Real-Time Measurements of Reactive Chlorine and Carbon Dioxide in Rocket Plumes

Abstract

PuHIc r^xsrting buncta) for this sajllecaon of information is eaimated to awerage 1 hour per response, incWng thf gathering and niraintaining the data needed, and oanplrting and revieimng the aaie<A)n of information ' Send commi ojilertion of intomation, including suggestions for reducing this burden, to Washington He*(guarters Services Dir Davis Highaay, Suite 1204, Arlington, VA 22202-4302, and The objecHves of Ws work were to measure reacBve chlorine (Cl. CIO, and CI202) and carbon dioxide (C02) and to examine the medianisms of ozcme loss in the plumes of various rodtets as part of an ongdng investigation of Uie impacts of rocket emissions on stratospheric ozone. This work has demonstrated that ozone losses in ix)cket plumes proceed at rates ttiat can be explained by 'standard' ozone toss diemistry involving Uie CIO radical -diemlstry that is analogous to tiat oaajrring in the winter polar vortices. This work has also helped to identify an emar in a key kinetic parameter. In combination vwth fest response measurements of Cl and CIO in ttie plume of STS-106, we have shmm ftat calculaflois based on ttie rBvised rate ronstant for CIO+CIO, along with caisideration of non-linear effects, can explain ozone loss rates vwttiin tie uncertainties of the measurements. Contract number F49620-99-1-0131 067 ObjectivesThe objectives of this work were to measure reactive chlorine (Cl, CIO, and CI2O2) and carbon dioxide (CO2) and to examine the mechanisms of ozone loss in the plumes of various rockets as part of an ongoing investigation of the impacts of rocket emissions on stratospheric ozone. Following a budget revision and change of priorities of the mission scientist during the RISO campaign, the project was rescoped to emphasize ultra-fast response measurements of Cl and €10 with ancillary measurements of CO2 in rocket plumes, with some ambient sampling to support the NASA/NOAA ACCENT campaigns of 1999 and 2000. Accomplishments/New FindingsAt the close of this 3-year project, we successfully met all of the objectives outlined in the original proposal, having demonstrated that ozone losses in rocket plumes proceed at rates that can be explained by 'standard' ozone loss chemistry involving theClO radicalchemistry that is analogous to that occurring in the winter polar vortices. This work has also helped to identify an error in a key kinetic parameter (the rate constant for the C10+ reaction CIO) as first reported by . In combination with fast response measurements of Cl and CIO in the plume of STS-106, we have shown that this rate parameter, along with consideration of non-lmear effects can explain ozone loss rates within the uncertainties of the measurements (unpublished results described in Year 4 Annual Progress Report).An unexpected resuh from this effort was the discovery of volatile particles likely composed of HNO3 and H2O in the fresh plumes of several small rockets (Atlas HAS and Athena II). These particles persisted long after the plume had diluted, indicating that our understanding of evaporative properties of...