United Launch Alliance is poised to fly its first U.S. national-security payload on the newly developed Vulcan Centaur rocket this evening from Cape Canaveral Space Force Station. The 202-foot vehicle, designated VC4S and fitted with four GEM-63XL solid boosters, is scheduled to lift off during a one-hour window that opens at 7:59 p.m. EDT. Launch Weather Squadron forecasts give the attempt a 75-80 percent chance of acceptable conditions, and fueling operations began Tuesday afternoon. Vulcan will attempt a direct, seven-hour injection of two satellites into geosynchronous orbit roughly 22,000 miles above Earth. Confirmed aboard is the $250 million Navigation Technology Satellite-3, built by L3Harris on a Northrop Grumman ESPAStar bus for the Air Force Research Laboratory. NTS-3 will conduct more than 100 experiments aimed at hardening future GPS-style navigation signals against jamming and spoofing. A second payload remains classified. The flight, labeled USSF-106, marks Vulcan’s first operational mission since the booster completed certification earlier this year and ends the Pentagon’s dependence on Russian-built RD-180 engines. Powered by two U.S.-made BE-4 engines from Blue Origin, the launcher is expected to generate about 2.9 million pounds of thrust at liftoff. “We officially end our reliance on Russian-made main engines with this launch,” mission director Col. Jim Horne said, calling the milestone a ‘historic point’ for assured U.S. access to space.