Radiation shielding - is it necessary in the Outer Solar System?

Hello again,

Just a few points,

>> ray shield but above that you have to take/make your own. The
>> primary
>> radiation hitting a dense solid causes secondary radiation that can
>> be
>> even more damaging that the first. This means you need a very
thick
>> barrier, to that end several metres of metal/rock is a good idea.
>> This can stop just about all the radiation or give you protection
>> better than you have on the ground at sea level.

>Yes, I addressed the issue of cosmic radiation in the first message
of this
>thread. The question is: according to a statistic that I have seen,
the risk
>of getting cancer due to exposition to cosmic radiation is much like
the
>risk of developing a cancer due to smoking. That is, while a solar
flare can
>actually kill everyone in an unprotected spaceship or in a
settlement
by
>exposing them to lethal levels of radiation, cosmic radiation seems
to take
>decades to kill someone - *if* the person is ever killed. That seems
to be

The point here is not the amount of primary cosmic radiation but the
secondary radiation. When a high energy cosmic ray hits a human body
you have a very good chance of it doing little or no damage (your
body
is not dense enough) in that case no problem. Now put a nice
solid/dense lump of steel or a thicker pick of aluminium in the way
of
the same cosmic ray you have a good chance of it being stopped. If
that was what happened, that is it just stopped, you would not have a
problem but that is not what happens. What you are going to get is
the particle being stopped and in its place getting a shower of
secondary, lower energy particles and if these then impact your body
(and a percentage of them will) you will have a problem, they will
cause a lot of damage. This is a bit of a paradox really, with
respect to cosmic radiation, the human body needs either a real lot
of
shielding or next to none, having a medium amount is the worst
situation. Solar radiation (all types except the most energetic -
rare with our star) works best with more shielding, that is a little
is better than none and a little more is better still and a lot more
is a lot better.

>the reason for the presence of a shelter against solar storms in
basically
>any manned spaceship designed for a Mars mission; but they never
have
a
>shelter against cosmic radiation.

Not really, this is just an extension of what I just said. A good
strong (really thick and massive) storm shelter is expensive to lift
to orbit. And only needed for worst case situations, the think skin
of
most space craft are fine for the short times they are used for. The
longer times of a Mars flight are considered as a risk the crew must
take but they are talking about placing the water (and food and
everything else) supply in tanks around the outside of the ship to
act
a shielding (this has its own dangers, like puncture)

>Of course cosmic radiation could be greatly worsened in the case of
a
nearby
>supernova or something like that, but such cosmic catastrophes are
unlikely.
>Therefore, I think that probably earlier space habitats will be
shieldless,
>having just shelters against MCEs and stuff. And, supposing that a
growing

My concern here is that having shelters is one thing, using them is
another. Even today it is not always possible to get people to
evacuate a house that is in danger from
fire/flood/storm/earthquake..the list goes on.

>space population lives some decades in such "exposed" space cities
(and with
>correspondingly lower life expectancies), I think that perhaps they
can
>simply get culturally used to that and never bother to build a
habitat with
>the heavy shielding necessary for protection against CR. (Given much
time,
>perhaps 20 or 40 thousand years, they would even adapt to this
harsher
>environment developing some genetically coded resistance; and
perhaps
that
>would take much less time in the case of using genetic engineering to
>speedup the process.)

Possible but not a subject I know a lot about, my wife is the one who
is into biology.

>However, there are *no* experiments involving prolonged permanence
of
humans
>outside Earth's magnetosphere (Mir and ISS are deep inside it), and
we will
>have to wait for a Mars mission or a Moon Base to see if in practice
cosmic
>radiation is really so "harmless" as those estimates say...

The harmless (less dangerous) one is the primary radiation but the
secondary is most definably not harmless.

>> Yes very true, they are rarer but that is a relative term, rarer is
>> not the same as non-existent, a large number of such asteroids are

>It is better to say how much rare they're expected to be. Current
computer
>simulations used to understand how the Oort Cloud was developed show
that
>something around 5% of the rocks out there are not comets, but rock
or metal
>asteroids. This region was formed by the ejection of planetesimals
from the
>Solar System due to the gravitational pull and push of the gas
giants, and
>some planetesimals formed closer to the Sun were also "used" on
that.
So,
>provided that you explore a lot of tiny worlds, you can find rocky
and
>metallic bodies in the Oort Cloud.

