LEAP 71 has successfully hot-fire-tested two different 20 kN methalox rocket engines designed with its Noyron Large Computational Engineering Model.
The company's conventional bell nozzle engine and full-scale aerospike engine both went from specification to first flame in under three weeks. LEAP 71 has confirmed they were also entirely 3D printed from a high-temperature copper alloy (CuCrZr) by Aconity3D.
Each engine is said to generate 2 tons of thrust (4,500 lbf) burning cryogenic methane and liquid oxygen (methalox), making them suitable for orbital-launcher applications.
While 'radically different' in shape and internal geometry, both engines were generated by the same Noyron model, relying on the same physics and logic. The aerospike — with its toroidal combustion chamber and central spike — promises higher efficiency, wider operational usability, and better deep-throttle performance than conventional engines. An aerospike has never successfully been flown into space, but LEAP 71 has now performed a successful hot fire test of one twice - the first coming in December 2024.
During this second test, the aerospike could only be operated for a single burn because of issues encountered during startup transients; however, it reached full chamber pressure at 50 bar and validated the fundamentals of the design. Meanwhile, the conventional bell-nozzle thruster reached steady state at nominal chamber pressure and thrust, validating the underlying physics models and operating above 93% combustion efficiency. The hot-fire provided important feedback about real-life pressures and temperatures, all of which fell within the expected ranges.
The hot-fire provided important feedback about real-life pressures and temperatures, all of which fell within the expected ranges. To improve startup and shutdown transients, especially for the aerospike, LEAP 71 will now integrate an advanced ignition system, which was also successfully tested during the week-long testing campaign.
LEAP 71 says the test campaign provides the latest validation of Noyron, which generates complex machinery directly from specification to production-ready design. It encodes first-principles physics, engineering logic, manufacturing constraints, and practical considerations into a coherent system that outputs directly to the fabrication process.
Exclusive: Behind the scenes at world first hot fire test of computationally engineered rocket engine
“Noyron is our ongoing attempt to comprehensively encode the process of engineering into a computational model that can operate independently of humans — radically compressing iteration times and making objects possible that were previously unfeasible. These physical tests — literally hot-firing the engines — generate crucial data that can only be obtained in the real world,” said Lin Kayser, co-founder of LEAP 71.
Space propulsion is one of LEAP 71’s key focus areas, with the company firing a Noyron-generated engine on average every four weeks over the past 18 months.
“Methane is a complex propellant to model,” said Josefine Lissner, CEO of LEAP 71 and Principal Architect of Noyron. “Contrary to the kerosene fuel we tested in the past, it undergoes significant density changes under different temperatures and pressures. So, Noyron’s predictions need to be spot on in order to produce working hardware. Also, the increased size of the engines comes with its own operational challenges.
“In the last 12 months we tested kerolox engines from 1.5 to 7.5 kN, using different materials and configurations. Noyron now delivers first-time-right rocket thrusters for kerosene and cryogenic liquid oxygen. We are confident that we are close to achieving the same for cryogenic methane. This test was an important step for us, validating that we can radically reduce the time for our customers to get to the launch pad with Noyron-generated engines.”
The newly tested 20 kN methalox engines represent roughly 10% of the thrust class LEAP 71 aims to hot-fire in 2026. Manufacturing validation of the 200 kN — and even larger 2,000 kN — methalox engine designs is already underway, making use of the largest metal 3D printing systems in the world.
