Editorial

Abstract

The Hopper, a concept for a reusable launch system was developed and found attractive in the frame of FESTIP, ESA's Furure European Space Transportation Initiation Programme Later, in the national German ASTRA programme this concept was adapted to newly emerged requirement and subjected to a detailed design loop. Taking off horizontally and staging at high sub-orbital velocity, the Hopper needs a rail-guided launch sled, downrange landing, re-transportation back to the launch site, and one, but only one upper stage. Horizontal take-off is used to improve safety and to reduce thrust requirement, and number, mass, and cost of main engines, and also problems with vehicle centering. Transportang of the cargo (e.g.) payload and expendable upper stage) in the RLV results in only one aerodynamically affected flight configuration. Staging at high sub-orbital velocity above the sensible atmosphere enables the use of only one standardised upper stage for all missions. Using a cryogenic upper stage the Hopper system is nearly optimally staged for the dimensioning GTO mission. The paper describes the consolidated unmaanned RLV concept and highlights areas of special interest, evolution potential, and further steps.