A rotor drive apparatus includes a rotor and a stator. The stator has a
gas injection orifice located on the axis about which the rotor spins.
The gas injection orifice communicates with a bearing gap formed between
a tapered surface of the rotor and an axially spaced tapered surface of
the stator. A gas is flowed from the gas injection orifice through the
bearing gap, thereby establishing a center-fed, radial-outflow gas
bearing supporting the rotor during rotation. In one implementation, a
separate flow of drive gas is fed to drive flutes of the rotor to drive
rotation. In another implementation, the center-fed, radial-outflow gas
flow is additionally utilized to impinge against the drive flutes to
actuate the rotation.