the vasimr is a state-of-the-art rocket design that uses plasma for rocket propulsion. chang díaz developed the concept of the vasimr in 1979, shortly following his graduate research in fusion and plasma-based rocket propulsion at the massachusetts institute of technology. after being selected as an astronaut in 1980, chang díaz served on seven different shuttle missions, a space record that he shares with astronaut jerry l. ross. after retiring in 2005 from nasa, chang díaz formed ad astra rocket company to develop and commercialize the vasimr technology.