Eleven months ago—just after SpaceX astonished the world by launching and landing its titanic Falcon Heavy rocket while beaming back images of a red Tesla leaving Earth orbit—company founder Elon Musk had already begun to look beyond the moment.

The Falcon Heavy was a big, capable rocket. But it wasn't large enough to fulfill his aspirations of reaching Mars. Neither did the company have a spacecraft capable of landing there. "They really need to be way bigger than that," Musk said of the Falcon Heavy rocket at the time. Moreover, he noted that the launch in early February 2018 had confirmed the company's ability to model rocket launches on computers. "It gives me a lot of faith for our next architecture. It gives me confidence that BFR is really quite workable."

In this case, BFR stood for Big Falcon Rocket. This vehicle has since been renamed "Super Heavy," and it will launch the spacecraft SpaceX is building to land on Mars, take off from Mars, and land back on Earth. The rocket is certainly titanic in size, but the spacecraft it will carry—since branded Starship—is the greater innovation. No nation or company has ever built a single vehicle capable of flying dozens of people into space (especially deep space), landing on distant worlds, and then flying back to Earth.

Since 2016, Musk has shared several different versions of the Starship in presentations. However, we are now starting to see test hardware. During the last two months, observers near the company's site in southern Texas have been taking photos of a silvery test-version of Starship that the company will use for a series of take-off and landing tests this spring. And Musk has been sharing some of these photos (and a lot of details about them) on Twitter.

A real geek

Yes, Twitter. When Elon Musk is not saturating his Twitter feed with memes, taunting the Securities and Exchange Commission, or touting Tesla, he can be found sharing all manner of rocketry details on the social media site. Musk will share a photo or make some statement or observation about his booster or spacecraft, and rocket fans will pounce with all manner of in-the-weeds questions. Often, Musk will respond in kind with his keen acumen.

These exchanges offer a bit of insight into the man and his passion for rocket geekery. (To offer one other buttressing detail: When ones goes to interview Musk about space, the advice a reporter gets is pretty simple: ask about the technical details. Musk doesn't want to answer questions like, "How does it feel to launch the world's biggest rocket?" Neither does he want to reflect on the past. He wants to dig into things like supersonic retropropulsion, direct injections to geostationary orbit, or the cryogenic properties of stainless steel.)

Elon Musk is a lot of things—an inspirational leader, resolute, brilliant, intimidating, brusque, and sometimes lacking in empathy. He has a rare quality of identifying problems in the world, finding solutions that he believes will make the world a better place, and then willing (and spending) those solutions into reality. But above all these things, Musk is a geek at heart, in the sense that geek means a "knowledgeable and obsessive enthusiast."

He is knowledgeable about rockets and obsessed with their details. In sharing all of these tidbits about Starship, Musk is telling the world that he is really (really) freaking excited about Starship. This, after nearly two decades of work to get to this point with SpaceX, is his Mars spacecraft, and he wants everyone to know about it.

So what do we know so far?

Musk began tweeting about Starship in earnest three days before Christmas. He apparently visited the test site in Boca Chica Village, Texas, a couple of days before the holiday to see the work up close. Efforts have proceeded since then, often at night, at a seemingly frantic pace as the company works to get a "test hopper" up and running. Musk has been receiving twice-weekly updates on progress at the South Texas-based facility.

This program will be similar to the "Grasshopper" test program SpaceX conducted in 2012 and 2013 in central Texas. That program intended to improve the company's ability to vertically land the Falcon 9 rocket. In this case, SpaceX will seek to fly a prototype version of the Starship to an altitude of about 5km and then land it. The test version of the vehicle has a full body diameter of nine meters but a truncated height.

Stainless Steel Starship pic.twitter.com/rRoiEKKrYc — Elon Musk (@elonmusk) December 24, 2018

Since December 22, Musk has tweeted about the Starship vehicle more than two dozen times. Among the details that can be gleaned from those tweets:

The vehicle's exterior will be made from a stainless-steel alloy that will not buckle and will remain stable on the launchpad even when unpressurized. The strength and weight of "full hard stainless" at cold temperatures is slightly better than carbon fiber, at room temperature it is worse, and at high temperature it is vastly better.

The metallic skin of Starship will get too hot for paint, so it will have a stainless mirror finish. It will need much less shielding as a result, and areas that take the brunt of atmospheric entry heating will be activity cooled with residual liquid methane. As a result, "Starship will look like liquid silver."

A "radically redesigned" Raptor engine will be ready for test firing early this year. This is the engine that will power both the first stage "Super Heavy" as well as the Starship. For the test hopper, there will be three Raptor engines (there will be seven on the full Starship). Engines currently on the vehicle are essentially mock-ups. The first engine for hopper test flights "is almost finished assembly in California."

SpaceX developed a "superalloy" to withstand the incredible pressures inside the Raptor engine and its hot, oxygen-rich gas. "Our superalloy foundry is now almost fully operational. This allows rapid iteration on Raptor."

Musk expects the first hopper tests to occur in March or April of this year, sooner than expected. "I will do a full technical presentation of Starship after the test vehicle we're building in Texas flies."