USA – Starship, SpaceX’s massive prototype rocket that may one day send humans to Mars, is poised for its next flight on Thursday.It will be the fourth test for the most powerful launch system ever built, vital to NASA’s plans for landing astronauts on the Moon later this decade and to SpaceX CEO’s Elon Musk’s hopes of one day colonizing the Red Planet.A two-hour liftoff window from the company’s Starbase in Boca Chica, Texas opens at 7:00 am local time (1200 GMT). Weather conditions look favorable, and the Federal Aviation Administration has given its green light.Three previous attempts…