SpaceX and Elon Musk just keep checking off the milestones, and they just accomplished another big one: test firing a used Falcon 9 rocket for the first time, a big step closer toward making Falcon 9 rockets fully reusable. The Falcon 9 rocket stage you see in the video below is the one that already launched and landed during a mission back in May, and now for the first tiem SpaceX has conducted a burn on it for about two minutes and 30 seconds, or the full duration.

That is a big step toward the company’s plans to launch a used rocket this fall, if it can find a customer. In addition, the company will try to reuse a Dragon cargo capsule for a cargo delivery mission to the International Space Station. Musk said he wants to make rocket boosters reusable, which would cause a massive reduction in cost of space flights and therefore lead to a new space age that could greatly accelerate human exploration and activities in space. Today, rockets are discarded after one use, costing the company that makes them huge amounts of money to build a new one for the next mission and making spaceflight very expensive.

SpaceX has so far launched and landed five different Falcon 9 rocket boosters since December 2015, but SpaceX has not yet reused any of them, which it will have to do if it will prove this concept will work. Simply getting the rocket back is not enough, the company must also show they can be used again.

The Falcon 9 used in the May 6 launch sent the Japanese satellite JCSAT-14 into orbit. While the rocket isn’t expected to fly again, it will be critical to understand how the boosters handle another burn.

It also gives SpaceX a leg up competitively, as it is experiencing competition from Amazon.com founder Jeff Bezos, who is spearheading private spaceflight company Blue Origin.

“Falcon 9 is a two-stage rocket designed and manufactured by SpaceX for the reliable and safe transport of satellites and the Dragon spacecraft into orbit,” according to the SpaceX website. “As the first rocket completely developed in the 21st century, Falcon 9 was designed from the ground up for maximum reliability. Falcon 9’s simple two-stage configuration minimizes the number of separation events — and with nine first-stage engines, it can safely complete its mission even in the event of an engine shutdown. Falcon 9 made history in 2012 when it delivered Dragon into the correct orbit for rendezvous with the International Space Station, making SpaceX the first commercial company ever to visit the station. Since then SpaceX has made multiple flights to the space station, both delivering and returning cargo for NASA. Falcon 9, along with the Dragon spacecraft, was designed from the outset to deliver humans into space and under an agreement with NASA, SpaceX is actively working toward that goal.”