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.

>I mentioned the transneptunian regions (Oort and Kuipier) just
wondering if
>settlements there would use *any* kind of radiation shielding at
all.
And of
>course I don't think that habitats in those places would use solar
power;
>colonization of the transneptunian world will be viable only if
>gain-effective fusion reactors are invented. (An that maybe not that
hard in
>space. Although I don't have the knowledge to make the correct
calculations,
>I strongly suspect that one could adapt the idea of the magnetic
mass
driver
>to make a viable fusion reactor in space. Imagine two patches of
magnetic
>acceleration a few tens of kilometers long and a few centimeters
thick. This
>device would magnetically accelerate deuterium droplets - perhaps
encased in
>an iron capsule - and make them collide against it other at the
center of
>the structure at a speed of hundreds of kilometers/second, making
them enter
>in fusion. Such a structure would be very expensive and difficult to
build
>on Earth due to gravity, atmosphere and environmental heat, but in
space it
>would be comparatively much cheaper and easier to construct.)

Possible but I can see a few small problems but they are really just
engineering not major breakthroughs. Of course there could be a
dozen
things I missed. Maybe a better way to generate power would be to
dangle a couple of very long conductive lines from a station (well
shielded) towards Jupiter from a close orbit. The very strong
magnetic field would be crossed by line/tether and a current
generated. This is what NASA tried a little while ago from the
shuttle. They had trouble with abrasion of the cable and also with
the release, things that could be fixed. Tidal action keeps it lined
up the right way and to increase power output you just add more
lines.
Just one of many ways to generate power in space. Also I seem to
recall something about Helium3 and fusion reactors, damn memory.

>> Nano-technology. Instead of all the work we were just talking
about,
>> you simply throw a handful of nano-bots on to a rock sit back and
>> wait. They self replicate, using the material around them and then
>> rebuild your rock to taste, kind of makes what we are talking about
>> look like steam age stuff. Just recently a team at .I believe
>> MIT,
>> designed a self replicating/designing robot, add the ability to
>> manipulate matter at the atomic scale and you have all you need.
>>
>
>I am extremely skeptical about nanotechnology as envisioned in many
sci-fi
>books, and as far as I know no one has yet developed a nanorobot,
just
>*micro*robots. However, I think that self-replicating robots are very
>promising, and self-replication robot *factories* even more
promising. They
>would have the same effect of cutting costs that nanorobots would
have, but
>would instead use "macroscopical", standard robotic technology.
(Though, of
>course, with great enhancements in the fields of cooperative
robotics, swarm
>intelligence and artificial intelligence as a whole.)

Yes, large macro sized units are easier to make and without a doubt
would be used but they do not have the ability to work at the atomic
scale. Also I understand that nano-bots are going to be VERY hard to
produce but even MICRO-bots would be able to perform incredible work.

I wouldn't write them off just yet.

>If we are going to fantasy and speculation, another alternative to
>nanotechnology would be biotechnology. (After all, living beings
*are*
>nanomachinery - all our biochemical and biomechanical process rely
on
the
>action of proteins and other organic molecules, that is, pieces of
machinery
>of nano-scale size.) Would it be possible to create biological
organisms
>adapted to space that could transform an asteroid into something
more
useful
>for humans? For example, a hollow "space tree" that would "eat" an
asteroid
>along some decades, growing all the time until becoming a giant
vegetable
>many kilometers long and with a hollow filled with oxygen? (And, of
course,
>it would have to be made of some kind of "superwood" to have enough
tensile
>strength.) At the present point of our bio and space technology,
that
seems
>very unlikely. But recently I have heard news about fungae and
bacteria
>colonies that developed at Mir's hull - in the *outside*; that gives
me some
>hope that someday, many centuries in the future, habitable space
organisms
>may be true... ;-)

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.

Here are a few web sites you might want to look at.

http://www.asi.org/

http://members.aol.com/oscarcombs/settle.htm

http://members.aol.com/oscarcombs/spacsetl.htm

http://www.spacefuture.com/

http://www.permanent.com/

Darren Brown.