Hovering

Why helicopters have big rotors

An interactive lesson with 6 steps, about 5 minutes: you predict, drag and solve, with instant feedback on every answer. It runs in your browser and needs JavaScript.

What you’ll learn

• Ideal hover power $P = \sqrt{T^3/(2\rho A)}$.
• Bigger rotors and denser air make hovering cheaper.
• Thin air on mountains, or on Mars, demands far more power.

Steps

1. Pushing air down
2. Double the rotor
3. Design a drone
4. Hovering at altitude
5. A heavier drone
6. Mars helicopter