10 ms·

If I recall correctly the Concorde used about 2 tonnes of fuel rolling on the ground alone.. I wonder how this new aircraft fares for fuel consumption? I belie

If I recall correctly the Concorde used about 2 tonnes of fuel rolling on the ground alone.. I wonder how this new aircraft fares for fuel consumption? I believe the Concorde is a marvel. You could travel faster than the rotation of the earth in it! However I don’t think we need more environmentally unsustainable travel.

catalogia 6y ago
It's hard to say how efficient this plane will be before it's built (or more details made public) but from what I've read sofar the big version, 'Boom Overture', is meant to use turbofan engines. That alone should provide significant fuel savings over the Concorde, which used turbojet engines with afterburners on takeoff. Even so, supersonic flight is less efficient than getting there a bit slower. Unfortunately, air resistance is nonlinear like that.
- ggm 6y ago
  Recent discussion of Concorde-2 discusses the fuel improvements which would have come with adding spools and turbofan to the motor, and wing changes, and larger fueltanks. Concorde didn't get to move beyond its first model. This boom jet is leveraging decades and decades of post-concorde engineering.
- gardenfelder 6y ago
  Seems to me that everything is nonlinear in the domain of aircraft, particularly when concerned with "efficiency". There is an equation [1] which makes it clear that the power required to maintain flight is a function of air density, drag coefficient, lift coefficient, wing area, and -- velocity cubed. All things being equal (which they never are), double the speed and you need 8 times the power. So in the most simplistic analysis (which is wrong, but instructive), consider that energy is a function of both power and time applied; if you double the speed to fly from say London to NY, would you cut the time to fly to less than 1/8th what it would otherwise be? To be clear, that's wrong, because of other factors; when you go faster in a given airplane, you can be more efficient at higher altitudes - mindful that wing size is dictated more by landing speeds than just how fast you want to go - if anything, you want smaller wings for weight, cost, and other considerations, but landing speed gets in the way. So, if you took the time to solve that equation for an airplane at, say, 30k feet, and for say 50k feet altitude, would you still get efficiencies over say, one of the modern , slower jumbo jets? [1] https://web.mit.edu/16.unified/www/SPRING/systems/Lab_Notes/airpower.pdf https://web.mit.edu/16.unified/www/SPRING/systems/Lab_Notes/... (edited for line spacing)
  - Moto7451 6y ago
    > Seems to me that everything is nonlinear in the domain of aircraft, particularly when concerned with "efficiency". The same physics applies to fast trains and other modes of transit. Fast electric trains have the advantage of not having to lug their fuel along with them at speed. > consider that energy is a function of both power and time applied; if you double the speed to fly from say London to NY, would you cut the time to fly to less than 1/8th what it would otherwise be? I think I understand what you’re trying to say, but note that by definition going twice as fast will get you there in half the time. Work and Energy are in alignment here because of the various efficiency losses you’re talking about. The Concorde did have some reprieve in that it flew 20k feet higher than the usual cruising altitude. https://aviation.stackexchange.com/questions/21881/at-what-altitude-did-concorde-go-supersonic https://aviation.stackexchange.com/questions/21881/at-what-a... Ultimately high speed transport is not about conservation of energy. It’s about conservation of human time. Weighing that against the environment and other factors are important but few people weigh their total use of energy in a given day.
    - ClumsyPilot 6y ago
      Fast electric trains are also, well, electric already. Powering planes in a sustainable marrer is not a solved problem.
      - Robotbeat 6y ago
        So I think that’s not really true. Even existing battery chemistry could do 1000km per stop (although it still needs certification for aircraft) and at comparable speed as HSR. That’s much longer than the California HSR project that was canceled, plus you just need a recharge (or swap) to continue on your way. With further efficiency improvements and battery chemistries in development right now like Li-S, we could potentially do 4000km flights (enough to reach Hawaii... and anywhere else using multiple hops, as Boom is planning). And shorter flights at higher than HSR speeds. HSR has its own unsolved problems. Like not being able to work over deep ocean... and insane infrastructure costs.
