How do you prevent turning but allow movement?

As a complete distraction from me working on my RPG, I'm working on space combat in Warcraft. So far, I've got the ships producing summoned missile units when they fire (so that the missiles expire after a while), and I want them to move forward - but I don't want them to be able to turn.

Is there a way I can keep their movement speed something other than 0, but not allow them to turn? The editor keeps setting their turn rate to 0.10, no matter what I set it to, which is annoying (and yes, I have allowed negative values in the editor).

Are you using UMSWE?

shift-enter on the turn speed, then put 0

No, just regular vanilla WE for me. I'm too hesitant to use UMSWE while in the middle of my RPG.

@Extarius: That did the trick, thank you! Wish I had known that before! :)

My problem is exactly the opposite of that. I want movement speed to be 0 and turn rate not to be. I enabled negative values but the minimum movement speed it allows me to do is still 1. I tried shift+enter but it still changes it to 1.