CAPE CANAVERAL, Fla. – SpaceX now targets 4 p.m. to 10 p.m. Monday for its Falcon Heavy test fire, according to News 6 partner Florida Today.

The test fire was delayed Friday for unspecified reasons.

The test fire was also delayed Thursday. Vapors were visible around the rocket and pad 39A just before the window opening, indicating that the 230-foot-tall rocket had at least been fueled for the first time.

When Falcon Heavy does finally fire its 27 Merlin engines for about 12 seconds, teams will analyze results from the operation before the rocket's first-ever flight around the end of January, according to CEO Elon Musk.

Falcon Heavy will officially become the most powerful operational rocket in the world when it lifts off from the historic pad with more than 5.1 million pounds of thrust.

And if the test fire and demonstration flight are successful, SpaceX's manifest will open up to new capabilities thanks to its ability to take heavier payloads to orbit. The company has signed at least two contracts -- one with Inmarsat and one with Arabsat -- to launch payloads on the Heavy.

At neighboring Cape Canaveral Air Force Station, meanwhile, a military missile warning satellite was hoisted atop a United Launch Alliance Atlas V rocket ahead of a planned liftoff next Thursday. The spacecraft, part of Air Force's Space Based Infrared System, or SBIRS, is scheduled to vault off the pad at Launch Complex 41 at 7:52 p.m.

By the numbers: Falcon Heavy

Height: 230 feet

Width: 40 feet

Cores: Three Falcon

Engines: 27 Merlin

Thrust: More than 5 million pounds at liftoff

Payload to low Earth orbit: 140,000 pounds

Landing Legs: Installed on all three cores