“We are building the first ship, the first Mars or interplanetary ship, right now,” Musk told screenwriter Jonathan Nolan on stage at the South By Southwest conference in Austin Sunday. “I think we’ll be able to do short flights, short up and down flights, sometime in the first half of next year.”

That timeline is surprisingly aggressive, and Musk admits that “historically people have told me my timelines have been optimistic.” The Falcon Heavy’s first launch was pushed back several times, and the Mars rocket is several times larger and more complex. The most that the public has seen of the rocket at this point is a design concept and a massive carbon-fiber fuel tank.

The rocket is currently code named BFR, of which Musk said: “It’s a bit of a Rorschach test in acronym form. [But] it is very big.”

Get Data Sheet, Fortune’s technology newsletter.

However optimistic the timeline, the BFR’s first test flights would just be a preview of an actual trip to Mars. SpaceX’s most recent plan hopes to send the first cargo missions to Mars in 2022.

Musk predicts that the first flights of the ship will unleash a flood of energy from other shipbuilders. “Once we have it, we’ll have a sort of point of proof, something that other countries and companies will go and do.” Musk says that he expects those other entities to eventually build interplanetary transport vehicles of their own.

Musk also reiterated that he sees SpaceX’s role as simply creating the pathway to Mars, and that he hopes entrepreneurs will build much of the infrastructure of a future Mars colony, including everything from “iron foundries to pizza joints to nightclubs.” He also speculated that “most likely, the form of government on Mars would be somewhat of a direct democracy,” in which residents would vote directly on particular issues.

Correction: This article previously indicated SpaceX planned to send crewed missions to Mars in 2022. The current timeline has only cargo missions queued up for that year. We regret the error.