Three interwined stories between a group of astronauts in space finding them race against time to find their way home to Earth.

This logline is a bit vague.

Even if there’s a group of characters there should be someone who’s the main protagonist, and with astronauts, there’d be a chain of command. Someone should drive the plot forward more than the others, so write the logline from their perspective.

Next, give them a clear, tangible goal, like be the first humans to travel to Planet X, (change to whatever fits) or on a rescue mission to get that one astronaut they left for dead on Mars. (Guess what movie I just re-watched.) They should have a goal/mission.

Who, or what are trying to stop them from from achieving their goal/mission. I reckon this is “Something disastrous” but it would help if it’s more specific than that.

Finally what are the stakes, what happens if they fail, and also if there’s a ticking clock, they have limited time to achieve their goal/mission before the disaster. For instance, they have to catch Matt Damon before the stripped down space capsule falls back down to Mars.