The United Launch Alliance Atlas 5 rocket, standing 197 feet tall and and weighing 1.2 million pounds, unleashes 2.4 million pounds of thrust from its main engine and four solid-fuel boosters at 6:42 p.m. EST (2342 GMT) Saturday to launch the GOES-R weather observer for NASA and NOAA from Cape Canaveral, Florida.

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.

The U.S. Air Force this week awarded SpaceX a contract to launch a Global Positioning System satellite in early 2019, concluding the second of as many as 15 competitions the military plans to run over the next year to pit SpaceX against United Launch Alliance for rights to lift defense and intelligence-gathering payloads into orbit.