If the attempt is successful, the company plans to refurbish and reuse the booster stage, making spaceflight history and paving the way for a significant reduction in the cost of access to space.
Achieving a practical, largely reusable spacecraft has been the holy grail of spaceflight for the past few decades, and for very good reasons. Propellant only makes up a tiny percentage (in the case of a Falcon 9 rocket, about 0.3 percent) of the cost of the craft, so being able to reuse all the hardware for multiple flights could potentially slash the cost of spaceflight by a factor of 10 or more.
NASA has been keeping a close eye on SpaceX's progress on the rocket reusability front, partly to investigate how the space agency might be able to land very heavy payloads on the surface of Mars in the coming years. As SpaceX was contracted to resupply the International Space Station, the space agency had a front seat as it witnessed the first stage of the Falcon 9 rocket attempt several boost-backs through the atmosphere leading to, so far, two successful soft landings in water – during the third and fourth ISS resupply missions, respectively.