How to complete this level in Ghen War?

I have reached this level in Ghen War where you is supposed to shut the hangar door so the goliat ship can´t take of. The problem is i don´t know how to shut it. I have walked around the whool level many times and looked and i have found a small button in the last room (where the ship is), but nothing happens when i try to use the arm on it. What am i supposed to do?