Visualization of a Capsule Entry Vehicle Reaction-Control System Thruster

Planar laser-induced fluorescence was used to visualize the reaction-control system jet flow emanating from the aft body of an Apollo-geometry capsule test article in NASA Langley Research Center's 31 in. Mach 10 Tunnel. The reaction-control system jet was oriented normal to the aft surface of the model and had a nominal Mach number of 2.94. The composition of the jet gas by mass was 95% nitrogen ( N2N2) and 5% nitric oxide (NO). The reaction-control system jet flow rate varied between 0 and 0.5 standard liters per minute, and the angle of attack and tunnel stagnation pressure were also varied. Planar laser-induced fluorescence was used to excite the NO molecules for flow visualization. These flow visualization images were processed to determine the trajectory and to quantify the flapping of the reaction-control system jet. The jet flapping, measured by the standard deviation of the jet centerline position, was as large as 0.9 mm, whereas the jet was 1.5-4 mm in diameter (full width at half-maximum). Schlieren flow visualization images were obtained for comparison with the planar laser-induced fluorescence. Surface pressures were also measured and presented. Virtual diagnostics interface technology, developed at NASA Langley Research Center, was used to superimpose and visualize the data sets. The measurements demonstrate some of the capabilities of the planar laser-induced fluorescence method and provide a test case for computational fluid dynamics validation. [PUBLISHER ABSTRACT]