Elon Musk, SpaceX’s CEO, described the launch as one of the most challenging in the company’s history.

On Tuesday, in a significant development which Elon Musk described as one of the most difficult in the company’s history, SpaceX’s Falcon Heavy rocket lifted-off from the Kennedy Space Center in Florida carrying 24 experimental satellites.

The text-book launch blasted off to cheers from onlookers at 2:30 a.m. (0630 GMT) and the boosters separated safely while the craft began its six-hour mission to deploy the satellites.

The mission, dubbed Space Test Program 2 (STP-2), is the third one for the Falcon heavy rocket, described as the most powerful launch system in the world.

The launch was commissioned by the U.S. Department of Defense, a key contractor for commercial space companies such as SpaceX.

In a statement, SpaceX said, it was “putting satellites into orbit for various agencies, including NASA, the National Oceanic and Atmospheric Administration (NOAA), various defense department laboratories, universities and a non-profit organisation”.