I am deeply appreciative of the great honour you have bestowed upon me in asking me to address you tonight. When Louis Bleriot made his memorable flight I was a boy of six and, I am sorry to say, not yet at school. In fact, I had to wait until I was nine to see my first aeroplane which, believe it or not, was a Bleriot monoplane fitted with a Gnome engine and flown by another pioneer aviator, B. C. Hucks.

The simplicity of the aircraft and the apparent ease of flight made a deep impression on my boyish imagination. So much so that the same imagination was quite affronted when it first saw the pusher biplanes with which we prepared to fight the First World War. Having had nothing to do with it, I can now claim it took a further 25 years for the advancing march of aviation finally to confirm my childish fancy!

Forty-two years ago—on 2nd August 1917—the first deck landing on a ship under way was made. A special platform had been constructed on the battle cruiser Furious, and it was on this prototype flight deck that Squadron Commander E. H. Dunning made the first successful aeroplane landing aboard ship. On touching down, his aircraft—a Sopwith Pup—was restrained manually by the (presumably) willing hands of a large number of officers and men. Two days later a second attempt ended in disaster. But from this beginning, like so many initial steps forward in aviation, a sad one, grew the Fleet Air Arm as we know it today.

The advent of the Skylark firings and the more recent trials of ballistic missiles such as the Black Knight firings, have demanded a continuous development of both ground and airborne instrumentation at Woomera Range; this in turn has raised the need for sighter rockets and instrumentation test vehicles with altitude capabilities in the 200,000-500,000 ft. range.

The need is currently being met by the rocket vehicles Long Tom and Aeolus. These rockets are of interest because they represent the first designed and built at W.R.E. that can be classed as high altitude rockets; also, they make possible the provision of relatively cheap and readily available vehicles for upper atmosphere research.

The main purpose of this note is to explain the apparent discrepancy which arises when the change in effective aspect ratio due to blowing, as predicted by the theoretically derived expression for the induced drag coefficient, is compared with what one intuitively expects from the general flow picture. If the jet sheet is considered as a chordwise extension of the wing (mechanical flap analogy), the general flow picture suggests that the effective aspect ratio of a wing without blowing is reduced by blowing. Maskell and Spence's relation for the induced drag coefficient, however, indicates that the effect of jet blowing is to increase the effective aspect ratio.

To predict the aerodynamical properties of a thin aerofoil, provided with a high velocity jet sheet in its trailing edge region, a simple procedure is proposed as follows. Two general separate cases concerned with the effect of a jet on an aerofoil are considered. In the first case, the jet is blown tangentially over the upper surface of the aerofoil, while in the second case, the jet is ejected at a deflection angle from the trailing edge. In this analysis a procedure which is similar to the classical Glauert treatment of thin aerofoils is applied.

Consider first the special case of a thin aerofoil placed at zero incidence in a two-dimensional inviscid flow of velocity V0, with a jet emerging with an exit velocity V1 at distance x1 from the leading edge and blown tangentially over the upper surface of the aerofoil (Fig. 1). It is assumed that an effectively attached flow may be obtained.

Expressions are found and curves given for the bending moment, direct force and shear force around a circular frame, in a cylinder partially filled with fluid. The maximum bending moment is found to occur when the cylinder is half full, and its position to be at the level of the fluid surface.

The analysis is an elementary one, that is, engineer's bending theory is assumed to hold in the cylinder. Hence the resultant pressure of fluid on the frame is balanced by a sinusoidal varying shear flow around the frame.

Although many investigators have set out to find a method of determining the buckling and failing stresses for unstiffened shear webs with flanged or unflanged lightening holes, it seems that so far no really satisfactory method has been found.

A number of empirical and semi-empirical expressions have appeared over the years which agree closely with the limited series of tests on which they are based, but which the writer has found not to agree with the general mass of experimental data which is now available on this subject.

Following a recent examination of the available data another attempt has been made to derive some expressions or formulae that would help the designer to estimate buckling and failing stresses of such panels, and as a first step a semi-empirical formula has been derived that appears to fit the test results reasonably well for the initial buckling case. It applies to panels with edges fixed.

The problem of launching rockets to explore conditions in interplanetary space formed the subject matter of a previous note by the author. In this note further aspects of such exploration by probes are considered.

The orbits considered in the previous note were elliptic, and touched the orbit of the Earth at the conclusion of each journey around the Sun. For journeys within the Earth's orbit it is of interest to consider the situation in which the probe first enters one of these elliptic orbits and then, at the point of closest approach to the Sun, is placed in a circular orbit around the Sun.