Explained: The tech behind 3D-printed rocket and how Agnikul Cosmos capitalised on it?

A couple of days back Agnikul Cosmos, the IIT Madras-incubated start-up, launched the world’s first rocket with a single-piece 3D printed engine from ISRO’s Satish Dhawan Space Centre Sriharikota. This remarkable feat has been achieved entirely through indigenous design and development. This Chennai-based space startup successfully conducted a sub-orbital test flight of its 3D-printed semi-cryogenic rocket, Agnibaan. 

Why is it that the launch of this 3D rocket is being hailed by space scientists and the space ecosystem? A 3D-printed rocket is a spaceship that incorporates components produced through the process of additive manufacturing utilising 3D-printing technology. When compared to conventional rockets, 3D-printed rockets demonstrate superior fuel efficiency, reduced weight, and significantly faster construction time. 

“3D-printed rockets can be manufactured with integrated engines and airframes, eliminating the necessity for any connections, seams, or welds. Additive manufacturing technology streamlines production pipelines by minimising the reliance on tooling and decreasing the quantity of necessary parts. This enables aircraft firms to participate in rapid prototyping,” explained space expert Girish Linganna. 

3D-printed rockets are primarily designed as satellite launch vehicles, used to move satellites and position them into precise, low-earth orbits. With further advancement, these technologies could potentially be employed for manned space travel and expeditions to Mars.

Currently, there is a wide range of objects that can be produced using 3D printing technology, and it is expected that even more items will be printable in the future. The main difficulty lies in deciding which objects should be printed and finding the most effective way to include these printed components into the larger system of the launch vehicle. 

When it comes to 3D printing in the space race, startups are equally competitive, each devising their own unique technique along the way. There are a total of seven forms of additive manufacturing, but two of them are particularly prominent: powder bed fusion, specifically selective laser sintering, and directed energy deposition. 

“Selective laser sintering (SLS) and selective laser melting (SLM) are 3D printing techniques that use a laser to fuse powdered metal layer by layer, creating a solid object from a digital design. In SLS, the laser heats the powder enough to solidify and bond it without fully melting, resulting in a porous structure. SLM, on the other hand, fully melts the powder, producing dense, solid parts,” said  Linganna.

Directed energy deposition (DED) is a 3D printing method that builds objects by precisely depositing and melting materials layer by layer, added Linganna. “It’s like a high-tech hot glue gun, but instead of glue, it uses a focused energy source like a laser or electron beam to melt metal powder or wire, creating complex three-dimensional shapes directly from a digital design. This method allows digital designs to be transformed into real, usable parts. The only size limitations are the base and the chamber where the part is created,” he said. 

Some parts of a rocket, such as oxidizer tanks, propellant tanks, engine nozzle bells, outer rocket bodies, and certain pipes, are suitable for 3D printing. The list also includes combustion chambers, injectors, pumps, and valves. Parts that don’t need to be extremely precise or strong can also be replaced with 3D-printed versions. However, items that need to withstand specific chemical, thermal, or strength conditions, or those that don’t fit well size-wise, should be made using traditional methods. This is also true for parts requiring precision beyond what 3D printers can achieve without a lot of finishing work. 

Agnikul’s co-founder and CEO, Srinath Ravichandran, has said that it usually takes 72 to 75 hours to 3D print one of these engines in raw form. The startup can complete two fully finished engines in a week. He further added they can produce two fully finished engines in a week. This process includes 3D printing, de-powdering, and heat treatment. In contrast, the traditional method takes 10 to 12 weeks to create a rocket engine of a similar size. 

Ravichandran has also said that their core engine is 3D printed as a single piece, including the fuel inlet, exhaust outlet, and everything in between, along with the igniter. This engine is then connected to the necessary plumbing, such as fuel pipes, pressure and temperature sensors, and valves. 

The history of 3D printing technology is inseparable from the contributions of Chuck Hull, the father of 3D printing. In 1983, Hull invented stereolithography, a method that forms solid objects by successively “printing” thin layers of an ultraviolet-curable material. His invention laid the groundwork for the development of 3D printing technologies that are now integral to various industries, including aerospace. 

The technical prowess of 3D printing lies in its ability to create complex geometries that are often impossible to achieve with traditional manufacturing methods. Aerospace engineers leverage this technology to fabricate lightweight, high-strength structures, optimizing the balance between performance and fuel efficiency. The process involves layer-by-layer construction, allowing for intricate designs with internal channels and cavities that enhance the engine’s efficiency and thrust-to-weight ratio. 

Agnikul Cosmos has utilised this technology to produce the Agnilet engine, a marvel of engineering that is printed as a single piece. This eliminates the need for assembling multiple small parts, thereby reducing potential points of failure and significantly cutting down production time and costs. The engine is designed to be powered by kerosene, a choice that strikes a balance between cost-efficiency and performance,” remarked Srimathy Kesan, founder and CEO of Space Kidz India, which is into design, fabrication and launch of small satellites, spacecraft and ground systems. 

ROSCOSMOS, the Russian space agency, has embraced 3D printing for its ambitious lunar program. Plans include 3D printing lunar shelters from Moondust, which aligns with the global trend of using in-situ resources for space construction. This innovative approach is expected to support long-term lunar missions and pave the way for further space exploration. 

The advancements in 3D printing for aerospace are not limited to engine design. NASA’s exploration into Rotating Detonation Rocket Engines (RDRE) showcases the potential of 3D printing in creating propulsion systems that could one-day power spacecraft to Mars. The RDRE’s design allows for continuous detonations within the engine, leading to more efficient fuel consumption and higher thrust compared to conventional engines. 

Selective SLS and electron beam melting (EBM) are among the techniques used to 3D print rocket engine components. These processes involve fusing metal powder into a solid structure using lasers or electron beams, respectively. The precision and flexibility afforded by these methods have led to the production of parts such as the thrust chamber, injector, turbopumps, and main propellant valves with unprecedented levels of detail and strength. 

“The economic implications of 3D printing in aerospace are profound. By reducing the number of components and simplifying the assembly process, the technology offers significant cost savings. Moreover, the ability to print on demand reduces inventory costs and waste, contributing to more sustainable manufacturing practices. The integration of 3D printing technology in aerospace engineering is a testament to human ingenuity and the relentless pursuit of innovation. As companies like Agnikul Cosmos and space agencies like NASA and ROSCOSMOS continue to push the boundaries of what is possible, we can expect to see more efficient, cost-effective, and environmentally friendly solutions in the aerospace sector,” added Kesan.