Tip jets can use compressed air. That would be more efficient.
https://en.wikipedia.org/wiki/Tip_jet
As with all cool concepts "Zee Germans" had the idea https://en.wikipedia.org/wiki/Focke-Wulf_Triebfl%C3%BCgel
https://en.wikipedia.org/wiki/Tip_jet
As with all cool concepts "Zee Germans" had the idea https://en.wikipedia.org/wiki/Focke-Wulf_Triebfl%C3%BCgel
The Dutch came up with the 'ornicopter': https://youtu.be/0Z2Rr39hiUs
(The presentation spends a lot of time explaining tail rotors, which this invention does not need. Skip to about halfway to see how it works.)