Power and Propulsion Element

The Power and Propulsion Element, usually shortened to PPE, is the propulsion and power module that NASA planned as the first element of the Lunar Gateway station and that has since been reassigned to the nuclear-powered Space Reactor-1 Freedom spacecraft. It is being built by Lanteris Space Systems, the company formerly known as Maxar Space Systems, under a 2019 fixed-price contract worth 375 million US dollars, and its project management now sits with the NASA John H. Glenn Research Center. The design descends from the propulsion bus of the Asteroid Redirect Vehicle, a solar electric spacecraft intended to capture a boulder from a near-Earth asteroid until that mission was cancelled in 2017. PPE was designed with a launch mass of about 5,000 kilograms, half of it propellant, and about 50 kilowatts of solar electric power from roll-out solar arrays feeding Hall-effect ion thrusters, backed by separate chemical thrusters. The plan to launch it joined to the HALO module on a Falcon Heavy was overtaken in March 2026, when NASA suspended the Gateway program and repurposed PPE for Space Reactor-1 Freedom. Its power systems were first switched on at the builder's facility in early 2026.