I've been thinking a bit about what makes scifi stories work, and it seems to me that the ones that work best are the ones asking questions, not the ones that have an answer, or a pat answer to whatever's going on in the world. They aren't even really about modern technology -- pick your favorite sci-fi, and then, using only the novel or tv/movies -- explain exactly how the engines work, or the miracle cure or the laser waepons. I'll bet good money that you can't do it. They seem more like the means to an end -- engines work because they need to get the hero to this or that planet in time to watch the situation blow up around his ears.
But they always seem to ask questions. Maybe all writing does, but scifi seems to have the distiction of asking questions that don't have easy answers. Romance seems to spend most of its time asking questions of the heart -- cheating spouses, love triangles, and so on. Mysteries usually center around figuring out who did the deed and why. These are fairly conventional -- after all, there are only two answers to "should I cheat on my wife" -- yes or no. And once you find the murderer and why he did it, there's no more questions. With a scifi, it seems that the questions are more fundemental and that they don't come down to a simple answer -- in fact sometimes the solution to the problem comes from seeing a different question.
Imagine that Earth is suffering from a plague. A nasty plague that rots your body from the inside out. The victims can't move, but they can think. After exploring around for some time, a cure is found. Unfortunately it can only come from killing living beings that may in fact be sentient. So what do our heros do? Do they leave the beings alone and sentence humans on earth to death? Do they kill the lil feckers and save humanity? It sounds like a scifi, yet the premise is essentially from stem cell debates. I'm asking the question in the scifi universe, but it's a down to earth question.
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*To understand what a real essay is, we have to reach back into history again, though this time not so far. To Michel de Montaigne, who in 1580 published a book of what he called "essais." He was doing something quite different from what lawyers do, and the difference is embodied in the name. Essayer is the French verb meaning "to try" and an essai is an attempt. An essay is something you write to try to figure something out.
Figure out what? You don't know yet. And so you can't begin with a thesis, because you don't have one, and may never have one. An essay doesn't begin with a statement, but with a question. In a real essay, you don't take a position and defend it. You notice a door that's ajar, and you open it and walk in to see what's inside.*