A kinetically controlled vapor reaction process for synthesizing silica areogel in a reaction container by injection of a precursor reagent vapor, a catalyst reagent vapor, super saturated steam as a component of the catalyst solution, and a hydrophobic reagent vapor amd continuously mixing vapor droplets of the precursor, catalyst and water reagents in a super saturated state to continuously nucleate in a hydrolysis/poly-condensation reaction and deposit as silica aerogel.