Pure rocket propulsion

The pure rocket will work at very high altitude and in the vacuum of space. The high speed of the exhaust gases and the added weight of the oxidant that must be carried, however, mean that it is extremely inefficient in comparison with air-breathing engines at low altitude.

The thrust of a rocket motor comes from the high pressure on the walls of the combustion chamber and exhaust nozzle. The same high pressure produces the acceleration and momentum change of the exhaust gases.

Rockets have been used to assist the take-off, and for experimental high altitude high speed research aircraft, but one production rocket aircraft was the Second World War swept tailless Messerschmitt Me 163. The motor used two chemicals, one of which was highly reactive and, if it did not explode during a

Fig. 6.40 Turbo-ramjet propulsion for very high speed flight

The Lockheed SR-71 was capable of flight at Mach 3+

Note the central shock-generating movable spike in the axi-symmetrical engine intakes, and the exhaust nozzles fully open for operation with reheat The photograph was taken as the aircraft was manoeuvring at a high angle of attack. The strong conical vortices generated by the fuselage strakes and the wing have been made visible by the clouds of water vapour produced (not smoke). The engines have flamed-out leaving spectacular fireballs. The engine has a very complex internal variable geometry, and any mismatch is liable to produce a failure of the combustion process, leading to flame-out (Photo from Duncan Cubitt, Key Publishing)

heavy landing, was liable to dissolve the occupant. It was reportedly unpopular with pilots!