The Defense Department confirmed the successful launch of new, low-orbit missile tracking satellites on the same day the public learned U.S. intelligence assesses Russia is developing a space-based nuclear weapon to destroy America's satellite network, highlighting the risk to Pentagon plans for proliferating new capabilities in low-earth orbit. The Defense Department today announced that a SpaceX Falcon 9 rocket lofted into orbit six satellites, two for the Missile Defense Agency -- a pair of Hypersonic and Ballistic Tracking Space Sensor...