Re: General Setting/Tech Musings

On Jul 13, 6:49 pm, MacFrag...@xxxxxxxxxxxxxx wrote:

[3] iron has N = 8.48E29 nuclei per cubic meter, pi*R^2 = 2.94E-29 m^2
nuclear cross sectional area, for L = 0.04 m. A sphere of Fe of
radius L has a mass of 2.13 kg.

So, iron seems to be the best deal here since it can stop most
particles for the least mass and decently low volume. How practical.
Just out of curiosity - does this have anything to do with iron nuclei
having the highest binding energy of all elements, or is this just a
correlation of unrelated things?

Just a coincidence. If you look at the mass needed to protect a
certain area against radiation, you will see that light elements are
slightly better. It is just when you need a spherical volume that the
r^3 bit drastically favors dense elements rather than low atomic
weight.


A couple of issues here - for an ideal heat engine that extracts work
between a heat source at a temperature T-H and a heat sink at a
temperature T_L, the efficiency is 1 - T_L / T_H.

Argh, that's really dodgy. On the one hand you want your radiators run
as hot as possible to save on area and mass, on the other hand you'd
like them to run cool for a good engine efficiency. I just looked up
the corresponding calculations on Rho, i.e. why you want the radiator
temp at 75% of the heat engine. Very strange.

Yeah. Annoying, but that's the way things work. Engineering is
always about trade-offs.


Now for how an MHD generator for nucleon decay would actually work.

That's pretty cool, I'll definitely save that for future reference.
But the power of such a generator is really ungodly, so I'm a bit
afraid this would be an awful can of worms to open, what with Jon's
Law and everything.
I'll have to scroll up later and check on the other matter decay
variants you mentioned; something that allows (or requires) using the
released energy to heat up propellant would be ideal for our purposes,
especially if it doesn't leave too much waste heat to be dealt with by
shipboard systems.

The best way would be to initiate nucleon decay in something heavier
than hydrogen. The decay energy would be given to the nuclear
fragments, which would be stopped quickly in the surrounding
material. A few percent of the nucleons disintegrating would result
in a pellet a few mm in diameter turning into a plasma every bit as
hot as fusioning D-3He. My best guess would be to use elements of
some intermediate weight to avoid too much prompt neutron radiation.

BTW it would help a lot if you had weblinks with
diagrams or illustrations, so I could understand the concept much
better than just from the written word.

I don't know of many for a lot of the nuclear and high energy physics,
but here's a link to a kind of fusion micro-pulse drive which might be
achievable in the next few decades
http://ffden-2.phys.uaf.edu/213.web.stuff/Scott%20Kircher/fissionfusion.html
The technique is very similar to ICF with a fast ignition laser,
http://en.wikipedia.org/wiki/Inertial_confinement_fusion
except that the fission of U238 triggered by anti-proton bombardment
is used to trigger the fusion reaction after ion beam compression.

For lasers, I put a lot of information up on my website (still under
development)
http://panoptesv.com/SciFi/DeathRay.html


To make the diamondoid stuff tough, you will probably need to include
a bunch of micro- and nano- scale structures in it (flawless diamond
would tend to fracture easily). If all the non-uniformities were
smaller than the wavelength of light, it could be as transparent as
diamond. Otherwise, I imagine it would be a milky translucence. Of
course, it will also have pipes of orange hot lithium flowing through
it, making it glow.

That's a very cool image. I made a few sketches these days, and I
think I now have a clearer image of how those torches should look
like.

Excellent!

Luke

.

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