Enlarge / Ship 28, the Starship for SpaceX's next full-scale test flight, fires up one of its engines on December 29 in Texas.SpaceX It's no secret that Elon Musk has big ambitions for SpaceX's Starship mega-rocket. This is the vehicle that, with plenty of permutations and upgrades, Musk says will ferry cargo and people across the Solar System to build a settlement on Mars, making humanity a multi-planetary species and achieving the billionaire's long-standing dream. Of course, that is a long wa...