Realistic NERVA engines?

[SciMan]

The only (physical) problem with that one is the "internally cooled transparent wall" section. Materials science needs to catch up with the requirements for that part.

The power density across that wall is enough to melt any transparent material that I know of, even fused quartz. And that's WITH active cooling.

[Streetwind]

Now this is a necro for the ages And even sal_vager fell for it!

For what it's worth, though, Nertea may have something to show re: Nuclear Lightbulb sometime in the near future... </rimshot>

I'll show myself out...

[NERVAfan]

Not especially - the reason nuclear tests stopped was more than "people are scared of the N-word", and a running NTR is looking at levels of radiation comparable to the grounds around Chernobyl mid-meltdown. It's not exactly insignificant.

That's why you use the NTR only in space, as an upper stage.

As architeuthis pointed out, there's almost certainly more radioactivity in an RTG than in an un-activated NTR reactor (the reactor is bigger, but the half-life is 10 million times longer so vastly less radioactive).