US2 sim settings

Download Universe Sandbox 2 from Steam if you don't already have it.
http://universesandbox.com/

To set up the correct integrator settings:

Go to the settings menu in-game. On the top row of setting tabs, click the arrow at the right end of the list of tabs to reveal the debug tab. https://i.imgur.com/yQnX3Mk.png

Click the down arrow next to Computation Device. You should see this: https://i.imgur.com/TdZzZFa.png

Change Integrator ID to PEFRL. This will sacrifice speed for better physical accuracy. Annoyingly, this setting will have to be re-set every time you run a new simulation, and every time you run a saved simulation. There's some indication that this may change in the future, but as of 11/16/2018 that's the way it goes.

Then, in the Sim settings on the bottom taskbar: https://i.imgur.com/w9Q9kya.png , click it, then click More.  Under the Gravity category, click the arrow next to Automatic Accuracy, to reveal the accuracy settings, and toggle Auto Accuracy OFF. Choose a Max Positional Error Per Step which fits, I'll go into more detail in a moment. Then turn on Sub-Stepping.

Max Positional Error Per Step depends upon the scale, intended accuracy, and time of the simulation. It will never be a perfect representation because infinitesimal errors will eventually create macroscopic unpredictability. For simulating the Solar System over about a thousand years, a max error of about 1 moon (one lunar diameter) is sufficient. For simulating satellite systems like that of Jupiter's moons or hypothetical multi-earth-moons, use only a few kilometers or so. You can use the timer on the bottom of the taskbar to ensure you only timewarp at an acceptable time rate. If it's far too slow, you can raise the max positional error.

If you use default integrator settings, you'll be able to play around with exploding and crashing planets just fine, but the solar system will fall apart after less than 500 years, and not even simple two-body orbits will stay stable. Using these new systems, what appears to be an unstable chaotic mess can turn out to be nearly rock solid orbits.