Houston, we have a problem.With no plot twists or surprises to speak of, “Space Cowboys” is a terrific movie to take your elderly nana to see.In this country, our somewhat inaccurate idea of getting older includes wrinkles, shawls and bland mushy food. Somewhere in the back of Dirty Harry’s mind, he must agree.The idea for Clint Eastwood’s new movie probably came right about the time senior space pioneer John Glenn launched into orbit again. But, as usual, the movie goes one better. In “Space Cowboys” we get not one but four old guys – specifically Tommy Lee Jones, James Garner, Donald Sutherland and the aforementioned Eastwood, who also directed this confused comedy/thriller.In the movie’s black and white opening sequence, we learn the four members of Team Daedalus were denied the opportunity to go into space when a monkey replaced them and NASA was turned over to civilians.The black and white opening is important for two reasons: Every thing that happens here will of course happen again two hours later; while the opening features young actors who look like the four stars, the stars have dubbed their own voices over the track. Any 19-year-old flyboy who sounds like Clint Eastwood has either emphysema or my immediate sympathy.Fast forward 42 years, and the boys get their chance when something goes haywire on a Soviet satellite that only Eastwood’s character can fix. He tells NASA yes, but insists they let him go up with his original crew.After the obligatory gathering of the old gang (who’s going to say no?), a very funny hour of the movie commences. We see the foursome train with astronauts less than half their age. We feel their pain – and their pain is funny.But somewhere around the last 45 minutes or so, the movie changes from “Grumpy Old Men” to “Armageddon.” There seems to be an endless amount of things to go wrong in space, and this movie’s last half cashes in on that theory.Secrets will be revealed, sacrifices will be made and the audience will gasp with surprise.Er, almost. The problem is, “Space Cowboys” doesn’t have nearly enough surprises to gasp at. If you are a gambling person, the odds are good you’ll know exactly what Eastwood and company are so shocked to find waiting for them in space.The only mystery of “Space Cowboys” involves a spiritually uplifting, but totally impossible last scene that defies any amount of science – be it movie science or scientific fact.For the college-aged viewers, the tensest part of the film was watching the NASA footage of the space shuttle taking off. A generation of people who watched the Challenger blow up on their second-grade classroom’s TV don’t need to be told bad things can happen in space.This isn’t exactly a bad movie, just a bad script. It is hard to believe that Eastwood, who created such an atmosphere of suspense with “In the Line of Fire,” could do so poorly with the second half of this movie.Based on the mostly middle-aged audience’s reaction, if you’re looking for a movie to bond with your parents or grandparents, this may be a good bet.The movie’s biggest sin is predictability. In a comedy, that’s allowable, but in a thriller – it’s unforgiven.