SpaceX CEO Elon Musk is talking up his Starship Mk1 prototype super-rocket in Texas, less than a week in advance of an eagerly awaited update on his plans for Starship trips to the moon, Mars and beyond.
Today’s sneak preview came in a flurry of tweets addressing some of the finer design points for Starship Mk1, which looks like a silvery silo equipped with rocket fins as it sits at SpaceX’s Boca Chica facility in South Texas. The 30-foot-wide, roughly 150-foot-tall prototype — and a similar Mk2 structure taking shape at SpaceX’s site in Florida — are meant to blaze a trail for an even bigger two-stage rocket, with the pointy-ended Starship sitting atop a Super Heavy first-stage booster.
During a live-streamed presentation that’s set for Saturday at the Boca Chica site, Musk is expected to discuss plans for testing and flying the Starship system over the next few years.
Japanese billionaire Yusaku Maezawa has already struck a deal with SpaceX to take a Starship flight around the moon by the mid-2020s, and is reportedly planning to sell a multibillion-dollar stake in his fashion retail company to cover the cost.
Musk has said Starship (previously known as the BFR) could take on flights to Mars by the mid-2020s, plus crewed trips to the moon and supersonic point-to-point trips between destinations on Earth. He didn’t address those beyond-Earth visions in today’s tweets, but in a discussion with his followers, he did get into the nuts and bolts of Starship design — including what’s going to be packed inside the prototype’s nose cone, or fairing.
Musk also said there are some aspects of the design that he’s not yet “fully bought into.” Here’s how the Twitter thread spun out:
Adding the rear moving fins to Starship Mk1 in Boca Chica, Texas pic.twitter.com/HWLihqihph
— Elon Musk (@elonmusk) September 22, 2019
Will the fairing be stacked by the 28th?
— Anthony Iemole 🇺🇦 (@SpaceXFan97) September 22, 2019
Yes. There’s a huge amount of hardware in the tip of the faring that being integrated on the ground, which is why we haven’t closed it out.
— Elon Musk (@elonmusk) September 22, 2019
Nose tip has forward movable fins, cold gas attitude control thrusters, header tanks for landing, composite pressure vessels, several large batteries, etc. Placed up there to balance high mass of Raptors & rear fins at the bottom.
— Elon Musk (@elonmusk) September 22, 2019
So it appears as two’s the magic number on this beast! Makes sense. Will they tuck in on ascent when attached to super heavy? 3 landing legs was super aerodynamically unstable on ascent (full stack) and also unstable on decent when landing.
— Everyday Astronaut (@Erdayastronaut) September 22, 2019
Stability is not an issue with 3
— Elon Musk (@elonmusk) September 22, 2019
When doing the final landing tail first with three huge landing legs / fins in the front of the airstream wouldn’t have been unstable? IS KERBAL LYING TO ME?!?!? 🤓😂
— Everyday Astronaut (@Erdayastronaut) September 22, 2019
Stability is controlled by (very) rapid movement of rear & fwd fins during entry & landing, as well as ACS thrusters. The smaller leeward “fin” would simply be used as a leg.
— Elon Musk (@elonmusk) September 22, 2019
Current analysis, which I’m not fully bought into, suggests that 2 rear fins with separate airframe-mounted legs will be lighter, so this is the plan for Mk1/Mk2
— Elon Musk (@elonmusk) September 22, 2019
Does this modification of the rear fin setup affect the fore (or top) fins or will they stay the same?
— Kalzsom (@Kalzsom) September 22, 2019
For aero control, it comes down to % of cross-sectional area moving vs not. Flexible as to whether front or rear, so long as within bounds of center of mass & pressure.
— Elon Musk (@elonmusk) September 22, 2019
Can the body flaps move in an axis other than dihedral? If they can only articulate dihedrally, how does that work when it gets to the tail down portion of landing? Doesn’t that portion of descent require some kind of canard articulation through the X axis?
— Everyday Astronaut (@Erdayastronaut) September 22, 2019