Context:

• SpaceX blasted off a secretive U.S. government payload known as Zuma, a mission whose nature — and the agency behind it — remains a mystery.
• Just what exactly needed such special protection and secrecy is still unknown.
• It was for the U.S. government and would be delivered to low-Earth orbit, but offered no other details.
• SpaceX has launched national security payloads in the past, including a spy satellite for the National Reconnaissance Office, and an X-37B space plane for the U.S. Air Force.