High gas prices, the need for alternate-energy sources, even global warming are tiny blips next to the problem encountered in the intriguing but ultimately unsatisfying sci-fi tale “Sunshine,” in which our friend Mr. Sun runs out of fuel.

From director Danny Boyle and screenwriter Alex Garland, the team behind the horror mini-hit “28 Days Later,” “Sunshine” recounts the bleak saga of a spaceship crew on a mission to recharge the sun, whose imminent death has cast Earth into a winter that will soon extinguish humanity.

The visually radiant film is wildly different in tone and style from the manic “28 Days Later” yet has a similarly flawed structure: A riveting beginning and middle with a finale that feels shallow and tacked on.

“28 Days Later” made it work through sheer, bloody energy. “Sunshine” is a slow, thoughtful build and appears on course for a wondrous, even revelatory conclusion.

So it’s inevitably disappointing when the film veers from a hushed “2001: A Space Odyssey” trajectory to a sort of “Alien” frenzy. The plot twists are neither surprising nor original, and “Sunshine” peters out with brightly crafted special effects but the dramatic punch of a gray, overcast day.

Set in 2057, “Sunshine” takes place mostly on board the Icarus II, whose crew of eight includes Capa (“28 Days Later” star Cillian Murphy), a physicist who has designed a nuclear bomb to reignite the sun.

Also on board: mission commander Kaneda (Hiroyuki Sanada); biologist Corazon (Michelle Yeoh); engineer Mace (Chris Evans); pilot Cassie (Rose Byrne); communications officer Harvey (Troy Garity); medical officer Searle (Cliff Curtis); and navigator Trey (Benedict Wong).

These eight are humanity’s last chance, but they make the trek to the sun under both the hope of returning home to their families on a saved Earth and a dark cloud over the fate of the first Icarus, which disappeared on the same mission years earlier.

The only clue is a crazed final video log by the first Icarus’ captain, Pinbacker (Mark Strong), before all contact with the ship was lost.

Boyle and Garland quickly establish an engrossing shipboard dynamic as characters clash, connect and contemplate their place in the cosmos during a long voyage that, like “2001,” is infused with the mundane, tedious realities of space flight.

The good, the bad, the strange and the very ugly in human nature emerge, jeopardizing the mission as the Icarus II crew struggles through mishaps and miscalculations.

Even with Earth’s future in the balance, some characters behave with pettiness or contemptible cowardice, while others act with great nobility and self-sacrifice. The mystery of the first Icarus mission slowly unravels, presenting both obstacles and opportunities for the new crew to complete its task.

Murphy is the nominal lead, yet the ensemble really rows together, with Curtis, Yeoh, Byrne and Garity delivering standout performances.

While “Sunshine” establishes its own look and mood, the filmmakers end up borrowing a lot of ideas and images from previous space tales, among them a harrowing airlock re-entry by some of the crew. Stanley Kubrick did it better in “2001” 40 years ago, but Boyle makes the sequence his own with thrilling action and grisly effects to show the hazards of the quick-freeze coldness of space.

“Sunshine” also pays coy homage to predecessors, including cult flicks such as John Carpenter’s sci-fi parody “Dark Star” (the captain of the first Icarus shares a similar name with a Carpenter character called Pinback).

Unfortunately, the early intensity of “Sunshine” wanes in the third act. The film becomes a ferocious jumble, and rather than a supernova finish, it winks out amid stale New Age notions of the continuity of life and connectedness of all things.

“Sunshine,” a Fox Searchlight release, is rated R for violent content and language. Running time: 108 minutes. Two and a half stars out of four.

Motion Picture Association of America rating definitions:

G _ General audiences. All ages admitted.

PG _ Parental guidance suggested. Some material may not be suitable for children.

PG-13 _ Special parental guidance strongly suggested for children under 13. Some material may be inappropriate for young children.

R _ Restricted. Under 17 requires accompanying parent or adult guardian.

NC-17 _ No one under 17 admitted.

A service of the Associated Press(AP)