SpaceX CEO Elon Musk posted a picture of SpaceX's Super Heavy booster, which is the largest rocket booster ever built, according to Teslarati. The booster is nearly 220 feet tall and will eventually be used to propel Starship spacecraft to orbit. "Booster 1 is a production pathfinder, figuring out how to build & transport 70-meter tall stage," Musk said.