The Raptor engine is the primary powerplant for SpaceX's Starship spacecraft, which is designed for missions to the Moon, Mars, and beyond. Unlike SpaceX's smaller Merlin engine that powers the Falcon 9 and Falcon Heavy, the Raptor uses a "full-flow staged combustion" (FFSC) cycle—a complex but efficient design that has only a few precedents in rocket history.
The FFSC cycle works by routing all propellant through two preburners before entering the main combustion chamber: a fuel-rich preburner and an oxidizer-rich preburner. This differs from more common cycles like the "gas generator" approach, where some propellant is simply vented as waste. The FFSC design in theory allows more of the propellant's chemical energy to be converted into thrust, which is why SpaceX adopted it for Raptor despite the engineering complexity.
When development began, the original Raptor 1 attracted attention for its messy appearance—described by author Brian Potter as a "tangle of pipes and wires." Over successive versions, SpaceX streamlined the design. The most recent version, Raptor 3, which first flew in May 2026, features a significantly cleaner layout. Comparative diagrams created by SpaceX enthusiasts (though not official) suggest several specific changes between version 1 and version 3:
The article introduces Raptor 3 and notes its significantly cleaner layout compared to the original Raptor 1, with lines bundled into a common umbilical and helium lines eliminated.
- Lines that were previously separate are now bundled into a "common umbilical," visible in photos of the Raptor 3 connected to its rocket. - Helium lines used to spin up the turbines initially have been eliminated; nitrogen is used instead, per some fan-made schematics. - A gaseous oxygen heat exchanger near the preburner, present in version 1, appears to have been removed. - A fuel line to the preburner that existed in version 1 is absent from the version 3 schematic.
These changes came alongside measurable performance gains. The primary source notes that the Raptor 3 provides about 35% more thrust than the Raptor 1. Elon Musk has commented publicly on several simplification efforts: the turbopump was shrunk (as part of the Raptor 2 update), preburner controllers were moved from being distributed across the engine into dedicated boxes, and many valves were combined into valve plates. As the engine design was refined, many of the extra sensors monitoring temperature and pressure were also removed, since the engine behavior became more predictable.
It is worth noting that much of the detailed engineering information comes from Elon Musk's comments, fan-made schematics, and SpaceX enthusiast observations—not from official SpaceX documentation or published engine teardowns. SpaceX does not publish official Raptor schematics, and no public teardown of a Raptor engine has been conducted. The changes described above reflect the best-assembled picture from available public commentary and speculation.