For the third time in 16 months, SpaceX is readying the most powerful launch vehicle in its fleet—the tripled-cored Falcon Heavy—to launch from historic Pad 39A at the Kennedy Space Center (KSC) in Florida late Monday, 24 June. The giant booster, whose 27 Merlin 1D+ first-stage engines produce approximately 5.1 million pounds (2.3 million kg) of propulsive yield, which SpaceX has noted makes the Heavy the world’s most powerful active launch vehicle by a factor of two, eclipsing the United Launch Alliance (ULA) Delta IV Heavy.
On this third mission, the “triple-niner” will build upon the test-flight experience gained during its two previous launches to trial the capability of reflying the same side boosters (B1052 and B1053) from its most recent launch last April. If it flies on time, during a four-hour “window” extending from 11:30 p.m. EDT Monday through 3:30 a.m. EDT Tuesday, 25 June, this will also mark the Falcon Heavy’s first mission in the hours of darkness. A customary Static Fire Test of the booster’s 27 engines was conducted late on Wednesday 19 June, after which SpaceX declared via Twitter its readiness to support a launch overnight on the 24th/25th.