Nozzle arrangement for an engine

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 comprising:

• a rocket nozzle;
• a rocket combustion chamber fluidly coupled by a rocket throat to the rocket nozzle, the rocket nozzle comprising a first portion adjacent to the rocket throat and a second portion remote from the rocket throat, and the second portion axially moveable relative to the first portion between a rocket position in which the first and second portions form a substantially contiguous rocket nozzle and an air-breathing position in which they overlap to define an annular throat therebetween, wherein the first portion of the rocket nozzle is a substantially frusto-conical portion with a larger diameter end lying in a radial plane and the second portion is a substantially frusto-conical portion with a smaller diameter end lying in a radial plane, with the smaller diameter end of the second portion comprising a substantially cylindrical portion extending substantially axially from a neck portion of the second portion;
• and when in the rocket position, the larger diameter end of the first portion engaging the neck portion of the second portion to form the substantially contiguous rocket nozzle in a substantially sealed engagement;
• and
• at least one air-breathing combustion chamber arranged to be fluidly coupled to the annular throat when the first and second portions of the rocket nozzle are in the air-breathing position.