SpaceX’s Mars plans are about to kick into overdrive.

Two years after Musk first unveiled the BFR in Australia, the vehicle now known as Starship is expected to receive a big unveiling later this month. The event, expected to be held at the company’s Boca Chica launch facility in Texas, will give founder Elon Musk and his team a chance to explain more about the project.

The Starship has been referred to as a Mayflower-class vehicle, thanks to its ability to move up to 100 people at a time into orbit. It’s expected to supersede SpaceX’s existing vehicles, while also paving the way for more ambitious missions. Musk has described manned trips to Mars, trips around the moon for private individuals, and even trips beyond to further reaches of the solar system.

It all starts with the Starship’s prototypes, the bizarre stainless steel constructions that have poked their head out in Texas and Florida. In April, a shortened version of the Starship dubbed “Starhopper” completed a tethered firing In July, the vehicle described by Musk as “R2D2’s dad” flew 20 meters into the air. Last month, it flew 150 meters into the air in a spectacular visual display.

SpaceX is aiming to build a city on Mars by 2050, and the Starship could be the key. Here’s what comes next for the rocket project.

SpaceX Starship: The Next Few Months

The biggest date for the general public is likely to be September 28. This will be the long-awaited update on the current state of Starship progress and future plans. It’s also the anniversary of the first time SpaceX reached orbit, when the Falcon 1 took off from the South Pacific in 2008. In the space of 11 years, SpaceX will have gone from tiny rocket-tinkerer to unveiling its prototype of a rocket that can take humans to Mars.

Powering the Starship is the Raptor, an engine fueled by liquid oxygen and methane. The use of more common materials enables astronauts to harvest fuel from other planets and set up depots, creating a planet-hopping network throughout the solar system. SpaceX has been gradually ramping up the speed of Raptor production, with Musk stating the goal is to produce a new engine every 12 hours by the end of the year. Considering each Starship needs around 40 engines, that’s perhaps a sensible goal to meet demand.

Evidence suggests the company is about to complete enough engines to finish one orbital prototype Starship. The “Starhopper” that flew last month used the firm’s sixth engine, or “SN6,” to complete its hover. NASASpaceFlight reported in August that “SN7” is on the test stand, and is not believed to be tied to any Starship vehicles.

A Raptor engine test fire. SpaceX

Versions eight through 13, the publication explained, are expected to be used to power the two prototype ships under construction in Florida and Texas, meaning three engines each. Musk mentioned on Twitter at the end of August that the team is about to ship “SN10,” but didn’t expand on or confirm what this engine would be used for. If the NASASpaceFlight report proves accurate, SpaceX is about to have enough Raptor engines to finish one of the two Starship prototypes.

That chimes with Musk’s other comments about the expected rate of progress over the next few months. The team is aiming for a flight of 20 kilometers in October using the Mk.1 Starship prototype, increasing the height more than 100-fold compared to the last hop that used the “Starhopper.”

The Raptor engine is also expected to reach a state where it can support orbital missions. Musk stated that the team is around two to three months away from reaching this capability with its engines. Musk has suggested that Starship Mk.1, fresh from its October hop, will attempt an orbital flight “shortly thereafter.”

The Starship taking off. SpaceX

SpaceX Starship: Where It Goes From Here

SpaceX is expected to host its first commercial launch with the Starship in 2021, assisting a telecommunications company. In 2023, the rocket is expected to send Japanese billionaire Yusaku Maezawa and a team of six to eight artists on a trip around the moon. The first manned mission to Mars is expected at some point later.

But while the Starhopper has a diameter of 30 feet, and the final Starship is expected to measure nearly 400 feet including the Super Heavy booster, Musk is already thinking bigger. Musk suggested that the next iteration could “probably” measure 18 meters in diameter, or 59 feet.

The first Starship is expected to offer the same amount of pressurized air space as an Airbus A380 plane. With a larger-diameter plane on the cards, perhaps the ambition to send a million people to start a Mars city could come even sooner.