A computer rendering shows Relativity Space's rocket Terran launching from Cape Canaveral's LC-16 launchpad. Relativity Space

Relativity Space, a three-year-old start-up that aims to build rockets using 3D printers, announced a contract Thursday with the U.S. Air Force to build and operate a launch facility at Cape Canaveral Air Force Station in Florida. "Cape Canaveral is the premier launch site in the U.S.," Relativity CEO Tim Ellis told CNBC. The five-year "multi-user" agreement means Relativity can begin operating out of Launch Complex 16, or LC-16, the historic location of hundreds of American space launches. There is no monetary exchange or lease payment to the Air Force for this contract. The agreement includes an option to extend for an exclusive 20-year term. "We have a very clear path toward having this be an exclusive use site for us in the future," Ellis said.

A computer rendering shows what LC-16 may look like with Relativity Space facilities. Relativity Space

The young start-up joins SpaceX, United Launch Alliance and Blue Origin as the fourth private company to have an orbital launch site at Cape Canaveral. LC-16 was built by the Air Force in the 1950s, as a missile test site. Ellis estimates the launch facilities represent more than $10 million worth of existing infrastructure. "We were impressed with Relativity's seasoned team and its innovative approach to space technology and we look forward to working with them as they continue the process to launch the Terran 1 vehicle from Cape Canaveral Air Force Station," said Thomas Eye, the director of plans & programs for the 45th Space Wing of the U.S. Air Force. Relativity's Terran rocket is mid-priced at $10 million per launch. The rocket market is typically divided between light vehicles, at $2 million to $5 million, and heavy vehicles, at $60 million to $400 million. The mid-sized Terran will be 95 percent 3-D printed, with less than 1,000 individual parts. Rockets typically have somewhere around 100,000 or more individual parts. Ellis said the launch site will be ready before they are expected to launch at the end of 2020.

A computer rendering shows what LC-16 may look like with Relativity Space facilities. Relativity Space