Short for Project Xylophone from Atlas Shrugged. Project X was funded by the State Science Institute to create the Thompson Harmonizer, which used the nature of cosmic rays and the spatial transmission of energy to create the ultimate weapon of mass destruction.

A demonstration of the machine's capabilities effectively neutralized a farmhouse and some nearby goats from a distance of 2 miles away with a single pulse of sound ray. Details on how the machine works are not mentioned in the book but I assume it uses the vibrations caused by the sound rays it emits to rip apart its targets.

Another demonstration of of the weapon's potential for mass destruction was the missfire of the weapon that resulted in the disintegration of the building housing the weapon and everything within a radius of a hundred miles. Personally, i prefer an old fashion nuke with it's devastating ecological effects.