Airborne in situ measurements of carbon dioxide: Instrument development and applications to rocket plume chemistry and dynamics

A light-weight, fast-response instrument used to make carbon dioxide (CO₂) measurements from airborne platforms is described in detail. The theory behind the measurement technique is discussed, and the components used in the instrument are described with a focus on weight and volume considerations. The instrument performance is then evaluated and characterized in terms of the various error sources that contribute to the overall precision and accuracy, including the linearity of the instrument response and the effects of pressure, temperature, and water vapor on the measurement.; In situ measurements obtained by this instrument were used to investigate processes occurring in the exhaust plumes of small rockets. Correlations of CO₂ with particle concentrations reveal a unique signature dependent on the combination of solid and liquid fuels used in each rocket. A deviation in the correlation of CO₂ and H₂O indicates longer lifetimes of volatile particles in the plume than previously believed, possibly due to the presence of HNO₃ on the particle surface. The longer particle lifetimes will increase the importance of heterogeneous reactions to ozone loss within the plume.; Large particle measurements in the plume were collected on several consecutive passes through the exhaust plumes of five rockets and the maximum particle density of each encounter was determined. The observed decay in the plume maximum particle density with time is used to validate published models and derive a dispersion mechanism consistent with observations. A simple chemical scheme is developed to determine the sensitivity of catalytic ozone loss to the choice of diffusion coefficient. Ozone loss is found to be a function of plume lifetime, increasing non-linearly as the diffusion rate of the plume decreases.