The notion of reusing rockets finally went mainstream in 2020. As the year progressed, it became clear that SpaceX launch customers have gotten a lot more comfortable with flying on used, or "flight-proven," first stages of the Falcon 9 rocket. One commercial customer, Sirius, launched its XM-7 satellite on the seventh flight of a Falcon 9 booster in December. Also, the first national security payload flew on a reused booster last month when the US National Reconnaissance Office launched its NROL-108 mission on the fifth flight of a Falcon 9 first stage.

NASA, too, agreed to fly future crewed missions to the International Space Station—beginning with the Crew-2 spaceflight in the spring of 2021—on used Falcon 9 rockets. And the US Space Force said it would launch its GPS III satellites on used boosters in the future as well. These are among the highest-value missions the United States has. //

NASA deserves credit for pioneering work in reusable spaceflight. The space shuttle was the world's first partially reusable launch system, with the orbiter and solid rocket boosters capable of multiple flights after significant refurbishment. But it wasn't cheap—the best independent estimate of the shuttle's cost over the lifetime of the program is about $1.5 billion per launch.