What are the lessons learned from nuclear reactor design and analysis?

[sanman]

The problem is that it just doesn't like staying inside a small, manageable volume

What about that Laser Thruster propulsion that I mentioned in another thread?

Some fellow from BAE Insitute says laser propulsion would be far better.

Well, even though photons have miniscule momentum/thrust, they would seem to be a propellant of boundless supply, since you can generate as many photons as you want as long as you have the energy, without suffering from any limitation of onboard supply.

Therefore a nuclear-powered laser thruster could generate as much photonic propellant as it had energy available for.

That guy from BAE Institute said that while his demo was only generating 35-microNewtons, it could be scaled up to kiloNewtons of thrust by using nuclear power.

I'm not quite sure how it works, though. Can anyone elaborate?
It seems that he's using a stationary laser source to hit against a vehicle equipped with some sort of resonant cavity. This resonant cavity then bounces the photons around and extracts more energy out of them than would otherwise be the case. By doing this, you get more thrust from your laser beam.

But so would this be suitable for earth-to-orbit launch? If you laser source is independent of the vehicle, then it could be as heavy as you liked. But you'd need the laser emitter to be poking through the top of the atmosphere to avoid being blocked by it. Could this then point towards some kind of buoyant floating launchpad, perhaps mounted on a dirigible/blimp? Your blimp could either be carrying the nuclear power supply, or else it could dangle a wire down to the ground where the nuclear reactor would be sitting.

 

[quetzalcoatl9]

Yes - hydrogen. That offers the highest specific impulse, and doesn't introduce decomposition as would NH₃ or CH₄. Thermal conductivity is reasonably good compared to other gases.

The turbo pumps developed for this program essentially evolved into those use for the Shuttle SSME's.

is the energy transfer mechanism completely thermal, or does the hydrogen ionize like in VASMR? (sorry, i just can't seem to find many details about NERVA online). if it's thermal, why would decomposition be a problem (for instance, why not use water or something more dense than hydrogen, like Hg) if it is all going out the back anyway? and wouldn't you get decomposition of the dihydrogen into protons (reactive) anyway?

i can only guess that (a) cryogenic storage of H2 isn't a problem for the <20 K environment of outer space or (b) the light mass of hydrogen offers the prospect of it's leaving the reactor fast enough that the reactive protons are less of a problem. (i.e., the material of the reactor can't be easily protonated?)

that is cool that the turbopumps for the SS had their origins in NERVA, it's amazing that they have never failed.

 

[Azael]

The turbo pumps developed for this program essentially evolved into those use for the Shuttle SSME's.

Thats a interesting fact. Has the NERVA program had any other off branches?

Reactor Design & Analysis - Lessons Learned

http://www-rsicc.ornl.gov/ANST_site/answinter_hth.pdf

Nice link