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The Race to Build the First Sustainable Supersonic Jet

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Re: The Race to Build the First Sustainable Supersonic Jet

#21

Post by ryanlol »

vilhelm_s wrote: post #8
polalavik wrote: post #4

Earlier quoted context omitted.

Sounds like you only fly first class. Have you ever flown 10+ hours in economy and felt ready for work (or even vacation) stepping off the plane?

This will be a private jet, and they are pretty expensive. Apparently flying in a Bombardier Learjet costs something like $7000/hour [1], while a first-class ticket is more like $1000/hour. [1] https://www.aircharterserviceusa.com/about-us/news-features/...

> while a first-class ticket is more like $1000/hour.

I usually pay like 160eur/hour for top tier F products like the Emirates A380.

I just paid a little over 4000 euros for a 32h round trip with that particular offering. I don’t chase after deals, I just tend to depart from a city without many F pax.

Of course, YMMV.

Re: The Race to Build the First Sustainable Supersonic Jet

#22

Post by ghaff »

johngalt wrote: post #20
leetcrew wrote: post #11

Earlier quoted context omitted.

as an aside, I don't understand how people can fly several hours on a commercial airline and then just start their day as if it didn't happen. I need at least a full 24hr cycle involving sleep in a real bed to get back to 100%.

It's mainly about routine. Given time and repetition people will get used to almost anything. The anxiety surrounding travel is what makes it exhausting. Once you are used to it, it fades into the background as a well optimized habit. It's like your work commute where you are just on autopilot and don't really think about it. Ultimately it becomes a few hours to yourself to just read, sleep, or get caught up.

Red-eyes are tough though it's not too bad in international business. I'm usually operating at about half speed when I overnight to continental Europe from the US East Coast.

On the other hand, flying cross-country on an early morning flight to SFO, I can pretty much be ready for a regular day when I land.

Re: The Race to Build the First Sustainable Supersonic Jet

#23

Post by ghaff »

smachiz wrote: post #15
chrisseaton wrote: post #3

Earlier quoted context omitted.

> they don't impact productive time Even flying in first class I’m sure I’d get there much more refreshed for a short four hour flight than an eight hour one, improving my productivity when I get there. And why are you only considering overnight flights?

Timezones. 6PM in NYC is midnight in Paris. Leave the office at 3PM and get to Paris at Midnight? Lost half a day leaving, still not getting into a hotel until 1AM best case. Leave NYC supersonic at 9PM, get to paris at 6AM, great, I might've been able to sleep 1h. On a normal plane I can leave NYC at 6PM, get to Paris at 8AM, and hopefully have gotten to sleep for 3-4h. This also doesn't account for block padding -…

My dad once told me he got upgraded to the Concorde on NY-LHR once. Aside from having the experience, he said it wasn't really a win. As he put it, with the regular first class, he got a nice meal on the plane and got into London in time for bed. With the Concorde, he got in in time for rush hour and had to immediately go out to dinner.

Re: The Race to Build the First Sustainable Supersonic Jet

#24

Post by jpeanuts »

In my opinion it is disingenuous to call any supersonic aircraft sustainable. Independently of any clever aerodynamic design to moderate the drag coefficient, aerodynamic drag always increases like the velocity squared. Doubling the speed will mean applying 4x the force for 1/2 the time, so all propulsive efficiencies being equal, you will expend twice the fuel to go the same distance - at an absolute minimum. In reality engine efficiencies decrease at high-speeds, and you won't be able to completely eliminate the Mach 1 "barrier" (drag peak), or design an aircraft that is equally efficient in takeoff/landing... so the factor will be bigger than that. But x2 fuel consumption is a hard lower bound.

I don't believe this can be called sustainable. Air transport is already a major contributor to CO2 emissions. We as a civilization badly need significantly more efficient ways to fly, not less efficient ways. To even slightly suggest that this might be helping the environment is deplorable.

Also, air transport is already miraculous. Going around the world in a day is not enough for you? Really? Buy a book.

Re: The Race to Build the First Sustainable Supersonic Jet

#25

Post by namirez »

jpeanuts wrote: post #24

In my opinion it is disingenuous to call any supersonic aircraft sustainable. Independently of any clever aerodynamic design to moderate the drag coefficient, aerodynamic drag always increases like the velocity squared. Doubling the speed will mean applying 4x the force for 1/2 the time, so all propulsive efficiencies being equal, you will expend twice the fuel to go the same distance - at an absolute minimum. In rea…

You are right but the reality is even worse. Fuel consumption is proportional to power (velocity * drag) rather than drag itself. When you go twice as fast, the travel time is halved, so the total fuel consumption quadruples.

And as you said, supersonic drag coefficients are typically larger than subsonic ones, which makes things even worse.

Re: The Race to Build the First Sustainable Supersonic Jet

#26

Post by melling »

jpeanuts wrote: post #24

In my opinion it is disingenuous to call any supersonic aircraft sustainable. Independently of any clever aerodynamic design to moderate the drag coefficient, aerodynamic drag always increases like the velocity squared. Doubling the speed will mean applying 4x the force for 1/2 the time, so all propulsive efficiencies being equal, you will expend twice the fuel to go the same distance - at an absolute minimum. In rea…

Nope, air transportation is not a major contributor to CO2.

