James Dean

FLORIDA TODAY

Editor's note: Join floridatoday.com at 6 p.m. for live SpaceX launch commentary and video.

A SpaceX Falcon 9 rocket is targeting a 7:21 p.m. Monday launch of a “behemoth” commercial communications satellite from Kennedy Space Center.

Weighing in at nearly 13,500 pounds atop the rocket, the fourth Inmarsat-5 satellite will be the heaviest load lofted by a Falcon 9 yet.

The 230-foot rocket will need all its fuel and 1.7 million pounds of liftoff thrust to deliver the spacecraft larger than a double-decker bus on its way to an orbit more than 22,000 miles over the equator.

More: Live: SpaceX Falcon 9 rocket launch with Inmarsat-5

More: How to watch today's SpaceX launch

As a result, SpaceX will not attempt to land the rocket’s first stage either at Cape Canaveral or at sea, and the Falcon 9 booster is not equipped with landing legs.

London-based Inmarsat, which has a Palm Bay office with about 200 employees, initially booked the mission on a Falcon Heavy rocket. SpaceX’s heavy-lift launcher could debut later this year, but for schedule reasons the mission was switched to the latest version of the Falcon 9.

The Inmarsat-5 Flight 4 satellite, built by Boeing, will complete Inmarsat’s four-satellite Global Xpress constellation focused on delivering high-speed broadband data to mobile customers including commercial aircraft and ships and the U.S. military.

“I’m sure we’re going to have a really, really exciting show (Monday),” said Inmarsat CEO Rupert Pearce. “Everyone at Inmarsat, SpaceX and Boeing is really, really pumped about this launch. It’s a very significant one for us at Inmarsat, because we call it the end of the beginning of the Global Xpress era.”

The launch weather forecast looks good, with an 80 percent chance of favorable conditions during a 49-minute window at KSC's pad 39A.

Contact Dean at 321-242-3668 orjdean@floridatoday.com.And follow on Twitter at@flatoday_jdeanand on Facebook atfacebook.com/jamesdeanspace.

Launch Monday

Rocket: SpaceX Falcon 9 (expendable)

Mission: Fourth Inmarsat-5 Global Xpress communications satellite

Launch Time: 7:21 p.m.

Launch Window: to 8:10 p.m.

Launch Complex: 39A at Kennedy Space Center

Weather: 90 percent “go”

Join floridatoday.com at 6 p.m. for countdown updates and chat, including streaming of SpaceX’s launch webcast beginning about 15 minutes before liftoff.

MORE: How to watch today's SpaceX launch