SpaceX's Mars colony plan: How Elon Musk plans to build a million-person Martian city

Artist's illustration of a SpaceX colony ship arriving at Mars. The company aims to help establish a million-person city on the Red Planet.  (SpaceX)

Elon Musk has put his Mars-colonization vision to paper, and you can read it for free.

SpaceX's billionaire founder and CEO just published the plan, which he unveiled at a conference in Mexico in September 2016, in the journal New Space. Musk's commentary, titled "Making Humanity a Multi-Planetary Species," is available for free on New Space's website through July 5.

"In my view, publishing this paper provides not only an opportunity for the spacefaring community to read the SpaceX vision in print with all the charts in context, but also serves as a valuable archival reference for future studies and planning," New Space editor-in-chief (and former NASA "Mars czar") Scott Hubbard wrote in a statement. [ SpaceX's Interplanetary Transport for Mars in Images ]

Musk's Mars vision centers on a reusable rocket-and-spaceship combo that he's dubbed the Interplanetary Transport System (ITS). Both the booster and the spaceship will be powered by SpaceX's Raptor engine, still in development, which Musk said will be about three times stronger than the Merlin engines that power the company's Falcon 9 rocket.