JKCalhoun 6y ago
Yeah, much more excited if there were talk of high-speed rail criss-crossing the U.S.
- Robotbeat 6y ago
  Electric aircraft like the Eviation Alice could do similar speeds and 1000km miles between stops. Comparable to HSR (early routes in CA were about 500km).
- TylerE 6y ago
  High-speed rail isn't high speed enough. Even with way faster than current tech and NO stops you'd still be looking at taking 12+ hours for what a plane can do in 5. That's ignoring the trillions it would cost. The US does not have the population density to make HSR viable.
  - axaxs 6y ago
    I'm still hoping for rail. It's much more carbon friendly, and has the opportunity to be way less stressful. I'd do 18 hours on a NY to LA if I could walk around, eat, talk, sleep, etc over a 5 hour misery ride in an airplane any day.
    - TylerE 6y ago
      A single NY-LA route alone would cost over $500 billion. High speed rail is well $100m/mile, just for the track.
      - axaxs 6y ago
        I'd like to see it thoroughly planned out, and a real cost estimate. Most of the trip is plainsland...simple. Getting through the Rockies, way more complicated. I've tried to read on the subject but estimates are an order of magnitude off between projects. All that said, of course, figuring out how to lower costs safely would be a great thing.
mrfusion 6y ago
Nice concise dismissal.
na85 6y ago
I think the real problem is that the Concorde wasn't fast enough to justify the cost. Whether you can fly JFK-CDG in 8 hours or 4 hours, when you factor in how irritating airports are, parking, security line ups, waiting for baggage, etc, it still takes all day to make the trip. Might as well save several thousand dollars and take a longer flight. I believe they would have to cut the flight time down to about an hour to justify Concorde pricing.
- projektfu 6y ago
  They could have their own special terminals and all passengers pre-cleared.
- eloff 6y ago
  Or fly it out of a private airport without as much irritating stuff, much like private jets do today.
- clintonb 6y ago
  > Whether you can fly JFK-CDG in 8 hours or 4 hours, when you factor in how irritating airports are, parking, security line ups, waiting for baggage, etc, it still takes all day to make the trip. Security lines weren't a thing until 2001. The Concorde operated from 1976 to 2003. The retirement was due to low passenger count due to a crash in 2000 and 9/11 in 2001.
  - robotresearcher 6y ago
    Security lines were absolutely a thing in the UK and France, where the Concordes flew from, due to terrorist campaigns.
  - grkvlt 6y ago
    im guessing if you really need, and can afford, supersonic travel then either it'll be like flying business/first or you'll have top tier ff status with the airline, and queues etc are much less of, or even a non issue.
    - 6y ago
dreamcompiler 6y ago
> You could travel faster than the rotation of the earth in it! You can do that in a conventional jet at latitudes far from the equator. You can walk faster than the earth rotates if you're very close to a pole (very very close).
- catalogia 6y ago
  > (very very close). Eh, within 15 miles or so. 4MPH * 24h = 96 mile circumference circle, 96 miles / 2pi ~= 15 miles.
  - speedgoose 6y ago
    ~24km.
  - iso947 6y ago
    You are going to struggle to walk at 4mph in Antarctica
    - ivalm 6y ago
      That’s why we need global warming!
    - catalogia 6y ago
      I think you could for a few moments at least. Of course if this is an endurance race, you're destined to lose ;)
alfalfasprout 6y ago
The reason for that is that the concorde used afterburners (basically, pump fuel into the high speed exhaust for extra thrust) which are incredibly inefficient. Great for a fighter jet where you need a sudden burst of extreme thrust, but not something you want a long-haul airliner to use. Boom uses turbofan engines to reach supersonic speeds which are much, much more efficient. In fact, many airliners could theoretically go past mach 1. The reason they don't is that the airframe itself doesn't have the correct shape to deal with transonic and supersonic speeds. I'd expect fuel consumption to be higher than a typical passenger jet but nowhere near concorde levels. Fuel consumption would also depend on the climb profiles of the plane, ideal cruise altitudes, etc. Since the more time you spend in subsonic flight and at lower altitudes the more fuel you burn (more friction and the aerodynamics and engines will be optimized for supersonic flight).
- NickNameNick 6y ago
  Concorde had afterburners, but only used them for take-off and breaking through Mach 1. And they were optional for both.
