When first mentioned by SpaceX in 2009, the term "Raptor" was applied exclusively to an upper-stage engine concept—and 2012 pronouncements indicated that it was then still a concept for an upper stage engine—but in early 2014 SpaceX confirmed that Raptor would be used both on a new second stage, as well as for the large (then, nominally a 10-meter-diameter) core of the Mars Colonial Transporter (subsequently, in 2016, on both stages of the Interplanetary Transport System and then, in 2017 on the Big Falcon Rocket).