Rarefied Gas Dynamics, Parts I and II

The field of rarefied gas dynamics encompasses a diverse variety of research that is unified through the fact that all such research relates to molecular-kinetic processes which occur in gases. Activities within this field include studies of (a) molecule-surface interactions, (b) molecule-molecule interactions (including relaxation processes, phase change kinetics, etc.), (c) kinetic-theory modeling, (d) Monte-Carlo simulations of molecular flows, (e) the molecular kinetics of species, isotope, and particle separating gas flows, (f) energy-relaxation, phase-change, and ionization processes in gases, (g) molecular beam techniques, and (h) low-density aerodynamics, to name the major ones.

This field, having always been strongly international in its makeup, had its beginnings in the early development of the kinetic theory of gases, the production of high vacuums, the generation of molecular beams, and studies of gas-surface interactions. A principal factor eventually solidifying the field was the need, beginning approximately twenty years ago, to develop a basis for predicting the aerodynamics of space vehicles passing through the upper reaches of planetary atmospheres. That factor has continued to be important, although to a decreasing extent; its importance may well increase again, now that the USA Space Shuttle vehicle is approaching operating status.

A second significant force behind work in this field is the strong commitment on the part of several nations to develop better means for enriching uranium for use as a fuel in power reactors. A third factor, and one which surely will be of long term importance, is that fundamental developments within this field have resulted in several significant spinoffs. A major example in this respect is the development of the nozzle-type molecular beam, where such beams represent a powerful means for probing the fundamentals of physical and chemical interactions between molecules.

Within these volumes is offered an important sampling of rarefied gas dynamics research currently under way. The papers included have been selected on the basis of peer and editor review, and considerable effort has been expended to assure clarity and correctness.