- paulmd 6y ago
  Concorde itself could have been much more efficient, there were plans for a "Concorde B" with high-bypass engines that would have carried a larger payload with additional range at higher efficiency. https://www.heritageconcorde.com/concorde-b https://www.heritageconcorde.com/concorde-b
  - dotancohen 6y ago
    Warning: That page contains a background animation that cannot be disabled, even when disabling page styles. I had to open it in W3M, which I'm glad I did as it was very informative.
    - mkl 6y ago
      Running this in the browser console worked for me: $('video').remove() (There aren't any other video elements.)
phunctional 6y ago
They are also working on a deal to use carbon neutral fuel from a company called Prometheus https://www.prometheusfuels.com/ https://www.prometheusfuels.com/
- chrisco255 6y ago
  Tried to read their FAQ but it is sort of handwavy. Do you have any links on the research behind this tech? I understand it uses CO2 from the atmosphere and solar + wind to build hydrocarbons? But what are the technical details there? How is this being done and why wasn't this done sooner?
  - D_Alex 6y ago
    Heaps of links in these comments: https://news.ycombinator.com/item?id=19842240 https://news.ycombinator.com/item?id=19842240
  - jabl 6y ago
    Kerosene from fossil fuels is a lot cheaper than synthetic fuels.
  - beambot 6y ago
    Article about Prometheus in Science: https://www.sciencemag.org/news/2019/07/former-playwright-aims-turn-solar-and-wind-power-gasoline https://www.sciencemag.org/news/2019/07/former-playwright-ai...
rvense 6y ago
Propeller planes used about half as much fuel per mile as early jets. Jets have caught up, but it took half a century to get back to earlier levels of fuel efficiency. Slowing down in general is an easy way to bring down energy usage, but it's often a hard sell.
- nopzor 6y ago
  basically true, but speed isn't the only reason why jets have dominated; being able to fly above the weather, noise, and (perceived) safety are factors too.
agurk 6y ago
Looking at the Concorde's fuel usage taxing is only part of the picture. All turbine engines are very inefficient at low power outputs due to the need to use energy to create sufficient compression for them to function. On top of this the Olympus engines generated a lot of thrust at idle, so much so that only two were used for taxing and it was still apparently tricky to control. While cruising at supersonic speeds the engines were actually the most efficient machines of their time achieving 43% thermal efficiency [0]. Despite being very efficient they still had high fuel consumption rates as the total amount of energy required to sustain those speeds is a lot higher than subsonic. Modern jet are in the 50%s thermally efficient [1] but despite airframe improvements there has been no way to improve fundamental aerodynamics so that supersonic energy costs aren't high. The Concorde did use reheat to take off and break the supersonic barrier which is very fuel inefficient. Using a modern airframes and engines that also don't need reheat will reduce fuel consumption but not to a level anywhere similar to a modern jetliner. [0] https://en.wikipedia.org/wiki/Rolls-Royce/Snecma_Olympus_593 https://en.wikipedia.org/wiki/Rolls-Royce/Snecma_Olympus_593 [1] https://www.nap.edu/read/23490/chapter/6#38 https://www.nap.edu/read/23490/chapter/6#38
- deleted 6y ago
  [deleted]
- throwaway_pdp09 6y ago
  I'm a bit suspicious of the qualification 'thermal' in 'thermal efficiency' which sounds like it's hiding something. From the wiki article on thermal efficiency https://en.wikipedia.org/wiki/Thermal_efficiency https://en.wikipedia.org/wiki/Thermal_efficiency, and I'm no wiser for reading it: "For a heat engine, thermal efficiency is the fraction of the energy added by heat (primary energy) that is converted to net work output (secondary energy)." Does thermal efficiency = actual efficiency in the case of jet engines? I find that difficult to believe.
  - Neil44 6y ago
    Yes thermal efficiency is a common rating for engines that work by burning fuel to make heat then turn that into useful power. You take the theoretical energy in a litre of fuel and work out how much of that the engine can convert into useful work.
iso1631 6y ago
I wonder what the fuel usage of a spacex starship doing a sub-orbital flight from say NY to Tokyo would compare with a 787 or a concorde doing the same journey.
credit_guy 6y ago
> I don’t think we need more environmentally unsustainable travel. Why do you think Boom is environmentally unsustainable? Boom is working with fellow YCombinator startup Prometheus to use synthetically produced fuels that are net zero emissions.

