Firm test-fires 3D-printed, fully cryogenic reusable rocket engine — Indian startup leverages SLM printing to create its first working prototype

It’s a safe bet that 3D printer aficionados would definitely own an industrial SLM (Selective Laser Melting) printer if they could, as the creative possibilities granted by them are endless. One such possibility is making actual working rocket engines, as Indian startup Othisis just demonstrated with a stationary test-fire of its fully cryogenic rocket engine, after a few failed attempts.

As a broad description, SLM printers work by depositing a layer of microscopic metal powder on a base, and then firing a laser that melts the powder into solid at specific places. The base then drops down a fraction of a millimeter, a new layer of powder is deposited, and the process repeats. All told, this results in layers around just 0.05 to 0.06 mm thick, made of metals and alloys that traditional consumer 3D printers can’t quite handle. Here’s an illustrative video of the process.

Othisis’ engine doesn’t yet have a name, but it’s a 5 kN fully cryogenic design, meaning that it uses both liquid oxygen (LOX) and methane as propellants, kept chilled in liquid state. As expected these days, the firm intends this design to be a VTVL (vertical take-off, vertical landing) reusable design. The Othisis design uses the chilled-fuel loop for cooling, plus both LOX and methane can be theoretically manufactured in-situ from CO2 and water.

Additionally, the burn is stronger than the commonly used Kerolox, while leaving behind almost no residue, lowering maintenance time and improving reusability turnaround. Drawbacks include lower fuel density (thus the need for larger tank sizes), trickier storage due to the low temperature, and potential hazards for handling.

Othisis has reportedly signed MoUs (memorandum of understanding) to carry payloads into space, even though it’s only been formally in business for two years. The company is the brainchild of Syed Affan, the creator of the Rocketry India Discord server, who founded the company while pursuing his undergraduate degree.