SpaceX conducts a full-duration static fire test with the upper stage of the Starship V3 vehicle that will conduct the Flight 12 test. The vehicle is made of stainless steel; the black comes from its heat shield, a set of 40,000 closely set hexagonal tiles. (Image credit: SpaceX) There are plenty of reasons to get excited about Tuesday's (May 19) planned test flight of SpaceX's Starship megarocket. For starters, it will be the first launch of Starship — the biggest and most powerful rocket ever built — in nearly seven months. And, while the mission will be Starship's 12th overall, it will mark the debut of the advanced new V3 vehicle, which features a number of important modifications and upgrades compared to its predecessors. (That helps explain the long launch lacuna.) Finally, while Starship will fly a familiar suborbital trajectory on Flight 12, it will do something completely new while it's up there — take a good, long look at itself.…