Virgin Orbit CEO Dan Hart and Cloud Constellation President Cliff Beek at the World Satellite Business Week in Paris, France sign an agreement for a dozen satellites.

Air-launch rocket builder Virgin Orbit took another step in making low-cost rockets a reality in a new deal with satellite developer Cloud Constellation.

The Virgin Galactic spinoff, which is owned by billionaire entrepreneur Richard Branson, on Tuesday signed an agreement to launch a dozen communications satellites for Cloud Constellation's SpaceBelt system. The rocket company expects to begin delivering on the contract with its LauncherOne system in 2019.

"These missions wouldn't have been possible even a few short years ago," Virgin Orbit CEO Dan Hart said in a statement at the World Satellite Business Week event in Paris.

The low-Earth orbit constellation will be the backbone of SpaceBelt, to create a space-based data storage network. The individual units, considered small by the commercial space industry, each weigh around 400 kilograms or more than 800 pounds.