Thanks to an influx of capital in the past decade, there are more than 100 young rocket companies estimated to be racing to orbit, hoping to be among the first to sate demand from a new market of smaller spacecraft.

Relativity Space fits squarely among those aspiring rocket ventures but with a twist: The three-year-old start-up is building its rockets almost entirely using two-story-tall 3D printers, unlike any others in the world. While the company is still working toward that first launch, the past year has seen Relativity pile up talent and resources.

Relativity's Terran rocket is aimed at the middle of the launch market – in a weight class between SpaceX's large Falcon 9 rocket and Rocket Lab's small Electron rocket. While both of those rocket makers have reached orbit multiple times, Relativity's first launch is not expected for about two years. And Relativity's valuation of about $100 million, using traditional venture capital metrics, is a fraction of Rocket Lab's more than $1 billion and SpaceX's $30.5 billion.

But a year ago, Relativity had about 10,000 square feet of space, 14 employees and one enormous world-class 3D printer.

Today, Relativity has more 60,000 square feet of real estate, 64 employees and is putting finishing touches on three additional 3D printers, each larger and more advanced than the company's first printer. Among those new staffers are veterans of technology giants: SpaceX, Blue Origin, Tesla, Google's Waymo, Virgin Orbit and more.

"At this point our team is just ridiculously legendary," Relativity CEO Tim Ellis told CNBC. "These are literally the best people in the industry, period."

Relativity added David Giger as vice president of launch vehicle development (he's essentially in charge of building Relativity's rocket) and Tim Buzza as a full-time adviser. Both Giger and Buzza were with SpaceX when the company was less than 50 employees and building its first rocket, the Falcon 1. They also knew Relativity co-founder Jordan Noone while at SpaceX.

"I'm really excited to really dive in with the team and get back into building a launch company ... [as well as] to leverage those lessons learned from Falcon 1, from Dragon as well and help this team push the boundaries" Giger told CNBC.

Relativity also recently brought on Josh Brost, a nine-year veteran at SpaceX who joins the start-up as vice president of government business development. Ellis said that Brost "secured over $3 billion in contract with the U.S. government and commercial entities" while with SpaceX.

"It's really the one-two punch: Brost, the person that was winning billions of dollars in contracts and Giger, the person executing billions of dollars of contracts," Ellis said.