Now that major space flight operations are under way in Russia and America there is a natural interest in such topics in this country among those working on aeronautics and guided missiles. At present one can only speculate on how this country will eventually contribute to space flight. As the Duke of Edinburgh has remarked, the difficulty is not due to lack of scientific talent but to the absence of surplus funds. Even so, we can make effective contributions in many ways and we should not lack boldness in seeking out possible ways of doing this. In the meantime, however, there seems to be a place for a review of the present technical situation and prospects for the near future, as seen from the standpoint of one in the British Aircraft Industry. As the majority of interplanetary flights will begin through the Earth’s atmosphere and many will finish by way of the same medium, the Royal Aeronautical Society can claim a special and legitimate interest in these matters. Ever since its inception the Society has encouraged the discussion of new technical advances, although its ability to do this has sometimes been hampered by the requirements of security. The same restrictions apply to this paper with the result that I have chosen to draw upon published material throughout, and to review the subject on a broad basis. I hope the work will not be less acceptable on these grounds.

The past ten years have seen a wide variety of axial gas turbine aero-engines pass through their development phase into military service. A new phase began when the first axial gas turbine engines to operate to a civil schedule entered service in 1956-7, powering the Britannia and Tu.104 aircraft. The coming years will see an ever-increasing percentage of the world’s air traffic being carried by axial gas turbine engines and it may be confidently predicted that in another ten years they will be the rule rather than the exception.

The enormous importance of reliability in civil operation is well known. Possibly less well known is the incredibly rapid build-up of running hours which occurs when an engine is introduced into civil operation. In six months of civil operation these may exceed the cumulative hours in the whole life of a military type, and will outstrip the total manufacturers’ bench experience in an even shorter time. With all the achievements in bench development and military service in the past ten years, the axial gas turbine engine is still in the “ kindergarten ” in relation to civil operation.

Rapid developments in the use of the helicopter were made in the Korean War. These were taking place at the time when there was considerable urge to introduce the gas turbine engine into the civil aircraft market. It was also a time when much effort was being expended on various forms of reaction propulsion, mostly for missiles. A number of new helicopter projects were started, taking advantage of the new knowledge in propulsion engineering; some utilised new gas turbine designs and others various forms of tip jet reaction. Liquid fuel rockets, ram-jets, pulse-jets and air pressure jets were tried. However, the main line of development continued to be the gradual improvement of direct mechanical drive.

Since Korea the natural trend has been first to convert existing helicopters to turbine engines. When new helicopters were designed wisdom dictated mechanical drive pending the gathering of sufficient experience with other forms of rotor power, and so far the accumulated knowledge of the mechanical drive has proved of greater value to helicopter progress than the potential advantages offered by the alternative engine forms.

The advent of the high altitude supersonic aircraft has brought in its train a whole host of complex control problems. As far as the engine manufacture is concerned, these are perhaps best indicated in the diagrammatic layout shown in Fig. 1

It is not my intention however, to go into the question of multiplicity of controls and their proper co-ordination, nor will I venture into the abstruse province of stability. I should like instead to concentrate on the fuel system itself, i.e. the supply and control of fuel to the main engine combustion chamber.

The Ordinary convergent exhaust nozzle is a perfectly satisfactory and efficient device for converting pressure in the jet pipe into velocity, so long as the pressure ratio across it remains below about 2.0; or, put another way, so long as the velocity at exit from the nozzle is not theoretically greater than that of sound at the jet temperature prevailing. If the pressure ratio is greater than this however, full expansion cannot take place and some losses in thrust occur. The pressure ratio across a jet pipe on modern jet engines is of the order of on the test bed, so already under these conditions some losses occur. The amount is insignificant however, but in flight at supersonic speeds the pressure ratio across the jet pipe may become very large, and in this case important losses result.

The subject of this paper is a wide one. Guided weapon development problems in one form or another have been my daily concern for more than ten years now and I must be highly selective in the brief time at my disposal on this occasion.

The object of guided missile development is to produce efficient weapons of war, that is, weapons of destruction able to neutralise an enemy threat or destroy the enemy if he dare attack. I make this statement every time I talk on guided weapons, and I make no apology for making it on this occasion. We must not at any time forget that we are concerned in the development of weapons to defend this country, that time is of the essence of the contract, that the product must stand up to storage, to usage by the Services, and must be ready for action after little warning, and so on. As in any other branch of engineering, we have to make the best use of the men, ideas, techniques and materials at our disposal in order to reach the desired objective.

A Method is described for providing warning of the onset of undesirable effects produced by flow separation on an aircraft wing. It is based on static pressure measurements near the trailing edge and appears to have advantages over alternative methods.

Recent work has suggested that certain effects of flow separation such as buffeting, aileron buzz and undesirable changes in loading, occur when a “ bubble ” of separated flow originating at the leading edge of a wing, or at a shock wave on its surface, first becomes sufficiently large to affect the flow at the trailing edge.

Published Works discuss the calculation of the natural frequencies of uniform beam systems, but not simple calculations on beams of arbitrary cross section. This note describes a simple method evolved for estimating the lowest natural frequency of an axial compressor blade, and compares its results with measurements and with other calculations. The logical extension of the method to calculating the frequency of any mode of any cantilever of arbitrary cross section is made in the Appendix.