Writer-director James Gray, who ventured far from his customary haunts on the streets of New York with his last film, “The Lost City of Z,” vaults even further away from his erstwhile hunting ground with this outer-space epic. “Ad Astra,” or “To the Stars,” nonetheless remains tethered to earth by its reliance on the “Heart of Darkness” template for its narrative thrust, to which is added a thread about a man struggling to resolve long-standing issues with his father. He just has to go to Neptune to thrash them out.

Of course, if you’re going to model your narrative on a literary classic, Conrad’s tale of a journey to the unknown is not a bad choice. After all, Matt Reeves used it recently in “War for the Planet of the Apes,” where the allusion to “Ape-okalypse Now” scribbled on a wall drew a connection not only to “Heart of Darkness” but to Francis Ford Coppola’s Vietnam War epic, which was modeled on it. Gray’s film also shows the influence of other classics—in visual terms especially, and probably inevitably, Stanley Kubrick’s “2001: A Space Odyssey.” It may even be that an episode featuring some baboons being used as test specimens on a research vessel is intended as a nod to Reeves’s movie as well as Kubrick’s.

The problem is that despite its grandiose aspirations, Gray’s film, apart from its technical excellence, falls short of rivaling the films that served as obvious inspiration for it.

It does, however, boast some stunning sequences, including the opening, in which astronaut Roy McBride (Brad Pitt), part of a team working on a mammoth space antenna, is thrown off the towering structure when it’s struck by an overwhelming power surge from parts unknown. Tumbling toward earth from an incredible height, he manages to open his parachute at just the right moment—having turned off an electrical switch on the antenna before letting go.

Roy’s presence of mind under such wildly stressful circumstances is, we learn, typical of his physical control—his pulse rate never goes above eighty. And yet in a stream-of-consciousness narration that runs through the entire film, it’s clear that his seemingly unflappable exterior conceals great inner turmoil (his wife, played by Liv Tyler, has just left him because of his emotional remoteness), principally arising from his feeling of having been abandoned by his father Clifford (Tommy Lee Jones), a legendary astronaut who departed earth when his son was a teenager in command of was called Project Lima, a ship designed to go into deep space in search of extraterrestrial life. After sixteen years, the Lima vessel suddenly disappeared, and it was presumed that Clifford and his crew were killed. Their last known position was near Neptune, the very spot where it’s been determined the recent power surge originated. It did great damage, and future ones could doom life on earth.

The suspicion among the generals (the most notable of whom is played by John Ortiz, smiling like a shark), is that the surge indicates that Clifford might still be alive and using the anti-matter power source aboard the Lima vessel to unleash the destructive force. Roy is asked to go to Mars and broadcast a plea to his father to make contact so that the danger can be averted. Roy agrees, though his inner thoughts disclose the psychological discomfort he feels, even if his outer expression does not.

That begins his series of adventures. The flight to the moon is relatively uneventful, but Roy’s time there is hardly that. The place has become a virtual war zone among hostile groups vying violently for the lunar resources, and to reach the launch vehicle he and the ship’s crew must survive assault from a squadron of enemy dune buggies. Once in flight, the vessel detours to answer a distress call from that research vessel that leads to another harrowing action sequence, the one with those baboons.

Roy must take over control of the ship when a nervous co-captain (Loren Dean) proves unequal to the task, but they make it to the Red Planet, where Roy sends his message to his father, with apparent success. But because of his emotional attachment, he’s then detached from the mission—a decision he’s unable to accept. With the help of a young woman (Ruth Negga) with a familial connection to the Lima Project, he gains unauthorized entry to the Neptune-bound ship—chalk up another impressive action sequence—and shepherds it to a reunion with his long-absent father. Their meeting will, however, be a fraught one, and ultimately Roy will have to learn—quite literally—to let go.

Gray stages the major set-pieces quite well, abetted by his visual effects crew (supervised by Allen Maris) and cinematographer Hoyte Van Hoytema, whose carefully calibrated images are often wondrous to behold. Kevin Thompson’s production design is also impressive, with the futuristic sets combining the austerity of Kubrick’s vision with the more lived-in feel of films like Ridley Scott’s “Alien.” The editing jointly credited to John Axelrad and Lee Haugen adds to the somber mood that prevails in the subdued expository scenes.

But while Pitt is physically an able partner of Gray’s efforts, the writer-director and his co-scripter Ethan Gross have made a major miscalculation in overburdening the picture with Roy’s interior rumination—most of which is banal, often verging on the worst sort of psychobabble. “2001” was hardly a silent film—its majestic, classically-based score is one of its most memorable aspects—but Kubrick kept dialogue to a minimum, giving his film a hushed, haunting quality. By contrast Roy’s near-constant babbling is a terrible irritant, giving even the most extraordinarily images an earthbound quality at odds with the visual impact. In space, the “Alien” tagline read, no one can hear you scream; in “Ad Astra,” unfortunately, we have to listen to Roy’s ramblings all too often.

Pitt nonetheless manages to give Roy an air of grave intensity, effectively carrying the film in human terms. The only other actors who register strongly are Jones, who brings a powerful presence to Clifford even if the character’s motives are never fully defined, and Donald Sutherland as Colonel Pruitt, an old comrade of Clifford’s who accompanies Roy on one leg of his mission and performs a function similar to that of Dr. Heywood Floyd at a significant point in “2001.” Negga makes an appropriately solemn impression as the woman who offers Roy more information on the Lima Project’s end, and Dean is convincing as a pilot in over his head.

Like its protagonist, “Ad Astra” reaches high, but only intermittently hits its target. It’s certainly watchable, but unlike its twin models is unlikely to achieve classic status.