On Mar 5, 9:24 pm, John Schilling <schil...@[EMAIL PROTECTED]
> wrote:
> On Tue, 4 Mar 2008 08:35:26 -0800 (PST), CharlesRCap...@[EMAIL PROTECTED]
wrote:
> This being rec.arts.sf.science, we can talk about the consequences if
> someone were to imagine up such a material as the One Impossible Thing
> allowed in their SF story, or we can explain why it actually is an
> impossible thing. Which would you prefer?
Well, there is a difference between unobtanium and handwavium. The
latter is impossible when considered with our current understanding,
the former is not impossible but no one can think of a way to do it.
Which may mean that it IS impossible, but it gives the author more
wiggle room. Handwavium must be strictly regulated lest a story become
unbelievable, and is proscribed for the so called "hard" science
fiction. Unobtanium has a lower "cost" in believability, particularly
if the author provides a good explanation and relies on a chain of
technology that is at least plausible if not probable. Now I'm sure
you already knew this, so I'm just stating it for the record.
Now as for the question you asked, I am looking for unobtanium (not
impossible just unobtainable with current tech and/or scientific
understanding) rather than handwavium (impossible given current
understanding of science, but allowable if the author gives a vague
enough explanation, a "hand wave" as it were, and makes the assumption
that the reader will play along) so in this case, the explanation of
why it really is impossible would be the preferred route.
If reduced mass radiation shielding moves from unobtanium to
handwavium, then I must thus discard it if I wish to remain "hard" in
my science fiction.
Now, I'm not expecting to reduce the mass needed for radiation
shielding to negligible status, though any reductions in mass would be
welcome. If for no other reason than I don't have to explain to the
reader that the hull is lined with lead, when I could explain that it
is lined with a high tech composite that works some small amount
better than just lead.
Luke did mention some things that help from a narrative standpoint, he
reminded me that the reaction mass of the ship is quite able to
provide protection from the engine/powerplant's radiation, which is
good since if you run out of reaction mass, then there isn't much need
to run the engine/powerplant. He also pointed out my confusion on the
differences between neutron and gamma radiation.
Robert hit dead on the point I was trying to get at, which is that how
much does random placement of atoms in a material "waste" the
protection of atoms that are shadowed? I'm guessing not much, but a
small amount. Perhaps a crystal form of a heavy metal might perform
better if its "tunnels" are arranged to be perpendicular to the angle
that must be protected. (Not necessarily arranged in a two dimensional
plane but perhaps a crystal structure designed to minimize the number
of shadowed atoms.) However I get the feeling by responses that this
method would be unlikely to generate any kind of reasonable reduction
in mass for the cost of manufacture.
So perhaps a composite material that takes advantage of the way that
neutron radiation causes byproducts. Perhaps a material made up of
alternating layers of heavy metals and hydrogen bearing materials
might be more effective on a mass basis than just masses of metals or
hydrogen alone. Actually I seem to remember something like that being
proposed in the past, but I don't remember the specifics of the
debate.
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