The launch window opens at 6.30pm EST.
Falcon Heavy's actual payload tomorrow is the Saudi Arabian Arabsat-6A communications satellite, weighing a little over 13,000 pounds.
Now it has been scrapped until Thursday.
SpaceX was forced to again delay the launch of Arabsat 6a because of bad weather at Cape Canaveral.
Although the rockets' second stage is identical, the first stage is comprised of three engine cores from the Falcon 9, the company's previous flagship rocket which has been in use since 2010. SpaceX will attempt to re-land the rocket's three boosters.
A demonstration mission in early 2018 drove Elon Musk's Tesla Roadster into an orbit reaching as far as Mars. Wednesday's launch marks the first time a Block 5 booster will be used for the big rocket. Falcon Heavy offers the USA military access to all of the desired orbits for its spacecraft.
The Falcon Heavy is powered by two side boosters and a central core stage.
SpaceX typically launches Falcon 9 rockets.
Why is Falcon Heavy special?
The launch can be viewed on SpaceX's webcast approximately 20 minutes before liftoff, with the rockets planned to separate from the satellite around 34 minutes after launch.
The Arabsat-6A Mission will be an important milestone for SpaceX, since it will help strengthen global internet, radio, television, and mobile communications for customers in Africa, Europe, and the Middle East. After booster separation, the two side boosters will attempt to land at SpaceX's two landing zones at Cape Canaveral Air Force base in Florida.
The next launch, however, will be the first commercial use of the Falcon Heavy. It has three rocket boosters, which are strapped together during launch and are created to then break apart and make pinpoint landings back on Earth. The core booster, however, crashed into the sea.
The Roadster could still look much the same as it did for the February 6, 2018, launch, just not as shiny with perhaps some chips and flakes from the extreme temperature swings, according to Giorgini. The U.S. Air Force's Space Test Program Flight 2 (STP-2) mission will carry as many as 25 small satellites, including: FormoSat-7 A through F, DSX, Prox-1, LightSail 2, GPIM, DSAC, ISAT and ELaNa 15 CubeSats.