It is based on the Shuttle-C concept which has been the subject of various studies since the 1980s. Derived from currently used Space Shuttle hardware, i.e. an Shuttle-Derived Launch Vehicle (SDLV), it is proposed to replace the winged Orbiter from the Space Shuttle stack with a simple non-winged side-mounted payload carrier. The designs of the Space Shuttle's External Tank (ET) and the four-segment Shuttle Solid Rocket Boosters (SRBs) would be reused.