# 2D How to find launch angle of a spaceship to meet an orbiting planet?

Hi everyone thanks for taking your time to help!

I am developing a game where planets are orbiting (always a perfect circle) and ships move between the planets. I need to be able to find what angle to launch a ship at so that it meets up with the moving planet? There is no gravity or anything of that sort. I am simply trying to determine what angle to launch a linearly moving object at with a constant speed in order to meet a circular moving object with a constant speed?

So in summary I have the following pieces of information:

-Planet A (origin) x,y coordinates at time of launch

-Planet B (destination) x,y coordinates at time of launch

-Planet B (destination) orbit / movement speed (constant)

-Spaceships's movement speed (constant)

I need to know:

-What angle to launch the ship at in order to meet Planet B while moving the ship in a straight line.

Thanks so much again!!

PICTURE - How to determine ship's launch angle?

• Show us which parts of the calculations you have a problem with. – Hidde May 30 '17 at 18:32
• Sorry, all of it, I don't even know where to begin with it. I have x,y coords of both planets and the velocity of the ship, and the circular velocity of the destination planet. I am trying to find a calculation that can give me a vector or angle that the ship would have to leave the origin planet at to reach the destination planet in a straight line at it's given velocity. The best solution I could think of currently would be to guess at an angle, run a simulation to test it and adjust that until I hit the target, but this would take tons of calculations and slow things down a bunch. – MT Worlds May 30 '17 at 18:42
• Related to math.stackexchange.com/q/344877/265466. – amd May 30 '17 at 19:11
• One way to get started is to compute the intersection of the rocket’s path with the target orbit as a function of the launch angle. That will let you compute the intercept time as a function of the angle, and then, in theory, you can find the angle at which the target planet is also at the intersection point at that time. – amd May 30 '17 at 19:22
• Thanks for the related question amd, that is the exact same question, doesn't look like he found an answer either. Hopefully someone can help. I will message that user also to see if he solved it, if he did I will post the solution here. Unfortunately your 2nd post doesn't help much in this situation since I do not know the rocket's path as I need to determine which direction to send it in. – MT Worlds May 30 '17 at 19:53