Can I revert a save file to another version?

[Mech_Jeb_42]

I am playing in 1.8.1 and the rest of my save files are in 1.9. Is there a way to perhaps revert or restore them to 1.8.1? I play w/ a lot of mods and most are in 1.8.1 so I was just wondering. Thanks! 

[jimmymcgoochie]

Did you start the save games in 1.8.x or 1.9.x? After a bit of testing I can confirm that a save game created in KSP 1.8.x, moved to 1.9.1 and loaded up, then moved back to 1.8.1 and with all references to 1.9.1 changed to 1.8.1 in the persistent.sfs save file, does indeed load up and work as expected.

I'm fairly sure you can't go back to 1.7.3 or earlier though due to a change in Unity version that came with 1.8, but I might try that now...

Edit: wow, it actually IS possible to go back to 1.7.3 from 1.8.x/1.9.x by editing the save file!

Edited April 12, 2020 by jimmymcgoochie

[Mech_Jeb_42]

Some were started in 1.8.1 and some were started in 1.9. I found that most of the mods were not yet compatible w/ 1.9 and went back to 1.8.1 and found that all my saves were in 1.9.

Also I'm kinda s a noob to modding and files as i normally use CKAN so i have no idea what you are talking about. 

It would be much appreciated if you could walk me through the proceses.

[jimmymcgoochie]

I'm going to assume that you have two instances of KSP right now, one in 1.9.1 and one in 1.8.1.

- Open your KSP 1.9.1 directory, in CKAN it's file > open KSP directory. Helpful little shortcut, that.

- Go to saves > the name of your save game. Find persistent.sfs which is the save file the game will load when you select it in the main menu. Copy that file.

- Switch to your KSP 1.8.1 directory (manage instances > your 1.8.1 instance through CKAN), open the directory and go to saves > your save game's name as before. Delete the existing version of persistent.sfs if there is one, then paste the copied persistent.sfs here.

 - Open up persistent.sfs in the text editor of your choice. (Notepad, VSCode, etc., not something like Word!) Note that I mean the copy and pasted version now in your 1.8.1 save folder and not the original in the 1.9.1 folder!

- Find every place in the persistent.sfs file that says 1.9.1 and replace it with 1.8.1, this is easiest using control(/command on mac)+F then searching for 1.9.1 then replacing each one it finds until it finds no more.

- Fire up KSP and load the save game.

That should do the trick! However if you're using some of the new parts or variants introduced in v1.9 (mainsail, skipper, thumper or the drain valve) in any of your active vessels they might not load correctly/at all; you have been warned...

Let me know if it works or not