Space Shuttle and Solid Rocket Motors

The launch of the space shuttle and other vehicles such as the Titan launch vehicles results in emissions directly into the troposphere and the stratosophere. Exhaust emissions include A1203 (30% by weight), CO (24%), HC1 (21%), H20 (10%), N2 (9%), C02 (4%), and H2 (2%) (Danilin, 1993). 

The major focus on the effects of exhaust emissions has been on the HC1 component and its role in ozone depletion and on the A1203 particles, which could provide a surface for the heterogeneous conversion of HC1 to active forms of chlorine. It has been proposed that if the HC1 were converted to photochemically active forms relatively rapidly, a mini ozone hole could form in the flight path of the vehicle (Aftergood, 1991 McPeters et al., 1991 Karol et al., 1992). 

The impact on the generation of active forms of chlorine by heterogeneous reactions on the A1203 particles is somewhat controversial (Prather et al., 1990 Danilin, 1993 Denison et al., 1994 Jackman et al., 1996). For example, the reaction of C10N02 with HC1 to generate Cl2, for example, proceeds relatively rapidly (reaction probability of 0.02) at 208-223 K on hy-droxylated a-alumina (Molina et al., 1997). However, it appears that this is not unique to the A1203 surface but rather is due to water layers adsorbed on the solid. 

A potential direct effect is the destruction of 03 directly on the particles, which appears, based on labo- 

FIGURE 12.10 Concentration of stratospheric particles with 1 /cm at altitudes of 17-19 km from 1976 to 1984 (adapted from Zolensky et al., 1989). 

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