Monopropellant catalytic thrusters have been used for decades in space systems due to their simplicity and reliability. However, the degradation or loss of the catalyst is a major lifetime limiting effect, both for hydrazine fueled systems as well as for newer hydrazine-replacement fueled systems. Currently there is no in-situ diagnostic technique to measure the health status of the catalyst in such devices. Herein, we report a gas-phase diagnostic technique for measuring iridium, a common catalyst material for monopropellant thrusters. Laser induced breakdown spectroscopy was employed to quantify iridium in the gas phase by thermally vaporizing various organometallic iridium compounds to known concentrations within a test cell and observing the resulting iridium optical emission lines that had no interfering lines in the region from other possible emitting species (such as nitrogen, oxygen, and carbon). A limit of detection for the iridium was determined to be 6.21 μmol/L (197 ppm by volume), and this, to our knowledge, is the first report on the quantitative analysis of gas-phase iridium by laser induced breakdown spectroscopy.

由于其简单性和可靠性，单组元催化推进器已在空间系统中使用了数十年。然而，催化剂的降解或损失是主要的寿命限制效应，对于肼燃料系统以及更新的肼替代燃料系统都是如此。目前没有现场用于测量此类装置中催化剂健康状态的诊断技术。在此，我们报告了一种用于测量铱的气相诊断技术，铱是一种用于单组元推进器的常用催化剂材料。通过将各种有机金属铱化合物热蒸发至测试池内的已知浓度，并观察所得的铱光发射谱线，在该区域内没有来自其他可能发射物种（例如如氮、氧和碳）。铱的检测限确定为 6.21 μmol/L（体积为 197 ppm），据我们所知，这是通过激光诱导击穿光谱对气相铱进行定量分析的第一份报告。