Depletion of stratospheric ozone by chlorinated exhaust of ammonium perchlorate based composite solid propellant formulations: A review
Manish Kumar Bharti, Sonia Chalia
The exhaust of a composite solid propellant (CSP) rocket can contain free radicals of NO, NO2, H, OH, Cl, ClO, etc., formed directly or indirectly, in its combustion products. Hydrogen chloride (HCl) gas is one of the main combustion products of solid rocket boosters (SRBs) using Ammonium Perchlorate (AP) as oxidizer in its grain. The exhaust of the composite solid propellant (CSPs) rockets undergoes afterburning due to high temperatures encountered during the combustion of propellants and this afterburning facilitates extensive conversion of considerable volumes of HCl to free radicals of chlorine (Cl·) and molecular chlorine (Cl2). The Cl· so discharged reacts instantaneously with nearby ozone molecules to start a catalytic destruction cycle as chlorine (Cl) is a known halogen accountable for the dissociation of ozone into oxygen. The continuous rise in the number of rocket launches per year poses a threat of intensified release of chlorinated compounds in the atmosphere which may results in substantial ozone layer depletion on shorter time scales. Though rocket exhaust usually comprises of numerous environmentally hazardous and ozone-depletion substances (ODS) depending on the ingredients used in the formulation of propellant grains, this study primarily focuses on the potential destruction of ozone caused by chlorinated compounds. This study presents a brief review of the interaction mechanism of chlorinated compounds of a rocket’s exhaust with local environment and henceforth imposed effects on local and global ozone concentrations.