How effective is simulation in fusion research? Many years ago i designed simulators for fission reactors and they were extremely accurate, sometimes approaching 1% accuracy in terms of core behaviour. It seems to me that it should be possible to determine whether ITER can exceed breakeven, for example, by designing a quality simulation before building the thing. I sometimes get the feeling the scientists are afraid to do simulations because they already know what the answer will be and it is politically unacceptable. Does anyone have any insight into how much simulation is being done in fusion research and what kind of accuracies the simulations are achieving?