This evening, SpaceX will announce the identity of a mystery passenger who has signed on to travel around the Moon in the company’s Big Falcon Rocket, or BFR. This customer will be the first private astronaut in history to go to the Moon (if no one else beats SpaceX to it) and one of a few dozen individuals to have ever gone to lunar space.

While the announcement is intriguing, we’ve been down this road with SpaceX before. In February 2017, Musk announced that the company had signed two paying customers to fly around the Moon on the Falcon Heavy rocket sometime in late 2018. Very few details were ever given about who those individuals were; all Musk said was that they weren’t from Hollywood, and they had both put down a “significant deposit” for the trip. However, during the Falcon Heavy’s inaugural flight this February, Musk admitted that SpaceX was going to skip the Moon trip with Falcon Heavy and go straight to putting people on the BFR instead.

It’s unclear whether this new customer is one of the two Musk was talking about last year. The only clue we have about the passenger is that he or she might be from Japan since Musk tweeted an emoji of the Japanese flag to someone who asked about the customer’s identity. We also don’t know anything about the type of mission this person will be partaking in, other than the fact that it’s a trip around the Moon. Will this person be alone on the trip or have an expert along for the ride? And if this is one of the passengers who signed up to fly on Falcon Heavy, what happened to the other one? Oh, and how much is this person spending on the ride?

Hopefully, SpaceX will provide some answers tonight at the press conference, which is supposed to get underway at 9PM ET. It looks like we may also get an update on the design of the BFR.

The BFR is SpaceX’s next-generation vehicle that the company hopes to fly to the Moon and Mars. Its design calls for a truly massive vehicle, one that towers 348 feet high, or the height of a 35-story building. It’s currently in development at the Port of Los Angeles near SpaceX’s headquarters, and the company has shown off and tested a few key pieces of hardware that have been developed for the vehicle, such as its giant propellant tanks and sub-scale versions of the rocket’s engines.

Musk gave numerous details about the BFR’s design at last year’s International Astronautical Congress, an annual space conference that’s held in the fall. The BFR is actually two vehicles in one: it consists of a huge booster rocket that’s supposed to propel a giant spaceship, the Big Falcon Spaceship (BFS), into orbit. The rocket portion will supposedly be propelled by 31 Raptors, a new type of monster engine that SpaceX has been working on for the last decade. Each Raptor is supposed to produce at least 380,000 pounds of thrust. With all that combined power, the BFR should be capable of putting up to 150 tons of payload into low Earth orbit, according to Musk. It will also use these engines to land back on Earth after launch, similar to the company’s Falcon 9 vehicles.

Meanwhile, the BFS, which should have room for around 100 passengers, was supposed to have six engines of its own that the vehicle will also use to land on the surfaces of other worlds. These engines included two smaller ones optimized for operating in atmospheres at sea level and four that can operate in the vacuum of space. These engines are also crucial for launching the BFS off those other worlds and back into space.

However, all of those design specs may change. When SpaceX announced on Twitter that it would reveal this customer on Monday, the company released a new rendering of the BFS in front of the Moon. And Musk has since tweeted new renderings of the spaceship-rocket combo. Sharp-eyed viewers noticed that the BFS had seven engines, instead of the original six, and that they all seem to be the same size. Additionally, the BFS now seems to be sporting a third fin that wasn’t there before. Musk said on Twitter that the design changed so that the landing legs would extend from the tips of the fins. The renderings also don’t show grid fins on the rocket, which are needed to steer the vehicle back to Earth, but Musk said they forgot to add them to the rendering.

But perhaps the biggest questions SpaceX should answer tonight revolve around the company’s finances and if it has the necessary funds to create the rocket. Musk once cited that the BFR’s development could cost around $10 billion, though it’s unknown if that number has changed. He also said that he thinks SpaceX can fund it with money from existing NASA contracts and by launching commercial satellites. Then, once the vehicle is built, it could be used to send cargo to the International Space Station, do Moon missions, and even send people on trips across Earth. However, SpaceX is known for selling rockets for less money compared to its competitors, and while the company claims it’s cash-positive, it’s unclear if its profits are enough to make a big dent in the BFR’s development.

Then there’s the big question of when. Musk, known for his optimistic timelines, said that he believes the BFR could make its first trip to Mars in 2022. And SpaceX president Gwynne Shotwell noted this month that the BFS portion of the vehicle would perform short hop tests by late next year. Those tests will likely involve launching the spaceship to a certain altitude above Earth and then attempting to land it back on the ground to see if it can touch down gently. As for how this Moon trip will fit into that timeline, that’s a question Musk will hopefully answer tonight.

Of course, developing rockets takes time. The Falcon Heavy took more than twice as long as Musk originally predicted. In 2011, he suggested a launch in 2013 or 2014, but it finally got off the ground for the first time this year. Serious BFR development seems to have gotten underway in the last few years, so that doesn’t leave much time before the supposed 2022 flight to Mars. It would be helpful if Musk could give updates on BFR milestones to give people a better sense that these dates might hold.

Tonight’s announcement will be live-streamed. Check back at 9PM ET to see what new details SpaceX releases.