(Serg) writes:

"Charles Talleyrand" wrote in message
...

I'm trying to imgaine cheap space flight. I'd also like to see it
sooner rather than later. Given this I believe we are limited to
chemical rockets.

If you are talking about cheap, but politically unrealistic
spaceflight, I don't think anything could beat Orion. More politically
plausible would be NTR , I think still cheaper then chemical (without
development cost).

As currently conceived, NTR doesn't fly --- literally. The reactor power
densities are so low that the thrust-to-weight ratio is less than unity;
hence, an NTR cannot even lift its _own_ weight in a 1 gee field, let alone
a spacecraft! One has to go to an "advanced" design like the DUMBO micro-
structured heat exchanger that can handle power-densities at least an order
of magnitude higher than current solid-core or "TRIGA pellet" designs.

The "Nuclear Light-Bulb" gaseous-core reactor design would be more
effective still --- if one could just figure out how to keep the "light bulb"
envelope from melting, while still efficiently transferring the radiative heat
to the propellant. (Sadly, Hydrogen tends to be rather more transparent than
most "light bulb" materials, so there is a slight technical problem in that
the "light bulb" wants to melt more than the propellant wants to get hot...
Also, I expect gas-core nuclear rockets to be at _least_ an order of magnitude
more Politically Incorrect than RTG-powered space probes --- which are already
routinely picketed by Greenpeace and the Union of Concerned "Scientists"...)


-- Gordon D. Pusch

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