The payload for the rocket's demo launch will be a red Tesla roadster, complete with a SpaceX spacesuit in the front seat. Because this is a test launch, there is no official payload; two more Falcon Heavy launches are scheduled for later this year. SpaceX will try to land all of the Falcon Heavy's boosters; the two flanking boosters will attempt a landing near the launch pad, while the middle booster will head for a drone ship. Whether SpaceX encounters success or failure, tomorrow's launch should be a thing to behold.

Update: It appears that SpaceX is now targeting 2 PM ET for the launch.

Update: It's now delayed to 2:20 PM ET. Sources say this is due to upper level winds.

Update: While you're waiting, check out this cool infographic about the Falcon Heavy's trajectory:

Update, 12:15 PM ET: The time is now scheduled for 2:50 PM ET. Keep in mind the launch window only extends to 4 PM ET.

Update, 12:48 PM ET: Launch time is now 3:05 PM, due to upper level winds.

Update, 1:08 PM ET: Launch time is now 3:10 PM, because of "clock management."

Update, 1:11 PM ET: Now we're at 3:15 PM. It's not looking good for a launch today.

Update, 1:42 PM ET: After a full stop in the countdown, we're back with a 3:45 PM ET launch time.

Update, 2:38 PM ET: Everything's looking good for a 3:45 PM ET launch. Propellant loading is underway for the rocket.