[Hugh R]

Very cool to see. About 25 years ago, I got involved in an atmospheric chemistry problem with the shuttle. They flood the concrete below the rocket exhaust with water before liftoff so the reflected heat doesn't melt the shuttle. The water vapor that you see is part exhaust, and part steam from the flooded concrete. The pH of the water vapor is about that of battery acid (1). We put out polished copper plates in a series of circles up to 1/4 mile away from the launch pad to evaluate the staining and pH from the hydrochloric acid in the water vapor.