Turborocket

A turborocket is a type of aircraft engine combining elements of a jet engine and a rocket.

Once a jet engine goes high enough in an atmosphere, there is insufficient oxygen to burn the jet fuel. The idea behind a turborocket is to supplement the atmospheric oxygen with an onboard supply. This allows operation at a much higher altitude than a normal engine would allow.

A turborocket typically comprises a multi-stage fan driven by a turbine, which is driven by the hot gases exhausting from a series of small rocket-like motors mounted around the turbine inlet. The turbine exhaust gases mix with the fan discharge air, before exhausting through a convergent-divergent propelling nozzle.

The turborocket design offers a mixture of benefits with drawbacks. It is not a true rocket, so it cannot operate in space. Cooling the engine might be troublesome since many turbojet engines require significant cooling air to prevent overheating (melting) crucial parts.

Note that there are several other systems for extracting oxidizer from the air as well, designs known as LACE.

Note: This is not to be confused with an air turborocket.