Abstract:
The development of the gas turbine which provided large thrusts from comparatively small front areas, and at the same time retained its thrust efficiency at high speeds, introduced the possibility of building a supersonic aeroplane. Existing aeroplanes displayed marked longitudinal trim changes at high subsonic speeds, and to pursue these problems into the transonic field, problems which must be solved before the supersonic aeroplane can fly, the Royal Aircraft Establishment in 1945 embarked upon a programme of research using air-launched rocket-propelled models. From the first conception of a simple model the research vehicle grew to a complex model aeroplane complete with auto-pilot, liquid-fuel rocket motor and radio telemetering equipment, aft-launched at 36,000 ft over a ground radar station. The first model, complete with prototype equipment was lost in turbulent air. On the second model launched the rocket motor failed to ignite. There was a period of 12 months further development of the rocket motor and ignition system, followed by the launch in October, 1948 of the third complete model. This model flew satisfactorily and the flight is analysed in this report. The model reached a maximum speed of M = 1.38. The static-pressure variations on the nose pitot-static-tube agree with available information, when allowance is made for the altitude change during flight. There is substantial agreement between measured thrust, longitudinal acceleration and drag, and the latter is in reasonable agreement with that predicted from wind-tunnel tests. The recorded tailplane angle agrees with that calculated from the instructions given to the auto-pilot, and with the predictions from wind-tunnel tests. The main body of the report contains a historical review of the project, brief descr{ptions of the test vehicle and experimental techniques, and the detailed analysis of the final successful flight trial. In a concluding section the project is discussed critically ; it is considered that the work done has shown the experimental method to be an exceedingly difficult one, and that the results it gives do not justify the effort it demands. No further developments are proposed, as alternative transonic research techniques have in the meantime been developed. In a series of appendices are given detailed descriptions of the test vehicle and its ancillary equipment, of the development work leading up to the final trial and of the experimental equipment and techniques. These detailed appendices will be of interest only to the specialist.
