Industrial gases underpin test-firing of India 3D-printed rocket | Additive manufacturing

India space startup Agnikul Cosmos (Agnikul) has successfully test-fired two fully 3D-printed semi-cryogenic rocket engines ahead of an upcoming orbital mission.

The company posted on X (formerly Twitter) a video of the 25-second test, which showed the engines being throttled across a range of thrusts by varying the speed of the electric motor, while a team of engineers looked on.

The company says this electric motor allows for higher accuracy and rapid response, which are two important features for handling complex trajectories. What makes this test firing special, however, is the use of metal additive manufacturing (AM) – a type of 3D printing that builds parts layer by layer.

“Along with the patented engine, many subsystems of the pump were also 3D-printed and assembled at our … Rocket Factory-1. The motor drives and associated control software were also fully designed and developed in-house,” stated the company.

The firing of the engines involved a combination of liquid oxygen and liquid hydrocarbon fuel – likely refined kerosene or RP-1 – while the AM process used to make the components involved a range of high-purity specialty gases.

Argon is used as a shielding or purge gas for the laser powder-bed fusion method in additive manufacturing. It uses a high-powered laser to melt and fuse tiny metal powder particles layer by layer to form a solid metal object.

Ultra-high-purity nitrogen could have been used as an atomisation gas for producing powders and as a chamber gas for steels where nitrogen won’t embrittle the alloy.

AM is gaining traction as it enables engine manufacturers to print a ‘single-piece’ combustion chamber/cooling jacket with very complex internal geometries that would be difficult or impossible via traditional methods like casting, forging, machining, and welding.

The test-firing is part of Chennai-based Agnikul’s aspiration to send its 3D-printed rocket on an orbital launch. The company carried out its maiden sub-orbital test flight in 2024 as part of a project named Agnibaan SOrTeD.

Agnikul plans eventually to build fully reusable rockets, allowing it to offer satellite-launch services at globally-competitive prices.

Speaking at the International Astronautical Congress in Sydney earlier this year, the firm stated that it is aiming to ensure that no part of its rocket is fully expended or left behind.

“We have consistently designed our vehicles to ensure that affordability and flexibility are never afterthoughts but are built in from day one,” said Srinath Ravichandran, co-founder and CEO of Agnikul.

The company has previously tested its technology at facilities owned by the Indian Space Research Organisation and the Indian National Space Promotion and Authorisation Centre.