Zach Rosenberg «SpaceX readies upgraded engines». Flightglobal, 16-03-2012 [Consulta: 17 gener 2018]. «SpaceX is in the midst of a variety of ambitious engine programmes, including the Merlin 2, a significant modification of the Merlin 1 series, and the Raptor upper stage engine. Details of both projects are tightly held.»
William Harwood «Elon Musk revises Mars plan, hopes for boots on ground in 2024». SpaceflightNow, 29-09-2017 [Consulta: 30 setembre 2017]. «The new rocket is still known as the BFR, a euphemism for 'Big (fill-in-the-blank) Rocket.' The reusable BFR will use 31 Raptor engines burning densified, or super-cooled, liquid methane and liquid oxygen to lift 150 tons, or 300,000 pounds, to low Earth orbit, roughly equivalent to NASA’s Saturn 5 moon rocket.»
Elon Musk (2017-09-29). Becoming a Multiplanet Species (video). 68th annual meeting of the International Astronautical Congress in Adelaide, Australia: SpaceX. Consulta: 2017-12-14 – via YouTube.
