Falcon 9 is a partially reusable two-stage-to-orbit medium lift launch vehicle designed and manufactured by SpaceX in the United States. It is powered by Merlin engines, also developed by SpaceX, burning cryogenic liquid oxygen and rocket-grade kerosene (RP-1) as propellants. Its name is derived from the Millennium Falcon and the nine engines of the rocket's first stage. The rocket evolved with versions v1. 0 (2010–2013), v1. 1 (2013–2016), v1. 2 "Full Thrust" (2015–present), including the Block 5 Full Thrust variant, flying since May 2018. Unlike most rockets, which are expendable launch systems, since the introduction of the Full Thrust version, Falcon 9 is partially reusable, with the first stage capable of re-entering the atmosphere and landing back vertically after separating from the second stage. This feat was achieved for the first time on flight 20 with the v1. 2 version in December 2015.