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Chennai-based private space startup AgniKul Cosmos has 3D printed what it claims to be the world’s largest single-piece 3D printed Inconel rocket engine, which has also received a US patent.
Measuring about one meter in length, the engine is printed as a single integrated structure that runs from fuel inlet to exhaust without welds, joints, or fasteners. According to Times of India (TOI), the approach is intended to lower manufacturing complexity, reduce points of failure, and cut production time by more than 60%.
In a LinkedIn post, Srinath Ravichandran Co-Founder & CEO at AgniKul wrote, “Humbled to introduce the world’s biggest single-piece 3D-printed inconel engine, a global first in both scale & complexity. This milestone marks a breakthrough in additive manufacturing at this scale & comes as a major extension of our earlier accomplishment of making & flying the world’s first single piece engine.”
AgniKul’s AM developments in private space sector
This achievement builds on a series of milestones that have marked AgniKul’s progress in propulsion technology. In February 2021, the private space startup test-fired Agnilet, a semi-cryogenic engine created in a single 3D printing run.
Agnilet was developed to power the firm’s Agnibaan launch vehicle, designed to carry payloads of up to 100 kg into low Earth orbits of about 700 km. At the time, AgniKul highlighted that the engine could be printed in under four days and at roughly a tenth of the cost of conventional assembly, demonstrating the potential of additive manufacturing in rocketry.
To scale this approach, AgniKul established Rocket Factory-1 in July 2022 at the IIT Madras Research Park in Chennai. Described as India’s first dedicated facility for 3D printed rocket engines, the site is equipped with a 400 mm x 400 mm x 400 mm EOS metal 3D printer and systems capable of handling end-to-end production. Designed to produce up to two Agnilet engines each week, the factory marked a shift from experimental testing toward steady manufacturing capability.
That capability was further demonstrated in May 2025, when AgniKul test-fired India’s first electric motor-driven semi-cryogenic rocket engine. Unlike conventional designs that use turbopumps or gas generators, the new engine employed an electric motor to circulate propellants, allowing thrust to be precisely varied by adjusting motor speed.
During the test, the system was throttled across a broad range of power levels, showcasing both flexibility and reliability. Many of its subsystems were produced at Rocket Factory-1, while the associated motor drives and control software were developed in-house.
The electric motor-driven engine is intended to power Agnibaan, which can be configured to carry between 30 kg and 300 kg depending on mission requirements as noted by India Today.
With the grant of a US patent for its single-piece 3D printed engine, AgniKul has now secured legal protection for its design and process in the US market, underscoring the wider progression of India’s private space sector from early-stage developments toward scalable launch systems.
3D printing reshapes rocket engine manufacturing
One of the benefits of 3D printing is that it allows the engines to be built as fewer pieces, eliminating complex assembly while cutting production time and costs.
A notable example of this was revealed when Edinburgh-based private rocket manufacturer Skyrora began full-duration testing of its updated 70 kN 3D printed rocket engine, produced using the company’s Skyprint 2 3D printers. Intended for Skyrora’s first commercial orbital launch, the new design reduced production times by 66% and costs by 20% while incorporating an improved cooling chamber to extend engine life.
Running 250 seconds each to simulate mission conditions, tests evaluated life cycle and operational envelope performance. Once qualified, the engine was said to become the first commercial closed-cycle system using Hydrogen Peroxide and Kerosene, offering higher specific impulse and efficiency for the Skyrora XL orbital vehicle.
Equity-funded rocket propulsion startup New Frontier Aerospace (NFA) successfully completed hot fire tests of its 3D printed Mjölnir rocket engine. The engine employed a full-flow staged combustion cycle, considered among the most efficient liquid rocket propulsion designs, making it suitable for reusable launch systems, hypersonic vehicles, and orbital transfer platforms.
Fueled by liquid natural gas (LNG), it offered the potential for net carbon-negative operation when sourced from bio-waste. Supported by funding from the US Defense Innovation Unit (DIU) and NASA, Mjölnir was planned for integration into NFA’s Pathfinder hypersonic VTOL UAS in 2026 and the Bifröst orbital transfer vehicle in 2027.
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Featured image shows the world’s largest single-piece 3D printed Inconel rocket engine. Photo via Srinath Ravichandran.
