On page 93 of Total Warfare, the Control Roll table has a "Situation" entry that indicates that a "Unit with velocity over 2x Safe Thrust in a atmosphere hex" triggers a control roll.
There's also an "Above 2x Safe Thrust" row in the modifier that doesn't appear to have the "in an atmosphere hex" restriction. Does the "Above 2x Safe Thrust" modifier apply to control rolls made in space (assuming they were triggered by some other applicable condition)?