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Funnily enough the SR71 at Mach 3.5 had a better mpg than a Boeing 747 below Mach 1. It’s kind of hard to compare apples to apples here - but at supersonic spee

Funnily enough the SR71 at Mach 3.5 had a better mpg than a Boeing 747 below Mach 1. It’s kind of hard to compare apples to apples here - but at supersonic speed, different engine technology can be used with better fuel efficiency…

gleglegle 4y ago
Per passenger?
- deleted 4y ago
  [deleted]
- Retric 4y ago
  No.
lfowles 4y ago
It also only carried 2...
taeric 4y ago
You also have to compare getting to that speed. And, of course, the comparison is dead when done per passenger. Might as well compare a missile in there, or a drone.
SkyMarshal 4y ago
Probably also because it flew much higher with less air density and drag.
AlphaCharlie 4y ago
The SR71 was flying at a much higher altitude to achieve lower drag and fits 2 pilots, 0 commercial passengers. If you want to compare apples to apples, I suggest you refer to the 2 metrics I mentioned: - gallons of fuel per miles flown - fuel used per passenger One without the other is a useless comparison as you pointed out.
- looping__lui 4y ago
  U miss the point entirely that supersonic planes work differently from “traditional” subsonic planes. Just assuming that “faster equals less fuel efficient” is not really correct. Turbofan engines are kind of draggy and not so fuel efficient close to Mach 1. Ramjets change your equation… :-)
  - taeric 4y ago
    The point is poorly made. Would be like talking about how fuel efficient the space station is for it's speed. Can only work if you ignore the trip to that steady state. So, for the blackbird, how does it do on take off? You know, when it is literally leaking fuel? :)
    - looping__lui 4y ago
      Maybe you just wanted to understand the point in a certain way so you could argue about it?
      - taeric 4y ago
        Certainly fair. I can't see any world where the comparison is relevant, though. :( Down thread it was pointed out that sports cars are more efficient than busses. Per vehicle. This is about the same idea, at best.
post-it 4y ago
A Ferrari probably has better fuel efficiency than a bus, yeah.
- dsr_ 4y ago
  True. An average city bus gets 7 mpg; an 812 Superfast gets 13mpg. The bus wins when carrying 3 or more passengers besides the driver. And in a city with dedicated bus lanes, the bus may win for route speed, too.
- looping__lui 4y ago
  And I guess the brains behind a Ferrari enjoy their work more than engineers designing said bus. And Ferraris will attract more attention than a bus. Maybe some things are just unnecessary. Conquering the useless and doing unnecessary things is what keeps me sane and happy. But our mileage on that topic might vary.
  - ClumsyPilot 4y ago
    > And I guess the brains behind a Ferrari enjoy their work more than engineers designing said bus If we want to improve lives of workers, I am game, but can we start by helping all the amazon can drivers that pee in a bottle?
    - fear_and_coffee 4y ago
      [dead]
    - looping__lui 4y ago
      Maybe start with taxing the rich higher taxes, have minimum wage, maximum allowable working hours and all that stuff. The country I live in does that. You unemployed with three kids? Government pays your housing, free education for school and college (which is the same for rich and poor) and free healthcare. Why does designing a Ferrari have anything to do with your broken society? It’s not about the Ferrari - it’s about middle class upwards being cheap. Pay higher taxes and your problems on “improve live of workers” will go away. I pay approx. 60-65% on my gross income. Do the same and we can start talking again.
tormeh 4y ago
Drag also works differently at supersonic speeds.
dragonwriter 4y ago
> Funnily enough the SR71 at Mach 3.5 had a better mpg than a Boeing 747 below Mach 1. The SR-71 had a maximum takeoff weight of 140,000lbs. The 747 has a maximum takeoff weight of 735,000-910,000 lbs, depending on model. That helps quite a bit for the former using less fuel per mile.
- thfuran 4y ago
  And a considerably higher percentage of the 747's weight is passenger/cargo as well.
- looping__lui 4y ago
  [flagged]
deleted 4y ago
[deleted]

gleglegle 4y ago

Per passenger?

deleted 4y ago
[deleted]
Retric 4y ago
No.

lfowles 4y ago

It also only carried 2...

taeric 4y ago

You also have to compare getting to that speed. And, of course, the comparison is dead when done per passenger. Might as well compare a missile in there, or a drone.

SkyMarshal 4y ago

Probably also because it flew much higher with less air density and drag.

AlphaCharlie 4y ago

The SR71 was flying at a much higher altitude to achieve lower drag and fits 2 pilots, 0 commercial passengers. If you want to compare apples to apples, I suggest you refer to the 2 metrics I mentioned: - gallons of fuel per miles flown - fuel used per passenger One without the other is a useless comparison as you pointed out.

looping__lui 4y ago
U miss the point entirely that supersonic planes work differently from “traditional” subsonic planes. Just assuming that “faster equals less fuel efficient” is not really correct. Turbofan engines are kind of draggy and not so fuel efficient close to Mach 1. Ramjets change your equation… :-)
- taeric 4y ago
  The point is poorly made. Would be like talking about how fuel efficient the space station is for it's speed. Can only work if you ignore the trip to that steady state. So, for the blackbird, how does it do on take off? You know, when it is literally leaking fuel? :)
  - looping__lui 4y ago
    Maybe you just wanted to understand the point in a certain way so you could argue about it?
    - taeric 4y ago
      Certainly fair. I can't see any world where the comparison is relevant, though. :( Down thread it was pointed out that sports cars are more efficient than busses. Per vehicle. This is about the same idea, at best.

post-it 4y ago

A Ferrari probably has better fuel efficiency than a bus, yeah.

dsr_ 4y ago
True. An average city bus gets 7 mpg; an 812 Superfast gets 13mpg. The bus wins when carrying 3 or more passengers besides the driver. And in a city with dedicated bus lanes, the bus may win for route speed, too.
looping__lui 4y ago
And I guess the brains behind a Ferrari enjoy their work more than engineers designing said bus. And Ferraris will attract more attention than a bus. Maybe some things are just unnecessary. Conquering the useless and doing unnecessary things is what keeps me sane and happy. But our mileage on that topic might vary.
- ClumsyPilot 4y ago
  > And I guess the brains behind a Ferrari enjoy their work more than engineers designing said bus If we want to improve lives of workers, I am game, but can we start by helping all the amazon can drivers that pee in a bottle?
  - fear_and_coffee 4y ago
    [dead]
  - looping__lui 4y ago
    Maybe start with taxing the rich higher taxes, have minimum wage, maximum allowable working hours and all that stuff. The country I live in does that. You unemployed with three kids? Government pays your housing, free education for school and college (which is the same for rich and poor) and free healthcare. Why does designing a Ferrari have anything to do with your broken society? It’s not about the Ferrari - it’s about middle class upwards being cheap. Pay higher taxes and your problems on “improve live of workers” will go away. I pay approx. 60-65% on my gross income. Do the same and we can start talking again.

tormeh 4y ago

Drag also works differently at supersonic speeds.

dragonwriter 4y ago

> Funnily enough the SR71 at Mach 3.5 had a better mpg than a Boeing 747 below Mach 1. The SR-71 had a maximum takeoff weight of 140,000lbs. The 747 has a maximum takeoff weight of 735,000-910,000 lbs, depending on model. That helps quite a bit for the former using less fuel per mile.

thfuran 4y ago
And a considerably higher percentage of the 747's weight is passenger/cargo as well.
looping__lui 4y ago
[flagged]

deleted 4y ago

[deleted]