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THE transformation of energy stored in the fuel into heat energy of exhaust gases was followed in the previous parts. The molecular changes occurring in the working fluid were investigated, as well as the changes of its physical constants due to the high pressures and temperatures. It is known that the combustion of hydrocarbon fuel results for the most part in the formation of CO2 and H2O as combustion products and consequently special attention is given to the behaviour of these gases since they constitute the working fluid of a rocket engine. The general equation of hydrocarbon combustion has the following form:

Specific Heat of Gases THE chemical reaction having been accomplished and the energy of fuel released, we can follow its further transformation. It can be assumed that in the first stage this energy is absorbed and stored in the surrounding gaseous medium composed mainly of combustion products. The mechanism of the absorption and preservation of energy by gases is given in their specific heat theory, and is based mainly on the assumption of the equipartition of energy among all degrees of freedom of gas molecules. Heat, being the equivalent of kinetic energy of these molecules, is stored in four different ways by the molecules, and assumes four different forms of energy, three of which are quantized without any doubt, i.e. the exchange of energy does not take place as a continuous flow, but by small packets of a definite size (quanta). The value of a quantum is equal to hp, where h is the Planck's constant and p is the frequency of radiation associated with the energy change.

WHEN the temperature of the gas reaches the high level, the molecules begin to break up into atoms or groups of atoms, which after recombination form new and smaller molecules of a simpler structure. For instance, tri‐atomic molecules after having been split form diatomic ones. This process is called the dissociation of gases. The newly‐formed molecules, when colliding, again form molecules of the original gas, so two processes are occurring simultaneously. However, the higher the temperature, the larger the percentage of dissociated molecules.

THE task of any recoil engine consists in transforming the chemical energy of fuel into the kinetic energy of gases leaving the nozzle. This article gives a brief survey of problems connected with transformations which the energy undergoes on the way from the fuel containers to the end of the nozzle. I have simplified as far as possible the problem, examining only the conditions in a rocket engine, without a gas turbine. Even in these simplified schemes the phenomena inside the combustion chamber and the nozzle are rather complicated and require careful examination.

IT is now possible to determine the temperature in the combustion chamber with greater accuracy than in Part V. However, to simplify the problem it is necessary to make a number of far‐going assumptions. A more detailed survey of phenomena occurring in the combustion chamber will be given in a later Part; at present we are merely enumerating the simplified schemes, which enable us to tackle the problem.

A GENERAL outline of the processes occurring in the working fluid of a rocket engine has been summarized previously, but the total picture is still far from complete, a number of important phenomena not having been taken into account. Their full analysis would be, however, beyond the scope of this paper, and may be left to specialists more qualified than the author to give an account of combustion processes.

USING the general theory of cylindrical shells, expressions have been derived for the maximum bending moment and shearing force in vessels closed at one end and subjected internally to (a) gas pressure, (b) hydrostatic pressure. The method has been used by S. Timoshenko (Theory of Plates and Shells, McGraw‐Hill, pp. 412–3) for the special case where one end of the vessels is built into a rigid foundation.

A NEW metal to metal jointing compound, possessing many salient features, has been developed in the Rolls‐Royce Laboratories as a result of considerable trouble which was experienced with well‐known types of joint washers or gaskets, and proprietary liquid jointing compounds, when these materials were applied to the joints of Merlin and Griffon engines in attempts to overcome oil leakage.

ROCKET and ramjet engines have not the universal application that gas turbines command and possibly on this account they have not had, until recent years, the development effort which gave such amazing results in turbine powered aircraft. Nevertheless, they have demonstrated quite dramatically in various parts of the world that they are power plants to be reckoned with. In Great Britain, their value for aircraft was appreciated somewhat belatedly and events have since decreed that the promise they showed should be smothered before it could become a vital fact. On the other hand their importance for missiles was realized at the conclusion of the 1939–45 war, but again they were not encouraged on anything like the scale that present events show would have been justified. Because of this lack of encouragement, British rockets and ramjets, instead of leading the world, as do gas turbines, are struggling hard to provide a modest rate of progress.

Under this heading are published regularly abstracts of all Reports and Memoranda of the Aeronautical Research Committee, Reports and Technical Notes of the United States National Advisory Committee for Aeronautics and publications of other similar Research Bodies as issued.