Musing in his Captain’s Log as his birthday approaches, James Tiberius Kirk, his eyes as blue as the lens flare that accompanies the first shot of the Starship Enterprise, finds himself in a funk. “Things are starting to feel a little … episodic,” he confesses, in what even a sympathetic viewer might interpret as a meta-statement, a confession of franchise fatigue. Chris Pine, who has played Kirk since the big-screen reboot in 2009, is on his third voyage. This character, originated by William Shatner, has endured a lot more. The larger “Star Trek” enterprise has been boldly going on for a half-century, and more hours of television and cinema than I possess the Googling acumen to tally.

So you can understand why James T., a good soldier and also a bit of a loose cannon, might want to break out of the rut, and the title of the latest movie, “Star Trek Beyond,” teases the audience with the promise of novelty and risk. It’s not necessarily a criticism to note that not much materializes. Directed by the action maven Justin Lin from a script by Simon Pegg and Doug Jung, the film answers the question “Beyond what?” with a diffident “Well, nothing, really. Don’t worry!” It should have been called “Star Trek Within” in honor of its determination to color inside the lines, obeying the ironclad conventions of brand and genre.

Which is not, in itself, a bad thing. Not every wheel needs reinventing, and one of the abiding pleasures of “Star Trek,” in its old and newer iterations, lies in its balance of stubborn consistency and canny inventiveness. The characters never change, but the stakes can shift wildly from one adventure to the next. Fans love “Star Trek” precisely because of its episodic nature, which allows for a certain amount of variation in theme and tone. Sometimes the future of the universe hangs in the balance. Sometimes Kirk and his crew have to deal with local disputes and personnel issues. Or weird random stuff, like tribbles or Joan Collins-related time travel.