2 ms·

Again, I'm not saying the concorde is a more efficient vehicle, I'm saying flying supersonically is more efficient than flying subsonically. The concorde was an

• TylerE 6y ago
  And I say that " I'm saying flying supersonically is more efficient than flying subsonically." is a complete load of rubbish unsupported by science or data.
  • jjk166 6y ago
    If you study aerospace engineering you derive this in undergrad. Again, the whole reason supersonic transports were pursued in the 60s was to reduce fuel costs, and the attempts were abandoned when turbofans proved a better method of achieving that goal.
  • valuearb 6y ago
    Then why did the Valkyrie B-70 have a longer range flying supersonic than subsonic?
• jandrese 6y ago
  As wind resistance increases with the square of the speed and is the major resistive force when traveling by air it's really hard to become more efficient by going faster. It's probably true that Concorde, with its supersonic optimized design would have been less efficient traveling at Mach 0.95, even when traveling at its optimum speed a subsonic optimized airliner is going to require significantly less fuel per passenger mile. I mean this is one reason Concorde failed: the oil crisis turned its high fuel consumption into a serious liability.
  • jjk166 6y ago
    Drag increases proportional to the square of velocity times the density. At higher speeds, you can fly at higher altitudes for a given lift to drag ratio. Higher altitudes -> lower air densities. Drag overall does increase, but at a slower rate than just looking at the velocity alone would suggest. The efficiency of jet engines increases with both altitude and airspeed (which is why subsonic airliners fly as close to the speed of sound as they can get btw). At and slightly above the speed of sound drag dominates, but engine efficiency eventually becomes more important again past Mack 1.6. The important thing to remember here is that at the same time as the concorde was being developed, another technbology, the high bypass turbofan, was also developed. This looks like and is commonly referred to by the layperson as a jet engine, but the two are very different. A Turbofan is 10 to 50 times more efficient than an afterburning turbojet, regardless of speed. The concorde didn't have turbofans, the planes it was competing with did. You slap the concorde's engines onto any other airframe and fly at any other speed, it's still going to burn an order of magnitude more fuel than a turbofan aircraft. Compare the concorde to turbojet powered aircraft it is competitive. The turbojet powered boeing 720 got 16 passenger miles per gallon and the 727 got 10. In that context the concorde's 17 at over twice the speed looks pretty good.
    • TylerE 6y ago
      So your argument continues to be that the aircraft that is provable, and AS YOU ADMIT, is less efficient, is somehow "more efficient" because "reasons".
      • jjk166 6y ago
        Again, that's not my argument. I will continue to assume good faith one last time. Drag is proportional to density times velocity squared flying through air with 30% the density at 2.5 times the speed thus produces (.3)x(2.5^2) = 1.875 times the drag. Using 1.875 times the power for 1/2.5 = 0.4 times as long requires (0.4)x(1.875) = 0.75 times as much energy. This is before you consider that jet engines moving at higher speeds and higher altitudes are more fuel efficient. The 737 uses turbofans which are much more efficient than the concorde's turbojets. Trying to compare their fuel consumption is meaningless unless you account for this. If you compare the concorde to a subsonic turbojet of its era, like the 727, the concorde burns significantly less fuel per passenger mile.