Acid droplet generation in SRM exhaust clouds

Abstract

The d r o~ radius isAnalysis of droplet nucleation upon A1 0 2 3 nuclei in typical SRM exhaust clouds is presented. The free energy released in the phase transition is evaluated as a function of HC1 molefraction and nucleating particle radius for the conditions found in the exhaust cloud from a Titan I11 launch 90 seconds after ignition. The surface thus derived is saddle shaped with a unique equilibrium at the saddle point, and a narrow and sharply defined droplet growth region. For this enviro2ent, specified at 298K, p =23582 dynes cm , pHC1= -H-0 -L 104.5 d p e s cm , thgLsaddle point occurs at X -8.8~10 , r-=1.3x10 cm, and the most efficien? c1droplet grokth proceeds at nearly constant HC1 cclcfraction. This is equivalent to a molality of 5.355. The free energy suface for these conditions is shown for a range of HC1 m lefractions yp to -9 0.2 and particle sizes of 10 cm < r <lo-cm.-P -