Graphite is a material with unique high-temperature properties. Its strength and modulus increase with temperature up to about 2000-2500°C., in which range it exhibits a higher strength than any known material. The development of new types of graphite (such as pyrolytic graphite, deposited from the vapour) and impregnated graphites, are both significant to future technology. The highly-oriented pyrolytic graphites in particular, with their marked thermal and mechanical anisotropy, and their superior mechanical properties (60 x 103 lb./in.2 strength at 2750°C, with 60 per cent ductility) offer distinct possibilities, particularly in composite structures. Graphite sublimes directly from the solid to vapour phase at 3700°C. at atmospheric pressure. As the sublimation energy is high, it is, at least in theory, a very efficient ablating material. It also has a high creep resistance. Surface reactions limit its value, particularly in oxidising environments, and coatings, or other methods of surface protection, are of high importance. The modulus of graphite is low, being about one-half of that for lead at room temperature, increasing with temperature to a maximum in the region of 2200°C. The properties vary in detail from one type of graphite to another, and with the direction in which measurements are made. Graphite has a low density (about 2·0) and is comparatively cheap, so that its low temperature limitations (zero ductility at room temperature) may be offset, at least in part, by a re-appraisal of the design factors. It can be joined and fabricated fairly readily, and appears to be a material of great value to advanced high-temperature projects in the future, where composite assemblies of various kinds will be essential.

A method of calculating turbulent boundary layers on infinite yawed wings is given, making use of a method of calculating turbulent boundary layers due to Spence and of an analogy between three-dimensional and axi-symmetric boundary layers. It is also shown that the displacement thickness is equal to that computed using chordwise components and that the streamwise momentum thickness is approximately equal to the chordwise momentum thickness. Shock-free flow and small boundary layer cross-flow are assumed.

The paper describes the development of a small-bore probe microphone, the frequency response of which is smoothed by arranging that the probe tube is terminated in its characteristic impedance.

The slender-body theory is applied to the determination of the unsteady aerodynamic forces on slender wing-body combinations when the body is stationary and the wing is deforming harmonically. The uniform body is circular in cross section, the wings are placed symmetrically and the wing deformation mode is necessarily symmetrical about a vertical plane through the body axis. The frequency parameter is restricted to that range for which the “cross-flow” potential equation is Laplace's equation. The case of an allmoving slender control surface on a body is treated in detail and numerical results are given for the forces and moments on body and control surface when the control plan form is triangular: the presence of a gap is neglected.

In assessing the merits of multiple versus single engines the possibility of a loss in reliability due to the use of more working parts must be considered. This paper gives a mathematical treatment of this problem and numerical examples illustrate the method.

The methods of the operational calculus are used to obtain a linear approximation to the shape of the mean camber surface of a quasi-cylinder in a supersonic flow in terms of its shell thickness and loading distributions. The analysis deals with a generalised quasi-cylinder; that is one which, although lying close to a mean cylinder, need not possess axial symmetry. The quasi-cylinder is also permitted to be within the small disturbance field of other separate components, e.g. a centre-body. Because the linearised theory is inadmissable for internal duct flows close to and beyond the first reflected characteristic cone, the present solution is likewise invalid close to and beyond the position where this characteristic meets the mean cylinder. The work given here enables the camber shapes of “ring-wings”, which have been used theoretically to reduce or even nullify the wave-drag of a central slender-body, to be found. An example illustrates the general method.