Rockets are built slowly—slowly and exceedingly carefully—which is in keeping with giant machines on which humans stake their lives and nations stake their prestige. In NASA’s cavernous Vehicle Assembly Building at Cape Canaveral, America’s next great moon rocket—the Space Launch System (SLS)—is being constructed with all that in mind. It is here too that TIME…

Watch TIME’s Exclusive Footage of NASA’s Most Powerful Rocket Ever Under Construction