Ok, radiation shielding is necessary *anywhere*

Salutations,

One point before I reply. First I must admit to a mistake, I called
it a Mass Coronal Ejection, a look at the space weather site attached
to NASA tells me that it's a Coronal Mass Ejection, a CME not a MCE,
a
minor point but I really don't like to pass on faulty data.

It seems that you and I are the only active people in here, how
disappointing. Tell me you have called this "Spacesettlers", I
assume
from that you are mostly interested in the human settlement aspect of
space exploration? Don't get me wrong, given a magic wand I would
spend the worlds military budget on getting us (the human race in
general) into a multi-planet/habitat situation. Just consider how we
currently have all our eggs in one basket. All it would take is a
single large lump of cosmic flotsam and even with twenty years notice
we still might not be able to do anything. In fact politics,
religion, the laws of physics and human nature could effectively
undermine any attempt to save ourselves. To that end the more places
we are the lest chance of any single, natural disaster putting a stop
to us. I was just wondering about your interests, your pseudonym
"DrOmni" would indicate a wide ranging interest, it would help to
know
if I was talking to a specialist or a polymath. The wonders of the
internet, I sit in my office in Australia and try to decide how to
answer a post from Brazil, not a simple thing. What to say well
here
goes.

>That is really interesting, Darren! Thanks for the lesson on
>primary/secondary cosmic radiation. I was not aware about this
difference,
>and now that you explained it I have to agree that radiation
shielding *is*

It is not really a difference so much as a way to describe two faces
of the same coin. There is not really a thing such as Primary and
Secondary radiation so much as radiation at various levels of energy
and penetrating power and what happens when a powerful (high energy)
particle hits something solid/dense. An example of this when
telescopes on the ground scan the sky looking for flashes of light
from high energy cosmic rays hitting the upper atmosphere and
bursting
into a shower of particles. The single particle is the primary and
the shower is the secondary, so to speak.

>a necessity *anywhere* in space. Any habitat would have to be built
with
>strong materials and all the ones that we know are metals, and they
would
>generate secondary radiation. So, I'm changing the subject of this
thread
>;-). (Of course I would not discard advances in materials science
that could
>make viable habitats made of "superplastics", but at the present
time
this
>is just mere speculation.)

They might not be plastic but all kinds of possibilities exist, there
is a page at one of the NASA sites that talks about research into
materials science.

>[snikt]
>> Possible but not a subject I know a lot about, my wife is the one
who
>> is into biology.
>>
>
>I know that there is some evidence of people with a genetic setup
that makes
>them very resistant to the deleterious effects of alcohol and
cigarettes,
>for instance. But I don't know if there is some equivalent
resistance
(in
>humans or animals) regarding radiation...

I'm on very shaky ground here but I seem to recall something about
micro-organisms that were able to take huge amounts of radiation and
survive. The problem as I see it is not the health of the mature
adult but possible damage to the genes in the reproductive cells
leading to a large (maybe too large) number of mutations, increasing
the genetic load to the point where the system collapses under the
drain on resources and loss of viability.

>[snikt]
>> Perhaps but there is lots of metal in closer, in fact consider the
>> planet Mercury, a (relatively) thin crust/mantel and a solid metal
>> (iron/nickel and others) core. A very large core in relation to
the
>> size of the planet. How hard would it be it bombard it with rocks
>> until you dug a large hole? Not the best place to work but then
>> mines
>> never are.
>
>Does Mercury have a solid or a melted core? I remember that it is
said that
>Mercury is very similar to the Moon (except for the metal core), so
a
mostly
>solid nucleus seems more likely... if that core could be reached,
than there
>would be an endless supply of metals.

