Why the whole plot of Interstellar doesn't make any sense (spoilers)

HOW could Cooper travel to space and send himself NASA coordinates if he DOESN'T KNOW the coordinates yet?

Where's the entrance to that loop? Where does it starts?

He can't go to space without the coordinates. & He can't send himself the coordinates if he won't travel to space.

See this image: http://content.screencast.com/users/Tim.M/folders/Jing/media/63fa31da-1720-4858-b0ec-fabac349ec93/00000333.png

Am I the only one, thinking that there's a huge problem with this "time loop"?