I've written a short story set in a sci-fi universe. It involves a spaceship traveling across interstellar distances, so I'm sure there are a bunch of issues I've hand-waved away regarding things like space rocks hitting my "massive bow shield" at 0.33c, and the spaceship has some elements that are clearly fantasy, such as a gravity generator.

But at its core, there's a (hopefully) realistic, multi-stage rocket bringing the fictional ship into space, then an antimatter-powered rocket getting it up to high enough speeds it can make the interstellar journey in a few years. Anti-matter rockets aren't a thing yet, but there are actual designs based on real science that ought to let me calculate basic things like thrust and fuel consumption and I'd think those are on-topic.

There are also real-world issues, such as what astronauts would eat during an extended journey, that I might ask about after doing more homework on the subjects, provided the answers don't already exist.

My Proposed Question

The specific question I'm concerned with is whether I calculated fuel requirements and trip times properly. I put a decent amount of effort into making sure the math adds up, and, while it's just a story and the math isn't that important, I want to make sure I did it right. Partly because I'm a nerd and I like as many parts of the story to be accurate as possible. And partly because it might help me understand space flight mechanics better, especially if I've made glaring mistakes.

Is the question "Is my math regarding travel between stars in a fictional spacecraft accurate?" on-topic for this site?

If so, is there a best way to approach it? I could go step-by-step through each phase of my flight plan in one question, with the generic question "did I do it right?". Or I could break up each chunk of the flight into a separate question.

There are certain elements that seem more inter-related than others. For example, the launch mass of the vehicle was calculated backwards. I started by knowing the time needed for the return trip for the plot to work. Then decided how much return payload was expected. Combined, those tell me how much fuel I need to leave the other star system. Which tells me the payload I need to bring to that system, provided I'm not getting more fuel while there. Etc. So "what's my launch mass from the origin planet?" seems like it shouldn't be separated from "what's my launch mass at the other star?"

On the other hand, I have a feeling I've over-simplified the process of leaving the origin star's gravity well. That isn't directly related to calculating the launch mass of the vehicle based on other factors, since we could just treat the escape process as having a certain linear distance, even if the actual path is a spiral. It might be beneficial to ask specifically about how to calculate the effective distance of leaving a star system. Or that might be a stupid way to think about it.

As I mentioned in my other question (the general on-topic-ness of fictional spacecraft questions), a lot of these questions could be reworded to sound like I'm talking about real spacecraft, with no mention of my fictional backstory. But I don't see why that would be an issue, since the fundamental question in either case is about the accuracy of my math on getting spacecraft X with engine Y to destination Z, and that answer should be answerable whether it's a real spacecraft Space X is thinking about building in 50 years, or a spacecraft I made up for a story.

If not on-topic, is there a site where such a question would be on-topic? World-building isn't a bad choice, but I'm interested in answers from people who know how actual space travel works rather than people (like me) who have a decent understanding of the basic physics and math involved, but maybe aren't so good at the details.

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    $\begingroup$ Just be aware there's very little overlap between "actual space travel" and interstellar flight. $\endgroup$ Jul 19, 2021 at 1:20

1 Answer 1


Is this question about evaluating my math regarding a fictional spacecraft on-topic?

It certainly can be! As long as it's about aspects of spaceflight that are connected to the real world then it could be fine. I think there have already been several well-received and answered questions by SciFi authors here asking about spaceflight aspects of their stories.

My Proposed Question; calculated fuel requirements

This seems perfectly fine, as long as your fuels and the propulsion system they are used in are based on conventional spaceflight principles. No Guild Navigators or faster than light engines consuming pixie dust please!

...question about evaluating my math...

Questions with specifics, details and previous work (e.g. "What have you tried?") are the best kinds of questions! Yes, please! :-)


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