I recently started writing a book expanding myself from my typical fantasy genre into SciFi. I have taken a start however I have reached an impasse and can not really decide how I should structure my story. Is their a specific way a Sci Fi story is structured since I am stuck and can not seem to progress in my story. Please help me find a solution to this problem.
Science fiction has some unique staples, but there are a million structures and styles. Certainly there's no single structure that encompasses everything from the taste of genius in "Flowers for Algernon" to the mind-bending dual view of causality in "Story of Your Life"; no single structure that captures both the dark paranoia of Philip K. Dick and the majestic anthropological explorations of Ursula Le Guin.
Don't try to conform to a formula. Instead, figure out what you see as the crux of your story, and figure out your structure according to that. Is your story about a fascinating species of aliens, or is it about the experience of living among people alien to you? The joy of exploration, or the hubris of mankind? Figure out what your story is about, and the structure will follow.
And in the meantime: read short fiction. There's a bottomless treasury online; at Forever and Uncanny and Escape Pod and a dozen others. That way you'll get a sense of the many story structures, unique or commonplace, that SF is capable of.
If you have written fantasy, sci-fi can be written in the same structure. Pretty much all stories follow a 3-4 act structure (the second act in the 3 act structure can be broken into two acts).
1) 25% of the story. You introduce your characters in their normal life, solving normal life problems, meeting each other in normal-life circumstances. Something happens (an inciting incident that pushes them out of their normal life to solve a problem).
2A) 25% of the story. The character isn't sure what they are doing, but are reacting to the problem as best they can. Usually ends in a setback or game changer, but doesn't have to.
2B) 25% of the story. Through flailing in (2A) the character has learned enough to come up with a plan. This is a more proactive phase, actually planning and executing. Can still have failures, and usually ends in one, but often followed by an epiphany or realization of what needs to be done to solve the problem.
3) 25% of the story. Concluding confrontations, or working solutions. Often full of close calls or harrowing (think Doc and the clock-tower in Back to The Future), then a short aftermath proving there is a new normal life, or life has returned to the previous normal.
Now I say 25% for each, but that can swing 10% either way. Don't count words and curse yourself if the inciting incident lands at 20%.
I am a discovery writer, which means I do not plan a plot or incidents beforehand, I don't write to an outline. I invent characters, and think about them a lot, and then start writing them doing things.
But that said, I also know to write to the above structure. That wasn't invented, it was discovered by distilling thousands of good stories and realizing this structure is a generalization of what good stories have in common, for a beginning, middle and end.
So, while I am writing the normal world, I am looking for an inciting incident that can flow from my characters. I know I want them to get together, but I am not sure how that happens. Once I find one, then I am looking for "reactive" actions to address it. And so on. My characters do what they do, but once I have enough "reactive" I start looking for what will give them a plan.
Your story is probably stuck in some act, and you don't have an idea to get out of that act and into the next. That is what you need to find, and why you stalled.
Classically speaking, science fiction explores the ramifications of some piece of future technology. But these days you can find science-fiction versions of plotlines from every genre. In practice, this means you can use any structure you want. If you want to write classic science-fiction, however, you should make sure it all goes back to the tech.