The cable trays of rectangular cross section that carry the cables over the hydrogen-oxygen (HO) tank surface on the Space Shuttle launch vehicle encounter high cross-flow velocities, induced by the bow shock from the solid rocket booster (SRB) at transonic and supersonic speeds. A few cable tray sections experience 90-deg crossflow and several sections are subject to cross flow between 60 and 90 deg. An analysis of the aeroelastic characteristics of these cable tray sections indicated that the structural integrity of the cable trays could not be ensured. Consequently, it was decided to use an aerodynamic fix, consisting of a 20-deg flow ramp, on the first Space Shuttle launch vehicle, which flew successfully April 12,1981.