Hard science fiction
Hard science fiction is the kind where the problem is the hero: a stranded crew, a failing engine, a number that refuses to add up until someone runs the sums again. The characters talk about orbital mechanics and oxygen budgets with the intensity others save for love, and the tension comes from physics that will not bend for anyone. Start with The Martian if you want the mood: rigorous, a little giddy, and hopeful about what careful people can work out.
