Torque control of FSW can be applied to welding the Ares I launch vehicle. In particular, the long and circumferential welds where work piece variation, machine deflection and changing thermal conditions create manufacturing challenges. By applying torque control instead of force control, the welding reliability will increase. Increasing the reliability of linear and circumferential welds that can range up to approximately 30 feet in length will increase the productivity of welding operations at NASA. There would be less weld defects due to the welding controls becoming unstable and causing weld defects. The vertical and robotic welding tools at Marshall Space Flight Center would be able to apply this technology almost immediately after project completion. Along with increasing reliability, torque control will be effective at reducing operating costs associated with FSW. Operations cost would be reduced by not having to replace or repair existing force sensors. Boeing, Lockheed Martin and other aerospace companies have FSW applications very similar to NASA that would benefit from torque control of FSW. As with NASA, these companies would increase the reliability of welding operations, in particular with very long linear and circumferential welds. In addition, they would experience reduced maintenance costs and the reduction in required capital investment for future endeavors with robotic FSW. Lastly, torque control of FSW could be used by numerous small businesses entering into the FSW market. This technology would provide a cost effective method for using traditional machine tools and industrial robots to perform FSW. Expensive force gauges and dynamometers would no longer be required. Potential small business users are the numerous automotive suppliers to General Motors, Toyota, Ford, and Chrysler. As these automotive companies begin to manufacture vehicles using FSW, many suppliers can utilize torque control of FSW.