An optical sensor for multi-species impurity monitoring in hydrogen fuel

Hydrogen is the fuel used by the National Aeronautics and Space Administration (NASA) for the Space Shuttle Main Engine (SSME), among others. The purity of the hydrogen fuel is very important for the performance of hydrogen-fueled engines. In the present work, we have designed, developed, and tested a state-of-the-art laser-induced breakdown spectroscopy (LIBS) based optical sensor to detect four important trace level impurities (i.e. nitrogen, argon, oxygen, and helium) in hydrogen as a rocket fuel. The sensor can simultaneously measure the concentrations of nitrogen, argon, oxygen, and helium in hydrogen fuel storage tanks and supply lines. LABVIEW® based software is also developed to control and operate the optical sensor. The software performs the data analysis and provides elemental concentrations (in ppm) of these impurities. The sensor has estimated limits of detection of 80 ppm for nitrogen, 97 ppm for argon, 10 ppm for oxygen, and 25 ppm for helium. This prototype sensor is easy to deploy in the field.