Carbon monoxide radiation in an equilibrium plasma torch facility

International audienceWe present spectrally resolved measurements of CO 4th positive radiation down to 170 nm under equilibrium conditions. The emission is calibrated in absolute intensity by using an argon discharge calibrated to NIST standards. The measurements were undertaken to validate radiation models available in the literature. NASA EAST measurements had noted a discrepancy between radiation model predictions and their shock tube measurements. Our goal was to perform these measurements under equilibrium conditions and compare against model predictions. To that end, we selected several datasets for the electronic transition moment available in the literature. These were used to calculate state-specific Einstein coefficients for use with the radiation code SPECAIR. Three datasets were tested and two were found to give good agreement with the experimental results

Experimental analysis of the interaction of carbon and silicon ablation products with expanding hypersonic flows

Thermal protection is required for vehicles entering planetary atmospheres to protect against the severe heating loads experienced. Characterization of candidate materials is often done utilizing plasma or arc-jet facilities, which provide steady-state testing of the thermal environments experienced during hypersonic flight, but do not correctly simulate hypersonic flowfields. Conversely, impulse facilities can reproduce flight velocities and enthalpies but have extremely short test times, prohibiting testing of thermal response. To better understand how these materials interact with hypersonic flows, experiments were conducted at the X2 expansion tunnel at the University of Queensland. Preheated strips of carbon-carbon and silicon carbide-coated carbon-carbon were mounted in a two-dimensional compression wedge and tested in Earth entry flow, marking the first time silicon carbide has been investigated in this facility. Calibrated spectral measurements were obtained in the near-stagnation and expansion regions for surface temperatures from 1900 K to 2600 K. Cyanogen emissions dominated while atomic silicon and dicarbon were also observed. Emissions for both materials displayed a similar increase near the wall, while emissions for silicon carbide-coated samples displayed a distinct rise downstream of the shock, which suggests a higher concentration of ablative species resulting from a higher ablation rate