Relativity Space claims its building-size Stargate rocket mill is the largest metal 3D printer in the world. (Relativity Space)

This article originally appeared as “A relativistic shift in launch vehicle manufacturing” in the Nov. 20 issue of SpaceNews Magazine

There’s no question that additive manufacturing, or 3D printing, has become an important technology in the aerospace industry. A growing number of companies are using the technology to make components for satellites and launch vehicles that are lighter or less expensive than if they were made with conventional techniques, if they could be made at all.

One company is taking that technology to an extreme — or, in its view, to a logical conclusion. Relativity Space, a startup based in Los Angeles that only recently emerged from stealth mode, plans to use 3D printing to produce entire launch vehicles, an approach it claims can be more cost effective than traditional manufacturing techniques.

For Tim Ellis, the mid-20s chief executive and co-founder of the company, printing an entire rocket simply makes sense. “It was really just looking at what was the inevitable conclusion of that technology,” he said in a recent interview. “Looking further into the future, it became obvious to us. We view it as autonomous manufacturing.”

By being able to manufacture a rocket with 3D printing, vehicles can be built faster and less expensively because far less human labor is needed. It also allows the company to revise vehicle designs quickly, without sunk costs in tooling tied to certain designs.

That requires advances in 3D-printing technology. Relativity has developed Stargate, which it claims is the largest 3D printer in the world that uses metals, in this case a proprietary alloy. “We have to develop this new process ourselves from scratch,” he said. “We have to make the technology itself. But, we believe that once it actually exists, it will be much faster to scale up and produce rockets at scale.” The company’s goal is to go from raw material to a rocket ready for flight within 60 days.

In other fields, 3D printing enables the creation of parts that would be difficult, if not impossible, to manufacture with ordinary techniques. The same will be true with launch vehicles, Relativity believes.

“The launch vehicle that we’re going to be flying is going to look totally different from those that are traditionally manufactured,” Ellis claimed. “You get much more organic structures than you normally get. The shapes and forms of what comes out of the printer, and what the launch vehicles look like, will be significantly different.”

Relativity’s 3D-printed Aeon 1 engine, shown on the test stand at NASA Stennis Space Center in Mississippi, is designed to produce 15,000 pounds of thrust. (Relativity Space)
Relativity’s 3D-printed Aeon 1 engine, shown on the test stand at NASA Stennis Space Center in Mississippi, is designed to produce 15,000 pounds of thrust. (Relativity Space)

He gave few specifics about how that would work, but did give one example. “A far fewer part count is a real advantage,” he said. “You get more highly integrated components that look very, very complex, but there are fewer of them. The complexity is driven by software, so you end up with these more organic-looking shapes that are more efficient.”

While the company has been developing technologies to 3D print launch vehicles, it has also been working on an engine for it. The Aeon 1 engine, powered by methane and liquid oxygen and producing more than 15,000 pounds-force of thrust, has undergone tests at NASA’s Stennis Space Center in Mississippi. The Space Act Agreement between NASA and Relativity for those tests was one of the few hints of the company’s activities while the company was in stealth.

“It simplifies a lot of the vehicle architecture,” Ellis said of the choice of propellants. That combination allows for what’s known as “autogenous” pressurization, where the propellants in effect self-pressurize, eliminating the need for helium bottles and plumbing to pressurize the tanks.

The company plans to initially put those technologies together into a rocket called Terran 1. The two-stage rocket will have nine Aeon 1 engines in its first stage and one in its second. It will be capable of placing up to 1,250 kilograms into low Earth orbit.

That payload capacity falls into a gap in the market. It’s much larger than the crop of small launch vehicles under development designed for payloads of no more than a few hundred kilograms, such as Rocket Lab’s Electron or Virgin Orbit’s LauncherOne. But it’s far smaller than the large vehicles in development or operation by companies like Blue Origin, SpaceX and United Launch Alliance.

Ellis said he sees Terran 1 as well suited to support the small satellite constellations under development. “We’ve had a lot of private conversations with potential customers who are showing a lot of interest in this payload class,” he said, not naming any specific companies. “We see that payload class being a sweet spot for constellation launch, whether it’s deployment or resupply of them.”

He added that, with the flexibility 3D printing provides to change designs, the company can resize the vehicle to meet market demands better than other vehicles. “Their plans change,” he said of constellation developers, “so we want to be a good partner with them while they’re defining their plans.”

Terran 1 is still several years away from its first flight. Relativity’s current schedule calls for a first launch in early 2021. That timeline, significantly longer than many other vehicles under development, is driven by the new technology needed to make the rocket, Ellis said.

Relativity is still a small, young company. It currently has 14 employees, many of whom are veterans of larger NewSpace companies including Virgin Galactic, SpaceX and Blue Origin, where Ellis worked before starting Relativity. The company is starting to hire more engineers — it expects to have 40 to 50 employees by the end of 2018 — which was one of the reasons why it decided now to open up about its technology and its plans.

That hiring is a mix of both aerospace engineers and those with 3D printing backgrounds, said Jordan Noone, Relativity’s chief technology officer and its other co-founder. “Aerospace engineers are some of the best cross-talent engineers out there,” he said, in terms of the broad range of issues they deal with.

The company has raised a little more than $10 million to date. That includes a seed round from Y Combinator, the Silicon Valley business incubator, and billionaire Mark Cuban. It later raised a Series A round led by venture capital firm Social Capital.

Ellis acknowledged the company will need to raise more money to fund both its technology development as well as the introduction of the Terran 1 rocket. “We’re always interested in talking with investors and partners to help with the financing,” he said, but wouldn’t say how much the company will need in the coming years.

Will all the emphasis on 3D printing technologies, though, it raises the question: is Relativity a space company using 3D printing as an enabling technology, or a 3D printing company that sees launch vehicles is the first of many markets?

“There’s no question that if you can fully automate and print a rocket, it’s applicable to a lot of the aerospace industry,” he said. The company is looking into other uses of those printers, although Ellis declined to discuss any specific examples. “But yes,” he said, “the technology is generalizable.”

However, Ellis made clear that Relativity is interested in 3D printing as a means to an end that involves a familiar destination for space enthusiasts. “We have a long-term vision of 3D printing a rocket on Mars,” he said. “That’s been part of the company since day one. It was actually the headline of our Y Combinator application.”

He said there was just one other company he knew of that had a core mission of going to Mars. He didn’t mention it by name, but SpaceX and its founder, Elon Musk, have long emphasized the goal of establishing a human presence on Mars. “We’re the second company saying this is want we want to go do this,” he said. “We’re building a part of the colonization process that no one else is really focusing on as their core technology.”

Could that mean rockets built — or, rather, printed — by Relativity will one day be launching people to Mars? “Not yet,” Ellis said. “How that ends up happening we’ll talk about later.

Jeff Foust writes about space policy, commercial space, and related topics for SpaceNews. He earned a Ph.D. in planetary sciences from the Massachusetts Institute of Technology and a bachelor’s degree with honors in geophysics and planetary science...