SpaceX CEO Elon Musk
© Refugio Ruiz / Associated Press
SpaceX Chief Executive Elon Musk answered questions about his plans to send humans to Mars in a Reddit Ask Me Anything session Sunday afternoon that prompted thousands of reader comments.

The question-and-answer session was intended as a follow-up to Musk's speech at the International Astronautical Congress in Guadalajara, Mexico, last month, in which he described plans to send up to 1 million people to Mars and turn humans into a multiplanetary species within 40 to 100 years.

His vision involves massive, reusable rocket boosters launching spaceships into a "parking orbit" where they are later refueled by propellant tankers. Eventually 1,000 spaceships carrying 100 people each would embark en masse for the Red Planet.

But there are fewer details on what they would do once they arrive. Musk has said a refueling station would be established on Mars to harvest methane fuel for the rocket so settlers could come back to Earth.

On Sunday, Musk said Hawthorne-based SpaceX would establish a refueling station first by sending its Dragon spacecraft on scouting missions, and later sending a spaceship laden with equipment to build the station.

The first crewed mission would be tasked with constructing a "rudimentary base" and completing the propellant plant.

Musk also described his vision for human habitats on Mars.

"Initially, glass panes with carbon fiber frames to build geodesic domes on the surface, plus a lot of miner/tunneling droids," he wrote. "With the latter, you can build out a huge amount of pressurized space for industrial operations and leave the glass domes for green living space."

He added that he hoped to release more details of Mars habitats when there were "actual live mock-ups."

"Maybe in a year or two," Musk said.

SpaceX already has completed development work on a massive, carbon-fiber fuel tank for the Mars ship, and it has test-fired the Raptor interplanetary transport engine, which is powered by methane fuel.

SpaceX has said it could send an uncrewed Dragon spacecraft to Mars as early as 2018 to test aspects like landing capabilities and navigation.

At the space conference in Mexico, Musk said the first manned Mars mission could launch in late 2024 with arrival at the Red Planet in 2025, though he acknowledged that date was an "aspiration."

On Sunday, Musk said the first crewed mission would have about a dozen people "as the goal will be to build out and troubleshoot the propellant plant and Mars Base Alpha power system."