I am greatly honoured to be here and to follow the distinguished men who have given this lecture in honour of the Wright Brothers in previous years. All of my famous predecessors have spoken on the subject of aeronautics. I will deal with aeronautics but only to describe its role in the development of manned space flight.

In their development of the aeroplane, the Wright Brothers recognised that there were many factors that they needed to master for successful flight. For example, they foresaw the need to train themselves to fly, showing truly remarkable foresight. They built and used their own wind tunnel. They combined the rare ability to recognise problems and to devise methods for their solution, all within the modest resources of their time. I have been very fortunate to live at a time where I could participate in so many phases of manned flight. As a boy, the Wright Brothers were a legend in my home. Later I was privileged to know Orville Wright when I was a young engineer at Langley Field and he was a member of the National Advisory Committee for Aeronautics (NACA).

A Euromech meeting on the aerodynamics of lifting bodies at high supersonic speeds was held at Churchill College, Cambridge on 30th and 31st July. Forty people attended from various European countries and 21 papers were presented. It is believed that these papers are fairly indicative of the range of current European work in this field. The present note gives a brief account of the work discussed at the meeting. A fuller report on the meeting is being prepared and will be circulated to all interested parties (copies may be obtained from the present author).

I want to begin by reminding you of the old friend of all of us, the late Captain J. Laurence Pritchard, who did more than anyone to record and analyse aeronautical history as it was happening. It was he who, in 1930, pointed my nose in the right direction and suggested that I should write a book on metal aircraft construction. The writing of that book showed me the gaps in my knowledge and I had to fill these in before the book was finished. I want to pass on to you–and particularly the younger members—some wise advice that JLP gave me then: “If you do not know a subject and want to learn, write or lecture about it. Then you will teach yourself”.

In view of the very wide scope of Operational Research in both the civil and defence fields, it is instructive to recall that it originated in wartime, as a means of increasing the operational effectiveness of combat forces. In the Second World War in particular it had a major effect on the efficient functional uses of the new radar equipment and achieved many other notable successes in increasing the effectiveness of our forces. It rapidly spread to all Services and in particular it was introduced into the Army through the formation in 1941 of the Army Operational Research Group, which in 1961 became the Army Operational Research Establishment, which in turn became in 1965 the tri-Service Defence Operational Analysis Establishment. Operational Research in wartime, functions in direct contact with the operational environment and the analytical predictions which it makes leads to direct application to the real world of war, the outcome in many cases being checked against the predictions. Operational Research in the original sense of investigation of operational factors continues to play a major part in peacetime in increasing the potential effectiveness of the services.

At BAC Filton the use of computers in missile work began early in the 1950s, much as elsewhere no doubt, by the company manufacturing its own analogue machines. The utilisation of computers was brought about by the need to develop the theoretical approach of design beyond the stage of hand computed calculations. Linear calculations could be long and tedious, and although ingenious exposure of the basic principles of missiles were often very instructive, they remained too simple to give complete reassurance.

As the development of missiles proceeded, the realisation of the complexity and extent of the non-linearities became more evident, casting doubt on the likely success of the missiles under design and manufacture. Typically with Bloodhound there was the fear that a twist/steer missile would not work, most missiles of the day being tail controlled cartesians. Would one be able to keep the body movements down to an acceptable minimum for the sake of aberration or ramjet extinction? Just what were the cross coupling effects from pitch and roll into yaw? Later, when what one might call the purely mechanical reliability aspects of trials were over, the need to understand the interaction of the various phenomena of missile flight began to dominate design thought.

Considerable research effort has been devoted to the experimental and theoretical study of turbulent boundary layers on flat plates. However, relatively little research has been done on turbulent boundary layers in the presence of transverse curvature. In this paper transverse curvature denotes curvature in a plane normal to the flow direction as shown in Fig. 1. In particular, flow along the outside of cylinders is considered.

In most of the experimental and theoretical investigations of the cylindrical boundary layers (see for example references 1 to 4) the effect of transverse curvature on the velocity profile, especially on the power law, was not considered. Exceptions to the above statement are Rao's inference on the velocity profile and Bonsignore's prediction of change in the index of the power law.

The concept of stability under constraint had been developed by Neumark and applied with considerable success to predict the speed instabilities in the flight of aircraft below minimum drag speed. This concept involves the removal (or partial removal) of one or more degrees of freedom of an aircraft by the deliberate application of some control to keep a chosen element of disturbance at a constant value. A partial constraint could thus be introduced in practice by a pilot trying to keep the wings level with the horizon by the use of aileron control, or keeping attitude constant with the use of elevator. Pinsker has recently used bank angle constraint stability of an aircraft as a means of defining a minimum acceptable value of nv.

This present note considers some aspects of longitudinal stability under constraint as applicable to the flight of a helicopter in the forward and the hover modes.

Figure 1 is a sketch of an “aerodynamic seal”. This type seal has potential application where it is necessary to control leakage of fluid through a clearance space bounded by one moving wall. For mechanical reasons it is necessary to maintain a clearance, in this case equal to the throat width t, between the inner wall I and the outer wall O. To prevent flow from the high pressure chamber H from passing into the low pressure chamber L, pump P supercharges fluid from H and forces it through nozzle J. The resulting fluid jet, which may be aided in following the curved surface by the Coanda effect, passes through the throat t and into diffuser D which recovers part of the entering velocity head. In the ideal case, with no losses and one-dimensional flow, the per cent recovery of inlet velocity head may be made as near to 100% as desired, since the diffuser recovery coefficient becomes asymptotic to 1-0 with increasing area ratio. Conversely, the dumping loss may be made as near to zero as desired. The attractiveness of this proposal hinges on diffuser performance. The pump is necessary to make up for the velocity head lost at the diffuser exit and for flow losses in the system. The pressure at the diffuser throat should be approximately that of the low pressure chamber for optimum performance. For large pressure ratios it may be necessary to stage two or more seals in series.

For flows at Mach numbers much less than unity the fully-developed wall shear stress in a circular pipe may be determined directly from a knowledge of the pipe radius, R, and the measured gradient in static pressure along the pipe, dp/dx. At higher subsonic Mach numbers it is conventional to apply a one-dimensional compressibility correction to make allowance for the acceleration of the fluid arising from the progressive decrease in density along the pipe. The correction procedure is to determine a “frictional” pressure gradient, dpf/dx, associated with wall shear stresses alone.