Falcon X

Falcon X was a proposed SpaceX launch system that never flew. The company formally announced it on 28 July 2010 as a reusable two-stage-to-orbit rocket in the heavy-lift to super-heavy-lift range, with a basic version able to lift about 38,000 kilograms to low Earth orbit and a three-core Heavy version about 125,000 kilograms. Its first stage was to burn liquid oxygen and rocket-grade kerosene (RP-1) on three Merlin 2 engines, while the upper stage was to use liquid oxygen and liquid hydrogen on a single Raptor engine. It was a scaled-up step beyond the Falcon 1 and Falcon 9 families, and the Heavy configuration is described as cancelled. It is recorded here as a design-only entry in the lineage of SpaceX launch vehicles.