Late Thursday night, Elon Musk tweeted that SpaceX’s next big rocket — the Falcon Heavy — will make its inaugural flight this November. It’s a new launch date for a vehicle that has had many tentative launch dates before, none of which have actually panned out just yet. But perhaps this time, the vehicle may finally fly when Musk says it will.

The Falcon Heavy is a larger variant of SpaceX’s current Falcon 9 rocket. It consists of three Falcon 9 cores strapped together, and will be capable of lofting around 140,000 pounds of cargo into lower Earth orbit. That will make it one of the most powerful rockets in history once it launches. And just like the Falcon 9, the Falcon Heavy will be partially reusable. All three cores are intended to return to Earth and land after launch, in order to be used again for future missions. In fact, SpaceX intends to use two used Falcon 9 cores that have already flown to space as the side boosters for this first flight.

Falcon Heavy maiden launch this November https://t.co/D4Dxq9d6hc — Elon Musk (@elonmusk) July 28, 2017

Yet this first flight was supposed to happen years ago. Originally, the Falcon Heavy was meant to debut sometime in 2013 or 2014, but its maiden voyage has been continuously pushed back since then. In 2015, the company said the rocket would launch in spring of 2016. That didn’t happen, and SpaceX eventually pushed the launch to sometime in late 2016. Then in September of last year, one of the company’s rockets exploded on a Florida launchpad, and the Falcon Heavy’s first flight was put on hold yet again. SpaceX keeps saying the flight will happen this year, and now Musk has set the target month.

First static fire test of a Falcon Heavy center core completed at our McGregor, TX rocket development facility last week. pic.twitter.com/tHUHc1QiKG — SpaceX (@SpaceX) May 9, 2017

But signs actually point to the rocket flying this year, though. In May, SpaceX showed off a video of the core Falcon Heavy booster undergoing a static fire test; that’s when the vehicle’s engines are turned on while the rocket is restrained. And pictures of SpaceX’s hangar at Cape Canaveral, Florida seem to suggest all three rockets that will make up the Falcon Heavy are already on site. Once the rocket is fully integrated, SpaceX plans to launch the vehicle from pad 39A at Kennedy Space Center — a launch site once used for Apollo and Shuttle missions that SpaceX leases from NASA.

it may not be a very smooth flight

However, even if the Falcon Heavy gets off the ground in November, it may not be a very smooth flight, since engineering the vehicle turned out to be way more challenging than originally thought. At a conference this July, Musk noted that combining three Falcon 9 cores together actually triples the amount of vibrations and acoustics the rocket will experience during launch. Because of that, the company had to restructure the center core to handle the new loads. Plus, SpaceX has only been able to test the three boosters separately up until now. But all three rockets — adding up to 27 engines — will need need to ignite simultaneously for the Falcon Heavy to fly. It’s something the company has never tried before and doesn’t quite know what to expect.

Given all these challenges, Musk lowered expectations about how successful this first flight might be. He doubted the Falcon Heavy would make orbit and even suggested it may not get very far at all. “I hope it makes it far enough away from the pad that it does not cause pad damage,” said Musk. “I would consider even that a win, to be honest.”