Status of the development and implementation of optical spectroscopic techniques on the DLR high enthalpy shock tunnel HEG

Abstract

An overview of the development and implementation of spectroscopic diagnostic techniques for high enthalpy facilities (with examples from HEG) is given. Spectrally and spatially resolved results with NO LIF at 193 nm on HEG are given for the free stream and for various models (European HERMES, Japanese HOPE, aerobraking configuration, cylinder, and sphere). The problems of luminosity, fluorescence quenching, nonlinear effects, and corrections needed for single-shot measurements are discussed with reference to the HEG results and to extensive tests carried out on a specially designed heated cell capable of providing controlled NO conditions in a flow system. Other spectroscopic techniques such as emission spectroscopy, tunable diode laser absorption, and flash lamp absorption are referred to briefly.

NO PLIF Visualizations of the Orion Capsule in LENS-I

“…NO PLIF has previously been used in high-enthalpy shock tunnel facilities at numerous laboratories, though RCS jet flows have not been investigated in these facilities to our knowledge. [21][22][23][24] The laser system used in the current work operates at 10 Hz allowing only one image per tunnel run. However, the current system produces pulses with 10x higher laser energy than the high speed system previously used at CUBRC, allowing larger (6‖x6‖) field of view (FOV) images to be captured with a good signal-to-noise ratio.…”