The planar librational motion of a dumb-bell satellite has been studied by several authors. In most cases the analysis has been restricted to circular or nearly circular orbits. In an elliptic orbit, the variation of the angular velocity of the satellite around the central body together with the change in the local gravity gradient provides the satellite with a mechanism for exchanging energy between the librational and orbital modes. In general, this imposes a limit on the orbit eccentricity for which stable (non-tumbling) librational motion is possible. This note investigates the bounds that must be placed on a disturbance applied to a slender gravity gradient stabilised satellite so that it will librate and not tumble. The determination of the stability boundary as presented here was arrived at by the numerical solution of the exact equation of motion, obtained using an IBM 7040 computer.

In the Years immediately following the Second World War, it became apparent that there was a lack of suitable wind tunnels in Great Britain to provide aerodynamic data at high speeds to meet all the needs of aircraft designers. The main firms had always had their own tunnels, but these were restricted in number and size because of the expense involved. Long-term research was carried out at the Royal Aircraft Establishment at Farnborough, but there was a need for a large-scale wind tunnel for more immediate development tests and especially for testing at transonic speeds.

The static hole error problem has been extensively investigated in the past. It has been shown that, for deep holes (for which the length l of the hole is greater than 1.5 times the diameter d of the hole), the difference between the indicated static pressure p0’ and the true static pressure p0 is a function of the boundary shear stress τ0, hole diameter d, the coefficient of dynamic viscosity μ and the mass density ρ of the fluid.

The investigation of axisymmetric states of stress by the matrix displacement method may, in principle, be carried out as an ordinary exercise of three-dimensional analysis, using TETRA 4, TETRA 10 or other suitable elements. However, this approach is clearly not the most efficient by not taking advantage ab initio of the inherent simplifications arising in an axisymmetric state; this leads to an unnecessary inflation of the number of unknowns and complexity of the mesh. A number of techniques to deal with this limiting condition of a three-dimensional state have been developed at the ISD. The theory for one specific element, TRIAX 6 which evolves most naturally from the tapered TRIM 6 element analysed in the preceding note 8 is presented.

When I was first asked to take part in this Colloquium I declined on the grounds that there had been too many reliability conferences already, and I feared that another would only take the time of good engineers off their day to day tasks of improving the reliability of British products. Having heard some of the contributions, I think I should revise that opinion. We have heard some good material. I was prevailed upon to say a few words on the problems of military aircraft and this I will do. I shall omit almost entirely references to equipment because, as I see it, the problems on the equipment side are fairly similar whether the aircraft is a military or a civil one.

“And as in uffish thought he stood,
The Jabberwock, with eyes of flame,
Came whiffling through the tulgey wood,
And burbled as it came!“

Scarcely has the final history of the steam train been written, than I am asked to write the history of the aeroplane, from the research facilities’ point of view. It can only be this nostalgia for the past which has enabled me to secure the willing help of so many people in the brief three and a half weeks allowed for the compilation of this paper. Of necessity it must be incomplete, but is, I trust, accurate.

It is Always rather risky to ask old people to talk about what things were like when they were young. Having turned on the tap you may not see how to turn it off again. Fortunately there is a circumstance which keeps this trouble under control. Old people remember a lot of things when there is no call for them to do so but seldom when there is. That is the reason why I have written down most of what I can say for this lecture.

I cannot attempt to give a complete or an objective picture of aeronautical science when I started thinking about it. The best I can do is to describe a few of the things which happened to me in those days to try to convey some picture of our primitive ideas.

I Would like to emphasise at the outset that the title of this short paper is “Some thoughts on contracting for reliability”, and that what I say does not necessarily represent the official policy of my Company, if indeed a company can have any very firm official policy on a subject which is amenable to so many and varied methods of treatment. For this same reason I am not attempting to recommend any particular treatment of the problem, but rather to talk around some aspects of the matter, and to try to consider how some equitable incentive method of contracting to produce a defined standard of reliability might be applied.