Did SpaceX’s secret Zuma mission actually fail? - The Verge

Also see SpaceX-Launched Satellite for the U.S. Military May Be Lost, Officials Say (Bloomberg) and The mystery behind the fate of a top secret satellite comes at the height of one of Elon Musk’s biggest rivalries (Washington Post)

"So what actually happened? No one is saying for certain, but there are a couple scenarios in which the Falcon 9 could have performed as it was supposed to and the spacecraft didn’t deploy correctly. Typically, SpaceX uses its own hardware on top of its rocket to send a satellite into orbit, what is known as a payload adapter. It’s an apparatus that physically separates the satellite from the upper part of the rocket and sends it into orbit. However, a previous report from Wired noted that Northrop Grumman provided its own payload adapter for this mission. And if that payload adapter failed, it would have left the satellite still attached to the upper portion of the rocket. That’s certainly a mission failure, but it wouldn’t necessarily be the fault of the Falcon 9."

Did SpaceX’s secret Zuma mission actually fail? - The Verge