Re: (TFT) Mars - Plants get too hot on Luna.

[Denis DesHarnais <denisdesharnais@gmail.com>]

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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