Despite exponential advances in computing power, many physical processes are still problematic relative to modeling and simulation. Consequently, researchers want to combine, or couple, computer codes to get answers. One such process being studied that could benefit from this approach is nuclear fusion. Coupled codes and the boost of the coming exascale computing—an entire order of magnitude more powerful than today’s leading systems—could contribute to bringing commercial fusion power more within reach. Researchers are endeavoring to make this happen using the Titan supercomputer at Oak Ridge National Laboratory.