On Friday, the US Space Force said it would launch two critical Global Positioning System missions on a used Falcon 9 rocket next year.

Doing so will save the military $52 million, officials said, as SpaceX agreed to lower compensation for the two missions in return for flying used hardware. This represents a significant step by the Space Force toward validating the use of flight-proven first stages of a rocket for the most critical national security missions.

“We’re looking forward to this journey with SpaceX as we get even more experienced with them and reusable hardware,” said Walter Lauderdale, Space and Missile Systems Center Falcon Systems and Operations Division chief, in a call with reporters.