June 21 (UPI) -- A SpaceX Falcon Heavy rocket is set to launch Monday night from Kennedy Space Center in Florida, carrying 24 government satellites and kicking off a busy summer of space activity.
It will be the third launch for the Falcon Heavy, the most powerful rocket in use today. SpaceX is calling the launch one of its most challenging ever, because it must release satellites into three different orbits.
It's also the first time that a Falcon Heavy will use previously flown side boosters, which have been refueled and fitted again after the Arabsat 6A satellite launch in April.
Among the satellites on board will be a government experiment to test a less toxic, more efficient spacecraft fuel and a new atomic space clock that will help coordinate space exploration, especially on missions to the moon and Mars.
Large crowds are expected to watch the nighttime launch, which is set for 11:30 p.m. EDT with a four-hour window in case of delays. Weather predictions as of Friday indicate there's a significant risk of storms for the latter part of Monday, bringing into question whether the launch will be postponed.
Not only is the rocket a sight to see at liftoff, but two side boosters should be visible as they fly back to a Cape Canaveral Air Force Station landing pad.
Kennedy Space Center will be open for the launch for a limited number of ticket holders.
The launch will elevate SpaceX's role with the military for complex national security missions, which have been dominated for years by United Launch Alliance, a joint venture of defense contractors Lockheed Martin and Boeing.
Three days later, on Thursday, the Air Force intends to launch the fifth of its national security communications satellites -- the Advanced Extremely High Frequency-5 mission. That will launch aboard a United Launch Alliance Atlas V rocket, with five solid boosters. It will mark the 80th Atlas V rocket launch.
On July 2, NASA will conduct its Ascent Abort-2 mission, the third of five launches required for certification of the Orion spacecraft intended to carry people to the moon and later to Mars. The launch abort system will be tested to ensure crew safety during the climb into space. The test will utilize a refurbished first-stage motor from a Peacekeeper intercontinental ballistic missile.
On July 21, SpaceX aims to launch another cargo mission to the International Space Station, CRS-18.
Then on July 25, a United Launch Alliance Delta IV Medium rocket is scheduled to carry an Air Force global positioning satellite into space.