This session provides a forum to present advances in plasma theory relevant to current and future space missions, such as MMS, Parker Solar Probe and Solar Orbiter, as well as space exploration including space stations, the moon and Mars. The special focus this year is “Integration of fluid and kinetic models of solar system plasmas”. One of the major challenges facing modellers is the vast range of temporal and spatial scales that must be encompassed, from the smallest kinetic scales such as electron gyro-radii, to the largest global scales which can be treated by fluid models. Furthermore, the strong variation in parameters between different parts of the heliosphere must be accounted for in integrated models. Presentations will cover various approaches for tackling these challenges, including new codes and methodologies, and their application to heliospheric plasma processes such as waves, turbulence and magnetic reconnection - and interfaces with observations from current space missions, and planning of future missions.