In 25 years will our primary means of getting to orbit be a refinement of the Chinese fire arrows of 1232? Elon Musk's reusable rockets should be really good by then. And Richard Branson's Virgin Galactic and Paul Allen's and Burt Rutan's Stratolaunch will probably be thriving businesses by then but how about SSTO (single stage to orbit space planes) or space elevators or orbital rings with sky hooks? Perhaps we will replace the rocket’s first stage with stratospheric tethered rings, stratospheric towers, stratospheric cloud cities using steel vacuum balloons, or . . . whatever.