Editing Mercury-based technology (section)

=== Mercury ion engine ===
The 'mercury ion engine' developed by NASA is sometimes cited as proof that the mercury vortex engine works, but it is rather different.  The mercury ion engine used electricity to ionise mercury vapour and accelerate it out of the rear of the vehicle, propelling it in the same way that a rocket is propelled.  A vehicle that left a trail of mercury vapour as it flew would obviously have drawbacks for use on Earth, suggesting that if the mercury vortex engine existed this was not it.  The use of mercury turned out to have another drawback - the mercury vapour tended to condense and build up on the outside of the spacecraft.  NASA switched to other substances such as xenon for later ion engines.<ref>https://www.nasa.gov/history/glenn-contributions-to-deep-space-1/</ref>