Photos: Atlas 5 rolls out for launch

United Launch Alliance will salvage the main engines through a mid-air recovery plan and reuse them again aboard the company’s new Vulcan rocket, saving 90 percent in booster propulsion costs, the company announced Monday.

Final preparations began this weekend at NASA’s Stennis Space Center in Mississippi to load super-cold liquid hydrogen and liquid oxygen into the massive core stage of the Space Launch System heavy-lift rocket for the first time as soon as Monday.

United Launch Alliance’s first full-scale Vulcan booster with two Blue Origin BE-4 engines arrived at Cape Canaveral Space Force Station on Saturday, the first time in more than a decade that a core stage from a new family of orbital-class rockets has rolled into the Florida launch facility.