catalogia 6y ago

It's hard to say how efficient this plane will be before it's built (or more details made public) but from what I've read sofar the big version, 'Boom Overture', is meant to use turbofan engines. That alone should provide significant fuel savings over the Concorde, which used turbojet engines with afterburners on takeoff. Even so, supersonic flight is less efficient than getting there a bit slower. Unfortunately, air resistance is nonlinear like that.

ggm 6y ago
Recent discussion of Concorde-2 discusses the fuel improvements which would have come with adding spools and turbofan to the motor, and wing changes, and larger fueltanks. Concorde didn't get to move beyond its first model. This boom jet is leveraging decades and decades of post-concorde engineering.
gardenfelder 6y ago
Seems to me that everything is nonlinear in the domain of aircraft, particularly when concerned with "efficiency". There is an equation [1] which makes it clear that the power required to maintain flight is a function of air density, drag coefficient, lift coefficient, wing area, and -- velocity cubed. All things being equal (which they never are), double the speed and you need 8 times the power. So in the most simplistic analysis (which is wrong, but instructive), consider that energy is a function of both power and time applied; if you double the speed to fly from say London to NY, would you cut the time to fly to less than 1/8th what it would otherwise be? To be clear, that's wrong, because of other factors; when you go faster in a given airplane, you can be more efficient at higher altitudes - mindful that wing size is dictated more by landing speeds than just how fast you want to go - if anything, you want smaller wings for weight, cost, and other considerations, but landing speed gets in the way. So, if you took the time to solve that equation for an airplane at, say, 30k feet, and for say 50k feet altitude, would you still get efficiencies over say, one of the modern , slower jumbo jets? [1] https://web.mit.edu/16.unified/www/SPRING/systems/Lab_Notes/airpower.pdf https://web.mit.edu/16.unified/www/SPRING/systems/Lab_Notes/... (edited for line spacing)
- Moto7451 6y ago
  > Seems to me that everything is nonlinear in the domain of aircraft, particularly when concerned with "efficiency". The same physics applies to fast trains and other modes of transit. Fast electric trains have the advantage of not having to lug their fuel along with them at speed. > consider that energy is a function of both power and time applied; if you double the speed to fly from say London to NY, would you cut the time to fly to less than 1/8th what it would otherwise be? I think I understand what you’re trying to say, but note that by definition going twice as fast will get you there in half the time. Work and Energy are in alignment here because of the various efficiency losses you’re talking about. The Concorde did have some reprieve in that it flew 20k feet higher than the usual cruising altitude. https://aviation.stackexchange.com/questions/21881/at-what-altitude-did-concorde-go-supersonic https://aviation.stackexchange.com/questions/21881/at-what-a... Ultimately high speed transport is not about conservation of energy. It’s about conservation of human time. Weighing that against the environment and other factors are important but few people weigh their total use of energy in a given day.
  - ClumsyPilot 6y ago
    Fast electric trains are also, well, electric already. Powering planes in a sustainable marrer is not a solved problem.
    - Robotbeat 6y ago
      So I think that’s not really true. Even existing battery chemistry could do 1000km per stop (although it still needs certification for aircraft) and at comparable speed as HSR. That’s much longer than the California HSR project that was canceled, plus you just need a recharge (or swap) to continue on your way. With further efficiency improvements and battery chemistries in development right now like Li-S, we could potentially do 4000km flights (enough to reach Hawaii... and anywhere else using multiple hops, as Boom is planning). And shorter flights at higher than HSR speeds. HSR has its own unsolved problems. Like not being able to work over deep ocean... and insane infrastructure costs.

JKCalhoun 6y ago

Yeah, much more excited if there were talk of high-speed rail criss-crossing the U.S.

