Anthony K. Hyder

A Century of Aerospace Electrical Power Technology

HE evolution of the aerospace technology is marked by a series of technology achievements across the spectrum of the engineering disciplines, and one of the more interesting stories in the history of the aerospace industry relates to the development of electrical power systems for aircraft and spacecraft. The research and development effort leading to today’ s systems has spanned 10 decades and has continued through world wars and economic depressions. It was dependent on a marriage of ideas from virtually all e elds of engineering: electrical, mechanical, materials, industrial, chemical, computer, and aerospace. It has achieved a remarkable state of technology even though it was never as prominent as the developments in propulsion systems, as elegant as breakthroughs in avionics, or as intensely studied as structures and aerodynamics. It has always been the “ other” system, one that everyone assumed would be there at the appropriate time. And it was. The evolution of aerospace electrical power systems from the early days of powered e ight through today is marked by a combination of serendipity, insight, innovation, and hard work. In this paper we will recall some of the early dife culties faced by aircraft designers, the processes through which they addressed the challenges, and how they went about creating the technology breakthroughs leading to today’ s aircraft and spacecraft electrical systems. At various points in the review, we pause to probe more deeply into the key technologies of that day to give the reader a better appreciation of the ingenuity of the early engineers who created this technology. Such a review could not hope to cover all of the topics of relevance or of interest, and so a subjective selection has been imposed, hopefully one that does not do too great an injustice to aerospace power history or to those who created it. The story is presented in two parts: e rst, the development of aircraft systems and, then, spacecraft systems. This is done, as the reader will see, because of the differences in the constraints, operational environments, and demands on the two systems. In one important aspect, however, they do share at least one common trait: not surprisingly, each benee ted from an opportunity to harvest existing technologies until the demand for power exceeded the ability

Repetitive Phenomena in Dielectrics

Insulating systems employing polyethylene terephthalate and polypropylene were tested for dielectric strength and time-to -break under pulsed and ramped voltages in the pulsewidth range of 0.2 to 5 ¿s with risetimes of 20 ns to 5 ps at a repetition rate of 500 pps. The dependence of dielectric strength and time-to-break on pulse shape was examined, with the result that none of the systems demonstrated a dependence within the specified range. It is demonstrated that this result, along with the observations made during the experiments, suggest that streamer breakdown occurred in some of the systems while thermal breakdown occurred in the others.

The Behavior of Systems in the Space Environment

Abstract : This ASI emphasized the basic physics of the space environment and the engineering aspects of the environments interactions with spacecraft. The objective of the ASI was to bring together the latest data characterizing the space environment and the analyses of the interactions of spacecraft systems operating in that environment. The first is the emerging perspective of the space environment that has resulted from the vast quantity of new data on space physics that has been obtained recently. These data have provided a revised understanding of the near-earth space environment as well as the interplanetary regions. The second is related to the worldwide renewal of interest in extended space operations for military, commercial, and scientific missions. The ability of the spacecraft engineers to properly design and build spacecraft to accommodate the interactions of their systems with the space environment will pace the future uses of space. The theme of the Institute was the enhacement of scientific communication and exchange among academic, industrial, and government laboratory groups having a common interest in the behavior of systems in the environment of space. In line with the focus of the Institute, the program was organized into three main sessions: an introduction to and historical perspective of the space environment; the physics of the interactions of materials and components with the space environment; and, lastly, the engineering of systems for operations in the environment.

A high-precision neutron time-of-flight facility

Abstract A high-precision neutron time-of-flight facility has been constructed. The facility couples the advantages of an intense monoenergetic neutron source produced by a pulsed and bunched ion beam with those of a high-energy resolution, high mechanical precision, heavily shielded neutron time-of-flight spectrometer-goniometer. The system provides the necessary incident neutron energy stability and resolution, scattered neutron energy and angular resolution, and unusual freedom from background radiations to achieve measurements of differential scattering cross sections with magnitudes as small as 1 mb/sr to better than 5% absolute accuracy. The measures required to achieve this sensitivity and accuracy include optimization of the mechanical, shielding, and electronic systems, as well as the procedures for obtaining and analyzing the data.

Introduction High-Brightness Accelerators

This volume contains the proceedings of the 1986 “High Brightness Accelerators” NATO Advanced Study Institute. The object of the Institute was to address issues concerned with the generation and applications of low emittance, high current beams. The scope of the workshop was very broad. It addressed the fundamentals of accelerator design both from the point of view of the needs of the high energy physicist and also from the perspective of more general applications. The range of accelerator designs and concepts reviewed varied from the TeV, low current devices to the multi-megampere, MeV accelerators used for the study of inertial confinement fusion. In almost all applications the beam brightness, the current per unit area per unit solid angle, plays an important role.

Overview of Applications and Needs

There is a rapidly growing recognition of the importance of early-time processes in physical phenomena, since long-time behavior of many processes of practical interest are governed by fundamental phenomena which occur in the sub-microsecond time scale. Typical of the areas in which this early time history appear important are the breakdown and conduction processes in vacuum, gases, liquids, and solids; electromagnetic radiation production and propagation; inertial and magnetic confinement fusion devices; throughout pulsed power technology; and in the performance of systems such as electric-discharge lasers and particle-beam accelerators.