A singular perturbation solution to the blunt-body stagnation-region flow of an inviscid, radiating gas has been obtained by means of the Poincař-Lighthill-Kuo, or perturbation-of-coordinates, method. A number of results for a gray gas have been presented in order to provide some physical insight into the effects of various parameters on the shock-layer enthalpy profiles and the radiant heat-transfer rates. A nongray absorption-coefficient model was developed which includes, in an approximate way, the important vacuum-ultraviolet contributions of bound-free and line transitions. This model was used to obtain solutions pertinent to the case of reentry into the earth's atmosphere. While the results are restricted to small values of the radiation cooling parameter, which characterizes the relative importance of radiation and convection as energy-transport mechanisms, they cover broad ranges of vehicle velocity, altitude, and nose radius, which are of practical interest. The characteristic enthalpy variation of the model absorption coefficient was found to be nearly independent of altitude and nose radius for fixed vehicle velocity except for velocities lower than 10.67 km/sec. Thus it was possible to correlate certain quantities by plotting these quantities as functions of the nondimensional adiabatic radiant heat-transfer rate for various altitudes and nose radii at fixed vehicle velocity. Among the quantities correlated was the cooling factor (the ratio of the stagnation-point radiant heat-transfer rate to the adiabatic radiant heat-transfer rate). The cooling-factor correlation is particularly useful because it eliminates the need to perform nonadiabatic calculations whenever radiant heat-transfer rates are desired. Also correlated was the factor by which the convective heat-transfer rate is reduced because of radiation losses in the shock layer. Finally, upper-bound estimates were made of the effects of absorption of precursor radiation by the free-stream air on the radiant and convective heat-transfer rates.

A second-order time-asymptotic solution to radiation-coupled stagnation-region flows is presented. The solution is applied to the hypervelocity flow over blunt vehicles of inviscid, nonconducting, equilibrium air, emitting and absorbing nongray radiation. Velocities, nose radii, and altitudes covered by the analysis are sufficient to bracket reentry trajectories of current interest. Radiative heat-transfer rates for the range of interest and typical profiles of pressure, density, enthalpy, temperature, and velocity are shown. The nature of time-asymptotic solution is discussed and it is shown o be a feasible means of achieving second-order accurate solutions to radiation-coupled shock-layer flows. Step-function models of the absorption coefficient are used in order to evaluate the divergence of the radiation flux vector. An analysis is carried out to determine what effect variations in the spectral complexity of the step model absorption coefficients used in the analysis will have on the thermodynamic and flow profiles of interest and on the nongray radiative heat-transfer rates. In this connection use is made of consistent model absorption coefficients having one to nine spectral steps with free-free, free-bound (including atomic line transitions), and molecular transitions taken into account. Relatively simple models of the absorption coefficient can be used with no significant loss of accuracy. An existing correlation for the cooling factor, the ratio of the radiation heat-transfer rate to the adiabatic radiation heat-transfer rate, is extended to larger velocities than heretofore considered.

Propulsion Re-Entry Physics deals with the physics of propulsion re-entry and covers topics ranging from inductive magnetoplasmadynamic (MPD) propulsion systems to launch systems and orbiting maneuvering systems. Problems of re-entry aerodynamics are considered, along with interaction problems in hypersonic fluid dynamics. Comprised of 31 chapters, this volume begins with a detailed account of the quasi-steady adiabatic vaporization and subsequent exothermic decomposition of a pure monopropellant spherical droplet in the absence of free and forced convection. The discussion then turns to results of calculations on MPD machines working in the intermittent and in the continuous mode; inductive plasma accelerators with electromagnetic standing waves; and spherical rocket motors for space and upper stage propulsion. Subsequent chapters focus on pulsed plasma satellite control systems; drag and stability of various Mars entry configurations; hypersonic laminar boundary layers around slender bodies; and effects of an entry probe gas envelope on experiments concerning planetary atmospheres. This book will appeal to students, practitioners, and research workers interested in propulsion re-entry and the accompanying physics.