A rotor assembly for an engine, comprising: a rotor, supported on bearings for axial rotation, a rotor portion forming a compression passage extending outwards from the axis, gases entering the rotor through inlets at the axis and flowing outwards through the compression passage; a combustion chamber supported within the compression passage near the maximum radius of the rotor having a closed outer end and combustion chamber gases inlets through which gases enter the combustion chamber, each combustion chamber having a fuel inlet, and; one or more expansion passages in fluidic connection with and extending radially inwards from the combustion chamber within a compression passage and fluidically connecting at or near the rotor axis to a combustion gas outlet tube that extends along the rotor axis, combustion gases created by combustion of fuel with inlet gases within the combustion chamber expanding as they flow inwards through the expansion passage.