Hacker News Board Hacker News, browsed like a classic message board
Live data from Hacker News

Will we ever fly supersonically over land?

newyorker.com

Post reply on HN
Print view View original

101–110 of 220 posts

Re: Will we ever fly supersonically over land?

#101

Post by blunte »

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? Or mechanical failure or weather which causes a diversion (how much ground do you cover just turning around?).

I find it hard to see legitimate overall benefits.

Frankly, I think we could make greater overall time benefits by optimizing airport and boarding improvements.

Re: Will we ever fly supersonically over land?

#102

Post by beerandt »

crazygringo wrote: post #40
beerandt wrote: post #27

Earlier quoted context omitted.

At energy and cost levels that exceed airline travel, per passenger-mile.

Do you have a citation for that? Quick Googling doesn't reveal any obvious authoritative answers (but a ton of guessing and unsubstantiated claims). The most authoritative/unbiased source seems to be this Wikipedia article: https://en.wikipedia.org/wiki/Energy_efficiency_in_transport But the head-to-head comparisons are mostly gaps when it comes to trains, and the sections on trains and planes are in completely diffe…

It was covered in a sustainable engineering class I took.

There's not much generic into about it because every rail route proposal is different, even between the same destinations. Depends a lot on geography and what's already there.

You basically need to do a full Life Cycle Analysis (LCA) for each route.

Sometimes they're included in the EIS for a proposed project. That's prob the best place to start.

But there's a reason most of the rail routes that keep getting proposed in the US are regional. Track and right-of-way is expensive, in both dollars and energy. Even moreso with high speed, where you need grade-seperated crossings and long, wide turns.

Most people think track is shareable or reusable, but the real world limits to track capacity (trains per day) makes economies of scale difficult to implement.

I posted it elsewhere, but the practical limit for non-high-speed rail is 300-400 miles, before airplanes start to make more sense.

High speed is difficult to even estimate, since we don't have much here to base it on.

Re: Will we ever fly supersonically over land?

#103

Post by flatiron »

the__alchemist wrote: post #82
FridayoLeary wrote: post #72

Earlier quoted context omitted.

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...

It happens in the Lake District and Wales reasonably often. Often the pilot/crew will go out and apologize to a farmer. Sometimes livestock allegedly die, although I'm not sure what the mechanism is.

That mechanism is trying to get compensated for dead live stock and pulling straws. Thunder is a sonic boom. It’s like saying thunder killed a cow.

Re: Will we ever fly supersonically over land?

#104

Post by blunte »

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.

Especially 100 year + old buildings with original glass.

Re: Will we ever fly supersonically over land?

#105

Post by pyrale »

fastball wrote: post #88
pyrale wrote: post #56

Earlier quoted context omitted.

What a rhetoric device. Is your preferred solution to let people die in droves to a mass extinction ?

My preferred solution is buttloads of nuclear, carbon neutral solutions to liquid fuel (e.g. pulling CH4 out of atmosphere with Sabatier) and general carbon capture.

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

Re: Will we ever fly supersonically over land?

#106

Post by fastball »

pyrale wrote: post #105
fastball wrote: post #88

Earlier quoted context omitted.

My preferred solution is buttloads of nuclear, carbon neutral solutions to liquid fuel (e.g. pulling CH4 out of atmosphere with Sabatier) and general carbon capture.

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?

Re: Will we ever fly supersonically over land?

#107

Post by bronco21016 »

ClumsyPilot wrote: post #28
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…

We coupd sctuallu fly even more efficiently, but slower, with turboprops

It looks like the future is a bit of a mashup of a turboprop and turbofan. Check out the efficiency of the Pratt and Whitney geared turbofans. On the A220-100 fuel burn (~3,800 pph) is comparable to a CRJ-900 with 35 more seats in a dual class configuration. That’s quite a leap. I’ll see if I can find someone to compare it to a B717 fuel burn, it’s the same number of seats.

Re: Will we ever fly supersonically over land?

#108

Post by shiftpgdn »

wpearse wrote: post #91
the__alchemist wrote: post #82

Earlier quoted context omitted.

It happens in the Lake District and Wales reasonably often. Often the pilot/crew will go out and apologize to a farmer. Sometimes livestock allegedly die, although I'm not sure what the mechanism is.

Best childhood memories are from doing walks in the Lakes and having jets zip past in the valleys below. Insanely close, too — I distinctly remember seeing the pilot’s visor and making out white text on the side of the aircraft.

Is the Lake District the infamous “Mach loop”?

Re: Will we ever fly supersonically over land?

#109

Post by beerandt »

jltsiren wrote: post #57
beerandt wrote: post #24

Earlier quoted context omitted.

Air travel is generally more energy efficient than trains, beyond a 300-400 mile range, depending on what you're traveling over/through. Track and right-of-way is a scarce resource with large amounts of embedded energy. The sky, not so much.

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 planning on sharing that track with other routes. And even worse if you have to use or cross a freight track.

So not only does efficiency have a min bounds, but also a local-max bounds, where you need a large enough marginal increase to justify the additional rails.

Whereas the airline equivalent is whether to schedule an additional flight. Which is easier to commit to than whether a new track is justified.

Re: Will we ever fly supersonically over land?

#110

Post by katbyte »

flatiron wrote: post #103
the__alchemist wrote: post #82

Earlier quoted context omitted.

It happens in the Lake District and Wales reasonably often. Often the pilot/crew will go out and apologize to a farmer. Sometimes livestock allegedly die, although I'm not sure what the mechanism is.

That mechanism is trying to get compensated for dead live stock and pulling straws. Thunder is a sonic boom. It’s like saying thunder killed a cow.

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