Re:Lilium – Electric vertical take-off and landing jet
by Symmetry on Friday April 21, 2017 @03:39PM
(#14168723)
A SR-20 has a single engine at the front of the plane rather than 36 scattered over the wings. They claim, at least, that that makes a big difference in aerodynamic efficiency.
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Re:Lilium – Electric vertical take-off and landing jet
by pdelbarba on Friday April 21, 2017 @04:13PM
(#14169034)
It does in some cases (see NASA X-57 where the fan is used to accelerate air over the wing, leading to a smaller wing with lower drag overall) but I'm not convinced in this case. Having a system that is efficient at high airspeed and high thrust generally requires a variable geometry propeller (constant speed prop in GA terms) because a 'lift fan' at high relative airspeed, would have to spin much faster than a 'cruise fan' like you would see on a regular aircraft meaning airflow over the blades is higher leading to higher drag on the blade than necessary.