An internal view of a prototype carbon-fiber fuel tank in development for SpaceX's Mars-bound Interplanetary Transportation System. SpaceX

Here’s What Elon Musk Said During a Reddit AMA on SpaceX and Mars

Oct 24, 2016

Last night, SpaceX CEO Elon Musk spent about two hours answering questions from Reddit users about the Interplanetary Transportation System, or ITS. The ITS is the core component of Musk’s plan to not only take humans to Mars, but to establish a self-sufficient colony there. He first outlined the plan in detail late last month at the International Aeronautical Congress (IAC) in Guadalajara.

The session, known as an Ask Me Anything (AMA), was a little understated by Musk standards—he only answered about 15 questions. But there were a few tantalizing gems. Here are the biggest things we learned:

They’re already testing components. Musk says that “in the coming weeks,” SpaceX will take a prototype of the Mars booster’s fuel tank out to sea on a barge and “take it up to 2/3 of burst pressure” to test it. The fuel tank is the size of a small office building and made out of an advanced carbon-fiber composite, one of the many entirely new technologies SpaceX is using or developing for the mission.

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Mars launch equipment will be easy to reuse. Musk wrote that “the big [ITS] booster will have an easier time of things than Falcon, as the mass ratio of the stages is lower and it will have lower density. Net result is that it won’t come in quite as hot and fast as Falcon [when landing on Earth], so Falcon should be a bounding case on the big booster.” Reusing ITS components is the linchpin of Musk's plan to make colonizing Mars feasible. He has said that eventually, a trip to the Red Planet could cost under $100,000.

Mars will look cool. Musk described future Mars surface habitats as geodesic domes built from glass panes, with mining droids digging pressurized caves to house industrial operations.

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Unscheduled trips to Mars will be possible. Musk confirmed what some knowledgeable observers had gleaned from ship specifications presented at IAC. The ITS rocket’s specifications should make it possible to fly between Earth and Mars outside of the so-called “synodic period,” when the two planets are aligned, as long as it’s not carrying a full payload. Because the planets only align once every 26 months, this capability could be vital in the case of medical or mechanical emergencies on Mars.

They’re probably changing the name. Musk said that “ITS just isn’t working” as the name for the Mars transit system. He said that internally he’s now referring to the rocket and spaceship as “BFR and BFS.” But as those apparently stand for Big F***king Rocket and Big F***king Spaceship, they’ll probably remain unofficial.

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