Hi, In the future I want to make a realistic game set in space. Part of the realism is physics and sizes/distances. Thus, one of the things I want to have solved before I even begin on designing the game graphically is that of navigation. Navigation will be done primarily through AI; i.e. the player will tell the ship where to go and it will go there. Before I even get into 3D, I must solve the problem of navigation in the 2D. I already pretty much have the equation for what the AI would do if there isn't any near solar masses to effect it gravity. What I have so far is this: If the ship is already pointing in the direction it wants to go: a = acceleration d = distance ra = rotational acceleration 1: forward thrust for t = sqrt(2*d/a)/2 - sqrt(pi/ra) 2: rotational thrust for t = sqrt(pi/ra) 3: negative rotational thrust for t = sqrt(pi/ra) 4: forward thrust for t = sqrt(2*d/a)/2 - sqrt(pi/ra) to explain: 1: accelerate toward target 2: half way there minus half the amount of time it'll take to turn around, start turning around faster 3: slow down the rotation to that the ship is facing the 180 degrees from original direction 4: slow down the ship to stop at the point you wanted. Pretty simple. But now comes the problem of gravity. How can I have a navigation AI account for the effects of gravity of nearby planets, moons, and the sun? Since the effects are negligible, I won't worry about other ships or other masses. If anyone can solve this for me, or even just point me in the right direction... feel free to post! Thanks Edit: PS, this is assuming ships with only rear primary thrusters and small side thrusters for rotation.