What is it about the exhaust gasses from the solid rocket boosters that makes them so corrosive?
Dr. Calle: The solid rocket boosters generate a very corrosive exhaust that consists mainly of alumina particles and about 70 tons of hydrochloric acid. There are no coatings that can withstand the direct impact of the highly corrosive exhaust from the solid rocket boosters. Coating selection for the corrosion protection of the pad is based on different zones classified in terms of solid rocket booster exhaust deposition: zone 1 receives direct rocket engine exhaust impingement, zone 2 includes surfaces that experience elevated temperatures and acid deposition, and zone 3 includes areas outside those of zones 1 and 2. This environment is very unique to NASA and is something that we will need to deal with for as long as we use solid rocket boosters to launch.
