Re:Hyperloop startup Arrivo is shutting down as workers are ...
by mpweiher on Tuesday December 25, 2018 @05:02AM
(#18756792)
> drag at sea level is a killer.
Yes. Apparently when jet turbines came along they were discounted as ever being useful for commercial/passenger airplanes because they were so incredibly inefficient. I mean, really incredibly inefficient.
What they didn't take into account is that the turbines allow you to fly at much, much higher altitudes. The reduced drag there more than makes up for the lower efficiency. And gets you a smoother ride and higher speeds as well.
Modern turbofan engines are much more efficient, but that's basically because they really are turbo-props with enclosed propellers, though we call them "high bypass turbofans".
And of course if jets have to drop to a lower altitude, for example because their cabin has become depressurised, range is drastically reduced.
Re:Hyperloop startup Arrivo is shutting down as workers are ...
by pfdietz on Tuesday December 25, 2018 @02:16PM
(#18758791)
They're turboprops, but they're turboprops that don't have the speed limit imposed by the need to keep propeller blade tips from exceeding the speed of sound.
Yes. Apparently when jet turbines came along they were discounted as ever being useful for commercial/passenger airplanes because they were so incredibly inefficient. I mean, really incredibly inefficient.
What they didn't take into account is that the turbines allow you to fly at much, much higher altitudes. The reduced drag there more than makes up for the lower efficiency. And gets you a smoother ride and higher speeds as well.
Modern turbofan engines are much more efficient, but that's basically because they really are turbo-props with enclosed propellers, though we call them "high bypass turbofans".
And of course if jets have to drop to a lower altitude, for example because their cabin has become depressurised, range is drastically reduced.