Robotbeat 6y ago
Electric aircraft like the Eviation Alice could do similar speeds and 1000km miles between stops. Comparable to HSR (early routes in CA were about 500km).
TylerE 6y ago
High-speed rail isn't high speed enough. Even with way faster than current tech and NO stops you'd still be looking at taking 12+ hours for what a plane can do in 5. That's ignoring the trillions it would cost. The US does not have the population density to make HSR viable.
- axaxs 6y ago
  I'm still hoping for rail. It's much more carbon friendly, and has the opportunity to be way less stressful. I'd do 18 hours on a NY to LA if I could walk around, eat, talk, sleep, etc over a 5 hour misery ride in an airplane any day.
  - TylerE 6y ago
    A single NY-LA route alone would cost over $500 billion. High speed rail is well $100m/mile, just for the track.
    - axaxs 6y ago
      I'd like to see it thoroughly planned out, and a real cost estimate. Most of the trip is plainsland...simple. Getting through the Rockies, way more complicated. I've tried to read on the subject but estimates are an order of magnitude off between projects. All that said, of course, figuring out how to lower costs safely would be a great thing.

mrfusion 6y ago

Nice concise dismissal.

na85 6y ago

I think the real problem is that the Concorde wasn't fast enough to justify the cost. Whether you can fly JFK-CDG in 8 hours or 4 hours, when you factor in how irritating airports are, parking, security line ups, waiting for baggage, etc, it still takes all day to make the trip. Might as well save several thousand dollars and take a longer flight. I believe they would have to cut the flight time down to about an hour to justify Concorde pricing.

projektfu 6y ago
They could have their own special terminals and all passengers pre-cleared.
eloff 6y ago
Or fly it out of a private airport without as much irritating stuff, much like private jets do today.
clintonb 6y ago
> Whether you can fly JFK-CDG in 8 hours or 4 hours, when you factor in how irritating airports are, parking, security line ups, waiting for baggage, etc, it still takes all day to make the trip. Security lines weren't a thing until 2001. The Concorde operated from 1976 to 2003. The retirement was due to low passenger count due to a crash in 2000 and 9/11 in 2001.
- robotresearcher 6y ago
  Security lines were absolutely a thing in the UK and France, where the Concordes flew from, due to terrorist campaigns.
- grkvlt 6y ago
  im guessing if you really need, and can afford, supersonic travel then either it'll be like flying business/first or you'll have top tier ff status with the airline, and queues etc are much less of, or even a non issue.
  - 6y ago

dreamcompiler 6y ago

> You could travel faster than the rotation of the earth in it! You can do that in a conventional jet at latitudes far from the equator. You can walk faster than the earth rotates if you're very close to a pole (very very close).

catalogia 6y ago
> (very very close). Eh, within 15 miles or so. 4MPH * 24h = 96 mile circumference circle, 96 miles / 2pi ~= 15 miles.
- speedgoose 6y ago
  ~24km.
- iso947 6y ago
  You are going to struggle to walk at 4mph in Antarctica
  - ivalm 6y ago
    That’s why we need global warming!
  - catalogia 6y ago
    I think you could for a few moments at least. Of course if this is an endurance race, you're destined to lose ;)

alfalfasprout 6y ago

The reason for that is that the concorde used afterburners (basically, pump fuel into the high speed exhaust for extra thrust) which are incredibly inefficient. Great for a fighter jet where you need a sudden burst of extreme thrust, but not something you want a long-haul airliner to use. Boom uses turbofan engines to reach supersonic speeds which are much, much more efficient. In fact, many airliners could theoretically go past mach 1. The reason they don't is that the airframe itself doesn't have the correct shape to deal with transonic and supersonic speeds. I'd expect fuel consumption to be higher than a typical passenger jet but nowhere near concorde levels. Fuel consumption would also depend on the climb profiles of the plane, ideal cruise altitudes, etc. Since the more time you spend in subsonic flight and at lower altitudes the more fuel you burn (more friction and the aerodynamics and engines will be optimized for supersonic flight).

