Ok, radiation shielding is necessary *anywhere*

From: "Darren Brown"
To:
Sent: Wednesday, October 11, 2000 10:57 PM
Subject: [spacesettlers] Re: Radiation shielding - is it necessary in the
Outer Solar System?

> Hello again,
>

Hello again,

[snikt]
> 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.
>

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*
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.)

[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...

[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.

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... ;-)

[snikt]
> 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.

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.

> 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).

[snikt]
> 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...

> 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/
>

Thanks. In fact, I already know those links, except for SpaceFuture, which
was down and so I could not check it to see if I have already visited that.

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

> Darren Brown.

[snikt]
Dr. Omni
ICQ # 53853815