Air-breathing ion engines for very low orbit satellites: 
<br /><a href='https://www.bbc.com/future/article/20250207-sky-skimmers-the-race-to-send-satellites-into-very-low-earth-orbits'>https://www.bbc.com/future/article/20250207-sky-skimmers-the-race-to-send-satellites-into-very-low-earth-orbits</a>