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Re: (TFT) Mars - Vasimr & Radiation.



Hi Denis,
  What percentage of cosmic rays does the Earth's
magnetic field stop?  Do you have a reference?

  A 6 month trip to Mars would hardly be a death
sentence due to radiation.  A complete there and
back trip would have 50 REM's of exposure over
more than 2 years.  This will have no immediate
effect and a 1% increased chance of cancer in 
the next 30 years.  Thousands of people have had
greater exposures to radiation with out dying.

  Warm regards, Rick

On Thu, 2011-25-08 at 09:34 -0400, Denis DesHarnais wrote:
> Hey Rick,
> 
> I wasn't really dissing Zurbin.  I found a lot of what he proposed to be
> interesting, even visionary.  I think some of his more hard core fans can
> get a little dismissive of anything short of immediate colonization of the
> red planet though.
> 
> While you're correct that the Earth's magnetic field does not stop cosmic
> rays, it does deflect many of them.  That, coupled with the effect of the
> atmostphere on the particles and the simple fact that being on Earth or in
> LEO allows the planet to shield us from a substantial proportion of the rays
> makes life on Earth possible, and the 1st and 3rd effects make ISS and Mir
> life tenable for shorter periods.  Being totally unprotected on a trip to
> Mars for a trip of six months ... it may be possible, or it may be a death
> sentance.  I don't think we really know for certain yet.
> 
> All of that aside, once we get there, the simple fact that we can find
> carbon in situ does make it a far better candidate for permanent bases than
> the moon, or really any other planet besides our own, so in that respect, I
> think we're in total agreement.
> 
> I hope that better explains what I was trying to say in my previous e-mail.
> 
> Denis
> 
> On Wed, Aug 24, 2011 at 9:30 PM, Rick Smith <rsmith@lightspeed.ca> wrote:
> 
> > Hi Dennis,
> > The point was made by Zubrin, that he would have
> > LOVED to have been invited to various talks where
> > they trashed his ideas and be given a chance to
> > defend them.  In scientific circles, you must expect
> > criticism of your ideas and be prepared to defend
> > them if someone says their are off.
> >
> > The Earth's magnetic field does not stop cosmic
> > rays.  We are bathed with them all the time.  In
> > fact, if scientists want to avoid them they have
> > to do experiments deep underground, and even then
> > they get an occasional bit of secondary debris
> > from super high energy ones.
> >
> > Yes, at solar maximum, a few of the lower energy
> > Cosmic Rays (CR) are deflected by the sun's magnetic
> > field.  But you pay for it with much higher chances
> > of a big solar flare.  Perhaps a couple such flares.
> > Overall, you are better going during a solar minimum.
> >
> > As for the radiation on the typical Mars plans,
> > there are more than a dozen humans (mostly Russian
> > cosmonauts) who have taken more cosmic ray radiation
> > than expected from long duration missions on Mir or
> > the ISS.  Not only have none of them experienced
> > any radiological effects (which is to be expected)
> > but none have shown any cancers (which is also to
> > be expected given the probabilities).  Radiation is
> > very, very well studied.  Far better than any
> > chemical carcinogen.  We know what to expect.
> >
> > As for adventuring on Mars, I wrote us some
> > incomplete rules for Barsoom for TFT long ago.  And
> > GURPS Mars has taken real Mars geography, and (like
> > Space 1899) added a Burroughs like (we don't have to
> > pay copyright) society and races to it.  I thought
> > it was quite well done actually.
> >
> > Warm regards, Rick
> >
> > On Wed, 2011-24-08 at 10:24 -0400, Denis DesHarnais wrote:
> > > Alas, poor VASIMR, I knew it well ... okay, maybe not  *well, *but
> > > well-ish.
> > > Still can't really blame the dude for not showing up when the invite
> > > included a promise for a nice public evisceration.
> > > The article was very interesting; however, I think the author is rather
> > > unwarrantedly dismissive of the effect of the Earth's magnetic field on
> > > cosmic rays.
