manner known to those of skill in the art disposed on the upper end of the blowout preventer stack 112 is a riser adapter 120 to allow connection of the riser string 122 to the blowout preventer stack 112 the riser string 122 is composed of multiple sections of pipe or riser joints 124 connected end to end and extending upwardly to the drilling rig 126 the drilling rig 126 further includes a moon pool 128 having a telescoping joint 130 disposed therein the telescoping joint 130 includes an inner barrel 132 that telescopes inside an outer barrel 134 to allow relative motion between the drilling rig 126 and the wellhead housing 110 a dual packer 135 is disposed at the upper end of the outer barrel 134 and seals against the exterior of inner barrel 132 a landing tool adapter joint 136 is connected between the upper end of the riser string 122 and the outer barrel 134 of the telescoping joint 130 a tension ring 138 is secured on the exterior of the outer barrel 134 and connected by tension lines 140 to a hydraulic tensioning system as known to those skilled in the art this arrangement allows tension to be applied by the hydraulic tensioning system to the tension ring 138 and the telescoping joint 130 the tension is transmitted through the landing tool adapter joint 136 to the riser string 122 to support the riser string 122 the upper end of the inner barrel 132 is terminated by a flex joint 142 and a diverter 144 connecting to a gimbal 146 and a rotary table spider 148 before and even after installation of the riser string 122 to.