Re: Mars halo mirror for terraforming?

On Feb 8, 6:19 am, "Alex Terrell" <alexterr...@xxxxxxxxx> wrote:
On 8 Feb, 05:43,Willie.Moo...@xxxxxxxxx wrote:





The Lagrange Point (L1 and L2) are

r = R * ( M2 / (3*M1))^(1/3)

FOR MARS

M2 = mars mass = 6.2e23 kg
M1 = solar mass = 2e30 kg
R = 2.28e11 m

r = 2.28e11 * ( 6.2e23 / 2e30)^(1/3) = 1.54e9 m = 1.54 million km.

FOR EARTH

M2 = earth mass = 6.0e24
M1 = solar mass = 2.0e30
R = 1.50e11 m

r = 1.50e11 * (6.0e24 / 2e30)^(1/3) = 2.16e9 m = 2.16 million km

We want to heat up Mars, and cool down Earth.

So, mirrors that intercept the sunlight falling on Earth would cool
Earth.

Mirrors that redirect sunlight falling past mars toward Mars, would
heat Mars.

Mars planetary radius is 3,400 km. A toroidal mirror 154,000 km in
radius and 958 km wide angled at 2.87 degrees relative to a line
between Mars and Sun, would cause light levels on Mars to rise to
Earth normal levels on Mars, and the light would come from the general
location of the Sun. The Sun would have a bright halo around it.

This would be extremely inefficient. Close to 1 trillion km2, but at
an angle of only 2.87 degrees. It would be better to have a double
mirror , or base it on the L2 position.

Correct, there are more efficient mirror structures one can design to
deflect light the 3.75 degrees needed at that distance. One can also
operate at 5,000 km at a shallower angle.

I wouldn't operate in the L2 position though, because it would produce
2 suns, not 1 - but that's just an artistic decision,you are quite
right, L2 works well for adding light to the planet. Just make it big
enough to provide an additional 147% of the solar side.

One could combine the two ideas. An increase of 23% in the sunlight on
the L1 side, and a second sun 123% as bright on the L2 side - might
work.

So Mars would have 2 suns and 2 moons. lol. Which would be
interesiting.


I believe you haven't taken into account solar light force in your
calculations.

Correct. That's more detail, but an easy one to figure out with
numerical methods. You can balance gravity, centrifugal and light
pressure forces to 'fly' a mirror system in this region of space.
Absolutely. The original Lagrange points are approximatons based
solely on gravity and centripetal forces.

Zubrin and McKay estimate a distance of 214,000km, and
their mirrors are heavier (and hence further) than the mirrors you
proposed.

I merely used the formula for Lagrange points without taking into
account light pressure forces. (or solar wind forces) I would like to
look at their calcuations. Are you sure it wasn't 2.14 million km?
Because on the L1 side, you'd have to go toward the Sun, to balance
light pressure. On the L2 side you'd have to go toward Mars, which
would bring you closer, perhaps considerably closer.

Yes, my mirrors are very light weight, a ton per square kilometer.
Maintaining their position in the face of solar wind is a problem.
There are many potential solutions however. The best will be selected
after a detailed analysis which hasn't been completed yet.

A 1272 km diameter disk centered on a line drawn between Earth and Sun
at L1, reduce the total influx of light on Earth by 1%. These light
levels are sufficient to reverse global warming despite higher levels
of CO2. The sun on Earth would have a dark spot in the center of it
covering 1% of its area.

Might be needed. Its fairly trivial for an orbiting infrastructure to
do this.

I agree. Its interesting that Gaia is telling us to begin thinking
about leaving the cradle. lol.

In both cases, the mirrors can operate solar pumped IR lasers, to beam
energy to both planets to power industrial infrstructure there.

2.16 million km is quite some distance - makes microwave transmission
impossible.

Agreed.

What's the efficiency of IR lasers?

Efficiencies of light pumped lasers have achieved 40% in the lab.
There is no reason that something close to this couldn't be attained
by solar pumped lasers. I assume in early stage planning that 20%
efficiencies are attained. Of course, low efficiencies are not a
problem when the mirrors that concentrate the sunlight to pump the
lasers, are being used to shadow the Earth. Adding energy to Mars
makes this use more of a problem.

And aren't they
distorted and absorbed by the atmosphere?

There are seveal windows in the Earth's atmosphere. One of these
occurs around 1,000 nm wavelength. Clouds reflect this pretty
efficiently. But, there are regions of Earth's surface, that are
largely devoid of clouds.

