Nine 1168-mm (46 in.) diameter Alliant graphite epoxy motors (GEM LDXLs) (strap-on solid rocket motors [SSRMs]) augment the first-stage performance and are a direct evolution from the GEMs currently used on Delta II. Three ground-ignited SSRMs have thrust vector control (TVC) to increase control authority. Ordnance for motor ignition and separation systems is completely redundant. Solid-motor separation is accomplished using redundantly initiated ordnance thrusters that provide the radial thrust to separate the expended solid motors from the booster.