DENSITY-MEASUREMENTS IN BALLISTIC REENTRY

The interdisciplinary application of experimental and numerical method s is the crucial strategy for the profound validation of numerical sim ulations of complex aerothermodynamic hows. Especially for the design of reusable heat shield materials the reliable re-entry heat flux pred iction from numerical simulation methods became important. In this con text free flight measurements gained an outstanding position for the v alidation of theoretical models describing the high-temperature phenom ena of thermo-chemically reacting hypersonic flows in interaction with the flight vehicle's surface. This article is devoted to present a gl obal concept for the application of a compact free flight sensor expos ed to the extreme thermal environmental condition of a controlled, bal listic re-entry. The validation strategy will be demonstrated for tota l density measurements proposed for the stagnation point of a re-entry capsule, since the density at the capsule surface reflects sensitivel y the interaction process of the hot gas and the wall. The partial val idation of the aerothermodynamic simulation tool was elaborated for la boratory experiments in the gun-tunnel and shock tube. The measuring p rinciple of the optical density sensor, the Phase-compensated Michelso n Interferometer (PMI), will be discussed in detail. Since the feasibi lity of these measurements are highly dependent on the thermal integra tion of the sensor, an effective thermal protection concept, based on modern ceramic matrix composite materials and high performance insulat ions, has been Verified in numerical analyses.