Research into manned spaceflight is shifting from low-Earth orbit to destinations much further away, like Mars and the asteroid belt. But society will have to invent many new technologies before it can plausibly send people to those distances.
A good plan today is better than a perfect plan tomorrow. Don't wait for an inspired ending to come to mind. Work your way to the ending and see what comes up.
Eventually, while researching, you'll learn something you didn't want to know. Some fact that ruins a plotline you had in mind. The good news is that sometimes, learning all the facts can make for a much more interesting story than you originally had in mind.
I study orbital dynamics as a hobby. My idea of a good time is sitting down and drawing on that knowledge to imagine a space mission from beginning to end, getting as many details right as I can.
Back in the days of Apollo, sending humans to the moon was the only viable way to get the scientific data we wanted. But now, with our computer and robotics technology, there's very little an astronaut can do on Mars that a well-designed rover can't.
Designing a station with artificial gravity would undoubtedly be a daunting task. Space agencies would have to re-examine many reliable technologies under the light of the new forces these tools would have to endure. Space flight would have to take several steps back before moving forward again.
Just so we're clear, Mark Watney is who I want to be. He has all the qualities I like about myself magnified without any of the qualities I dislike. Mark Watney isn't afraid to fly.
I was born too late to experience Apollo 11, though I do trek to Dad's house every time there's some space event. There's something awesome about crossing your fingers and watching a tense Mission Control room do their thing.
Thanks to our modern era, facts are incredibly easy to come by. A few web searches for your subject matter, and you have all the information you could dream of.
There's more to research than just looking up facts. Eventually, you have to make subjective calls. If you're writing a science fiction novel, there's probably some speculative technology in it. You'll have to decide how to project existing technology forward in a plausible way.