A SpaceX Falcon 9 rocket blasted off from California on Saturday and placed a constellation of satellites in orbit, marking the company’s first launch since a fireball engulfed a similar rocket on a Florida launch pad more than four months ago. The two-stage rocket lifted off from Vandenberg Air Force Base at 9:54 a.m. carrying a payload for Iridium Communications Inc., which is replacing its entire global network with 70 next-generation satellites.