The Stargate printers work well when you need to print large parts quickly, but for parts that require more precision, such as the rocket’s engine, Relativity uses the same commercially available metal 3D printers that other aerospace companies use. These printers use a different printing technique, in which a laser welds together layers of ultra-fine stainless steel dust.
Ellis says the real secret to Relativity’s rockets is the artificial intelligence that tells the printer what to do. Before a print, Relativity runs a simulation of what the print should look like. As the arms deposit metal, a suite of sensors captures visual, environmental, and even audio data. Relativity’s software then compares the two to improve the printing process. “The defect rate has gone down significantly because we’ve been able to train the printer,” Ellis says.
With every new part, the machine learning algorithm gets better, until it will eventually be able to correct 3D prints on its own. In the future, the 3D printer will recognize its own mistakes, cutting and adding metal until it produces a flawless part. Ellis sees this as the key to taking automated manufacturing to other worlds.
“To print stuff on Mars you need a system that can adapt to very uncertain conditions,” Ellis says. “So we’re building an algorithm framework that we think will actually be transferable to printing on other planets.”
Not everyone is convinced that Relativity’s approach to rocket manufacturing is the way forward, at least for Earthly concerns. Max Haot, the CEO of Launcher Space, a startup that also uses 3D printing, says “everyone is leveraging 3D printing as fast as they can” in the aerospace industry, in particular for engine components. “The question is whether 3D printing aluminum tanks is worth it when compared to the traditional tank manufacturing methods,” Haot says. “We don’t think so, but let’s see where they take it.”
Relativity has already inked deals worth several hundred million dollars with several major satellite operators, including Telesat LEO and Momentus. But Arjun Sethi, a partner at Tribe Capital, which invested in Relativity, sees more than launch services in its future. He compared it to Amazon Web Services in the way it could provide critical infrastructure to smaller space companies.
Sachdeva, of Northern Sky Research, thinks Relativity’s expertise in aerospace 3D printing could have lasting value beyond its rockets. “Even if we don’t get to the point of full rocket manufacturing on Mars, Relativity may be able to manufacture other components in orbit,” Sachdeva says. “That’s a pretty big development for the industry as a whole.”
Still, rockets are its first goal. So far it’s been testing its 3D-printed engine, pressure tanks, and turbopumps. But there’s plenty more to do.