Source: SpaceX test fires rocket engine that could propel humans to Mars - CSMonitor.com The Raptor represents something of a departure from SpaceX's typical design ethos, as it relies on a a mix of liquid methane and liquid oxygen, as opposed to the simpler kerosene and oxygen mix used by the Merlin family of engines. But, unlike kerosene, liquid methane and oxygen can in principle be sourced in situ, using the water and carbon dioxide present on Mars. This is the way to go, even for fool-cell vehicles. Hydrogen has too many handling problems but methane or my favorite, anhydrous ammonia are practically benign. Source: Elon Musk Unveils SpaceX Raptor Engine Test for Interplanetary Transport Back in 2012, Musk described the Raptor engine as working similarly to the engines that propelled NASA's space shuttles, with a two-stage cycle that is more efficient than the current Merlin engines used by the company's Falcon 9 rocket. Rather than using liquid oxygen and kerosene as fuel as the Falcon 9's engines do, Raptor will use liquid oxygen and methane to reduce energy costs as well, Musk said at the time. Works for me. Bob Wilson
There is a chance that some of us old birds will survive long enough to witness parallel ignition of 42 Raptor engines on Musk's 'BFR'. That would be a thing.
