This paper introduces the series of Second Century papers which will appear in the Journal during 1968. The reasons which led the Publications Committee to arrange this series is explained and the authors and the titles of their papers are listed. The papers consider possible changes in aeronautical science, engineering and operations from now until a century ahead on many topics including Propulsion, Aerodynamics, Computing, Navigation, Control, Space Flight, Hovercraft, Aeronautical Education and Law for Aerospace.

This paper sets the scene for the others by reviewing how the aeronautical future looked to Cayley in the early nineteenth century, to those attending the 1893 International Conference, to Lanchester, Thurston and Roxbee Cox. The changing nature of forecasting is illustrated by the Lockheed SST market study of 1965 which is given as an example of present-day predictive techniques using computers.

The interest in Canada in the design and manufacture of utility aircraft with a short take-off and landing (STOL) performance may be traced back to the difficulties of surface transport in the early development of the country and the widespread use of bush aircraft.

The leading characteristics of the STOL aircraft are examined with particular reference to design features essential to a short take-off and landing. The choice of powerplants and lifting systems is discussed with emphasis on the requirements for powered lift in the larger sizes of aircraft. The augmentor-wing is described as an example of an integrated propulsion lifting system with promise of a high performance.

The phases of the take-off, transition, climb and landing manoeuvre are reviewed to illustrate the relative importance of various parameters in design and operation. The importance is stressed of good stability characteristics and effective controls for manoeuvring in a confined air space and a consistent landing performance.

The requirements of a para-military mobile force tor a rapid response, deployment overseas and transportation in an area are examined. Some estimates are given of the probability of finding suitable airstrips in a particular region and the cost of constructing new airfields in a dynamic situation. The operating environment in potentially troubled areas of the world is examined briefly to provide guidance in design. The costs of a military supply system are discussed using various modes of transport which include trucks, helicopters, STOL and conventional transport aircraft with results which suggest that the system employing STOL aircraft in the tactical theatre has advantages in cost and effectiveness.

Attention is drawn to the growing requirement for shorthaul, commuter and air taxi aircraft with STOL characteristics. Reference is made to the increases in air travel and the widespread use of large transport aircraft which have encouraged the movement of airports from urban centres at a time when city growth and congestion render surface transport increasingly difficult. The relative costs of commercial systems using the helicopter and STOL aircraft are examined. It is shown that the cost of STOL ports is not an excessive portion of total system costs when all factors are taken into account. Some forecasts are made as to future development trends in transport systems using STOL aircraft.

Among the most interesting aircraft development programmes currently in progress is the Flight Test Programme of the F-111, an aeroplane that is being built for both the USAF (the F-111 A) and the US Navy (F-111B). Although the operational envelope of this aeroplane is only a modest step forward into new regions of flight, the dictates of its multi-mission role over the largest Mach-altitude envelope ever achieved by a tactical aeroplane is a significant advancement in the “state of the art”.

To accomplish these mission objectives, which include short take-off and landing distances, sustained supersonic operation at low altitudes, and a Mach 2.5 capability at high altitudes, the F-111 is configured and equipped with a number of unique design features and advanced systems. This discussion is intended to present a brief description of the more interesting features and a progress summary of the F-111 flight test programme.

The terms “cost-effectiveness” and to a lesser degree “cost-benefit” analysis have become familiar words in the technical and national press, the former usually in relation to defence projects—the latter in relation to social projects, such as transport, power generation and building. Indeed, at the time of the last General Election the political correspondent of a national newspaper wrote, “Mr. Heath and Mr. Callaghan, Chancellor of the Exchequer, vied with each other in stressing the importance of cost-effectiveness, which used to be known as getting value for money”.

The apparently simple concept of “value for money” raises three important issues:

(i) how is “value” of defence and social projects quantified?

(ii) what is the “money” involved, i.e. what are all the relevant costs? and

(iii) what are the information and decision processes that are used in attempting to obtain “value for money“?

Some approaches are indicated for determining, and if necessary raising, the potential utilisation of training equipment, the objectives being:

—to reduce costs;

—to avoid or defer new capital investments;

—to secure more flexible rostering through increased

availability.

The problem is approached from a systems standpoint.

