How SpaceX Streamlined the Raptor Engine

Filed by feed-ingest on 2026-09-18 from Construction Physics (Brian Potter), published 2026-09-17. Full text extracted from the post (not paywalled). Source: https://www.construction-physics.com/p/how-spacex-streamlined-the-raptor

Brian Potter, Sep 17, 2026.

If you’re reading this, there’s a very good chance you’ve seen this famous image of three iterations of SpaceX’s Raptor rocket engine. The Raptor engine was developed for SpaceX’s Starship spacecraft (the Falcon 9 and Falcon Heavy use the Merlin engine); it was first test-fired in 2016, first flew on Starhopper in 2019, and first flew on a Starship prototype in 2020 and on the full Starship stack in 2023. Since then, it’s continued to improve, going from the tangle of pipes and wires you can see on the Raptor 1 to the smooth, streamlined design of the Raptor 3, which first flew in May of this year.

The evolution is so dramatic that many folks initially believed that it wasn’t real; Tory Bruno, the then-CEO of space launch company United Launch Alliance, tweeted that there was “no need to exaggerate this by showing a partially assembled engine,” which was followed by SpaceX president Gwynne Shotwell tweeting a picture of the Raptor 3 firing successfully.

This streamlining has come alongside meaningful gains in performance, with the Raptor 3 providing about 35% more thrust than the Raptor 1.

SpaceX doesn’t publish official Raptor schematics, and no one has done a teardown. Potter reconstructs the change-set from Elon Musk comments, Everyday Astronaut interviews, NASASpaceFlight forum speculation, and fan schematics (Elisei Maslov 2019; “hisdirt”; Livingjw/HVM 2022; TheSpaceEngineer Jan 2025). Those schematics are unofficial.

How the Raptor engine works

The Raptor is a full-flow staged combustion (FFSC) engine. Prior to Raptor only two FFSC engines had been built, neither of which successfully flew: the Soviet RD-270 (never flew) and the US Integrated Powerhead Demonstrator (never a full engine). SpaceX obtained some IPD equipment when Raptor work started in 2012.

In a full-flow engine there are two preburners. All propellant is routed through them: one fuel-rich, one oxidizer-rich. Both exhaust streams enter the main chamber. The claimed reliability edge is that high mass-flow lets the turbines run cooler and at lower pressure — attractive if the company is betting on reuse.

Architecture across Raptor 1 → 3 has not changed: oxygen pump/turbine/preburner on top, fuel pump/turbine/preburner on the side, regenerative cooling of the nozzle with fuel, autogenous tank pressurization, nitrogen purge lines, igniter lines.

What actually changed

From Musk (reply to Yishan Wong, Sep 5) plus the 2022 Starship update:

• Development sensors and their wiring were stripped as the engine was dialed in (some may have moved internally).
• Main-chamber spark igniters present on v1 were gone by v2 — hot preburner streams may not need them.
• Bolted flange connections replaced by welds (mass and leak paths down; serviceability down). Early Raptor 3 photos still showed a large bolted flange that later photos eliminated.
• Piping moved internal via 3D printing of components. Musk has said SpaceX “has the most advanced 3D metal printing technology in the world”; in 2024 the company licensed Velo3D’s 3D metal printing tech. Close-ups of Raptor 3 appear to show print lines.
• Internalizing lines and adding internal cooling let SpaceX drop the heat shield and fire-suppression mass that had protected the external tangle. The biggest mass change Raptor 1 → 3 is vehicle-side hardware, “almost certainly largely the heat shield.”
• Raptor 2 also: turbomachinery through chamber/nozzle/electronics redesigned; turbopump shrank; preburner controllers moved into boxes; many valves combined into valve plates (Everyday Astronaut / NSF 2022).
• Fan schematics (caveat: unofficial) also show a common umbilical bundling small lines on v3; helium spin-up and helium valve-control lines gone in favor of nitrogen; a GOX heat exchanger near the preburner eliminated; a fuel line to the preburner present on v1 absent on the v3 schematic.

Thrust: Raptor 3 ~35% more than Raptor 1.

What this is not

Potter’s close: streamlining made the engine simpler in the sense that individual external parts vanished, but it added huge internal complexity. Problems are not ironed out: Starship Flight Test 13’s first launch attempt aborted automatically at T-0 this past July when several Raptor 3 engines failed to start. Raptor 3 first flew May 2026.

This post is a mechanism-of-manufacture note for rapid-reusability-to-orbital-compute-capex-arbitrage (engine-cost / reuse cadence), not a reason to mint a new AI-infrastructure chain and not a named purchase-order for Starship orbital compute.

Primary URLs

• Construction Physics: https://www.construction-physics.com/p/how-spacex-streamlined-the-raptor