University College London Rocket Team Hot-Fires a 3D-Printed Cryogenic Engine

The Test

UCL Rocket, the student rocketry team at University College London, has completed its first hot-fire test of a cryogenic regeneratively cooled rocket engine. The engine runs on liquid oxygen and isopropanol, producing 7 kN of thrust. The combustion chamber and other critical components were additively manufactured by Chinese metal 3D printing firm Eplus3D using an EP-M400S powder bed fusion system and CuCrZr copper alloy.

The static test marked a significant step up from the team's previous engine. In 2025, UCLR ran the Excelsior engine for the Race 2 Space competition. That engine used nitrous oxide as the oxidizer and produced 5 kN. It was one of the few engines in the competition to survive all required tests. The new campaign moves to a more demanding propellant combination and higher thrust, with cooling channels that are far harder to produce by any method other than additive manufacturing.

The Coolant Blockage Problem

The test did not go entirely to plan. Pre-test inspection found that roughly one third of the active coolant-channel area had become blocked by metallic swarf introduced during final subtractive post-machining. With less cooling capacity available than the design called for, the team could not run the engine at full throttle. They reduced the baseline to 50 percent throttle and added a small quantity of polydimethylsiloxane to the fuel to lower wall heat flux.

Despite the restricted cooling, the engine completed its full ignition sequence. The CuCrZr combustion chamber survived the test with no visible thermal erosion or structural deformation. That result is meaningful: it confirmed the material quality of the print and the integrity of the wall structure even under compromised cooling conditions. The altered test parameters mean the chamber was not evaluated under its intended operating envelope, but the data still advances the program.

What the Blockage Reveals

The coolant-channel obstruction is as instructive as the successful hot-fire. Additive manufacturing can produce the complex internal geometry that regenerative cooling demands. But swarf from post-machining can close off those passages before the engine ever fires. This test highlighted that the print itself is only part of the process. Cleaning, inspection, and careful handling during finishing operations determine whether the part actually performs as designed.

Eplus3D said the campaign gave UCLR validation data on combustion chamber behavior, cooling sensitivity, and cleanliness requirements across the full production chain: printing, post-machining, cleaning, inspection, assembly, and testing. Each link in that chain matters more when the channels inside your combustion chamber are smaller than a pencil lead.

Why Student Teams Matter for Metal AM

Student rocketry programs are a proving ground for additive manufacturing in ways that corporate R&D labs are not. Budget constraints force teams to use AM for parts that would be prohibitively expensive to machine conventionally. Failure modes get documented and shared openly. Every hot-fire test that does not end in a fireball is a data point that the wider industry can learn from.

UCLR's test joins a growing list of student teams using 3D-printed metal propulsion hardware. The Excelsior engine proved the concept. The new 7 kN LOX/IPA engine demonstrates that the approach scales to more aggressive propellants. The coolant blockage lesson will shape how future chambers are cleaned and inspected. If the team clears its next test at full cooling capacity, that will be the real milestone.