LEAP 71 Successfully Tests Two Fully 3D Printed Methane Rocket Engines in Just Weeks

LEAP 71 has reached a major milestone in space propulsion, successfully hot fire testing two different rocket engines that were designed by software and fully 3D printed. The engines, each capable of generating 20 kilonewtons of thrust, were designed, built, and tested in less than three weeks, an unusually fast timeline in the aerospace world.

The engines were created using LEAP 71’s proprietary computational engineering system, called Noyron, and manufactured entirely through metal additive manufacturing (AM). Both engines burn liquid methane and liquid oxygen, a propellant combination known as methalox that is increasingly more common in modern rockets due to its performance and cleanliness. Companies like SpaceX and Blue Origin already use (or plan to use) methane-based engines for next-generation spacecraft.

What makes this achievement stand out is not only how fast it happened, but also how it was done. LEAP 71 designed not one engine, but two very different ones: a traditional bell-shaped engine and a full-scale aerospike engine. Although the two engines look and work very differently, both were created using the same computational model.

From design to fire in less than three weeks

According to LEAP 71, both engines went from initial specifications to their first hot fire test in under three weeks. In traditional aerospace programs, similar development cycles can take many months, or even years.

Each engine produces some two tons of thrust, and was manufactured from a high-temperature copper alloy (CuCrZr) using metal 3D printing systems from Aconity3D. Copper alloys are ideal for rocket engines because they can handle extreme heat, but they are difficult to make using traditional manufacturing methods.

The successful tests suggest that LEAP 71’s design-to-manufacturing pipeline is working as planned.

Two engines, two approaches

The first engine has a more familiar design: a bell nozzle, commonly used in today’s launch vehicles. During testing, this engine reached steady operation at its target pressure and thrust levels. LEAP 71 reported combustion efficiency above 93 percent, validating the underlying physics models used by Noyron.

The second engine is more unconventional. It uses an aerospike design, which replaces the traditional nozzle with a central spike, the company explained. Aerospike engines are attractive because they can perform well at different altitudes, but they are extremely difficult to build. Although the concept has existed for many years, no aerospike engine has yet flown in space.

During the test, the aerospike engine reached its intended internal pressure, operating at 50 bar, which is about 50 times normal atmospheric pressure. Although the engine was only fired once due to startup issues, the test still validated the core design. What’s more, this marked the second successful hot fire test of LEAP 71’s aerospike engine, following an earlier test in December 2024.

For LEAP 71, physical testing is a critical part of validating its computational approach. Co-founder Lin Kayser noted “Noyron is our ongoing attempt to comprehensively encode the process of engineering into a computational model that can operate independently of humans. These physical tests—literally hot-firing the engines—generate crucial data that can only be obtained in the real world.”

The hot fire tests provided real-world temperature and pressure data, all of which fell within expected ranges. That feedback will now be used to further refine the system, including improvements to startup and shutdown behavior. LEAP 71 has already tested an upgraded ignition system as part of the same testing campaign.

Scaling up fast

Rocket propulsion is one of LEAP 71’s main focus areas, and the company has been moving quickly. Over the past 18 months, LEAP 71 says it has fired a Noyron-generated engine roughly once every four weeks.

“Methane is a complex propellant to model,” indicated Josefine Lissner, CEO of LEAP 71 and principal architect of Noyron. “So Noyron’s predictions need to be spot on in order to produce working hardware.”

In the past year, the company tested smaller kerosene-based engines with thrust ratings ranging from 1.5 to 7.5 kilonewtons. With the new 20 kN methalox engines, LEAP 71 is now operating at a much higher thrust class, and the best part is, it’s only getting started.

The newly tested engines represent about 10 percent of the thrust levels LEAP 71 plans to test in 2026. Manufacturing validation is already underway for much larger engines, including designs in the 200 kN and even 2,000 kN range. Those systems will use some of the largest metal 3D printers in the world. With these tests completed, LEAP 71 is now preparing to move into much higher thrust classes over the next year.

Images courtesy of LEAP 71