Proton is an active expendable heavy-lift launch system. The commercial launches are operated by International Launch Services. Proton is now built only in 1 variant, Proton-M. There were also 2 other variants which are currently retired: Proton, Proton-K. The vehicle operates out of Launch Sites 200 and 81 at Baikonur.
I recommend turning on "Advanced tweakables" in KSP settings.
To download each variant of Proton, go to the "Files" section.
Here are my other projects.
Proton-M, Proton-K
8S810K
8S811K
8S812
Proton-K
T-0:00:01 - Main Engine Ignition
T-0:00:00 - Lift Off
T+0:01:28 - Second Engine Ignition
T+0:01:30 - Main Engine Cut Off
T+0:01:31 - First Stage Separation
T+0:03:10 - Second Engine Cut Off
T+0:03:12 - Second Stage Separation
T+0:03:14 - Third Engine Ignition
T+0:03:22 - Fairing Deploy
Proton-M
T-0:00:01 - Main Engine Ignition
T-0:00:00 - Lift Off
T+0:01:10 - Second Engine Ignition
T+0:01:12 - Main Engine Cut Off
T+0:01:13 - First Stage Separation
T+0:02:52 - Second Engine Cut Off
T+0:02:54 - Second Stage Separation
T+0:02:56 - Third Engine Ignition
T+0:03:04 - Fairing Deploy
Calculated with full thrust.