Experimental and Numerical Diagnostics of Flow Properties in the HEK-X Expansion Tube

Abstract This study proposes a scheme for understanding the flow conditions in a super-orbital expansion tube. Visualization experiments and computational fluid dynamics (CFD) analysis were combined to analyze the flow dynamics of the JAXA HEK-X superorbital expansion tube. Experiments were performed at shock wave velocities of 6–8 km/s using a wedge and hemisphere probe setup, with oblique and bow shock waves visualized using a dual camera system. Atomic O-777 nm emission was also measured at the stagnation point of the hemispherical probe using the band-pass filter to compare the CFD with radiation analysis results. The CFD results, validated with visualization and 777 nm radiation measurement results, mean that the temperature, density, and velocity of the test flow can be identified, and the degree of oxygen atom dissociation in the test flow can be accurately predicted, including the degree of accuracy.