5 ms·

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.

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.)
- gsnedders 6y ago
  The Mk622 engine was still a turbojet, albeit improved. Primarily its gains came from a more efficient compressor, providing more oxygen to the combustion chamber.
- valuearb 6y ago
  The Concorde B was a bandaid on a massive gaping wound.
robin_reala 6y ago
Expected fuel burn per passenger is minimum 3x a ‘normal’ business class seat on a modern plane: https://theicct.org/news/reviving-supersonic-flight-significant-harmful-environmental-consequences https://theicct.org/news/reviving-supersonic-flight-signific... Either way, it’s fairly obscene.
- dzhiurgis 6y ago
  While fuel cost is minor part of total flight cost (most is staff + depreciation), I wonder how much will be saved by a good satellite network. Being able to work on a plane at some point starts to pay itself off.
  - nemetroid 6y ago
    Fuel costs accounted for 23.7% of airline operating expenses in 2019 [1], I think that's more than a minor part - especially if you triple it. 1: https://www.iata.org/contentassets/ebdba50e57194019930d72722413edd4/fact-sheet-fuel.pdf https://www.iata.org/contentassets/ebdba50e57194019930d72722...
adev_ 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. To put things in perspective, Concorde was using two Olympus engines designed originally in the 50s. It was already a marvel that they can run for such a range at Mach 2.0 when designed 70 years ago. A lot of things improved since. Most fighter jets can supercruise at supersonic speed without afterburners nowadays.
- jacquesm 6y ago
  Concorde used four engines. Two engine ETOPS over water wasn't a thing back then, first real relaxation of that rule was in '76. see: https://en.wikipedia.org/wiki/ETOPS https://en.wikipedia.org/wiki/ETOPS
  - adev_ 6y ago
    Of course four. My apologies, too quick to type.
masklinn 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. Concorde didn't use afterburners "at speed". The afterburners were used for takeoff, and to go through the mach wall. Concorde burned insane amounts of fuel on the ground because turbojets are very inefficient at low-speed. Not unlike the SR-71's really (though the SR-71 also had such extreme high-speed bypass it was basically using ramjets at speed).
- philjohn 6y ago
  Didn't SR-71's also leak fuel when on the ground?
  - masklinn 6y ago
    Yes but that's a separate concern. The engines were not efficient at slow speed / ground levels even ignoring the "leaks until it gets hot enough to seal the pipes" issue, the blackbird was designed to hit peak efficiency above Mach 3 (generally speaking all jets are designed to hit peak efficiency at their cruising speed, and the blackbird was designed for a cruising altitude of mach 3.2).
  - imtringued 6y ago
    That's only because they decided to not use tanks inside the wings. The wings themselves contained the fuel. You can certainly build a non leaking SR-71 if a higher weight is acceptable.
    - masklinn 6y ago
      > That's only because they decided to not use tanks inside the wings. It's not only that. It's because they didn't have alloys which would handle the thermal constraints without significant expansion, so they had to design for that expansion. And in the same way rail tracks handle expansion by leaving gaps, that's what they did. Furthermore, due to limited room and systems able to handle the temperature gradients, the fuel acted not just as fuel but also coolant, heat sink and even hydraulic fluid for some propulsion components (e.g. the afterburner nozzles and inlet guide vanes used JP7 as hydraulic fluid).

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.)
gsnedders 6y ago
The Mk622 engine was still a turbojet, albeit improved. Primarily its gains came from a more efficient compressor, providing more oxygen to the combustion chamber.
valuearb 6y ago
The Concorde B was a bandaid on a massive gaping wound.

robin_reala 6y ago

Expected fuel burn per passenger is minimum 3x a ‘normal’ business class seat on a modern plane: https://theicct.org/news/reviving-supersonic-flight-significant-harmful-environmental-consequences https://theicct.org/news/reviving-supersonic-flight-signific... Either way, it’s fairly obscene.

dzhiurgis 6y ago
While fuel cost is minor part of total flight cost (most is staff + depreciation), I wonder how much will be saved by a good satellite network. Being able to work on a plane at some point starts to pay itself off.
- nemetroid 6y ago
  Fuel costs accounted for 23.7% of airline operating expenses in 2019 [1], I think that's more than a minor part - especially if you triple it. 1: https://www.iata.org/contentassets/ebdba50e57194019930d72722413edd4/fact-sheet-fuel.pdf https://www.iata.org/contentassets/ebdba50e57194019930d72722...

adev_ 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. To put things in perspective, Concorde was using two Olympus engines designed originally in the 50s. It was already a marvel that they can run for such a range at Mach 2.0 when designed 70 years ago. A lot of things improved since. Most fighter jets can supercruise at supersonic speed without afterburners nowadays.

jacquesm 6y ago
Concorde used four engines. Two engine ETOPS over water wasn't a thing back then, first real relaxation of that rule was in '76. see: https://en.wikipedia.org/wiki/ETOPS https://en.wikipedia.org/wiki/ETOPS
- adev_ 6y ago
  Of course four. My apologies, too quick to type.

masklinn 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. Concorde didn't use afterburners "at speed". The afterburners were used for takeoff, and to go through the mach wall. Concorde burned insane amounts of fuel on the ground because turbojets are very inefficient at low-speed. Not unlike the SR-71's really (though the SR-71 also had such extreme high-speed bypass it was basically using ramjets at speed).

philjohn 6y ago
Didn't SR-71's also leak fuel when on the ground?
- masklinn 6y ago
  Yes but that's a separate concern. The engines were not efficient at slow speed / ground levels even ignoring the "leaks until it gets hot enough to seal the pipes" issue, the blackbird was designed to hit peak efficiency above Mach 3 (generally speaking all jets are designed to hit peak efficiency at their cruising speed, and the blackbird was designed for a cruising altitude of mach 3.2).
- imtringued 6y ago
  That's only because they decided to not use tanks inside the wings. The wings themselves contained the fuel. You can certainly build a non leaking SR-71 if a higher weight is acceptable.
  - masklinn 6y ago
    > That's only because they decided to not use tanks inside the wings. It's not only that. It's because they didn't have alloys which would handle the thermal constraints without significant expansion, so they had to design for that expansion. And in the same way rail tracks handle expansion by leaving gaps, that's what they did. Furthermore, due to limited room and systems able to handle the temperature gradients, the fuel acted not just as fuel but also coolant, heat sink and even hydraulic fluid for some propulsion components (e.g. the afterburner nozzles and inlet guide vanes used JP7 as hydraulic fluid).