A full-scale BE-4 engine developed by Blue Origin, the space company founded by Amazon.com’s Jeff Bezos, is installed on a test stand in West Texas for a series of hotfire tests that United Launch Alliance will closely examine before settling on the reusable methane-fueled engine for its new-generation Vulcan rocket.

SpaceX plans two Falcon Heavy launches this year for the U.S. Space Force in July and October, and United Launch Alliance has four national security space missions on its 2021 schedule, according to a military spokesperson.

This collection of photographs shows the Air Force’s Global Positioning System 2F-12 navigation satellite being encapsulated in the United Launch Alliance Atlas 5 nose cone and hoisted atop the rocket for flight on Friday morning.