With Hurricane Irma looking increasingly likely to hit Florida, the center is being locked down in preparation.
ULA CEO Tory Bruno disputes that ULA was even afforded the opportunity to participate in the bidding process, however. It's also the first time the company is launching the Boeing-built X-37B.
It was the Falcon 9's 16th successful launch and re-entry and the seventh time the reusable rocket achieved a landing on solid ground, as opposed to the company's floating landing platforms.
The X-37B, also known as the Orbital Test Vehicle (OTV), is one of two known craft of its type in the US Air Force's fleet and part of a classified program whose details are shrouded in secrecy.
On its last mission the "spaceplane" stayed in orbit for nearly two years, but it's unknown how long the current mission is expected to last.
While the specifics of the X-37B's mission aren't available to the public, it will be "conducting experiments" post-launch.
The X-37B, which looks somewhat like a miniature version of the retired Space Shuttle, has a wingspan of just under 15 feet and weighs around 11,000 pounds. In May, SpaceX launched a classified payload for the National Reconnaissance Office, NROL-76. Four earlier missions rode United Launch Alliance Atlas 5 rockets launched from Cape Canaveral. This mission is expected to carry some experimental payloads and deliver small satellites, along with testing electronics and heat pipe technologies over long-duration spaceflight.
We do know that the experimental program is created to help work out the kinks in reusable spacecraft, and there are two X-37B vehicles, built by Boeing.
On its last mission, the solar-powered X-37B stayed in orbit for 718 days before returning to land on May 7 - longer than any of its previous flights. This marks the space plane's fifth mission, according to SpaceX.
Artist's concept of the X-37B spaceplane in orbit.
Today's launch is going to be the last for a while from the Kennedy Space Center.