The previous design iteration of BFS called for flat tails to connect the tanker and the passenger version and facilitate propellant transfer through acceleration.

But the new version is depicted to have three large, unmovable tailfins, doubling as landing struts, reaching well beyond the fuselage.

How can two such ships dock together?

Are they going to rotate 180 degrees with respect to each other around the longest axis? Or dock by nose? Or will the tanker version have different fuselage? (as it has not go to Mars and land there)

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    $\begingroup$ Couldn't one ship just rotate 30 degrees on the long axis relative to the other one? Then the fins wouldn't collide. Note: this comment should not be construed to imply that I think this ship will ever fly. $\endgroup$ Sep 18, 2018 at 21:03

1 Answer 1


I think your first mistake is stating "that the three large tailfins are unmovable"

Elon Musk specifically noted that the top fin is unmovable and mostly for symmetry. The two side fins will move as the flight circumstances dictate. He even mentioned how much power it takes to move them in the Lunar passenger announcement video.

Since they are movable I do not think they will be a problem to docking the tails and transferring fuel.

  • $\begingroup$ I don't think their ability to move will make any difference. They don't seem to be able to move up and out of the way above the engines, so rotating them out of phase from each other is the only way the engines will be able to get close to eachother. $\endgroup$
    – Sdarb
    Sep 20, 2018 at 18:41

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