Complex sentence: The merger created the Jet Propulsion Research Institute (RNII), headed up by the military engineer Ivan Kleimenov and containing a number of enthusiastic proponents of space travel, including Valentin Glushko.
Split into simpler sentences: The merger created the Jet Propulsion Research Institute (RNII), headed up by the military engineer Ivan Kleimenov. However this merged group contained a number of people who were enthusiastic proponents of space travel, including Valentin Glushko.