted.

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.

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 con…

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]

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

Re: Will we ever fly supersonically over land?

#178

Post by cherryturnover »

ClumsyPilot wrote: post #123
katbyte wrote: post #110

Earlier quoted context omitted.

very loud sounds can panic/shock animals and if it's too much for them, they die.

Well, in that case, when will we start jailing bikers with loud exhausts for the deaths of old people from heart attacks?

God that would honestly be a dream come true actually

Re: Will we ever fly supersonically over land?

#179

Post by secfirstmd »

FridayoLeary wrote: post #72
Judgmentality wrote: post #69

Earlier quoted context omitted.

How loud was it and how often did you experience it?

They did it near London once by in error. One little Typhoon can produce an unbelievably powerful sonic boom. I felt it as a loud crack/thump on my roof. Now, imagine a Concorde going supersonic...

If I recall correctly. The recent examples of Typhoons going super sonic over London were QRA aircraft hammering it down the country to pick up suspicious aircraft. In some of those cases they are allowed do it
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