The emission and chemistry of reactive nitrogen species in the plume of an Athena II solid‐fuel rocket motor

In situ measurements of NO, NO y , HNO 3 , ClO, CO 2 , H 2 O and particles were made in the plume of an Athena II solid‐fuel rocket motor (SRM) with instruments onboard the NASA WB‐57F high‐altitude aircraft. By normalization to CO 2 , the NO y emission index was calculated to be 2.7±0.6 g NO 2 (kg fuel) −1 . HNO 3 is a significant and evolving component plume NO y . The principal source of HNO 3 is thought to be the heterogeneous reaction between ClONO 2 and HCl on emitted alumina particles. These measurements provide the first experimental evidence for the production of HNO 3 and the activation of chlorine on SRM‐emitted alumina particles in the lower stratosphere.