It is going to take leadership from the top down. Only when we have a President who is eager and serious about expanding the space exploration program, and is intelligent enough to understand the ramifications of space flight, will nuclear power and propulsion systems ever come of the drawing board. And it will only do so if the American People pressure congress into it....

Conversely, and alternative pathway could be that of a commercial venture. This sounds far fetched until one realizes that to do all of the neet things like have hydrogen fuel cell powered vehicles, synthetic hydrocarbon fuels, and alcohol from cellulose, we are going to need platinum group metals. Tons of it. Hundreds of tons of it each year...
Metals like platinum, iridium and especially rhodium are ideally suited for the use of catalysts which are necessary over a broad spectrum of industry. Current market values for platinum (about $1200 per troy ounce) and rhodium (about $4500 per troy ounce) indicate the current supply is not able to meet the demand. An expanded supply at lower cost could greatly improve the applications of such metals to catalysts, and will interestingly enough, lower the cost of proton exchange membrane fuel cells--a key technology for applications in the automotive industry.

If we want these things, then we will have to go out and get them: Nickel-iron asteroids contain riches almost beyond belief...a single 1 km nickel-iron asteroid can contain more than 300,000 metric tons of precious metals--of which most of this is platinum group metals. Several metal rich asteroids reside in near earth orbit, or earth orbit crossing trajectories.

A prospecting mission would be ideal to locate and characterize the surface compositions of these bodies...

A follow up mission to send a relatively large vehicle to the body to mine it...

Such a vehicle will almost certainly have to be nuclear powered.