> > > I am a big fan of terraforming, but the hardcore "Case for Mars" fans get
> > a
> > > little non-chalant about radiation en-route.  Maybe if we plan a trip for
> > > the following
> > > solar maximum we might get there with existing technology (i.e. 13 years
> > > from now).  I'd love for it to be sooner, but I think we'd need to send
> > up
> > > people
> > > who were okay with the strong possibility of dying on the way, which
> > means
> > > non-American astronauts, I guess.  We're all far too pragmatic in this
> > > country
> > > to really embrace the "give me Mars or give me death" ethos.
> > >
> > > As far as KREEP goes, all of I've got is the wiki article (and those
> > > referenced in it):
> > >
> > > http://en.wikipedia.org/wiki/KREEP
> >
> >
> > >
> > >
> > >
> > > Denis
> > >
> > > On Wed, Aug 24, 2011 at 7:39 AM, Rick Smith <rsmith@lightspeed.ca>
> > wrote:
> > >
> > > > If you go to the Mars Society site, there is an
> > > > essay that is called, "The VASIMR Hoax"
> > > >
> > > > http://www.marssociety.org/home/press/tms-in-the-news/thevasimrhoax
> >
> >
> > > >
> > > >
> > > >
> > > > Which pretty much puts paid to the technology.
> > > > Dr. Chang Diaz was invited to drive across town
> > > > and defend his claims, but he failed to show
> > > > up and only those who were critical of his work
> > > > were at the conference.
> > > >
> > > > Your point about having a base on the poles and
> > > > periodically directing light into the greenhouses
> > > > with mirrors or light pipes is a good one.
> > > >
> > > > Luna has not had much volcanism, and no hydrology
> > > > which are the major ways of concentrating ores.
> > > > Thus, the moon is likely made up of Junk Rock,
> > > > where the various elements are mixed together
> > > > but useful ores are rare or non-existent.  I
> > > > know a fair bit about Lunar geology (tho admittedly
> > > > some years old), and had not heard anything about
> > > > ores of Rare Earth Elements (REE).  If there is a
> > > > link that discusses this I would be very interested
> > > > in hearing about it.
> > > >
> > > > Sorry for the long time before I replied to this.
> > > > I've been quite busy.
> > > >
> > > > Warm regards, Rick.
> > > >
> > > >
> > > > On Wed, 2011-10-08 at 09:00 -0400, Denis DesHarnais wrote:
> > > > > Hey Rick,
> > > > >
> > > > > That's a very interesting prospect.  If we end up going with a
> > > > > nuclear/plasma rocket ala Franklin Chang Diaz (or something else that
> > can
> > > > > attain those speeds), such that we can get our astronauts there
> > alive, we
> > > > > could have a real shot at colonizing the near solar system within a
> > few
> > > > > decades ... maybe less.
> > > > >
> > > > > I wonder if the roast/freeze equation on the moon could be altered if
> > a
> > > > > colony could be built in the permanent "twilight zone" along the
> > > > day/night
> > > > > hemisphere boundary - maybe in the KREEP-rich Oceanus Procellarum, or
> > > > maybe
> > > > > along the side of a convenient crater that gave similar shelter?
> >  Also, I
> > > > > would think that PV cells would be much more efficient on the moon,
> > given
> > > > > the minimal attenuation of solar radiation from the moon's
> > atmosphere.
> > > > > Solar thermal would also be pretty efficient, so maybe the energy to
> > run
> > > > > artificial light during the darker periods would be easier to come
> > by.
> > > >  What
> > > > > do you think?
> > > > >
> > > > > Also, it would be kind off awesome to beat China in the rare earth
> > > > elements
> > > > > market by mining them off the moon.  Probably not practical, but
> > awesome
> > > > > nonetheless.
