I'm trying to figure out the best way to accurately simulate the impact that formed Earth's moon. The idea would be to use particles/grains that each have their own gravitational force. For simplicity, all particles have the same mass and density. My questions are:

1. What type of simulation would be the most optimal for this?

2. How do I give the particles from one planet an initial velocity?

3. How do I set up the simulation so that every particle exerts a gravitational force (weakens by the square of the distance)?

Did you ever figure this out? I am working on the same thing. Right now, because I saw nasa's simulation was using SPH, I am using flip sims with initial sphere sources and a simple pop wind to move theia towards the proto earth. Then I am using a compbination of pop attracts to simulate gravity, and popaxisforce to give the sim an orbit. The problem I am having is to have the moon form out of the debris. In ahve tried using an animated object as SOP input for another pop attract to have the particles slowly form into the moon, but strangely as soon as I add that the whole sim disapears.