Future launching systems. Second prospective phase: 1981-1982. Two-level reusable cryogenics

Conditions are discussed for staging a partially or fully reusable launch vehicle having a first stage with glide return and a second stage with ballistic reentry. Both stages use LOX-LHZ fuels and have identical motors. The mission objective is to insert into a 200 Km circular low orbit a payload with a minimum weight of 10 tons. The second stage has a propulsion system with stockable fuel capable of putting the payload directly into a 200/800 orbit and of retransferring the empty second stage to a 200 Km circular orbit, deorbiting the second stage for reentry maneuver, and braking the second stage. Trajectories, kinematic conditions for separation, thermal protection, storage tank specifications, and refilling are examined as well as the possibility of payload retrieval.