STENNIS SPACE CENTER, Miss.—David Giger bounded up 26 steel steps and emerged onto a rocket engine test platform. Off to his left, an unbroken stand of stately pine trees spread out over the Mississippi lowlands. Straight ahead, Giger had a clear view of two Apollo-era test stands through the trees. “It’s quite a view,” he said.

Here, the past meets the future. Giger and his company, Relativity Space, seek to create the most futuristic of rockets. To do so, they have come to the NASA center where rocket scientists tested the mighty engines that carried humans to the Moon half a century ago. Relativity has, over the last two years, steadily occupied more buildings and test stands here as part of its quest to build a rocket made almost entirely of 3D-printed parts. And if that goal were not fantastical enough, Relativity also seeks to automate as much of the rocket assembly and test process as possible, with the ultimate goal of additively manufacturing a rocket on the surface of Mars.

It is a wild, seemingly impossible dream—and yet it has captured the fancy of aerospace investors. Relativity has raised $185 million in four years and hired industry leaders like Giger. Now the program manager for the company’s Terran 1 rocket, Giger spent more than a decade at SpaceX, where he led development of the Crew Dragon spacecraft. Today he superintends Relativity’s plans for launching its first rocket into space, perhaps as early as next year. So as we stood on top of the E-4 test stand in Mississippi last month, I tried to do more than simply admire the view.

I wanted very much to see if Relativity Space could possibly be for real.

Relativity's origins

The company’s co-founder, Tim Ellis, grew up in Plano, Texas. To pass the time during his early teenage years in the sprawling but rather dull suburb north of Dallas, Ellis played with LEGOs. Passionately. For 14 to 16 hours a day, he would design his own spaceships from large piles of black LEGOs (because they looked most “cool”). He’d build his own designs, admire them, and then break them apart. To this day, one of Ellis’ thumbs is permanently bent backwards from this effort.

This mix of creativity and desire to build things led Ellis to the University of Southern California in 2008, where he majored in aerospace engineering. While there he got involved with the university’s Rocket Propulsion Lab, a student group that builds amateur rockets. He befriended another aerospace engineer, Jordan Noone, who would go on to lead the club as it sought to become the first student organization to launch a rocket beyond the edge of space, 100km above the Earth’s surface. Although they failed, their experiences setting off rockets in Mojave, California, and Black Rock, Nevada, led the pair to prestigious aerospace internships and then jobs. Ellis would go to Blue Origin and Noone to SpaceX.

Ellis worked full time at Blue Origin for two years, from 2014 to 2015, in the propulsion department. At the time the company had moved deep into testing the BE-3 engine and started preliminary work on the much larger BE-4 rocket engine. While at the company’s headquarters outside Seattle, Ellis looked for ways to bring additive manufacturing into the production process. “I started the metal printing program there,” Ellis said. “I was kind of a young, optimistic engineer. I thought printing was going to take off and replace the entire factory.”

It didn’t. Ellis and Noone began talking to one other regularly, during their late-evening commutes home. They spoke about the slow pace of rocket manufacturing. Ellis lived in downtown Seattle, and Noone commuted from SpaceX’s headquarters in Hawthorne, California, to Pasadena. Both were just at the beginning of their careers, trying to establish themselves at companies already considered technology leaders in the space industry. Perhaps it was because they were young—neither was even yet 25 years old—but they felt as though things weren’t moving fast enough. Ellis and Noone looked at the rockets and spacecraft being built at SpaceX and Blue Origin, and they saw processes that were still labor intensive. They saw untapped potential in the emerging technologies of 3D printing and automation.

“Initially, we were just conceptually talking about things,” Ellis said of the late-evening phone calls. “Eventually we realized we both wanted to have a company that was all-in on the technology, to really achieve breakthroughs.”

So they went for it. Ellis and Noone quit their jobs at the end of 2015. A few days later, at the beginning of the new year, they founded Relativity Space to bring about the future they envisioned.

Ellis, who took the role of chief executive officer, remembers the first email he sent from his new Relativity Space account. It was to Mark Cuban, the owner of the Dallas Mavericks and an investor famed for his starring role on the television show Shark Tank. They shared a background in North Texas, and Cuban invested in technology start-ups, so Ellis figured his out-of-the-blue effort was worth a shot. He received a reply five minutes later. Initially, Ellis asked for $100,000. They began to talk.

“I felt like I was on Shark Tank,” Ellis said. “He ended up writing us a check for $500,000.”

Soon, Ellis and Noone were accepted into Y Combinator, a prestigious program that provides investment opportunities and advice to start-up companies. The initiative has an infamously low acceptance rate. Over the next three months, the pair of engineers began to hammer out their idea for a company that would 3D print its rockets, and they developed the first prototype of their Stargate printer to demonstrate its ability to print real hardware. At the end of this period, they participated in the program’s Demo Day to pitch their ideas to many of Silicon Valley’s most notable investors.

After the program, Ellis and Noone set themselves a hectic schedule to see if they could raise enough money to make Relativity a going concern. Over six weeks, Ellis said, they held 90 in-person meetings or phone calls to explain their plans in depth and woo potential investors. After this, Relativity Space raised $10 million in series A funding. They were a real company.