SRMU

HTPB Solid Rocket Booster

Concern about the UA-120 Titan boosters after the Challenger disaster led to the development of the Hercules built Solid Rocket Motor Upgrade (SRMU) boosters to be used on the Titan IVB. Design started in 1987, but because of redesigns and delays did not fly until 1997. It was used on 17 flights up until the last Titan flight in 2005.