National Ignition Facility to be dedicated Friday

In Livermore, California the "worlds most powerful laser" and "the largest optical instrument ever built" will be dedicated Friday. Its function is to fuse deuterium and tritium into helium in a nuclear fusion reaction, the same energy-generating process that happens inside our sun. Unlike the sun, where enormous quantities of hydrogen are fused to helium for free, the National Ignition Facility plans to fuse hydrogen contained in a 2 mm-wide capsule, and came with a price tag of $3.5 billion. Is it worth it? If it's paving the way for commercial-scale carbon-free energy generation through nuclear fusion, then by almost any measure this work is priceless, and $35 billion, or even $350 billion would be a sensible investment for such a return. If on the other hand it is a very expensive toy for scientists to tinker with a phenomenon that will never grow to a mature technology, then I'm sure there are plenty of other places such a large sum of money could be put to use. In my opinion, these high-risk, high-returns projects are worth it.