In my book there are occasional battles between space ships or fleets which can span hours due to the distances involved. Most of the combat is done using missiles which can accelerate at e.g. 750g with enough fuel for 30 minutes, which means they have a range of about 40 lightseconds. Ships move with 200g and are pretty much constantly accelerating in various directions to change their momentum.

This becomes fairly complicated over time, because I have to keep the momentum of all ships and missiles in mind when calculating things like time to impact, distances and all of that. I'm currently doing all the calculations manually, which is extremely tedious and time consuming, not to mention error prone.

I've tried to find a tool where I can say "Ship A is at X,Y,Z and is accelerating at A gravities. Here is Ship B. Now step through it second by second, occasionally changing the vectors or adding new objects (missiles)." I have yet to find a tool like that and if I program it myself, I don't have time to write the book.

Does anyone know a tool (free or not) I can use to simulate my space combat?

  • $\begingroup$ I have never tried it, but maybe Universe Sandbox is what you are looking for? It does mostly focus on smashing planets together, but it might also be able to simulate objects with negligible gravity. $\endgroup$
    – Philipp
    Jun 7, 2018 at 14:53

2 Answers 2


If you are not afraid of some hacking, Kerbal Space Program may be your answer. It's a game, but with physics reasonably close to what you have in real life. It has time warp option and good trajectory and time calculations.

You will need some add-ons:

  • HyperEdit to put things where you want them to be.
  • One of the "infinite fuel" mods or tricks, unless you actually want to care about that.
  • MechJeb or something similar if you want autopilot, and for your purposes you probably want.
  • One of the "real solar system" or planetary system editors, to set up a scene.
  • Mod that allows acceleration of not focused ships. I have one installed, with solar sail or ion engine, will fill this bullet point when I'm near my computer.

This should do a reasonably good job to simulate movement in space.

Note about relativity: 750 g acceleration for 30 minutes gives us merely 4.4% of speed of light. This is substantial, but too small for most readers to notice difference. Thus, KSP being Newtonian only does not disqualify it. And OP asked for Newtonian anyway.

Of course, Cort Ammon reminded me of Obligatory XKCD!

Webcomic about XKCD teaching orbital mechanics

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    $\begingroup$ +1. Obligatory XKCD $\endgroup$
    – Cort Ammon
    Jun 7, 2018 at 14:34
  • $\begingroup$ KSP is a good suggestion, however relativistic speeds are involved... Is there a mod for that? $\endgroup$ Jun 7, 2018 at 14:42
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    $\begingroup$ While KSP is great for understanding Orbital Mechanics, I don't think it's ideal for simulations involving multiple accelerating crafts, especially if that acceleration is changing. It's also not ideal if OP is specifically ignoring orbital mechanics, though there are ways around that I think. $\endgroup$ Jun 7, 2018 at 14:54
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    $\begingroup$ @Renan While relativity might be important for other use-cases/books, I've decided to ignore it because it makes matters too complicated and readers probably don't care either way. I've still limited my ships to 0.4c (or FTL which breaks all rules anyways) where time dilation is minimal, so the readers that do care won't yell too much (I hope). $\endgroup$
    – user48721
    Jun 7, 2018 at 15:25
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    $\begingroup$ @SCMorfildur I hope that, too. This is what I know, so I'm sharing. $\endgroup$
    – Mołot
    Jun 7, 2018 at 15:30

Children of a Dead Earth is a space combat game with near-future technologies with a big accent on actually simulating what would happen. Now, it may be a bit too realistic for what you want, and the focus on near-future tech may limit its scope compared to the more fantastic systems generally found in SF. However, there are great insights to be found in it.

Note that the simulation isn't perfect: it has been developed by one person, so its scope is necessarily limited and some elements are not quite as finely modeled than others. Still, it is probably the most advanced space combat simulation tool available on market at the moment.

As a side-note, its newtonian simulation is more advanced than in KSP, as it always simulates the influence of all bodies instead of only the closest one. KSP is easier to handle and more adapted for sketching long distance travels with no combat (say, the Voyager probes), while CoaDE will give a more exact result.

  • $\begingroup$ I've tried to use it, but the ship design is just too limited for my requirements. It doesn't support handwavium. Creating sci-fi ships with constant acceleration and simulating the combat requires more time than calculating everything myself. It also only has a resolution of 1 minute, not second. It seems to be highly scientifical, but it's not what I'm looking for. $\endgroup$
    – user48721
    Jun 10, 2018 at 18:04
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    $\begingroup$ @SCMorfildur You can mod it to add handwavium materials. Some fusion fuels are in the workshop or on the forums. You can also use black box modules to simulate arbitrarily powerful systems. $\endgroup$
    – Eth
    Jun 11, 2018 at 13:18

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