Requires Kopernicus, Sigma Dimensions, and Principia. OPM is recommended.

Realistic Rescale re-scales all planets and orbits to make both achieving orbit and traveling between planets much more difficult than it is in stock. Large manned interplanetary travel is really hard with conventional propulsion systems. Many bodies are approximately 3.2x the size and 6.4x the distance as they are in the stock game.

Changes:

Most planets rescaled to around 6.4x the semi-major axis of their stock orbits. Most planets rescaled to around 3.2x the size of their stock counterparts. Most planets now have axial tilts similar to their real-life counterparts. Gravity of all gas giants increased. Jool capture takes similar delta-v to stock. Eve now slightly smaller than Kerbin with lower gravity and no moons, and rotates retrograde. Mun now much further away and with an inclination of around 5 degrees to the ecliptic, making eclipses rare. It's still reachable with a Tantares N1, SSTU SLS, or SSTU Saturn V. Minmus and Gilly have been rescaled to be around 0.3 times the size of Phobos and Deimos respectively, and now orbit Duna. Ike is now a Psyche/Vesta analog. Laythe, Vall, and Tylo now rescaled to have similar size/orbits/gravity to Europa, Ganymede, and Callisto respectively. Retrograde Bop. Eeloo and Slate rescaled to be closer to the scaled-down sizes of Enceladus and Rhea, respectively. Gravity changed to be much lower both for realism and Principia compatibility. Tekto now smaller and less steeply inclined above the plane of the Sarnus system. Moons of Urlum all made much smaller. Tal moved to roughly resonant orbit with Wal because Principia hates moonlets.