R. Hermann

The atmosphere is the environment, in which re-entry occurs, hence it must be known in its undisturbed condition. A simplified density distribution is assumed. The general equations of motion, valid for a body during re-entry, are discussed. They are specified and simplified for ballistic re-entry (no lift), and the resulting trajectories studied. Then the equations of motion are specified for lifting vehicle re-entry, solved and the resulting flight corridor discussed. For the hypersonic flow around the body, the thermodynamic state of the gas at the stagnation point is of great importance. Stagnation enthalpy as function of flight velocity is derived, and stagnation pressure and temperature are presented as functions of both flight velocity and altitude. A large amount of stagnation enthalpy is absorbed in dissociation. A simplified model of the air, with only oxygen and nitrogen in dissociation is used to calculate the degree of oxygen and nitrogen dissociation as function of temperature and pressure in general. Then it is discussed as function of velocity and altitude during reentry. Basic bodies for the study of flow in hypersonic aerodynamics are flat plate, hemisphere, and blunt cone. Interaction between boundary layer and shock wave, producing an induced pressure on the flat plate is of significance at high Mach numbers and low Reynolds numbers. Theory and wind tunnel experiments are compared. In contrast, the pressure distribution and velocity gradient near the stagnation point of a sphere are little affected bv viscosity and are well approximated by Newtonian theory. Finally, the dissociation of oxygen in flow around a sphere is calculated for a particular free flight condition. The oxygen dissociation distribution and the resulting temperature distribution on the surface of a sphere, assuming thermodynamic equilibrium, are discussed as calculated for typical hypersonic high temperature wind tunnel conditions. The phenomena discussed are only a small number of typical cases out of a multitude of problems.

WGL-Tagung 1961, Freiburg im Breisgau

Conference Paper

englisch

A4, 14 Seiten

Jahrbuch der Wissenschaftlichen Gesellschaft für Luftfahrt, 1961, Jahrbuch der Wissenschaftlichen Gesellschaft für Luftfahrt; S.131-144; 1962; Braunschweig : Vieweg

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Bestellbar

1962