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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

#41

Post by perl4ever »

grizzles wrote: post #32

I flown many long haul flights. The first time I heard Musk propose using rockets for international travel I thought it was insane. I still do. But if they are accident free for the next 10 years; would I then? Probably - if they could manage to keep my trip under ~3Gs.

I think we have some data already on the probability of accidents - I believe I read that a SpaceX rocket failed to land properly after something like 50 successes...but it was a "soft" landing in the water?

NASA lost 2 shuttles out of about 135 flights...

So if I was going to make a ballpark estimate without further information, I'd say 98% of the time you should get there safely...and that's better than the coronavirus!

People will often tell you how irrational it is that we demand such safety from commercial airlines, so isn't 98% really good enough?

Re: The Race to Build the First Sustainable Supersonic Jet

#42

Post by ncmncm »

The only way this thing could be honestly sustainable would be if it were hydrogen-powered.

That might also be a prerequisite for profitability. But the airframe would need to be quite different from current designs because hydrogen tankage needs a lot more room than kerosene fuel would. Extra space on an aircraft is fairly cheap to provide. What is difficult is more weight, including extra fuel needed to get enough range at higher speed. Hydrogen fuel fixes that by having 3x energy per kg.

Re: The Race to Build the First Sustainable Supersonic Jet

#43

Post by satya71 »

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…

IIRC from my course work drag is proportional to the 4th power of velocity, not squared. But that's for subsonic motion.

Re: The Race to Build the First Sustainable Supersonic Jet

#44

Post by smachiz »

FDSGSG wrote: post #36
GordonS wrote: post #35

Earlier quoted context omitted.

This doesn't seem possible - I have never seen first tickets that cheap from anywhere to anywhere. Can you provide a few example routes?

Most Emirates long haul flights departing from AMS,BCN or MXP seem to be that cheap, I'm sure there are other cheap airports but I'm too lazy to look. This is probably the case with all the euro airports that don't charge super high fees and lack large quantities of F pax. I'm seeing MXP-HKG at 4000eur for a round trip, MXP-BKK for 3800eur. There are probably even better deals available if departing from some third w…

I think you’re seeing corona virus at work. Those F tix are usually more from what I’ve seen.

Re: The Race to Build the First Sustainable Supersonic Jet

#45

Post by kelnos »

phunctional wrote: post #37

What about Boom Supersonic? They are partnering with Prometheus fuels that pulls carbon out of the air and turns it into fuel and also focusing on a commercial jet rather than private. There isn't even any mention of sustainability other than in the title of this article.

This definitely read to me like a paid (by Aerion) puff piece. No surprise there's no mention of competitors.

Re: The Race to Build the First Sustainable Supersonic Jet

#46

Post by rayiner »

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…

As someone who studied aerospace engineering hoping to see advanced like this, I find your attitude incredibly depressing. Cutting off our ambitions at the knees is not the path to the future.

Re: The Race to Build the First Sustainable Supersonic Jet

#47

Post by smachiz »

ghaff wrote: post #23
smachiz wrote: post #15

Earlier quoted context omitted.

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.

Yeah, for sure. You still burned your whole day and nothing but pain to show for it.

Still wish I got to fly it though!

Re: The Race to Build the First Sustainable Supersonic Jet

#48

Post by melling »

perl4ever wrote: post #40
cletus wrote: post #30

Earlier quoted context omitted.

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. Pe…

"It's the difference between able to go for the day or not" Which points to how increases in capability and efficiency can stimulate demand, which could be a bad thing from an environmental perspective.

And in the meantime, enough emissions from fossil fuels to generate electricity is emitted every year to cover a couple decades of flying.

Re: The Race to Build the First Sustainable Supersonic Jet

#49

Post by DoingIsLearning »

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.

> The anxiety surrounding travel is what makes it exhausting.

That is actually a really good insight. I mean reading it, it seems obvious, it's just that I never realised it.

Re: The Race to Build the First Sustainable Supersonic Jet

#50

Post by mrpopo »

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…

Air transportation is a major contributor to CO2, if you limit the scope to the people who use it. It is estimated that about 80% of the world's adults have never taken a flight, and 94% of the world's adults have not taken a flight in over a year.

So, the real picture is that this 2.5% of global CO2 emissions are caused by as few as 6% of the population, who also are incidentally the richest and bear a high personal carbon footprint in other domains than transportation.

EDIT: I'll add to this that the aviation sector is growing, and therefore its global contribution to GHG emissions will grow as well in the future. Discounting the carbon footprint of the aviation sector based on today's numbers is a mistake.

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