REVIEWED BY STEWART WAY 1 THE author, who through his own pioneering contributions is eminently qualified, has brought out a most useful and welcome book on MHD power generation. The book is clearly written and will be useful to graduate students, practicing engineers, and MHD specialists. Greatest value will accrue by reading the book from .start to finish, but it will also be very valuable as a reference work. Chapter 1 introduces one to the elementary ideas of the MHD generator in simplest terms, with appropriate reference to the role and significance of the magnetic Reynolds number. Equilibrium ionization and conductivity are discussed in the second chapter, with consideration of the generalized ohm's law, Hall effects, and ion slip. Chapters 3 and 4 go into a thorough discussion of flow phenomena in the MHD generator, engineering consequences of the Hall effects, electrode segmentation, load circuits, finite electrode effects, and influence of nonuniformities in conductivity. An entire chapter is devoted to the most important subject of nonequilibrium ionization, the conditions for its realization, and the problems and difficulties it may lead to. Another chapter deals entirely with magnets, their optimization and coil design considerations, with discussion also of superconducting magnets. The last two chapters take up design and engineering considerations including brief but good treatments of sidewalls and electrodes. Power plant arrangements using MHD generators are also treated, including central station systems, rocket-driven generators for short bursts, and nuclear-heated plants for commercial and space power applications. Additional useful reference information on conductivity properties, physical constants, etc., is given in appendices. Though this book tends to be oriented more toward generators using seeded noble gases than combustion products, it is a quite general and lucid treatment of generator fundamentals and problems, and will therefore be highly useful to investigators of all types of MHD power systems.

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A programme of shock tube experiments has been conducted to study the refraction of plane shock waves at interfaces between two gases. Shocks of strength ζ = 0·85 (weak) and ζ = 0·30 (fairly strong) were allowed to impinge, at various angles of incidence, on interfaces between air/CO2and air/CH4, and the resulting configurations were photographed through a Mach-Zehnder interferometer. From the interferograms, measurements were made of the strengths of the reflected waves, and of the angles of refraction, and the values were compared with the theoretical calculations of Polachek & Seeger (1951). Within the range of parameters for which the refraction model assumed by the theory is applicable–the so-called ‘regular refraction’ region–the observations were in excellent agreement with the theoretical predictions.When the study was extended to ranges of the parameters for which the theory is clearly inadequate, a succession of rather complex ‘irregular refraction’ patterns was observed. Although these configurations were highly interesting qualitatively, each of them involved curved shocks, non-uniform regions of flow, and other less simple processes which discouraged any formal theoretical analysis. On a less rigorous basis, however, it could be shown that these patterns were internally consistent, and that each represented a distortion of a regular refraction process which was reasonable under the prevailing aerodynamic conditions.Certain observations in these refraction experiments appear to be of some significance outside the specific problem. (i) The sensitivity of strong shock refractions to the values of the specific heat ratio λ for the two gases suggests a possible technique for the measurement of λ and its temperature dependence. (ii) Two of the irregular refraction patterns display a transition process which would be equally appropriate to the onset of the Mach configuration in the shock reflection problem. (iii) Some irregular refractions can be considered as special cases in the problem of the interaction of a shock and a boundary layer.

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