We still don't know what Northrop Grumman commissioned SpaceX to launch for the US government, but whatever it is won't get there tonight. In a move that leaves Elon Musk's calendar open for the Tesla electric semi-truck reveal (still scheduled for 11 PM ET), SpaceX said it's standing down on the Zuma mission "to take a closer look at data from recent fairing testing for another customer." The launch, which is scheduled to include a landing attempt by the Falcon 9's first stage, could go off tomorrow night, but no new launch date has been confirmed.