"Christopher M. Jones" wrote in message ...
sanman wrote:
What would you all recommend as a promising High-Energy Density
Material?

Uranium, Plutonium, Deuterium...

Or if you want to be more exotic, anti-matter. There is still the "slight"
problem fission or fusion will usually produce neutrons, some of these will
produce gamma rays, fission has nice radwaste like Strontium-90 and so on.
Not very nice to run inside a biosphere, which is where we need the better
propulsion anyway! *sigh*

If you want high ISP, low thrust propulsion for deep space IMHO the problem
has already basically been solved with ion engines in their many variants.

The problem is to get out of this gravity well we call Earth we want reasonably
high ISP and high thrust, with low toxicity.

All the fission rockets designs I know usually try putting the fission bits
directly in the exaust to enhance performance, which is not nice. Fusion is
a bit useless unless you propose to use fusion bombs, which actually work and
have nice energy density. Once again you get gamma rays and ****.

Then we have the microwave/laser propulsion concepts, which are nice. Except
that you need a beam in every gravity well and lasers are still ludicrously
expensive. I suppose the idea is not too dissimilar from the space elevator
(large infrastructure costs, fixed position, etc) but with higher energy costs.

So I think the best bets are gas core nuclear, without emission of rad waste,
and microwave/laser propulsion. Orion pollutes too much, the space elevator
requires unobtanium.

The cold fusion lunatic fringe claims to be able to do net positive D+D nuclear
fusion without any emission of neutrons whatsoever. If this is actually true,
great, we may have just solved all of our problems. But I wouldn't put much
faith into it.