This afternoon, SpaceX is set to launch a used Falcon 9 rocket for the second time ever. The rocket will take off from SpaceX’s launchpad in Cape Canaveral, Florida, and it’s sending a communications satellite into a super-high orbit around Earth. The launch is scheduled to occur as early as 3:10PM ET, but SpaceX has until around 4PMET to fire up the Falcon 9. You can watch a live stream of the launch above — coverage should begin around 3PM ET.

The satellite being launched today is BulgariaSat-1, which is owned and operated by Bulgarian TV service provider Bulsatcom. It’ll be riding into orbit on the same Falcon 9 that SpaceX used to launch 10 satellites for Iridium in January of this year.

That’s SpaceX’s primary mission. But the company will also once again try to land the Falcon 9 rocket’s first stage — the 14-story core that contains the rocket’s main engines and fuel — on a drone ship in the Atlantic Ocean. If successful, this would be the seventh time SpaceX has landed one of its rockets at sea, and the 12th overall.

Don’t expect the attempt to be easy, though. Because the rocket is sending BulgariaSat-1 to such a high orbit, it will experience more force and heat upon reentering the Earth’s atmosphere than any other Falcon 9, according to a tweet from Elon Musk. “Good chance rocket booster doesn't make it back,” Musk wrote.

SpaceX already demonstrated that its Falcon 9s are capable of launching, landing, and launching again when it sent a recycled rocket to space in March. Another successful launch and recovery of a recycled rocket would help the company move beyond the proof-of-concept phase of reflying boosters and move toward treating its rockets as truly reusable. This means SpaceX doesn’t have to build a completely new rocket for every launch, but it also significantly lowers the price tag for the company’s customers.

Of the dozen or so launches scheduled for the remainder of 2017, SpaceX has said that nearly half of those missions could use recycled rockets. SpaceX’s push for reusability doesn’t stop with the rockets, either. The company reflew one of its Dragon cargo capsules for the first time ever earlier this month.

Today’s launch was originally slated to take place last weekend, but it was scratched by SpaceX because of a problem with valve in the fairing, the cone at the top of the rocket that holds the satellite. The delay means it will be a busy weekend for SpaceX: it also plans to launch a group of satellites for the company Iridium on Sunday from the Vandenberg Air Force Base in California. It would be the quickest turnaround ever for SpaceX, which has typically launched rockets weeks or months apart.

Update June 23rd, 1:05PM ET: SpaceX has pushed the launch time back one hour. This post has been updated.