NickNameNick 6y ago
Concorde had afterburners, but only used them for take-off and breaking through Mach 1. And they were optional for both.
paulmd 6y ago
Concorde itself could have been much more efficient, there were plans for a "Concorde B" with high-bypass engines that would have carried a larger payload with additional range at higher efficiency. https://www.heritageconcorde.com/concorde-b https://www.heritageconcorde.com/concorde-b
- dotancohen 6y ago
  Warning: That page contains a background animation that cannot be disabled, even when disabling page styles. I had to open it in W3M, which I'm glad I did as it was very informative.
  - mkl 6y ago
    Running this in the browser console worked for me: $('video').remove() (There aren't any other video elements.)

phunctional 6y ago

They are also working on a deal to use carbon neutral fuel from a company called Prometheus https://www.prometheusfuels.com/ https://www.prometheusfuels.com/

chrisco255 6y ago
Tried to read their FAQ but it is sort of handwavy. Do you have any links on the research behind this tech? I understand it uses CO2 from the atmosphere and solar + wind to build hydrocarbons? But what are the technical details there? How is this being done and why wasn't this done sooner?
- D_Alex 6y ago
  Heaps of links in these comments: https://news.ycombinator.com/item?id=19842240 https://news.ycombinator.com/item?id=19842240
- jabl 6y ago
  Kerosene from fossil fuels is a lot cheaper than synthetic fuels.
- beambot 6y ago
  Article about Prometheus in Science: https://www.sciencemag.org/news/2019/07/former-playwright-aims-turn-solar-and-wind-power-gasoline https://www.sciencemag.org/news/2019/07/former-playwright-ai...

rvense 6y ago

Propeller planes used about half as much fuel per mile as early jets. Jets have caught up, but it took half a century to get back to earlier levels of fuel efficiency. Slowing down in general is an easy way to bring down energy usage, but it's often a hard sell.

nopzor 6y ago
basically true, but speed isn't the only reason why jets have dominated; being able to fly above the weather, noise, and (perceived) safety are factors too.

agurk 6y ago

Looking at the Concorde's fuel usage taxing is only part of the picture. All turbine engines are very inefficient at low power outputs due to the need to use energy to create sufficient compression for them to function. On top of this the Olympus engines generated a lot of thrust at idle, so much so that only two were used for taxing and it was still apparently tricky to control. While cruising at supersonic speeds the engines were actually the most efficient machines of their time achieving 43% thermal efficiency [0]. Despite being very efficient they still had high fuel consumption rates as the total amount of energy required to sustain those speeds is a lot higher than subsonic. Modern jet are in the 50%s thermally efficient [1] but despite airframe improvements there has been no way to improve fundamental aerodynamics so that supersonic energy costs aren't high. The Concorde did use reheat to take off and break the supersonic barrier which is very fuel inefficient. Using a modern airframes and engines that also don't need reheat will reduce fuel consumption but not to a level anywhere similar to a modern jetliner. [0] https://en.wikipedia.org/wiki/Rolls-Royce/Snecma_Olympus_593 https://en.wikipedia.org/wiki/Rolls-Royce/Snecma_Olympus_593 [1] https://www.nap.edu/read/23490/chapter/6#38 https://www.nap.edu/read/23490/chapter/6#38

deleted 6y ago
[deleted]
throwaway_pdp09 6y ago
I'm a bit suspicious of the qualification 'thermal' in 'thermal efficiency' which sounds like it's hiding something. From the wiki article on thermal efficiency https://en.wikipedia.org/wiki/Thermal_efficiency https://en.wikipedia.org/wiki/Thermal_efficiency, and I'm no wiser for reading it: "For a heat engine, thermal efficiency is the fraction of the energy added by heat (primary energy) that is converted to net work output (secondary energy)." Does thermal efficiency = actual efficiency in the case of jet engines? I find that difficult to believe.
- Neil44 6y ago
  Yes thermal efficiency is a common rating for engines that work by burning fuel to make heat then turn that into useful power. You take the theoretical energy in a litre of fuel and work out how much of that the engine can convert into useful work.

iso1631 6y ago

I wonder what the fuel usage of a spacex starship doing a sub-orbital flight from say NY to Tokyo would compare with a 787 or a concorde doing the same journey.

credit_guy 6y ago

> I don’t think we need more environmentally unsustainable travel. Why do you think Boom is environmentally unsustainable? Boom is working with fellow YCombinator startup Prometheus to use synthetically produced fuels that are net zero emissions.