It sounds like maybe you sent them way out in the space outside the immediate planet area. That causes the speed of any human ships to drop, to prevent thnincentive for wildgoose chases, etc. If you bring your ship back inward, he'll pick up speed again. If that doesn't seem to be it, you couldpost a save. But if it was eminent damage, your speed would go to zero, not one, and would show engine damage, etc.