Story by mguenot@businessinsider.com (Marianne Guenot,Morgan McFall-Johnsen,Kate Duffy) • 13m ago SpaceX launched its new Starship mega-rocket on Thursday after a frozen valve stopped the first attempt. The mega-rocket exploded about three minutes into its flight but managed to clear the pad. Musk previously said he estimated a 50% chance of success. SpaceX launched its new Starship mega-rocket toward space for the first time on Thursday, after canceling its first attempt due to a valve issue. Stacked atop its Super Heavy booster at SpaceX's new launchpad in Boca Chica, Texas, the black-and-silver vehicle was poised to prove itself as the biggest,...