There are over 100,000 flights daily. They account for about 2.5% of CO2 emissions yearly.

You know what is? Coal power plants that generate electricity.

Maybe we should focus on electricity generation from coal. I’m a little surprised that more hasn’t been done.

https://www.carbonbrief.org/mapped-worlds-coal-power-plants

13 years ago Google attempted their REhttps://www.forbes.com/sites/williampentland/2014/11/30/why-...

Re: The Race to Build the First Sustainable Supersonic Jet

#27

Post by Johnny555 »

polalavik wrote: post #4
smachiz wrote: post #2

Feels like a losing battle against physics, combined with it only being really valuable in a single direction. Overnight flights from east coast to EU are late enough that they don't impact productive time, and largely get in early enough for a full day of work. Making that flight shorter - as anyone who's done a DEN-NYC redeye will tell you - doesn't actually help productivity. Sure, on the return flight, it would b…

Sounds like you only fly first class. Have you ever flown 10+ hours in economy and felt ready for work (or even vacation) stepping off the plane?

I wouldn't be surprised if economy class on this future supersonic jet costs the same as first class (or at least business class) on a traditional jet.

Though either way, even after a 9 hour business class flight, I'm certainly not ready to go to work when I get there even though I had a lay-flat seat.

Re: The Race to Build the First Sustainable Supersonic Jet

#28

Post by nbadg »

jpeanuts wrote: post #24

In my opinion it is disingenuous to call any supersonic aircraft sustainable. Independently of any clever aerodynamic design to moderate the drag coefficient, aerodynamic drag always increases like the velocity squared. Doubling the speed will mean applying 4x the force for 1/2 the time, so all propulsive efficiencies being equal, you will expend twice the fuel to go the same distance - at an absolute minimum. In rea…

I don't personally want to make a value judgment about whether or not you could call supersonic air travel sustainable, particularly since it's fairly meaningless to remark on outside of a broader conversation (in much the same way that the "greenness" of electric cars is more complicated than saying they're zero-emissions, since you need to consider the power plants that are ultimately fueling them, plus the batteries, motors, manufacturing...).

But I do want to note that supersonic aerodynamics are extremely complicated, and I think it's just as disingenuous to say that drag always increases with the velocity squared in supersonic regimes. Strictly speaking you're right, but the drag coefficient itself is changing too, and in fact it converges to a value below that of its approximately-constant subsonic value. Also note that airlines are already traveling thoroughly within the transonic region.

I do agree that ultimately, in-atmosphere supersonic flight will consume more fuel than commercial airlines today. However, to say anything more specific than that, I think you really need to start doing a proper aero analysis; once you're transonic (or beyond), you've stepped outside the realm where napkin math is physically valid.

For a brief, okay discussion of drag coefficient changes wrt mach number, here's a link: https://onlinelibrary.wiley.com/doi/pdf/10.1002/978047011785...

Re: The Race to Build the First Sustainable Supersonic Jet

#29

Post by DuskStar »

jpeanuts wrote: post #24

In my opinion it is disingenuous to call any supersonic aircraft sustainable. Independently of any clever aerodynamic design to moderate the drag coefficient, aerodynamic drag always increases like the velocity squared. Doubling the speed will mean applying 4x the force for 1/2 the time, so all propulsive efficiencies being equal, you will expend twice the fuel to go the same distance - at an absolute minimum. In rea…

> But x2 fuel consumption is a hard lower bound.

Can't you gain a bit of that back by flying higher than a subsonic design could?

Re: The Race to Build the First Sustainable Supersonic Jet

#30

Post by cletus »

melling wrote: post #26
jpeanuts wrote: post #24

In my opinion it is disingenuous to call any supersonic aircraft sustainable. Independently of any clever aerodynamic design to moderate the drag coefficient, aerodynamic drag always increases like the velocity squared. Doubling the speed will mean applying 4x the force for 1/2 the time, so all propulsive efficiencies being equal, you will expend twice the fuel to go the same distance - at an absolute minimum. In rea…

Nope, air transportation is not a major contributor to CO2. There are over 100,000 flights daily. They account for about 2.5% of CO2 emissions yearly. You know what is? Coal power plants that generate electricity. Maybe we should focus on electricity generation from coal. I’m a little surprised that more hasn’t been done. https://www.carbonbrief.org/mapped-worlds-coal-power-plants 13 years ago Google attempted their…

The real villain here is coal-powered planes!

Ok, in all seriousness, the efficiency story for air travel is... complicated. So you claim planes account for 2.5% of CO2 emissions but air travel and transport is still a relative luxury enjoyed by a privileged few so that's not necessary accurate.

I found this [1] that shows planes to be much worse than automobiles (per passenger per km) but again, it's complicated.

Personally I don't mind the investment in supersonic travel. After all, it's hard to know what fruit this will ultimately bear. Some people have asked what's the difference between crossing the Atlantic in 4 hours instead of 8? It's the difference between able to go for the day or not.

[1]: https://youmatter.world/en/plane-or-cars-which-means-of-tran...

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