Eli5: what are the benefits of a normal helicopter design vs a quadcopter we see on drones?

Question

Eli5: what are the benefits of a normal helicopter design vs a quadcopter we see on drones?

In: 210

Answer 1

quad-coptors (drones) require instant torque in order to make the microsecond corrections that they need to make every microsecond to stay afloat. You need electric engines to do that – combustion engines have to rev up to produce torque.

However, batteries are *WAY* less energy dense than gasoline is, so in order to have a drone as big as a helicopter, you’d need a prohibitively heavy amount of batteries.