Ignition, the part the hasn’t been done before, requires a large reactor. We don’t know how to generate self-powering reaction or run for long periods. ITER sca

Ignition, the part the hasn’t been done before, requires a large reactor. We don’t know how to generate self-powering reaction or run for long periods. ITER scale is only way to do that. Plasma is hard to simulate because it is chaotic and includes fluid mechanics and self-generated magnetic fields. There have been effects that have been discovered that weren’t predicted by theory. Simulation can’t be done at finest enough level. We also don’t know the parameters for ignition.