Abstract: A nozzle arrangement for an engine that is operable in both an air-breathing mode, in which the engine combusts air taken in from atmosphere with hydrogen from a store thereof, and in a rocket mode, in which the engine combusts oxygen from a store thereof with hydrogen from the store thereof. The nozzle arrangement may include a rocket combustion chamber fluidly coupled by a rocket throat to a rocket nozzle. The rocket nozzle includes a first portion adjacent the rocket throat and a second portion remote from the rocket throat and axially moveable relative to the first portion between a rocket position in which they form a substantially contiguous rocket nozzle and an air-breathing position in which they overlap to define an annular throat therebetween. The nozzle arrangement may also include at least one air-breathing combustion chamber arranged to be fluidly coupled to the annular throat when the first and second portions of the nozzle are in the air-breathing position.