  We consider a gas of free chiral fermions trapped inside a uniform rotating
spherical shell. Once the shell becomes transparent the fermions are emitted
along the axis of rotation due to the chiral and mixed anomaly. In return,
owing to momentum conservation, the shell is propelled forward. We study the
dependence of the magnitude of this effect on the shell parameters in a
controlled setting and find that it is sensitive to the formation of an
ergosphere around the rotating shell. A brief discussion on a possible relation
to pulsar kicks is provided.
