Effusion cooling consists in forcing a gas under pressure through a porous material thereby absorbing heat from the material and forming a heat insulating layer on the exposed surface. The internal heat transfer between the porous material and coolant is considered and the heat transfer coefficient obtained from experiment. An approximate analysis for the heat insulating effect based on a heat balance method is derived in detail and applied to experiments with porous plugs set into the side of a duct carrying hot gases, and to porcras cylinders swept by hot gases. It has been found that this analysis applies reasonably accurately to the results of these experiments and of most of the published data. The manufacture of porous materials is discussed briefly and a representative list of commercially available materials is included. The application of effusion and sweat cooling to the blading and combustion chamber linings for gas turbines, rocket motors and the outside skin of flying vehicles is considered.

The first ten years following the end of the First World War saw a steady “run down” in the armed forces and during this period what still existed in the field of aero-engine development was inspired, mainly, by participation in long range pioneering flights, distance records and international speed events—such as the Schneider Trophy Contest.

Research and development were limited by the funds available and it was not until about 1935, when the Government decided on an “all out” policy to re-equip the Royal Air Force with equipment to match the growing aerial strength of Germany, that aero-engine development received the support it needed. It was somewhere in this period that marked the “renaissance” of the development of aero-engines.

Real gas effects are among the major complications of hypersonic flow and this is illustrated by examples of the temperatures and pressures attained when a flow is brought to rest. Once dissociation appears, these depend to a marked extent on the type of compression.

In designing for the alleviation of aerodynamic heating there are two distinct cases. The first is the uncontrolled re-entry of a freely falling body, for which it is best to have a shape with a high pressure drag. The second is sustained flight, for which a shape with low pressure drag could be better, radiation giving appreciable control of surface temperature.

Low pressure drag accords with design for aerodynamic efficiency and there is scope for research on three-dimensional lifting shapes. There is some discussion of this and also of the philosophy of securing maximum amounts of separated flow.

Finally, there is continual emphasis on the need for experimental research, since hypersonic flow fields may differ considerably from those that would be expected by extrapolation of conventional supersonic experience.

The Twelfth Louis Blériot Lecture, “The Griffon Aircraft and the Future of the Turbo-Ram-Jet Combination in the Propulsion of Supersonic Aeroplanes” was given by General Noël Daum, Technical Director, Nord Aviation, on 12th March 1959 at the Institution of Mechanical Engineers, Birdcage Walk, London, S.W.I. Sir Arnold Hall, M.A., F.R.S., F.R.Ae.S., President of the Society, presided.

Before introducing the Lecturer, Sir Arnold presented the Society ̓s Gold Medal, the highest award the Society can confer, which the Council had awarded to Monsieur Marcel Dassault and which they felt it would be particularly appropriate to present on this occasion—their annual joint meeting with the Association Francaise des Ingenieurs et Techniciens de l ̓Aéronautique (A.F.I.T.A.)

Several years ago it became apparent that there was a need for some means of reversing the thrust of jet engines on landing—the equivalent of reversing pitch propellers on piston and turbo-prop engines.

Many different designs were investigated on the drawing-board, with experimental backing in some cases, and when the best configurations had crystallised detail work started on a reverser for the Avon engine. While this was being developed a second design, identical in its main principle but different in many small ways, was prepared for the Conway engine.

The Prime Purpose of this initiative Halford lecture is to speak of the man and his work.

It may seem rather peculiar to preface such a lecture with an obituary but as I wrote one of them with deep feeling in my heart I make no apology for quoting parts of it to start this lecture and later, to expand on those aspects of his rich life which may be of interest.