NASA was also considering reusable two stage to orbit for the shuttle back in the 1960s. By 1998 NASA was proposing Liquid Flyback Boosters: https://ntrs.nasa

NASA was also considering reusable two stage to orbit for the shuttle back in the 1960s. By 1998 NASA was proposing Liquid Flyback Boosters: https://ntrs.nasa.gov/api/citations/19980237254/downloads/19980237254.pdf https://ntrs.nasa.gov/api/citations/19980237254/downloads/19... Those were still winged boosters, but were not helicopter-caught and did RTLS. Musk didn't invent the concept.