Also, 1,000 nm is very near the 1,108 nm bandgap energy of silicon.
So, a centralized solar collector site in a cloud free region,like a
desert, can be used as a solar pumped IR laser receiver station.

A solar collector in the desert, like in Nevada, Arizona,or
California, is illuminated about 1,900 hours per year. There are
8,766 hours in a year. So, this is 21.6% of the time.

Sunlight has a total energy of 850 watts per sq m. Conversion
efficiency of silicon is about 18% - so, we're talking 153 watts
electrical per sq m.

Combining these two figures, each sq meter of solar panel produces
290.7 kWh of electrical energy per year.

IR energy totals about 380 watts per square meter when the sun is
shining. So, if an IR laser beams 380 watts per square meter at these
same panels, it doesn't send any more IR energy than the sun
provides. The silicon converts this IR beam to electrical energy with
over 90% efficiency - that's 342 watts electrical per square meter.

Now, in the desert where these panels operate, they are cloud free 85%
of the time, so, that's .7,451 hours per year.

Combining these two figures each sq meter of solar panel, used as a
power receiver for IR solar pumped lasers, produces 2,548.2 kWh of
electrical energy per year.

Since the sun still shines on this power reciever, the addition of the
satellite raises total output to 2,838.9 kWh of electrical energy per
square meter per year. Nearly 10x as much!

Which gives the ratio of value of the two systems.

I produce solar panels at $0.07 per peak watt. I could add solar IR
laser in space and pay as much as $0.63 per peak watt, and still be
ahead operating this way. If I get paid through carbon credits, or
some sort of UN funding mechanism, then, its all to thte good.


I would propose lasers to send power from Earth Moon L1 to a lunar
base, which is only 60,000km. I assume a grid to grid efficiency of
25%.- Hide quoted text -

Well, that's possible, but it doesn't reduce energy on Earth.

I would say that a large mirror array at L1 be used to reduce heating
of Earth, and a portion of that energy 20% - be beamed to an IR
reformer in GEO and that GEO sat redirect the energy with nearly 100%
efficiency, to ground receivers in the desert that convert it to DC
electricity with nearly 90% efficiency.

Those recievers drive electrolysis units that break down water into
hydrogen and oxygen. The hydrogen is distributed by pipeline
throughout North America, and is used first,to power coal fired
plants. The coal is traded for hydrogen, and more hydrogen is used to
hydrogenate the coal into liquid fuels like gasoline, diesel fuel,fuel
oil, and jet fuel and gas fuels, like propane, butane, methane. The
hydrogen is also liquified locally and used directly as demand grows
for it. Hydrogen is also piped to homes and industry, and used in
fuel cells. The water created is filtered and consumed. Hydrogen is
also combined with nitrogen in the air to form ammonia on demand for
agriculture.

Once operating in the US, similar systems can be set up in the major
deserts around the world, and a hydrogen gas pipe network is
established in every major land area of Earth, and a hydrogen economy
is established worldwide.



.

Relevant Pages

  • Re: if you were president
    ... energy, and focus were applied to it and the alternatives. ... Most of our power sources rely on the sun -- fossil, wind, solar. ... energy over its lifetime/ to create another solar panel. ...
    (misc.writing)
  • Re: Hey, Moonbats! Man-Made Global Warming Is a Hoax!
    ... as they have been for the entire history of the Earth. ... The Earth rotates around the Sun. ... The energy reaching the Earth from the Sun ... >rates cause increases and decreases of solar energy hitting the Earth. ...
    (alt.politics.bush)
  • Re: on energy conservation....
    ... sun, but during the summer the sun is high enough in the sky so that ... The building, a so-called positive energy house, actually produces ... The solar panels on the roof produced almost 9,000 ... kilowatt-hours of electricity in the first year. ...
    (uk.politics.misc)
  • Re: Into the Sun
    ... The Sun won't even notice. ... If a deep-space celestial object with the size and mass of the Earth's ... surface of the Sun at solar escape velocity. ... One place to begin is comparing the energy released to the sun's ...
    (sci.astro)
  • Re: {OT:} How about that? A scientist says...
    ... not, AFAIK, emitting more energy than it is receiving from the Sun. ... That Mercury, Venus, the Earth and Mars share the same wobbly orbit ...
    (alt.autos.toyota)
Loading