Abstract: A flyback booster (200) comprising an aircraft (203) housing a launch vehicle stage as a removable rocket propulsion module (502) and several space launch vehicles using variations of the flyback booster (200) are disclosed. This flyback booster (200) functions as the first stage of a multistage space launch vehicle. The stage used in the flyback booster (200) and the upper stages of the multistage space launch vehicle (213) are selected to optimize the launch cost for a specific payload.