Hunh so for pure lifting our standard helicopter design is apparently the best. How did we stumble on the perfect design half a century ago? Was it sheer luck and constraints or can you actually do the math for this to work it out?

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regularfry 2 hours ago | parent | next [-]

The article makes reference to this being expected from the physics, but I don't think it's particularly intuitive why it should be the case. Unless it's as simple as smaller swept areas needing higher tip speeds for the same lift? That would make the energy loss to drag worse for multirotors.

	▲	snovv_crash an hour ago \| parent [-]
		Higher aspect ratio blades are more efficient. It maximises disc area for a given mass of blade (linear-squared relationship). Blade is held straight due to tension not purely from torsional strength, so it can be made from a material with high tension strength like carbon fibre which is light. Also it positions the fastest moving blade area far out from the fuselage where there is less blown-drag. The downside is that the tail rotor is purely loss. Potentially a similar efficiency could be achieved with two large rotors, but then you end up needing to use cyclic roll to counter drag-induced cyclic yaw, or adding extra pitch mechanisms on each motor mount to make differential yaw.

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somat an hour ago | parent | prev | next [-]

I am surprised it was not a coaxial design(think the mars copter, but designed for a real atmosphere)

	▲	reliablereason 10 minutes ago \| parent [-]
		I would think coaxial designs suffer as the lower rotor works in more turbulent non laminar air.

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whatever1 2 hours ago | parent | prev | next [-]

We have also achieved optimal teapot design for perfect flow thousands of years ago.

We have some times very good intuition and ideas.

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ballooney 39 minutes ago | parent | prev [-]

For a given lift, a larger, lower speed rotor is strictly more efficient than a smaller faster one, all else being equal. So no surprises that when efficiency matters we don’t see quadcopter-type designs. The reason they became ubiquitous is because they are so mechanically simple, all the control can be done with cheap electronics, no need for the great mechanical complexity of a swashplate.