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Comment by ChuckMcM | Hacker News Reader

Just penciling in the math that means a quad copter is pretty straight forward with this motor. 200kg for a "megawatt" of thrust. Now all we need are batteries that are 3x as power dense as the current best of class and you'll be able to hop from home to the office in your 'quad'.

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There's a startup in my area that are working on an electric helicopter: http://volocopter.com/ - they use 18 rotors, probably because bigger motors get heavy really quickly, but also for redundancy.

I believe that they use many small motors instead of a big one because quadcopter like planes are controlled by changing blade speed and that bigger blades have much more inertia which limits the speed at which the rotation can bee accelerated. Helicopters spin their blades at a constant speed and vary the angle of attack of the blades to obtain the same control which means it is less affected by inertia.

Why would you use batteries? Fuel gets lighter as you use it, and the density is already there. Automate maintenance so you can use turbines.

My guess would be electric might be simpler and easier to maintain and with electric you can charge at home.

Maintaining EVs is cheaper and easier than fuel-based vehicles.

I've thought the same thing, perhaps efficiencies for generating electricity for fuel engines are too low currently? Anyone have any stats?

Not my area of expertise here, but since quadcopters are all about torque, I speculate that electric motors (with their flat-ish torque curve) are much easier to design for?

mass per kilowatt hour. That is the magic number. While a gas turbine can be slightly over 52% efficient it weighs a lot. You can plot weight over kilowatt hours, which is useful since at small numbers of kilowatt hours batteries are a huge win, and then at some point you get a cross over where the fact that fuel is more energy dense it has compensated for the weight of the turbine and generator infrastructure.

I believe pluggable, human carrying quads have potential in couple of industries like building maintenance, firefighter ladder replacement or lift alternatives.

Problem is the power delivery, you'd need around 20kW of power. That is not available just about everywhere and requires fairly thick cable.

I want a cable laying snake..

There's a startup called Plugless that makes wireless charging equipment for cars[1] (basically a scaled-up version of the wireless phone chargers). The current version puts out around 3.3kW continuous - not quite that 20 kW, but in the ballpark. Perhaps that technology could be developed to suit that niche.

[1]https://www.pluglesspower.com/look/?jump=tech#tech-specs

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