There’s lots of Catholic-themed SF for you (not all written by Catholics, but the ones that I know who are have an asterisk*):
Fr. Robert High Benson* - “Lord of the World” and “The Dawn of All” (a Catholic dystopia and utopia, respectively)
“Utopia” by St. Thomas More* - hey, science fiction by an actual Saint (although Chesterton has been proposed for canonization, so we may have more.)
“A Case of Conscience” by James Blish (Manicheanism)
“The Quest for St. Aquin,” “Balaam” and “Star Dummy,” short stories by Anthony Boucher* I love the alien version of the Lord’s Prayer in the latter story, as did C.S. Lewis.
“The Man,” “Bless Me Father For I Have Sinned,” “The Messiah,” “The Fire Balloons,” and “The Dog in the Red Bandana” by Ray Bradbury.
“A Clockwork Orange” by Anthony Burgess* (yeah, the book is deeply concerned with Catholic themes of free will - make sure you get the British edition with the final chapter that is missing from the American edition), also his “The Wanting Seed” (Augustinianism vs. Pelagianism)
“The War With the Newts” by Karel Capek* (Social Justice)
“The Man Who Was Thursday” by G.K. Chesterton* (The nature of God - and much more)
“The Pre-Persons” by Philip K. Dick and “Croatoan” by Harlan Ellison (Abortion)
“Catholics” by Brian Moore (The Latin Mass)
“Children of Men” - P.D. James (Openness to Life)
Most anything by Dean Koontz* since his conversion, especially his Odd Thomas books, or my favorite (because I love dogs) “The Watchers.”
Anything by R.A. Lafferty*, especially “Past Master” and “The Flame is Green”
Walter Miller* - “A Canticle for Leibowitz” (Church history, and monasticism, and human dignity), but also his “Conditionally Human” (abortion)
Walker Percy* - especially his SF works “Lost in the Cosmos,” “Love in the Ruins,” and “The Thanatos Syndrome.”
Jerry Pournelle* - “Inferno”
Tim Powers* - most anything, but especially “Declare”
Fred Saberhagen* - especially “Love Conquers All” and “Brother Berserker”
Clifford Simak - “Project Pope” and “Mastodonia”
Morris West - “The Shoes of the Fisherman” - as has been said, if you stick a president in a near-future SF story, it becomes a “political thriller.”
Gene Wolfe* - anything and everything, but especially his short stories “The Detective of Dreams,” “La Befana.” Man, I love his writing.
Oscar Wilde* - “The Selfish Giant” A sweet fable from a man who reached out to the Church at the end of a tragic life.
Poul Anderson - “Operation Chaos”
Mary Doria Russell - “The Sparrow” and “Children of God” - the problem of evil (and, Jesuits in space!)