shooting-game | Simple alien shooting game built using python3 | Game Engine library

Don't do this manually. The only time you should manually do the calculation is when you have access to Unity's source code but an average Joe don't. Even if you get it working with your calculations the code can break anytime.

Unity 2017.1 introduced the Physics.Simulate function and Physics.autoSimulation property. Physics.autoSimulation is used to disable physics then Physics.Simulate is then called to manually simulate physics and return the position the Rigidbody object would be in the future.

Your landing point is at 0.15. First, disable physics with Physics.autoSimulation = false;, Add force to your Rigidbody with velocity or the AddForce function. Put Physics.Simulate(Time.fixedDeltaTime); in a loop and make it run continuously until you reach your landing spot or until pos.y < 0.15 becomes true. After the while loop exits, you should obtain the new position and store it in a temporary variable. You can now re-enable physics with Physics.autoSimulation = true; and reset the transform.

It would also be helpful to implement a timeout so that when the projectile do not reach the landing-spot within the time provided then break out of the loop. This prevents possible infinite loop in your game.

Here is a struct which holds the landing position, rotation and time result: