WASHINGTON — Relativity Space, a startup using 3-D printing to manufacture small launch vehicles, will move its headquarters to Long Beach, joining several other launch vehicle companies in that Southern California city.

Relativity announced Feb. 28 that it is moving into a 120,000-square-foot facility in Long Beach that will serve as its new headquarters and launch vehicle manufacturing facility. Company officials had said for months that they were looking for a larger facility as they outgrew existing space in Los Angeles.

The company has already started moving people to the facility as well as the 3D-printing systems it uses to manufacture launch vehicle components. Eventually the site will be able to support 300 employees, double the company’s current headcount, and host production of its Terran 1 rocket.

Relativity’s founders said the new factory is the latest step in their efforts to demonstrate how additive manufacturing can reshape the space industry. “I’m confident our autonomous factory will become the future technology stack for the entire aerospace industry,” Tim Ellis, chief executive of the company, said in a statement.

The company expects to perform a first launch of the Terran 1 rocket in 2021 from a site it will develop at Launch Complex 16 at Cape Canaveral Air Force Station in Florida. Relativity currently tests engines at NASA’s Stennis Space Center in Mississippi, and has long-term plans to develop a launch vehicle production facility there.

Relativity will join several other launch companies that have their headquarters in Long Beach, a city once known for aircraft factories. Virgin Orbit set up operations in the city in 2015, when the air-launch project was still part of Virgin Galactic. SpinLaunch, a company working on an alternative, centrifugal launch technology, has its headquarters across the street from Virgin Orbit.

Rocket Lab announced Jan. 14 it was in the process of moving its headquarters from nearby Huntington Beach to Long Beach, setting up a new facility that will also produce Electron rockets and their Rutherford engines and include a mission control center. The company said that facility should be open in the second quarter of this year.

“We liked Long Beach as an area. I think there’s a densification of aerospace talent there,” Peter Beck, chief executive of Rocket Lab, said in an interview during the SmallSat Symposium in early February. “We found a building that was being built that was able to meet our needs.”

“Long Beach has a long heritage of aerospace and space innovation,” said Dan Hart, president and CEO of Virgin Orbit, in a separate interview during the Smallsat Symposium. “The talent is there, and what’s really cool is that the next generation of talent is being trained there, so there will be longevity of innovation.”

“The space economy continues its growth in Long Beach with the addition of Relativity,” said Robert Garcia, mayor of Long Beach, in a statement about Relativity’s move to the city, calling the company’s work “groundbreaking for new jobs and new technologies in the space sector.”

While the city is gaining one space company, it is losing another. Sea Launch, which based its mobile launch platform and command vessel at the Port of Long Beach for more than two decades, is in the process of departing. The launch platform was recently loaded on a special transport ship, which will take it to the Russian city of Vladivostok. S7 Group, which acquired Sea Launch’s assets from RSC Energia in 2016, plans to operate the venture from Vladivostok, but has not set a firm date for resuming launches.