Two Photon Laser Induced Florescence of Krypton Fueled Resistojet Thruster Interaction With Ambient Neutrals

Environmental effects during thruster testing result in discrepancies between test results and actual performance in space. Specifically, the buildup of ambient neutral particles in the test chamber affects measurements of thruster performance. Therefore, measurement of the distribution of ambient neutrals in the test chambers is required to fully assess thruster performance. However, non-intrusive, spatially localized neutral diagnostics are difficult and scarce. Here, we use two-photon laser-induced fluorescence (TALIF) to excite neutral ground-state krypton non-invasively. Spatially resolved neutral number density, temperature, and velocity in the exhaust plume of a krypton-fueled resistojet thruster and chamber are measured, and the effect of ambient pressure on thruster performance is investigated. A Qauntel Qscan laser generates the desired wavelength of light over 6 ns pulses at a repetition of 10 Hz. Fluorescence is captured using an Andor iStar iCCD fast-gated camera. We present preliminary TALIF measurements of the interaction between a krypton-fueled resistojet exhaust and neutrals. Neutral krypton density and exhaust velocities as functions of position and time and how these change with background pressure are shown.