The Bristol Odin is a ramjet

Ramjet

A ramjet, sometimes referred to as a stovepipe jet, or an athodyd, is a form of airbreathing jet engine using the engine's forward motion to compress incoming air, without a rotary compressor. Ramjets cannot produce thrust at zero airspeed and thus cannot move an aircraft from a standstill...

 engine originally developed by Bristol Siddeley Engines, later taken over by Rolls-Royce

Rolls-Royce plc

Rolls-Royce Group plc is a global power systems company headquartered in the City of Westminster, London, United Kingdom. It is the world’s second-largest maker of aircraft engines , and also has major businesses in the marine propulsion and energy sectors. Through its defence-related activities...

. Odin was specifically designed to power the Sea Dart missile

Sea Dart missile

Sea Dart or Guided Weapon System 30 is a British surface-to-air missile system designed by Hawker Siddeley Dynamics and built by British Aerospace from 1977...

. Unlike the earlier Thor

Bristol Thor

The Bristol Thor was a 16" diameter ramjet engine developed by Bristol Aero Engines for the Bristol Bloodhound anti-aircraft missile....

 ramjet powering the Bristol Bloodhound missile, Odin is an integral part of the Sea Dart airframe. A biconic intake at the front of the missile transfers air, via a transfer duct, to the ramjet combustor, which is located towards the rear of the missile. Thrust is provided by the combustion products exiting the engine at high velocity, via a fixed area ratio convergent-divergent nozzle. The only significant moving part in the engine is the turbopump

Turbopump

A turbopump is a gas turbine that comprises basically two main components: a rotodynamic pump and a driving turbine, usually both mounted on the same shaft, or sometimes geared together...

. This extracts 'ram' air in the transfer duct to drive an air-turbine, which is connected to the fuel pump. The air exiting the turbine is dumped overboard.