HAARP (High-Frequency Active Auroral Research Program) is a high-powered radio transmission research facility in Alaska jointly operated by the US Navy, Air Force and several universities; a BIG particle gun.
RCON is a text based protocol completely unrelated to the Source RCON protocol. It is designed with readability, ease of implementation, and human usability in mind.
A recoilless rifle (RCLR) or recoilless gun is a type of lightweight tube artillery that is designed to allow some of the propellant gases to escape out the rear of the weapon at the moment of ignition, creating forward thrust that counteracts some of the weapon's recoil.