This revolutionary new propulsion system is set to change space launches
If you’ve ever watched one of the test launches of SpaceX’s 120-metre-tall Starship, you may have been amazed that such an enormous rocket can get off the ground, let alone reach outer space. That’s all thanks to its specially designed Raptor engines – six of them in its upper stage and an unprecedented 33 in the Super Heavy first stage. SpaceX is unusual among launch vehicle manufacturers in designing and constructing its own engines, rather than buying them from another supplier. But this gives it the flexibility to tailor the engines to its exact needs – and in the case of Raptor, it has led to one of the most revolutionary rocket designs to date.
Apart from its sheer size, Starship will be a record breaker in another way: it will be the world’s first completely reusable space launch system. That’s in contrast to earlier designs such as NASA’s Space Shuttle and SpaceX’s own Falcon 9 rocket, which were only partially reusable. It’s this goal of complete reusability that’s driven the radically new design of the Raptor engine. It’s powered by methane – an unusual choice for rocket fuel, but one that reduces soot buildup inside the engine and eliminates the need for major refurbishment between flights. The other really innovative feature of Raptor is its use of ‘full-flow staged combustion’ (FFSC). This is a particularly efficient engine design that was first tackled, without success, by Russian engineers in the 1960s. It wasn’t until SpaceX’s work with Starship and Raptor that an FFSC engine actually made it off the ground. This kind of design also has the advantage of creating a less extreme environment inside the engine’s pipework.
Starship actually uses two different variants of the Raptor engine – one designed to give best performance at sea level and the other optimised for use in the vacuum of space. All 33 of the engines in the Super Heavy booster are sea level types, while the upper stage uses a mix of three sea level and three vacuum variants. Since it was originally conceived, the Raptor design has undergone
