At one point in “Solo: A Star Wars Story,” a sort of prequel to the 1977 blockbuster that might instead have been subtitled “When Han Met Chewie,” a character barks out a command: “Stick to the plan—do not improvise!” That could have been the mantra of the powers overseeing this mega-franchise at Disney, and perhaps the reason why the original directors, Phil Lord and Christopher Miller, known for their looseness and irreverence (“21 Jump Street,” “The Lego Movie”), were dismissed in mid-shoot and replaced by Ron Howard. In that respect “Solo” qualifies as what is usually called a troubled production, but in this case whatever discomfort might be involved in that status is unlikely to extend to the audience: the movie is a thoroughly reliable addition to the “Star Wars” corpus, closely mimicking the spirit of the first two movies in the series if not managing to recapture their magic.

As “Solo” begins, Han (Alden Ehrenreich) is an orphan on Corellia, a dirty, crime-ridden planet where he is one of the minions of Lady Proxima (voiced by Linda Hunt), a huge wormlike mob boss. He has stolen a vial of a precious mineral called coaxium, but wants to keep it in order to secure an escape for him and his girlfriend Qi’ra (Emilia Clarke). His skill as a driver gets them to the space terminal where they can bribe their way onto a ship, but their pursuers capture her, leaving him with no choice but to join the imperial army in order to avoid prison.

Three years later, he’s trapped in a hopeless battle on a planet the Empire is trying to conquer, and tries to go AWOL and join forces with a crew of thieves—unscrupulous Beckett (Woody Harrelson), his partner Val (Thandie Newton) and voluble pilot Rio Durant (voiced by Jon Favreau). Beckett betrays him to the authorities, however, and he finds himself forced to fight to the death with captured Wookie Chewbacca (Joonas Suotamo). After a tussle, he convinces Chewie to make a joint jailbreak, and the impressed Beckett welcomes them aboard his ship to help with his upcoming score—the theft of a shipment of refined coaxium from a train as it crosses a bridge high in the mountains.

There are losses in the resultant spectacularly staged, vertiginous struggle with defenders and pirates—lives as well as the cargo—but Solo has proven his value to Beckett, and together they’re off to the space yacht on which Dryden Vos (Paul Bettany), Beckett’s boss, announces that he will allow them to live only if they complete the job by stealing unrefined coaxium from the mining planet of Kessel, getting it to a refinery on Savareen before it explodes, and then transporting it to him. Joining them on the mission will be Qi’ra, who by some means has wound up as one of Vos’s most trusted aides.

To have any chance to succeed, they’ll need a fast ship, which takes them to a gambling den where they find Lando Calrissian (Donald Glover) and secure the services of his ship, the Millennium Falcon, as well as his expert robot pilot L3-37 (voiced by Phoebe Waller-Bridge). And they’re off on their dangerous journey, which will of course boast a great many twists, reversals, triumphs, close shaves, betrayals, face-offs and, needless to say, extravagant set-pieces. It’s an exciting ride, leavened with welcome doses of humor, much of it provided by Lando, whom Glover plays as a debonair rogue, and L3-37, whose volatility in trying to free her kind from subservience to biological masters has a distinctly radical tone.

That’s not to say, though, that Ehrenreich fails to make his mark. He brings a goodly measure of strutting energy to Han, and if it takes him a while to settle into the character Harrison Ford made so memorable, that’s a function more of the script, by “Star Wars” veteran Lawrence Kasdan and his son Jonathan, than the actor; it’s designed to show the character developing gradually rather than springing forth full-blown from the first moment, and Ehrenreich conveys that concept nicely.

Unfortunately, Ehrenreich never manages to develop much chemistry with Clarke, despite the supposedly destined romance between Han and Qi’ra. That’s not for lack of trying on his part, but the script stubbornly refuses to provide much heart to their relationship, and Clarke remains a pretty cool customer throughout. In fact, there’s more of a connection between Han and Suatamo’s Chewie, which—given what’s known of the future—is as it should be; as the film ends, Han doesn’t say that it’s the beginning of a beautiful friendship, but he might as well do so. The give-and-take between Han and Beckett, played by Harrelson with a nice combination of the gruff and the avuncular, is not quite so strong, but he makes you believe the crook’s importance to the development of Solo’s later persona. Among the others, Bettany brings suave malevolence to Vos, and Newton stern competence to Val.

Especially given the circumstances under which he took over the production, Howard has done a more than creditable job, working with editor Pietro Scalia to maintain a high energy level and with production designer Neil Lamont to create a sense of tactile physical reality not unlike that George Lucas achieved in the first films of the original trilogy and, more recently, J.J. Abrams did in “The Force Awakens.” There’s a substantial amount of VFX, of course, and under the supervision of Rob Bredow it’s managed well, but happily it’s kept within reasonable bounds; “Solo” doesn’t look, after the fashion in so many big-budget movies nowadays, more like an animated movie than a live-action one. Bradford Young’s widescreen cinematography, happily free of 3D, is atmospheric, and John Powell contributes a score very much in the John Williams vein, using many of the old themes.

“Solo” is certainly not a groundbreaking “Star Wars” story, but at least it doesn’t just tread well-known ground the way the second trilogy did. It’s comfortably familiar rather than boringly, and grandiosely, so. It’s easy to see how it could lead to a sequel of its own, and that wouldn’t be unwelcome.