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World-first firing of air-breathing electric thruster
In a world-first, an ESA-led team has built and fired an electric thruster to ingest scarce air molecules from the top of the atmosphere for propellant, opening the way to satellites flying in very low orbits for years on end.
[...] Replacing onboard propellant with atmospheric molecules would create a new class of satellites able to operate in very low orbits for long periods. Air-breathing electric thrusters could also be used at the outer fringes of atmospheres of other planets, drawing on the carbon dioxide of Mars, for instance.
"This project began with a novel design to scoop up air molecules as propellant from the top of Earth's atmosphere at around 200 km altitude with a typical speed of 7.8 km/s," explains ESA's Louis Walpot.
A complete thruster was developed for testing the concept by Sitael in Italy, which was performed in a vacuum chamber in their test facilities, simulating the environment at 200 km altitude.
(Score: 0) by Anonymous Coward on Wednesday March 07 2018, @05:38PM
At ultra-low densities, molecules don't interfere much with each other, so drag is simply determined by kinetic energy. It's that equation K=0.5mvv with vv being v squared.
At high densities, the fluid is viscous. Drag can be much higher.