How does ISRO’s 3D-printed rocket compare with other international 3D rockets?

The Indian Space Research Organisation (ISRO) successfully carried out a critical test on a 3D-printed liquid rocket engine on Friday. This test marked a significant advancement in incorporating additive manufacturing (AM) techniques into India’s space exploration efforts. With the successful completion of the full-duration hot test, ISRO has shown that it is feasible, and efficient, to use AM technology in building rocket engines for its PSLV programme. 

The 3D-printed liquid rocket engine was developed by ISRO’s Liquid Propulsion Systems Centre (LPSC). It uses Earth-storable bipropellant combinations, nitrogen tetroxide and monomethylhydrazine as propellants in a pressure-fed system. The engine was produced together with WIPRO 3D, an industry partner, and underwent testing at ISRO’s Propulsion Complex at Mahendragiri. 

The engine that was tested, called the PS4 engine, is mainly used in the fourth stage of the Polar Satellite Launch Vehicle (PSLV) and in the Reaction Control System (RCS) of its first stage (PS1). The RCS in the first stage of a rocket helps control its direction during launch. By adjusting the rocket’s orientation, the RCS ensures that it follows the correct path right from the start, which is crucial for a successful mission. The PS4 twin bipropellant liquid engine, which is typically made through traditional machining and welding, is used in the fourth stage of the PSLV. Each engine delivers a thrust of 7.33 kN in vacuum conditions. It is also utilised in the RCS of the PSLV’s first stage (PS1), according to an ISRO release. 

3D printing is also known as Additive Manufacturing (AM). “3D printing is a process where objects are created by adding material layer by layer, following a digital design. This method allows for complex shapes and structures to be made more efficiently and with less material waste than traditional manufacturing techniques. The PS4 engine was re-engineered using Design for Additive Manufacturing (DfAM) principles, simplifying its structure from 14 parts to just a single piece and removing 19 weld joints. 

The engine was produced using a Laser Powder Bed Fusion method, significantly reducing material usage from 565 kg to only 13.7 kg of metal powder and cutting production time by 60 per cent. The method involves spreading a thin layer of metal powder and selectively melting it with a laser to build parts layer by layer, allowing for precise, complex geometries and efficient use of materials,” explained space expert Girish Linganna. 

Before the successful 665-second test, the engine went through various developmental tests and simulations. These included earlier tests of the injector head, extensive flow and thermal modelling and structural simulations, totalling 74 seconds of testing to confirm its performance parameters. 

“Space agencies worldwide are adopting AM due to its efficiency and customizability. NASA, for instance, has leveraged AM in its propulsion systems to reduce the number of parts and shorten production times, while improving design flexibility. The reduction in component weight provided by AM is especially valuable in space missions, where weight minimisation is critical,” said Linganna.

This technology is transforming the manufacture of aerospace components on Earth and is also seen as pivotal for manufacturing in space, which could be essential for extended space missions, added Linganna. “As AM technologies evolve, their contribution to space programmes is expected to grow, opening up new avenues for innovation and operational efficiency,” he said.

He further says that NASA has implemented AM techniques in its Rapid Analysis and Manufacturing Propulsion Technology (RAMPT) project. This initiative aims at creating lighter and more efficient components for liquid rocket engines intended for future space missions. 

“A key achievement of this project is the development of the thrust chamber assembly, which includes the combustion chamber, nozzle and connectors. The RAMPT project has demonstrated how AM can achieve considerable reductions in costs and component weight, thereby enhancing NASA’s propulsion capabilities,” said Linganna.

Experts point out that 3D-printed rocket engines require high-performance alloys that can withstand the extreme heat, pressure, and stresses of rocket propulsion. For instance, it requires copper alloys which offer excellent thermal conductivity and resist high temperatures, making them suitable for combustion chambers and Inconel which is a nickel-chromium superalloy and is known for its strength and heat resistance, ideal for various engine components. 

Additionally, it requires Titanium Alloys which despite being lightweight possess high strength, making them valuable for components requiring both durability and minimal weight. 

“We at Space Kidz India built the World’s lightest Satellite ‘KalamSAT’ in 2017 with carbon fibre polymers and it was widely spoken about through a sub-orbital flight that took the world by storm. 3D printing is revolutionising the aerospace industry, particularly in rocket production. This technology allows for complex, lightweight engine parts to be manufactured on-demand, reducing costs and development times,” Srimathy Kesan, founder and CEO of Space Kidz India told THE WEEK. The aerospace startup is pioneering in the design, fabrication, and launch of small satellites, spacecraft and ground systems.

“Traditional methods involve assembling numerous parts, which can be expensive and time-consuming. 3D printing simplifies the process by creating entire engine components in a single print. This reduces welds and potential failure points, leading to more efficient and reliable engines,” said Kesan. 

Other companies using the 3D technology

Companies like Relativity Space in the US are at the forefront of 3D-printed rocket technology. Their entire Terran 1 rocket is built using a giant metal 3D printer, significantly reducing lead times and part count. Established players like SpaceX are also leveraging 3D printing for specific engine components. Their SuperDraco engines, used for manoeuvring their Crew Dragon capsule, feature complex 3D-printed combustion chambers. 

“Indian startups like Agnikul and Skyroot are catching up in 3D-printed rocket technology. Agnikul is developing India’s first single-piece 3D-printed engine, Agnilet, using a special high-performance alloy. Skyroot plans to use 3D printing extensively in their Vikram series rockets, aiming for frequent, low-cost launches. The use of 3D printing in rockets is a global trend, with countries like China actively developing their own technologies. This competition is driving innovation, pushing the boundaries of what’s possible in rocket design and manufacturing. 3D printing has the potential to make space exploration more accessible and affordable. As the technology matures, we can expect to see even more innovative and powerful 3D-printed rocket engines take flight,” added Kesan. 

Kesan further explains that 3D printing can significantly reduce launch costs by streamlining production and minimising parts. This could open doors for more frequent space missions and wider participation in the space industry. This apart, the ability to quickly iterate on designs through 3D printing allows companies to test and improve engines faster, leading to more efficient and powerful engines. 

“3D printing enables the creation of intricate engine geometries that would be impossible with traditional manufacturing techniques. This paves the way for next-generation engines with improved performance. However, there are also challenges to consider, material limitations, current 3D printing materials may not possess all the desired properties for high-performance rocket engines,” said Kesan. 

“Research into new materials is ongoing. Ensuring the quality and consistency of 3D-printed engine parts is crucial for safety and mission success. Rigorous testing and quality control procedures are essential. Besides that scaling up 3D printing for large engine components remains a challenge. As the technology matures, we can expect to see advancements in this area,” added Kesan.