> > > > >
> > > > > Denis
> > > > >
> > > > > On Tue, Aug 9, 2011 at 10:38 PM, Rick Smith <rsmith@lightspeed.ca>
> > > > wrote:
> > > > >
> > > > > > Hi Dan,
> > > > > >  The main problem with artificial light is it is so
> > > > > > expensive.  One square km of plants needs the power
> > > > > > to run a large city.  The plants on the farms of
> > > > > > Rhode Island (that agricultural giant) would require
> > > > > > more power than the civilization of the whole Earth.
> > > > > >
> > > > > >  That is the main problem of growing crops on Luna.
> > > > > > Its 28 day long day means that the plants roast and
> > > > > > freeze.  (Apart from the fact that all the volatiles
> > > > > > that plants need except oxygen are missing from the
> > > > > > moon.)  Mars is the one place in the solar system
> > > > > > apart from Earth where plants can grow using natural
> > > > > > sunlight.
> > > > > >
> > > > > >  Plants can take 1/3 as much light as Earth gets and
> > > > > > still do OK.  This means that plants that don't need
> > > > > > strong sunlight can do well on Mars.  Beyond Mars it
> > > > > > gets very hard to grow plants with only natural sun
> > > > > > light.  (But on the asteroids you could use natural
> > > > > > sunlight and a quite modest amount of artificial
> > > > > > light to help.  Rotate your asteroid so it has about
> > > > > > a 24 hour day tho.)
> > > > > >
> > > > > >  Artificial light (which has the correct wave lengths)
> > > > > > can grow plants.  However, getting a broad spectrum
> > > > > > light is a more expensive than the cheaper lights.
> > > > > >
> > > > > >  Mars' atmosphere is enough to screen out all
> > > > > > normal solar radiation and most of the solar radiation
> > > > > > from a solar storm.  (People should go into storm
> > > > > > shelters for a few hours during the coronal mass
> > > > > > ejection.)  The cosmic ray dose is less than half of
> > > > > > deep space.  (The ground stops half, and the thin
> > > > > > atmosphere actually helps a bit.  Remember that the
> > > > > > scale height is 3 times Earth so even tho the pressure
> > > > > > is 1/100 Earth's, it protects as if the pressure was
> > > > > > 3/100th's Earth's.)  This is fine for explorers.  If
> > > > > > you were going to live all your life on Mars, you
> > > > > > would want a habitat that had a meter of dirt over
> > > > > > you.  But being completely underground is not needed.
> > > > > > You can have windows.
> > > > > >
> > > > > > If you were going to have mines on the Asteroid belt,
> > > > > > you would likely end up with a triangle trade:
> > > > > >
> > > > > > -- High tech, low mass materials from Earth to Mars.
> > > > > > -- Low tech food and crafts (clothes, plastics, wire,
> > > > > > metals, ceramics, etc.) from Mars to the Asteroids.
> > > > > > -- High value metals, gold, platinum, rhodium, palladium,
> > > > > > etc. go from the Asteroids to Earth.
> > > > > >
> > > > > > It is at least 50 times cheaper to go from Mars surface
> > > > > > to Ceres as it is to go from Earth's surface to Ceres,
> > > > > > so anything that can be built on Mars would be.  Only
> > > > > > the highest, most complex items would be shipped from
> > > > > > Earth.
> > > > > >
> > > > > > Warm regards, Rick.
> > > > > >
> > > > > >
> > > > > > On Tue, 2011-09-08 at 18:54 -0400, dwtulloh61@cox.net wrote:
> > > > > > > Hey Rick,
> > > > > > >
> > > > > > > Assuming subsurface water exists in sufficient quantity to
> > support
> > > > life,
> > > > > > do
> > > > > > > you think it would ever be possible for humans to live
> > underground in
> > > > > > some
> > > > > > > sort of self-sufficient capacity there?
> > > > > > >
> > > > > > > Everything I've read suggests that plants do not grow well in
> > > > artificial
> > > > > > light
> > > > > > > which, if true, presents a serious problem to developing a
> > > > > > self-sustaining
> > > > > > > in space.
> > > > > > >
> > > > > > > Dan
> > > > > > > =====
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