Investigation of Hypersonic Retropropulsion Using Planar Laser-Induced Iodine Fluorescence

The upper limits of currently available technology to adequately slow high mass Mars entry systems during the entry, descent, and landing phase of missions are quickly being approached. Supersonic/hypersonic retropropulsion is one method being considered to bridge the technology gap to decelerate proposed high mass systems. However, the majority of work enhancing our understanding of the complex interaction of a supersonic or hypersonic freestream interacting with a retrorocket was conducted in the 1960s and 1970s, and limited in scope. Renewed interest has indicated the need to better understand fundamental aerodynamics of the flow, as well as extend the knowledge-base of possible retropropulsion configurations.

The following work utilizes a non-intrusive optical diagnostic technique, planar laser-induced fluorescence with iodine as the fluorescing species, to obtain qualitative planar visualizations for a range of thrust conditions, quantitative 2D velocity, and temperature for a central single-nozzle propulsive decelerator jet and novel peripheral quad-nozzle propulsive decelerator jet configuration in Mach 12 freestream flow. Quantitative planar propulsive decelerator jet mole fraction was also measured for the quad-nozzle configuration in Mach 12 freestream flow. This work provides a unique data set useful for computational verification and validation, and furthers the understanding of fundamental aerodynamics associated with the highly complex flowfield. Experimental measurements will be compared with computational fluid dynamics results from the University of Michigan.