Chemical rockets stage: they drop empty tanks and engines so the remaining vehicle does not haul dead weight. Electric thrusters almost never do. US11230394B2, granted to MIT on January 25, 2022, asks why not, claiming the "staging of ion propulsion thrusters."
The CPC is compact: B64G 1/405 (electric propulsion arrangements), B64G 1/64 (means for stage separation), and F03H 1/0018 (ion engines). The pairing of an electric-propulsion code with a stage-separation code is the entire idea in two classifications — staging, applied to ion thrusters.
The mechanism addresses a real limit of small-satellite electric propulsion, particularly electrospray and ion arrays: the thruster units themselves are a meaningful fraction of the spacecraft's mass, and they wear out. Once a unit's emitters or grids are spent, it is just mass. The claimed approach lets the spacecraft discard expended thruster units mid-mission, improving the mass fraction available for the remaining maneuvers — exactly the staging logic, transplanted to electric propulsion.
This is an academically elegant claim, and the inventor list — including Paulo Lozano, MIT's electrospray-propulsion authority — signals it comes from the front edge of the field. For cubesat and smallsat designers, where every gram and every millinewton-second counts, the idea has obvious appeal.
Claim-scope reality: staging is ancient in chemical propulsion, so the novelty is specifically in applying and implementing it for ion thrusters, and the claim is bounded accordingly. Its value is as foundational university IP that licensees in the smallsat-propulsion space might build on. The record is a good example of where the genuinely new thinking in electric propulsion is happening — in the academic labs, then licensed out.