...That is the question.

In my previous question, I asked about coilguns, how powerful we could make them and their plausibility. In that thread, and the discussion I had with Starfish Prime afterwards, I came to the conclusion that even the level of sci-fi technology I was aiming for, which is pretty small-scale compared to most other sci-fi settings, is beyond what we know can be accomplished.

That's not to say that we definitely can't create short-barreled coilguns with muzzle velocities in the dozens of kilometers per second, or fusion rockets with both high thrust and high efficiency, but we don't know for sure that they are even possible. It may be that there's an upper limit to technological progression, and that making starships that do what I want them to do just isn't possible, and therefore isn't realistic. If such an upper limit exists, it is all but certain that Star Trek is well beyond it.

With this in mind, is there really any point to going into great detail about how the universe works, and trying to make it as realistic as possible, when I know personally that it probably isn't possible? If I'm going to shrug my shoulders and go ahead and give my ships engines that I know would realistically melt within ten seconds, should I even bother to explain what those engines are and how they work? Or should I handwave and be nebulous?

I'm sort of leaning towards keeping the technology level theoretically possible, if you had absurdly ridiculous efficiency, but just keep it in the background without going into any detail about it. That way, if someone who likes poking at sci-fi realism - like me - comes along, they'll take a look at the numbers and go either 'that could work' or 'that's unrealistic' rather than 'that's completely absurd'.

  • $\begingroup$ I am not sure this is suited here or a better match for our meta. Here it sounds like asking for opinions. $\endgroup$
    – L.Dutch
    Commented Sep 3, 2019 at 6:56
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    $\begingroup$ Well, that's why I stuck the 'worldbuilding-process' tag on it. I'm asking for people's opinions... on how I should worldbuild. $\endgroup$ Commented Sep 3, 2019 at 7:07
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    $\begingroup$ This is the whole hard or soft science fiction game, it's up to you which version you choose to write. $\endgroup$
    – Separatrix
    Commented Sep 3, 2019 at 7:26
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    $\begingroup$ There is IMHO only one rule, be consistent (Martian sciencing his way out of trouble only to be eventually saved by a ship using Hitchhiker's Guide's improbability drive would probably not sum up to a good story) $\endgroup$
    – Mori
    Commented Sep 3, 2019 at 8:16
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    $\begingroup$ @TheDyingOfLight random-walk jinking will play exceedingly badly with droplet radiators, for obvious reasons. Whether or not torch drives are useful thing (they probably are, in moderation) is kinda drifting away from the key part of the question, so I'll save this particular discussion for another day ;-) $\endgroup$ Commented Sep 3, 2019 at 18:11

3 Answers 3


This very much depends on the sort of story you want to write and whether the technology itself is effectively a character in that story.

  • Star Wars. It's entirely fantasy, it has wizards and magic swords, for all practical purposes they might as well be riding horses or flying carpets as in spaceships. Everything runs on handwavium and technology is entirely driven by the needs of the story.

  • Star Trek. A space soap. Space is a set allowing them to meet a new race every week rather than having to deal with only the immediately available characters. The technology is still handwavium but it's more of a character by virtue of its tendency to fail. Certain aspects of the technology are occasionally a limiting factor of the story.

  • Mars trilogy (Kim Stanley Robinson). The technology is a hard limit on the things they're able to do and all actions of the technology must be justified as possible. Technobabble is hard limited by actual physics or accepted tropes (space elevators).

So as you can see, it's about what you want to do. If for example you want to write a "space road trip" you can do it Star Trek style where it's all about who you meet at significant points along the way, or you can do it hard scifi style where it's about the interactions between the crew in their stl ship for year after year.

Remember though, normal people almost never talk about how things work. Consider the mobile phone, we might complain about lack of signal, we sometimes talk about the need for more masts or capacity, but actually we technobabble about 5G and GPS which out of context are entirely meaningless terms, and never talk about how the thing actually works, even when it doesn't.

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    $\begingroup$ In my view hard scifi has a terrible tendency to get left behind by technology years before its supposed to and the stories can date very badly, going into excessive detail about valves being a classic example, but then I'm also a big fan of straight fantasy. $\endgroup$
    – Separatrix
    Commented Sep 3, 2019 at 14:08
  • $\begingroup$ Yeah, there's a lesson about plausibility being more or less orthogonal to detailed techno-nerdery... being sparing of the detail also allows an author more wiggle room around potentially being wrong (KSR has come unstuck a few times there, and their fixes to their fictional universe seemed particularly jarring to me. YMMV, of course) $\endgroup$ Commented Sep 3, 2019 at 18:14

Write what you know.

You are conflicted about your desire for certain SF tech and your inability to explain them. Clearly that interests you. You can get good traction from that for your story!

Your engineering characters have the same concerns and are conflicted in the same way. You can have one or more scenes where they walk thru the tech.

I picture Oz the grizzled engineer laying out why the thrusters he is currently maintaining were held to be theoretically impossible when he was in school. One of his classmates got expelled for pranking the professor who humiliated him for his theories about more powerful thrusters. Of course that classmate went on to build the thruster that carries his name, and he even named the flagship of his company after that professor. Oz is still not sure why the professor was not right; it seems like the thing should melt. He is glad that so far it has not.

Scenes like this will give readers a basis in fact (about coilguns etc), acknowledge that your SF tech is edgy, and also let them learn some about your characters.

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    $\begingroup$ This actually reminds me of something my dad told me. When he was in college, he wrote an engineering paper proposing an airliner with jet engines far larger than anything that existed at the time. His professor gave him a low grade because such engines were considered implausible. Today, my dad works for Boeing, designing aircraft that use jet engines even larger than the 'implausible' ones he laid out in his report. $\endgroup$ Commented Sep 3, 2019 at 17:00

Circular Coilgun

Why not make the coilgun circular like a collider and keep circulating low mass projectiles until they reach high speed and then release them. It works for atom smashers so should work in principle. The limiting factors is the strength of the magnets and size of the ring. The bigger both are, the faster you can go.

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    $\begingroup$ I think you are missing the point of the question. It is not about making this one specific example work, it is about the general problem about whether or not you should bother to go into details about technologies you can not fully explain anyway. $\endgroup$
    – Philipp
    Commented Sep 3, 2019 at 13:08
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    $\begingroup$ Hey @Thorne. Go put this scheme under the authors previous question about coilguns. It is a good answer to that question. worldbuilding.stackexchange.com/questions/154298/… $\endgroup$
    – Willk
    Commented Sep 3, 2019 at 15:46

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