New York (CNN Business) Rocket startup Relativity Space has yet to fire anything into space. But customers are already writing big checks.

Relativity, which is building rockets to launch small satellites , said Monday that a company called Spaceflight is purchasing up to six launches. It marked the company's third major contract announcement in just five weeks.

Tim Ellis, Relativity's CEO who co-founded the company just over three years ago, said Relativity is attracting more attention because people are excited about its novel approach to manufacturing. Its rockets will be 3D-printed top to bottom.

"People are really starting to rally around that as the future of rocket technology," Ellis told CNN Business. "3D printing allows us to evolve extremely quickly."

Relativity says it will be able to reconfigure its 3D printers to change the design of its rockets and nimbly respond to satellite companies' needs.

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