Not endless but it might as well be for all practical purposes. And
yes, I think the latest state of play gives Mercury a liquid inner
core but the outer is solid and very close to the surface, only a few
hundred kilometres (I know that sounds like a lot but not if you
throw
really big rocks)

>
>The method of rock bombardment might work, but one could also build
giant
>mirrors in orbit and vaporize directly a hole (along some years or
decades)
>by concentrating sunlight in some point of the surface. (And
remember,
>sunlight is almost seven times stronger in Mercury than on Earth,
and
the
>planet does not have an atmosphere to absorb or reflect part of an
incoming
>beam.)
>
>Hum, for some reason, it seems that I love projects involving
rock-cutting
>lasers or drilling beams... ;-)

Yes, you do seem to like drills, while I think a big hammer is
cheaper, not better, just cheaper.

>Yes, the method of directly generating electricity by extending
wires
in
>space is very ingenious, elegant and efficient, but it has two weak
points:
>
>1) You have to have a strong magnetosphere at hand, so probably it
would be
>viable only in the neighborhood of the gas giants, as in your example
>involving Jupiter.
>
>2) What you're doing is converting kinetic energy into electricity.
That
>means that your station would spiral inward Jupiter as its movement
would be
>converted into electricity - and eventually it would fall into the
planet.
>Of course, if your "station" has enough mass (e.g., it is in fact an
adapted
>asteroid), the amount of kinetic energy would be enormous and
sufficient to
>keep the station in orbit for a long, long time. (Centuries or
millennia,
>perhaps. I have just made a quick and error-prone calculation and
found out
>that an asteroid with a mass of 1.6x10^15Kg - 10Km diameter,
supposing a
>rock-density of 3000Kg/m^3 - orbiting at 10 Km/s, would have enough
kinetic
>energy to power its entire surface with 1 KW of light - about the
sunlight
>power at Earth - during more than seven millennia. Of course I
should
do a
>more accurate calculation using potential gravitational energy, but
that
>gives us at least an idea of the magnitude of the "lifespan" of such
energy
>generation method.)
>
>I think that disadvantage (1) is the one that is really restrictive,
but
>even though that method certainly has its niche of applications.

The gas giants are really big so there is a lot of room to put power
plants but it occurs to me that I read that some of Jupiter's inner
moons were in fact inside the magnetosphere. If that is the case
then
all you need do is cover the surface with wires and sit back.

>> Just one of many ways to generate power in space. Also I seem to
>> recall something about Helium3 and fusion reactors, damn memory.
>
>Helium 3 would lead to fusion reactors that would require less power
to get
>nuclear "ignition" and where kinetic energy of protons generated
during the
>reaction could be directly converted into electricity by magnetic
induction.
>Therefore, Helium 3-deuterium reactors would be more efficient and
easy to
>get working than the deuterium-tritium reactors under experimentation
>nowadays. Of course Earth does not have Helium-3 - it can be found
on
gas
>giants (Uranus, due to its smaller mass, could be a candidate for
Helium-3
>mining) and also on the Moon, where the Helium-3 generated by the
Sun
gets
>trapped in titanium occurring in the lunar soil (or something like
that).

The moon is a lot closer that Jupiter or Uranus, a good place to
start, in fact the moon is a good place to build a large fusion
reactor, if anything went wrong, well there isn't a lot they could
damage, is there. But you should have a look at
http://antimatter.phys.psu.edu/documents.html . This group have also
been reported on in Science and New Scientist
http://www.newscientist.com/home.html and on the NASA site.

>> The Reality Dysfunction, The Neutronium Alchemist and The Naked God
>> by
>> Peter Hamilton, a three book series that has living habitats as
part
>> of the setting for the stories, there are also others by the same
>> author that use this setting.

>Cool! I think that I already have some candidates for my next
purchase at
>Amazon.com ;-). And I was just hit by the curse that plagues wanna-be
>science fiction authors: there is always someone who had the same
idea that
>you thought was completely original...

Always the way, still if you borrow one person it's plagiarism but if
you borrow from ten people it's research.

>Talking about the Artemis Project... Have you seen the news about the
>Chinese space program and their desire to send people to the Moon?

Yes but I don't know if I would be quick to volunteer, the Chinese
satellite program has been threatened with having its insurance
revoked due to the number of launch problems, including total
destruction of the rocket. Don't know if I'd feel safe enough.

Darren Brown