What are the L/D ratios of the two Solar Impulse airplanes? I haven't been able to find them.


1 Answer 1


Solar Impulse1 had 4 × 7.5 kW (10 hp) electric motors and a MTOW of around 4400 pounds, and was able to cruise at 43 mph, with 11 foot propellers.

Solar Impulse 2 had 4 × 13 kW (17.4 hp) each at 5100 lbs, and was able to cruise at 56 mph, with 13 foot propellers.

According to this article, the lift to drag ratio was around 37:1.

Rough calculation of 4 × 17.5 hp cruising at half throttle generating 4 pounds of thrust per hp

5100 lbs/(4×17.5 hp×4 lbs/hp×0.5) = 36.4

This is quite good for powered aircraft$^1$. Airliners range in the high teens, with the U-2 at 25.6.

$^1$ unless they can retract their power unit into the fuselage


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