SpaceX will attempt to launch its Starship megarocket on a key test flight Tuesday, months after two launches both failed when the upper-stage vehicle exploded and rained debris over the Gulf of Mexico and parts of the Caribbean. Tuesday’s uncrewed launch — Starship’s ninth test flight — is set to blast off from SpaceX’s Starbase facility in Texas, during a launch window that opens at 7:30 p.m. ET. The 400-foot-tall Starship is the most powerful rocket ever developed and consists of tw...