How Metal 3D Printing Is Reshaping Rocket Engine Development — Two Recent Milestones

Lessons learned:
The team emphasized the need for tighter process control across printing, post-machining, cleaning, inspection, assembly, and testing — and a better understanding of cooling sensitivity and cleanliness requirements .

Earlier Eplus3D & UCL Rocket — Excelsior Engine for Race 2 Space

Prior to the LOX/IPA engine, Eplus3D and UCL Rocket developed "Excelsior," a regeneratively cooled bipropellant engine for the UK's Race 2 Space 2025 competition. That engine was printed in AlSi10Mg aluminum alloy on an EP-M400S four-laser LPBF system . The earlier generation also used a nitrous oxide (N₂O) architecture prior to the switch to LOX/IPA .

Leap Space — Serrano Engine for Bighorn Launch Vehicle

Colorado-based Leap Space unveiled the Serrano engine in August 2026 as the first major hardware piece of its Bighorn orbital launch vehicle . Key facts:

• The thrust chamber is printed as a single part using large-scale direct metal laser sintering (DMLS) .
• Serrano is a variant of Leap's proprietary Cayenne propulsion system, a dual-mode LOX/methane architecture .
• It builds on the flight-proven Anaheim engine at a larger scale to enable rapid iteration and production .
• Leap's design philosophy targets ~90% fewer parts than conventional launch vehicles, supporting high-cadence, low-cost manufacturing . Leap's Bullfrog suborbital vehicle, which uses the same core technology, completed its first flight in May 2026 .

Broader Industry Shift

Metal additive manufacturing is maturing from prototyping into production of flight-critical propulsion hardware across multiple companies:

• Part consolidation: Complex internal cooling channels, injectors, and entire thrust chambers can be printed as single monolithic parts, eliminating hundreds of traditionally welded or brazed joints .
• Speed: Leap Space states that a single-print thrust chamber enables rapid test-and-learn cycles, and companies like LEAP 71 have demonstrated engine design-to-hot-fire in under three weeks .
• Weight and efficiency: Regenerative cooling designs enabled by AM (e.g., CuCrZr with conformal channels) allow higher chamber pressures and temperatures without active film cooling, improving specific impulse.
• Production scale: Companies are planning production rates of 30+ engines per year per manufacturing line, which is only feasible with AM-driven part simplification .