GODSPEED: Falcon Heavy rocket set to attempt SpaceX’s “most difficult launch ever.”

First of all, this is the first time the Air Force has flown payloads on a Falcon Heavy rocket. And while this mission will not be carrying anything critical to national security—such as large satellites valued at $1 billion or more used for observation, communication, or other purposes to advance the national interest—Air Force officials will be watching closely.

The US military is in the middle of determining which providers among SpaceX, United Launch Alliance, Blue Origin, and Northrop Grumman will win lucrative launch contracts from 2022 to 2026. The Air Force is only expected to pick two winners, and SpaceX has said its Falcon Heavy rocket can meet all nine of the Air Force’s “reference orbits,” which means sending heavy payloads to some exotic orbits that require a lot of energy to reach.

The unique profile of Monday night’s mission will help demonstrate that the Falcon Heavy rocket’s second stage does indeed have the capability to reach all of these orbits. After the rocket launches and its second stage separates, it will perform four separate upper-stage engine burns, and then, almost like a school bus, drop off satellites at three different locations. These maneuvers will require precise performance by the upper stage over the course of six hours.

It all begins in just a few hours.