The Enterprise (NX-01) fires the main Plasma Cannon  
 
 
 
 

 

  
Plasma cannons were the precursors to phase cannons. Cargo vessels were commonly equipped with one turret, designed to break up asteroids and meteors.

The Enterprise was equipped with several plasma cannons during the first days of its mission, but would eventually be upgraded with the more advanced phase cannons.

Earth Y class freighters, were typically equipped with a single plasma cannon. The captains of these freighters, however, would often upgrade them at the first chance they got. Often referred to as "popguns", to achieve a weapons lock, the target had to be within a 9 kilometer range.