Some or all of the features on this page require the Cheats Expansion in-app purchase.
Infinite Fuel is a setting of Sandbox Mode. If it's turned on, the amount of fuel in a rocket stays the same. Using this mode requires the player to have the Cheats Expansion.
Use of unlimited fuel[]
Using unlimited fuel may be considered cheating in many cases. Due to that, it's not used for normal missions. It's most commonly used for testing purposes and to make large builds, such as rockets that need more space than the build space has. In other cases it's used in missions that are impossible without using sandbox mode: e.g., Sun Return Mission.
A rocket flying with the infinite fuel option enabled.
The infinite fuel option can be selected in this setting path: World menu > Menu > Cheats > Infinite Fuel. If enabled, Infinite Fuel will be shown in both physics view and map view. Assume that before the setting is enabled the rocket has 90% fuel. Once the setting is enabled, the rocket remains at 90% fuel, and fuel would not be drained. However, if the rocket has no fuel before enabling this setting, it will still have no fuel and the message "Out of fuel" will still appear.
Reactionless engine[]
Docking Port Engines require no propellant to provide thrust, but are uncontrollable, and don't seem to work in some cases. They require 60 FPS to work.
RCS thruster bug[]
An example of a rocket using the infinite RCS fuel bug.
Until version 1.5, the RCS Thrusters could switch to electricity after all fuel had been consumed. This state would not update until the RCS is updated (ie. restarted).
The fastest way to achieve this is to place plenty of RCS alongside with a small fuel tank. The high number of RCS thrusters would quickly drain all available fuel. The RCS would then use electricity, which could be provided easily with the RTG or the Solar Panel, both small and large. This bug was fixed in version 1.5.