↑ Todd, David (20 November 2012). "Musk goes for methane-burning reusable rockets as step to colonise Mars". FlightGlobal Hyperbola. Diarkibkan daripada asal pada 28 November 2012. Dicapai 22 November 2012. ‘We are going to do methane,’ Musk announced as he described his future plans for reusable launch vehicles including those designed to take astronauts to Mars within 15 years, ‘The energy cost of methane is the lowest and it has a slight Isp (Specific Impulse) advantage over Kerosene’ said Musk adding, ‘and it does not have the pain in the ass factor that hydrogen has.’ ... SpaceX's initial plan will be to build a lox/methane rocket for a future upper stage codenamed Raptor. ... The new Raptor upper stage engine is likely to be only the first engine in a series of lox/methane engines.
