Radiation Measurements in Low Pressure High Enthalpy Flows from VUV to near IR region

Abstract

This investigation focuses on optical emission characterization carried out in low pressure arc-jet plasma flows applied for the investigation of radiation relevant to Mars exploration and re-entry into Earth. Experiments were performed in the plasma wind tunnel Phedra of the ICARE laboratory, equipped with an arc-jet producing low pressure and supersonic non-equilibrium plasma flows. Spectral emission from 110 nm to 900 nm, have been measured in 97% CO2-3% N2 and 80% N2-20% O2 plasmas operating with a wide range of plasma conditions in order to evaluate the contribution of VUV radiation with respect to the total one. This investigation contributes to get a set of experimental data, giving access to atmospheric entry plasma models used for predicting heat fluxes. Nomenclature HSpecific enthalpy, MJ/Kg V arc Arc voltage, V I arc Arc current, A C p Calorific capacity of water, J/mol K m c Water flow rate of the cathode cooling circuit , l/ṡ m a Water flow rate of the anode cooling circuit , l/ṡ m gas Gas mass flow rate, g/s ∆T c Water temperature increase of the cathode cooling circuit, K ∆T a Water temperature increase of the anode cooling circuit, K λ Wavelength, nm I em Spectral emission intensity, arbitrary unit R U V U Contribution of the VUV radiation, %

Survey of CO2 Radiation Experimental Data in Relation with Planetary Entry

“…PHEDRA ICARE facility (former SR5 at CNRS Orléans in France) is an arc-jet dedicated to the investigation of low-density flows. Several studies [45][46] have been conducted to investigate Mars plasma flows. Recently, a test campaign [46] has been conducted in this ground test for measuring Mars plasma radiation from 110 nm to 900 nm.…”

“…Several studies [45][46] have been conducted to investigate Mars plasma flows. Recently, a test campaign [46] has been conducted in this ground test for measuring Mars plasma radiation from 110 nm to 900 nm. Tests have been performed with a 97% CO 2 -3% N 2 mixture, at enthalpies in between 4.16 and 35 MJ/kg.…”

“…The emission spectra obtained are shown in Figure 50, in the left part for the VUV region, in the right part for the UV, VIS, and NIR. CO(4+) system, C 2 Swan and CN Violet systems can be identified, as well as molecular lines for CO + and CO, and atomic lines for O and C. However, the conditions, in term of flow enthalpy and pressure, for which these spectra have been obtained, are not documented in [46].…”

Survey of high-enthalpy shock facilities in the perspective of radiation and chemical kinetics investigations

“…However, no VUV measurements were performed for these studies. So far the only VUV data obtained in Europe have been measured in plasma torches for air [176][177][178].…”