A good place to start if you want to understand the purported rationale for the NIF (stockpile stewardship), I suggest reading and understanding this light introduction to modern nuclear weapons.
<a href="http://en.wikipedia.org/wiki/Thermonuclear_weapon" rel="nofollow">http://en.wikipedia.org/wiki/Thermonuclear_weapon</a>
(the rhodes books, Making of the Atomic Bomb is required background reading, as is Dark Sun, if you want to get into the backstore).<p>In particular:
The NIH experiment recapitulates many of the design aspects of a thermonuclear weapon, but does so in a highly controlled lab environment.<p>I'm a biophysicist. I know a fair amount of engineering, although I'm not a weapons physicist. Nonetheless, after years of reading about the NIF and various fusion projects I've come to believe that there is little justification for their expenditure. In particular, we can do stockpile stewardship without this device, more cheaply, nor does NIF present an economically viable method to production of power at a large scale in even the most rosy predictions.<p>I still think the experimental design is cool, but I can't see this as a rational expenditure (HUGE opex and capex) compared to other investments we could be making.<p>Most likely scenario I see in 20 years is that china will be mass-manufacturing small, safe fission reactors and making a mint selling them to the rest of the world. That's got far less reqiurement for massive capex and opex. It's just that the western nations decided to go stupid about fission because OH GOD NUCLEAR MUTATIONS and stop investing in building more reliable, safer, and smaller plants.