Air turborocket

The air turborocket as described in Chapter 14 of 'Tactical Missile Propulsion' (Volume 170 of American Institute for Aeronautics and Astronautics Tactical Missile Book Series) is a form of combined-cycle jet propulsion. The basic layout includes a gas generator, a device which produces high pressure gas when activated, which produces a fuel-rich pressurized gas. This gas drives a turbine/compressor assembly which sucks atmospheric air into a combustion chamber into which the fuel-rich gas also traveled. This mixture is then further combusted before leaving the device through a nozzle creating thrust.

Benefits

The benefit of this setup is increased specific impulse. For the same mass of fuel as a rocket motor, the overall output of the air turborocket is much higher. In addition, it provides thrust throughout a much wider speed range than a ramjet, yet is much cheaper and easier to control than a gas turbine engine. The air-turborocket fills a niche (in terms of cost, reliability, ruggedness, and duration of thrust) between the solid-fuel rocket motor and gas turbine engine for missile applications.

Air turborocket vs. standard rocket motor

In applications which stay relatively in the atmosphere and require longer durations of lower thrust over a specific speed range the air turborocket can have a weight advantage over the standard solid fuel rocket motor. In terms of volumetric requirements, the rocket motor has the advantage due to the lack of inlet ducts and other air management devices.

ee also

* http://history.nasa.gov/SP-4404/ch7-5.htm
* http://www.islandone.org/LEOBiblio/SPBI102.HTM