Tidal Force

The force of gravity depends on the distance to the object that is exerting the gravitational force. On a large object orbiting closely to its orbital parent, the force of gravity on the side of the object closer to its parent will be significantly larger than the force on gravity on the more distant side. This difference in forces will tend to deform the object, causing it to bulge and stretch. This stress is called the tidal force, as the tidal force from the Moon is responsible for the ocean tides on Earth. In extreme cases, this deformation can cause an object to break apart, a process known as Roche fragmentation. If the tidal force in an object changes over time, the changing deformation in the object will cause internal friction and produce tidal heating.

Settings

 * Roche fragmentation can be toggled on and off in the Create Fragments in the full Sim Settings Menu.
 * Tidal heating can be toggled on and off in the Thermodynamics section of the Sim Settings Menu.

Models
Universe Sandbox calculates the tidal force acting on an object with a mass of M and radius R due to another object with mass Mi at a distance of d in a simulation with a gravitational constant of G using
 * $$F_i = \frac{2 M M_i G}{d^3} 2R.$$

The total tidal force is calculated by adding the forces from all the other objects in the simulation.