Chlorine and oxides of nitrogen (NO X ) released into the atmosphere contribute to acid rain (ground level or low-altitude sources) and ozone depletion from the stratosphere (high-altitude sources). Rocket engines have the potential for forming or activating these pollutants in the rocket plume. For instance, H2/O 2 rockets can produce thermal NO X in their plumes. Emphasis, in the past, has been placed on determining the impact of chlorine release on the stratosphere. To date, very little, if any, information is available to understand what contribution NO X emissions from ground-based engine testing and actual rocket launches have on the atmosphere.