Drone’s view of Sunday’s SpaceX rocket landing

Space station commander Chris Cassidy and Robert Behnken floated back outside Tuesday for their fourth spacewalk in less than a month, completing preparations for future upgrades including the eventual installation of an airlock that will allow commercial experiments to be moved into and out of vacuum as required.

Ready to double its Florida launch capacity with two pads, SpaceX is preparing to loft a reused robotic cargo ship toward the International Space Station Wednesday with a recycled Falcon 9 booster, debuting a rebuilt launch complex knocked offline more than a year ago in a fiery blast during pre-flight testing.

After an exhaustive investigation, SpaceX engineers have identified the most likely cause of the spectacular explosion of a Falcon 9 rocket during a pre-launch test Sept. 1 that destroyed the booster and its $195 million satellite payload, the company announced Monday.