Closing Notes
摘要
Access to space with reusable winged flight vehicles started with the SpaceSpace Shuttle Orbiter Shuttle Orbiter in 1981. The orbiter was launched like a rocket and returned to Earth as a glider. Soon after worldwide studies were beginning which aimed at airbreathing access to space. Pure airbreathing single-stage-to-orbit (SSTO) access proved to be impossible, two-stage-to-orbit (TSTO) with an airbreathing lower stage and a rocket-propelled upper stage seemed to be the solution.