4 ms·
Most of the energy cost is pushing the air out of the way. This is just as true for a train as a plane. I suppose the plane also has to spend some energy as lif
by xhkkffbf 3y ago
Most of the energy cost is pushing the air out of the way. This is just as true for a train as a plane. I suppose the plane also has to spend some energy as lift, but my impression is that this sort of comes along as part of the cost of pushing the air out of the way.
Has anyone done this calculation?
- silverquiet 3y agoMy very basic understanding of the physics of air resistance is that it increases at the square of speed, so a plane that's going at 500 miles/hour must use massively more energy than a trane traveling at 100 miles/hour.
- dividefuel 3y agoThe air is thinner at cruising altitude, though of course thicker at takeoff altitude. I'm sure longer flights are much more efficient than shorter, but whether they ever overtake trains I'm not sure.
- alwayslikethis 3y agoFun fact once flights go above a certain length they get less efficient because all that fuel they are carrying actually requires more fuel to move, which in turn needs to be carried. I don't think it's the energy efficiency that's the issue here. Even if trains are less energy efficient, they can much more easily be powered off renewable sources.
- lesuorac 3y agoI mean sticking with the assumption it takes the same amount of energy you still need to show that a jet engine is as or more efficient as a train engine. Which it seems to not be [1]. [1]: https://en.wikipedia.org/wiki/Energy_efficiency_in_transport#US_Passenger_transport https://en.wikipedia.org/wiki/Energy_efficiency_in_transport...
- dividefuel 3y agoI'm honestly surprised how relatively close these values are. This says personal trucks use about 2x as much energy as mass transit. I would've thought the ratio would be much higher.
- ljf 3y agoThe passenger numbers seem low to me - but I can only assume they come from research - so the passenger figures will skew that. A full bus (60 people?) would be far more efficient.
- The_Colonel 3y agoA missing consideration is that most modern railway is electrified while the airplanes will have to stick with burning fossil fuels for a while.