The investigation has been mainly confined to Link equipment, but the solution can be utilised for all auxiliary equipment, e.g. radar, where failures occur during or outside the use phase. Visual aids and pure flight aspects such as motion are not taken into consideration.

The flow in a two-dimensional curved wall jet with different initial gaps between the nozzle exit and the leading edge of the wall was probed at various stations along the jet. The jet slot thickness, the jet exit velocity and the radius of the wall were kept constant. It was found that the region close to the leading edge of the wall behaved like a settling zone. In this zone the type of flow changed from a free jet to a curved wall jet. The length required for settling depended on gap size and was less than that of the plane wall jet. Gap effects on surface pressure distribution and angular position of separation were examined. The hysteresis phenomenon associated with gaps was investigated.

In the theory of small vibrations the motion of a system can be characterised in terms of either geometrically compatible displacements or dynamically admis-sable impulses (1,2,3). However, the number of generalised displacements required to describe the motion of a system need not be the same as the number of generalised impulses required for the same purpose. The reason for this difference is that in either or both formulations certain zero frequency modes may be present. If the co-ordinates which describe such modes are eliminated then the number of displacement and impulse co-ordinates required to describe the oscillatory modes will be equal and one can then transform one formulation to the other by means of Legendre's transformation(4).

When side force is produced by the injection of a secondary gas into the supersonic region of an axi-symmetric nozzle, the body shape of the obstruction caused by the secondary flow induces a cone-shaped separation region upstream of the port. From the apex of the cone a conical shock front is developed. Part of the total side force produced is due to the excess static pressure acting on the nozzle wall in

(a) the separated region, and in

(b) the wall area lying between the separated region and the trace of the shock on the nozzle wall.

In such a field the static pressure is not uniform downstream of the shock but varies from point to point on the nozzle wall areas in question. This aspect of axi-symmetric flow makes attempts to correlate theoretical and experimental work difficult. It was considered that basic information about the important parameters, which influence side force, could best be obtained in experiments with two-dimensional nozzles. Here the circular secondary port is replaced by a rectangular port, the separation zone is wedge-shaped, the shock has a plane front, and in theory, the static pressure is uniform between the port and the point at which the boundary layer separates.

This paper discusses the various aspects of flow separation on wings and aerofoils at subcritical Mach numbers. It is shown that in general the onset of non-linearities in the aerodynamic characteristics, for plane constant-section wings, can be related to the initiation of regions of flow separation somewhere on the wing and often near the wing tip.

Empirical correlations are produced, tor plane wings of constant symmetrical section, enabling estimates to be made of the lift coefficient for onset of separation at either the leading or trailing edge of the wing.

A correlation of stall types on aerofoils, due to Gault, is extended in application to the estimation of initial stall and separation types for plane wings of constant symmetrical section. Suggestions for extending the application of this correlation to the estimation of section stall type for cambered, twisted and non-constant section wings are made.

The ESRO II Satellite is due to be the first satellite to be launched as part of the joint co-operative programme between NASA and the European Space Research Organisation and as such, represents the first endeavour by the latter organisation to bring together various experiments in a satellite. While it is true to say that other satellites have been produced in Europe, this is the first integrated payload involving experiments from different countries to be realised in Europe.

The paper describes briefly the satellite and details the scientific experiments. The remainder of the paper is concerned with the aspects of project management involving four different nations and the technical programme.

The various systems developed by, or under the responsibility of Engins MATRA, and which are related to the dynamics of the satellite, i.e.: the de-spin system, the precession damper, and the spin-up system will be described as well as the Attitude Control of the ESRO II spacecraft.

Before discussing these particular subjects, the general characteristics of the ESRO II satellite will be recalled:

The orbit is nearly polar (approximately 98° inclined to the equator) and has perigee at 350 km and apogee at 1200 km; the orbital plane precessions, in the retrograde sense, by about 1° per day; the orbit is thus synchronous with the sun's apparent motion. The launch time was chosen at 6 pm so that the orbital plane be, and remain, perpendicular to the sun's direction, at least in a first approximation. This is assuming a polar orbit and neglecting the angle between the plane of the Ecliptic and the plane of the Equator.