兴趣爱好Get exclusive promotions and updates sent straight to your inbox. Want to find out more about how SpaceX and others plan to get to Mars? Subscribe to MUSK READS+ for exclusive interviews and analysis about spaceflight, electric cars, and more. Of particular focus are immediate objectives for the two-stage, 400-foot-tall reusable launch vehicle known as Starship. SpaceX has conducted three Starship test launches from its Brownsville, Texas "Starbase" location.   The booster, though, did successfully put the Starship upper stage, known as Ship 31, onto a suborbital trajectory. During its time in space, SpaceX briefly reignited one of the vehicle’s Raptor engines, a test of that capability needed for deorbit burns on later missions. But perhaps the biggest challenge—as always, with rockets—is fairly mundane: its mass. The goal with a rocket is to build the lightest possible vehicle with the greatest amount of performance. In theory, it sounds simple. But in practice, containing volatile liquids at high pressures is anything but simple. And with a fully reusable launch system, SpaceX has the added challenge of building vehicles that can withstand the rigor of launch, perform in a vacuum, and then return screaming through the atmosphere to land back at sea-level pressures.
