Standing in front of a gleaming full-scale prototype of SpaceX’s new interplanetary craft—known as Starship—Elon Musk was visibly excited Saturday night as he spoke about his vision for the future of humanity . He posed a simple question: Do we want a future where humanity is out among the stars, or do we want to be forever confined to Earth?

Musk would prefer the former. “I think we should do our very best to become a multiplanetary species and extend consciousness beyond Earth, and we should do it now,” he said before a crowd gathered at the company’s facilities in Boca Chica, Texas, not far from the Gulf of Mexico.

Behind him, the massive prototype towered above the flat Texas landscape, looking, with its stainless steel skin, like something from a 1950s science fiction movie. “It’s going to be pretty epic to see that thing take off and come back,” Musk said of the shiny vehicle that served as the backdrop for his talk, which was his usual mix of grand-scale vision with engineering details about his company’s latest invention.

Within a month or two, Musk said the rocket will blast off—sans crew—to an altitude of 12 miles, then return to the ground to land on its legs.

The prototype, known as Mk1, is one of two identical rockets being assembled by SpaceX as part of an intracompany competition. The other, Mk2, is under construction in Cape Canaveral, Florida. Musk and SpaceX are betting that the competition will improve the final Starship design and speed up the development process.

Musk first teased the idea of an interplanetary craft three years ago at a meeting of the International Astronautical Congress (IAC) in Guadalajara, Mexico, where he spoke about SpaceX’s plan to make humanity a multi-planet species. The plan was nothing if not ambitious. The ship would carry as many as 100 people to Mars at a time, and would be lifted by a separate, massive booster outfitted with dozens of engines. In true SpaceX fashion, both parts would be fully reusable.

“The critical breakthrough that's needed for us to become a spacefaring civilization is to make space travel like air travel,” Musk said on Saturday. “A rapidly reusable rocket is basically the holy grail of space.”

For nearly two decades, he and his team of engineers have worked to make reusability mainstream. The company landed its first rocket in 2015, but took two years to reuse its first booster. Now it routinely does both, launching used boosters more often than new ones.

Musk’s progress report on Starship was timed to coincide with the anniversary of SpaceX’s first successful launch 11 years ago. In the decade since, the company has been steadily launching satellites to orbit and delivering cargo to the International Space Station, and is on the verge of transporting NASA’s astronauts to the space station (delays on that front prompted agency Administrator Jim Bridenstine to put out his own gently scolding statement a day before Musk’s much-anticipated talk).

Each of these achievements has brought SpaceX one step closer to the ultimate goal of reaching Mars. “The point is to inspire the public,” Musk said on Saturday evening. “People need things to be excited about, and space travel is one way to do it.”

To reach orbit the Starship will need to ride atop a “Super Heavy” rocket booster, which will be powered by as many as 37 Raptor engines. The Raptor is SpaceX’s next-generation methane-fueled rocket engine. Boasting twice the thrust of the Merlins that power SpaceX’s Falcon fleet of rockets, Raptor is one of the most powerful rocket engines ever made. (SpaceX's competitor, Blue Origin, is also developing a methane-fueled engine called the BE-4.)

Three Raptors will power the Mk1 Starship on its initial launch to 12 miles altitude later this year, while the orbital prototypes that follow will pack six. Standing over 160 feet tall and weighing roughly 1,400 tons (when fully fueled), the Starship is a behemoth even without the Super Heavy. Once mated, the duo will be among the most powerful rockets ever made, in a class with NASA’s Saturn V moon rocket and the final version of the agency’s yet-to-fly Space Launch System. During Saturday’s presentation, Musk boasted that the Super Heavy/Starship combo will produce twice the thrust of the Saturn V.

SpaceX has spent the last three years tweaking the Starship’s design. Like the Atlas rockets of the early space program, its skin will be made of stainless steel as opposed to carbon fiber composites, a design decision Musk discussed at length on Saturday . Aside from the massive price difference ($130,000/ton for carbon fiber versus $2,500/ton for steel), a metallic vessel won’t need as much thermal shielding (the 301 stainless steel alloy stands up to reentry heating better than other materials), so the overall vehicle is much lighter than you would expect with steel.

With its reflective skin and retro-looking fins, Starship will be unlike anything ever sent to space. Musk describes the vehicle as a chimera of sorts—a cross between a rocket booster, a crew capsule, and a skydiver. Like SpaceX’s other rockets, Starship is capable of landing itself, but how it returns to Earth is very different—the craft will essentially belly flop through the atmosphere before landing upright on its landing pad.

“This is quite a new approach to controlling a rocket,” Musk said on Saturday. “It’s much more akin to a skydiver. It will look totally nuts to see that thing land.”

In August, SpaceX tested Mk1’s predecessor, a simpler prototype called Starhopper. Outfitted with a single engine, and looking like a flying water tower , Starhopper soared above the Texas landscape for nearly a minute. It rose to an altitude of 500 feet, flew sideways, then landed in a different spot. The Mk1 vehicle will attempt the same thing as soon as next month.

So far, Starship and Super Heavy have just one flight on their manifest. Last September, Musk revealed that Japanese billionaire Yusaku Maezawa booked the first trip aboard Starship—a jaunt around the moon scheduled to occur sometime in 2023. Not much else has been said about that plan since. But during Saturday’s presentation, Musk thanked Maezawa for providing much of the money that has enabled the rapid development of Starship.

The ever-optimistic Musk says that Starship could start carrying people very soon. “I think we could potentially see people flying next year,” he said. Musk has a habit of making big promises on unrealistic timelines, and, despite SpaceX’s impressive achievements, putting humans on Mars still seems like fantasy.

But this time last year, the site of his speech was just a mound of dirt, and now it’s sprouted a suborbital vehicle the company says will fly in just a few weeks. Perhaps the notion of boots on Mars isn’t as outlandish as it sounds.