Half a can of soda. The main electronics controller visible in the photo is likely 20x20 or 30x30mm, the standard for FPV style drones.

Wire guided is still the primary means of guiding torpedos from submarines, because it gives you an unjammable, un-interceptible, consistent communication interface, and in torpedoes the wire spools out for tens of kilometers.

If you want something really cool, look up old fashioned TV guidance. We built weapons that guided based a TV signal, and edge detection in that signal. In 1958.

Pretty sure they were in the thousand feet range, not multiple kilometers…