The Korolov escort missions suffer from a large increase in difficulty between apprentice level (where most freighters can defend themselves) and journeyman level (when Charon frigates start appearing). Although higher value freighters will be attacked by more gunships, this has little impact on difficultly compared to the presence of a Charon frigate.

For intermediate value freighters (i.e. Journeyman level) the attacking frigates could be replaced with Drake-class missile ships

johnbwatson 8 Jun 2015:

Also, Charon Frigates often spawn out of range, and park there. They should either park closer to the path or simply attack the freighter directly.

george moromisato 20 Jun 2015:

I've fixed this by adding a Drake for the intermediate levels (as you suggested in your mod).