India's Agnikul launches 3D-printed rocket in sub-orbital test after initial delays

After two years of preparation and four delays over the past several months due to technical glitches, Indian space startup Agnikul has successfully launched its first sub-orbital test vehicle, powered by its unique 3D-printed rocket engines, space agency Indian Space Research Organisation said Thursday.

Called Agnibaan SOrTeD (Sub-Orbital Technology Demonstrator), the single-stage launch vehicle lifted off Thursday morning local time from the startup’s mobile launchpad at the Satish Dhawan Space Center on South India’s Sriharikota island. Data from the test flight will contribute to the development of the startup’s Agnibaan commercial orbital launch vehicle.

Agnikul initially conducted full countdown rehearsals for the launch in March and postponed the liftoff due to some minor observations. The startup also prepared the launch twice in April and once earlier this week, each time calling it off just before liftoff due technical issues surfaced during last-minute inspections. Today, Agnikul finally accomplished its long-anticipated mission after the rocket lifted off from the spindle-shaped island located on the East Coast of Andhra Pradesh and splashed down in the Bay of Bengal.

The 6.2-meter-tall vehicle is made of carbon composite, which gives it a liftoff mass of 1,268 lbs; at its heart is the 3D-printed semi-cryogenic engine that Agnikul manufactured in-house, each of which provides 6.2 kN of thrust.

Agnikul co-founder and CEO Srinath Ravichandran told TechCrunch in an interview before the launch that it takes 72 to 75 hours to 3D print one of the rocket engines in raw form. The startup can produce two fully finished engines in a week, including taking them from the 3D printer, de-powdering them, and passing them through heat treatment. This is unlike the traditional process, which takes 10 to 12 weeks to create a rocket engine of a similar size.

“We stand out because of the single-piece component where there is no human intervention in the process; what comes out of the printer is of full length, without any welding or tightening or anything of that sort,” he said over a call.

Elaborating further on the single-piece part that makes Agnikul stand out in the competition, Ravichandran said the core engine, which is “where the fuel enters and exhaust leaves and everything in between, and the igniter,” is 3D printed in one shot as a single piece of hardware. The engine is then connected to the plumbing apparatus, such as fuel pipes, pressure and temperature sensors, and valves.

Though Agnikul claims its 3D-printed engine is a world first, companies including Relativity Space and Rocket Lab adopted 3D printing for their rockets much earlier. However, Ravichandran claimed all these companies have not entirely used 3D printing.

“They are still not offering what people should be offering, which is what we are offering, which is extremely flexible and configurable ways to get to space,” he asserted. “If you have a 1 or 1.5-ton capacity vehicle, which is what Relativity or any of these other companies have, that’s like forcing people to do a rideshare, forcing them to figure out, wait for people to come in together, and again, the same set of problems of not getting dropped in the last mile.”

Agnikul chose inconel as the material for the engine design. It remains strong at high temperatures and is 3D printable. However, since the alloy is an extremely poor heat conductor, the startup’s biggest challenge was removing the heat.

“Taking heat out involved a lot of iterations of designing the cooling channels,” Ravichandran said.

The other challenge for Agnikul was to ensure the vehicle remained completely hazard-free while being a mobile system. The startup decided not to use solid-fuel systems, which are highly explosive, and instead made the vehicle a completely liquid propulsion-based system. It also preferred to avoid using a model that requires even a remote connection to an explosive material.

“Any of the systems that require jettisoning, like if some phase separation from the pad or separation in two stages and so on, these are all pneumatic systems,” Ravichandran stated.

Agnikul has designed the vehicle to be modifiable “even in the last minute,” the co-founder said, offering a tailor-made solution to organizations looking to launch any specific small satellites.

Founded in late 2017, Agnikul initially experimented with 3D-printed components, such as igniters, cooling channels, and fuel injection points. However, it gradually pushed the boundaries and started combining different elements to avoid welding and tightening — moving away from conventional methods.

“There is no shortcut to engineering something like this. You just have to go through the regimen and keep on iterating,” Ravichandran asserted.

He said the startup went through at least 70 or 80 iterations, particularly for fuel injectors, and eventually designed an “injector plate,” combining all of them in one component. Similarly, the startup went through at least 20 iterations of its cooling chambers with different geometries.

The startup took about six to nine months to make its first set of engines from scratch and then spent almost a year making that engine actually fly, the executive said. Agnikul raised $26.7 million in funding late last year to get it to this point.

Retired scientists from the Indian Space Research Organisation and researchers from IIT Madras are helping Agnikul develop vehicles for commercial launches. Ravichandran said the startup is already in talks with over 40 potential customers, and letters of intent have been signed with some. However, an orbital launch of Agnibaan would take at least six months.

India’s space sector has attracted global attention for some time. Last year, the South Asian nation became the first to land its spacecraft on the lunar south pole and introduced its space policy to boost private participation. The country, home to around 190 space tech startups, also recently updated its policy to raise limits on foreign direct investments in the space sector. Now, Indian space startups are setting the ground to take the country’s space sector to new levels by demonstrating their technologies and making them ready to generate revenues from customers worldwide.