From a post to ALT.BOOKS.DAVID-WEBER dated October 30, 1997:

Hyper translation

Does the transition have to be made under impeller drive or Warshawski sail, or either?

   

    Outside a grav wave's area of influence, you do not necessarily have to be underway to make a hyper transit; it's just a little safer because the forward movement gives you more dimensional stability when you crack the wall. If, however, you are making transit into a grav wave, you must have rigged at least one set of Warshawski sails, or grav shear will destroy your vessel as you enter the grav wave's area of influence.