RP-1 Realistic Progression One Welcome to Realistic Progression One (RP-1), one of the most challenging and rewarding experiences available in KSP. RP-1 provides a well-developed and carefully balanced career mode for use in conjunction with Real Solar System (RSS) and Realism Overhaul (RO). As the sequel to RP-0, realism, features, and gameplay experience are improved and deepened. We used to say that it was a lightweight career addon, but it has become a lot more in the recent y