Very low orbits offer sharper imaging and stronger signals, but the residual atmosphere there drags a satellite down fast, and carrying enough propellant to fight that drag forever is impossible. US12006923B2, granted to the von Karman Institute on June 11, 2024, proposes turning the enemy into the fuel, claiming an "intake system for an atmosphere breathing electric thruster."
The CPC is precise: F03H 1/0043 (electric propulsion using ionized gas) and B64G 1/405 (electric propulsion arrangements). Two codes, one bold idea — an electric thruster fed not from a tank but from an intake.
The mechanism is the intake, and the intake is the hard part. At very low orbital altitudes the atmosphere is whisper-thin, so the system must collect and compress that sparse gas efficiently enough to feed an electric thruster. The thruster then ionizes and accelerates the collected gas to produce thrust that counters drag. If the intake captures enough, the satellite can sustain a very low orbit indefinitely without carrying propellant — which is why the claim is specifically about the intake, not the thruster.
This is genuinely clever frontier propulsion: air-breathing electric propulsion has been studied for years as the key to persistent very-low-Earth-orbit operations, where the payoff for Earth observation and communications is real. The institutional source — a European fluid-dynamics research institute — fits; the unsolved problem here is fundamentally one of rarefied-gas dynamics.
The honest limit: this protects a specific intake-system design, and air-breathing electric propulsion remains largely a research-stage capability with formidable efficiency hurdles. A granted claim is not a flown, fuel-free satellite. Read it as a marker of where persistent-VLEO research is pointing — and as a reminder that the intake efficiency this patent targets is exactly the bottleneck standing between the concept and a working system.