A frequently-seen concept
in science fiction
, wherein a military
force in interplanetary
or interstellar space
is patterned off of the old navies
classes are typically organized into categories correspoding to so-called "wet navy
" types -- cruiser
s, et cetera
-- and the same rank
system is used.
The space navy concept originated with Gene Roddenberry's Star Trek, wherein Starfleet is patterned off of the United States Navy, even so far as to have its major training facilities located in San Francisco. For the ultimate extension of the concept in all of its awe-inspiring majesty, the Imperial Navy from Star Wars is an excellent example. Lots of huge, powerful ships intended to conquer, destroy, and Seriously Intimidate. The UN Spacy from the myriad Robotech spinoffs isn't bad either.
As they are most frequently incarnated, space navies involve fleets of large ships carrying troops, starfighters and materials from world to world (just as modern wet navies carry troops, jet fighters and materials from port to port). Space navies also often carry out exploratory missions for their respective governments, leading to all sorts of interesting situations.
Space navies are one of the ultimate geek fantasies. What geek wouldn't want a Star Destroyer or two at his or her command?