I interviewed Steve Englehart back in 2009 and he doesn't remember much about the game, either the Atari 8-bit or ST versions.
According to programmer Dan Oliver, the "E" for the E-Beam weapon stood for "Electric" (it's not mentioned in the manual). Also not mentioned in the manual is why your battleship fires torpedos. According to Dan, he wanted it to be a ship but designer Chris Horseman wanted it to be a submarine. From Dan, "The ship view was the second view I did (the map was first). Chris was talking about and or wanting subs, so my graphic looks like what I thought the bow of a sub would look like on the surface, maybe to make Chris Horseman happy."