I have found that the -force-opengl command does not work directly from the ksp app but instead from the terminal command to launch ksp itself the way this is done is:
1. Right click kerbal space program
2. click "open package contents"
3. open the folder "MacOS"
4. Drag the file named KSP into terminal
5. put 1 space and type -force-opengl
This should work on all ksp versions on High Sierra