For Elon Musk, Starship is really a Mars ship. He envisions a fleet of Starships carrying settlers to the red planet in the coming years.

And for that eventual purpose, Starship, under development by Mr. Musk’s SpaceX rocket company, has to be big. Stacked on top of what SpaceX calls a Super Heavy booster, the Starship rocket system will be, by pretty much every measure, the biggest and most powerful ever.