SpaceX's megarocket, the Falcon Heavy, is poised for flight. Perched atop NASA's historic Pad 39A, the behemoth will lift off sometime during a 4-hour window that opens tonight (June 24) at 11:30 p.m. EDT.
Assembly in a hangar near the launch pad, where the triple-barreled rocket is put together with explosive bolts, has taken multiple days.
The explosive bolts will come into play just after launch, when the two side boosters separate.
The boosters will return for a landing at Cape Canaveral and should be visible for miles around as they touch down.
Musk, the company's CEO, said on Twitter Wednesday that the launch will be the toughest yet.
This is the first mission to reuse the side boosters that flew on a previous Falcon Heavy mission.
The view of the rocket lifting off at night will be able to be seen for hundreds of miles.
Taxpayers are paying the bill for the launch. The rocket will carry several payloads for NASA and the Air Force.
An atomic clock for space navigation and some space weather research equipment will be on board. Falcon Heavy is the cheapest way to get those items into space.