4 pm ET Sunday Update: SpaceX delayed the launch of its Falcon Heavy rocket one day until Sunday evening, at 5:56 pm ET (22:56 UTC), after preparations for an attempt Saturday fell behind schedule. But now the rocket and local weather in Florida are cooperating for an on-time liftoff of the triple-core booster.

The twilight launch attempt should look spectacular, and you can watch live beginning about 10 minutes before the launch window opens.

Original post: Nearly five years have passed since the massive Falcon Heavy rocket made its successful debut launch in February 2018. Since then, however, SpaceX's heavy lift rocket has flown just three additional times.

Why? It's partly because there is simply not all that much demand for a heavy lift rocket. Another factor is that SpaceX has increased the performance of its Falcon 9 rocket so much that it can complete a lot of the missions originally manifested on the Falcon Heavy. However the main reason for the low cadence has been due to a lack of readiness of payloads for the new rocket, particularly from the US Department of Defense.

But now this trickle of Falcon Heavy launches may turn into a flood. As early as Saturday, from Florida, the first of potentially five launches of the heavy lift rocket this year could take place.

First up is the USSF-67 mission. This will be the second Falcon Heavy mission for the US Space Force, and the rocket will be carrying two payloads into geostationary orbit. The first of the two vehicles on board is named CBAS-2, for Continuous Broadcast Augmenting SATCOM. This is essentially a communications relay satellite, which the Space Force says will support operations by augmenting "existing military satellite communication capabilities and continuously broadcast military data through space-based satellite relay links."

The second payload, called Long Duration Propulsive ESPA-3A, is actually a spacecraft "bus." It will host five different, smaller payloads and provide power and propulsion before dropping these vehicles into various orbits. Among these five payloads is a prototype "crypto/interface encryption" satellite that will deliver secure space-to-ground communications capability.

"This is a complex mission and truly represents what Assured Access to Space is about and is why we’re so enthusiastic about this upcoming launch," Maj. Gen. Stephen Purdy, program executive officer for Assured Access to Space, said in a news release.

SpaceX completed a hot fire test of the rocket on Tuesday, and declared that the vehicle was ready for liftoff. The rocket will use a brand new core stage and side-mounted boosters that have been flown into space one time (as side-mounted boosters on the USSF-44 Falcon Heavy mission that launched on Nov. 1 2022). SpaceX will again attempt to recover these side boosters at its land-based landing zones for a future mission. The center core will be expended.

The launch is scheduled for 5:55 pm ET (22:55 UTC) from Launch Complex 39A at Kennedy Space Center. Weather conditions are favorable for the launch attempt.

The timing for this launch is noteworthy, as the launch window opens just 10 minutes after sunset. This will be the first time that the Falcon Heavy rocket has launched in twilight, and it should be visible for hundreds of kilometers up and down the Florida coast. Trevor Mahlmann will be on hand for Ars to provide unique views of this large launch vehicle.

Future Falcon Heavy missions this year include a commercial mission for the satellite communications company ViaSat in March, the Space Force's USSF-52 mission in April, a commercial mission for EchoStar in May, and the Psyche asteroid mission for NASA in October. All of those dates, as ever in the launch business, are subject to change.