While the very first space combat game (Triplanetary) had fuel on the rockets, most space combat systems don't use fuel at all.

With the popularity of television series like The Expanse and Babylon 5, audiences are more interested than ever a touch of realism in their space combat games. The most effective way to add accuracy to space combat, with the least amount of additional rules overhead, is to acknowledge the Tyranny of the Rocket Equation.

Konstantin Tsiolkovsky was one of several people to derive the equations governing rockets in the early 20th Century, and his is the name most commonly associated with it. If you've ever heard the term "delta-V" (Δv), that's "total change in velocity," and it comes from his work.

This product provides a small amount of background on the Rocket Equation, and describes use cases. The bulk of the product are simple to use lookup tables: Cross reference the percentage of your ship's mass devoted to fuel with the tech level of your engine, and you get the total number of fuel points in "thrust units per turn," which map to whatever game scale your game uses. There are three tables covering three different possible groups of settings, and it will work with any game with a ship construction system.