Can I run a mod free install for steam KSP?

[Buster Charlie]

Right now I run a pretty mod heavy build, however a lot of the community challenges forbid mods, or some mods. Is there an easy way to run a second mod free install of ksp if I'm using the steam version?

[FullMetalMachinist]

Absolutely, it's the same as doing it without steam. Just move your current, modded, folder from the steam directory to somewhere else (to get there go to KSP in steam, right click, and click on browse local files). Then, in steam, just re-download KSP from steam. 

Now, your modded game will only be able to be launched from the KSP.exe from wherever you moved it, and steam won't track the hours played any more. 

[Snark]

Another way, that doesn't require re-downloading anything, just copy your current KSP directory tree to a new location.  Then, in one of them, just delete everything in GameData other than the "Squad" folder and you're good to go.

[YTNewneo]

Yes like the posters before me already said, you can make copies of the "Kerbal Space Program" folder that is located in you steam directory and just copy it somewhere else. that is how i have my steam version always without any mods and updated to the latest version, and i have another Folder on my Hard drive with a few different KSP Folders with different mods installed. That way you can have one for Real Solar System mod, one for Interstellar Mod, and any other versions that you would like to have. Also makes sure any update does not immediately break you modded game.