English: A SpaceX Falcon Heavy rocket is ready for launch on the pad at Launch Complex 39A at NASA’s Kennedy Space Center in Florida on June 24, 2019. SpaceX and the U.S. Department of Defense will launch two dozen satellites to space, including four NASA payloads that are part of the Space Test Program-2, managed by the U.S. Air Force Space and Missile Systems Center. The launch window opens at 11:30 p.m. EDT on June 24. The four NASA payloads include two technology demonstrations to improve how spacecraft propel and navigate, as well as two NASA science missions to help us better understand the nature of space and how it impacts technology on spacecraft and the ground.