Motorjet
A motorjet is a rudimentary type of jet engine which is sometimes referred to as "thermojet", a term now commonly used to describe a particular and completely unrelated pulsejet design. Design. At the heart the motorjet is an ordinary piston engine (hence, the term "motor"), but instead of (or sometimes, as well as) driving a propeller, it drives a compressor. The compressed air is channeled into a combustion chamber, where fuel is injected and ignited. The high temperatures generated by the combustion cause the gases in the chamber to expand and escape at high velocity from the exhaust, creating  a thermal reactive force that provides useful thrust. Motorjet engines provide greater thrust than a propeller alone mounted on a piston engine; this has been successfully demonstrated in a number of different aircraft. A jet engine also can provide thrust at higher speeds where a propeller becomes less efficient or even ineffective; in fact, a jet engine gains efficiency as speed rises, while a propeller loses it (outside of a certain design range). This gives better efficiency in either operating range than an aircraft powered by just a propeller or a jet. The same is true of the dual-powerplant  aircraft experimented with after the turbojet became practicable, which were equipped with both a piston-driven propeller and a turbojet engine. History. Motorjet research was nearly abandoned at the end of World War II as the turbojet was a more practical solution to jet power as it used the jet exhaust to drive a gas turbine, providing the power to drive the compressor without the additional weight of a piston engine that generated no thrust. One of the primary advantages of the motorjet layout was that the reciprocating engine provided power for the compressor and no turbine power section was  needed. However, metallurgy and understanding of the design of turbines had advanced to a point after World War II where it was feasible to create a turbine to operate reliably in the high-velocity hot-gas environment downstream of the combustor, and the motorjet idea lost focus.