h a l f b a k e r yIdea vs. Ego
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How to generate power on Mars? Solar panels are fine to
rove around a few kg of robot, but what about energy
intensive things: concentrating gases, shaping rocks for
construction, and the like? One remedy for scarce
resources is abundant power.
There is nothing to burn on Mars so it will
have to be
nuclear. There are those slow nuclear reactors like on
the
Soyuz but the output is nothing compared to a nuclear
steam turbine. Steam requires water and water is
precious
on Mars. Steam engines reclaim the water but water is
squirrelly and it is easy for it to escape.
I propose that a "steam" engine using mercury as the
working medium would be well suited for martian use.
Mercury offers the following advantages.
1. Vaporization at higher temperature. Cooling rate is
faster when temperature differences are greater. An
engine relying on phase change must get the working
fluid back to liquid. Higher temperature vaporization
means more rapid cooling / conversion back to liquid.
2. Very low volatility means less risk of atmospheric loss
from evaporation or sublimation; on Mars this would be
an important consideration when handling water.
3. Volume increase on phase change should be
comparable
to water.
4. Unlike water, mercury does not expand on freezing
and
so poses less risk of expansion-related damage to
machinery and containers.
5. Water has a propensity to dissolve salts, which then
corrode/ precipitate and otherwise damage machinery.
There might be airborne salts on Mars. Salts are
insoluble in mercury.
As a sidenote considering dust: I am thinking of the
cleaning power of water. Part of how it works is to
dissolve dust, but the kinetic interaction between fluid
molecules and loose contaminants (dust) is a big part of
cleaning. Fluid scrubs things.
Water used for cleaning is contaminated by the particles
it carries away. Mercury would offer the same kinetic
interaction and
stay clean, liberated dust particles floating to the
surface to be skimmed away.
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Annotation:
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There is something of a long-range desire to terraform
Mars, so that you can walk about without a pressure suit.
This Idea would make the task more difficult --lots of
mercury to remove from the environment! |
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" I am thinking of the cleaning power of water " |
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Hey, won't a large portion of life support systems on Mars be dedicated to scrubbing CO2 sequestration? |
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Near the poles the temperature at night plummets to minus 195 degrees F (minus 125 degrees C).
Carbon Dioxide changes from the gas to solid phase (dry ice). At atmospheric pressure, sublimation/deposition occurs at -78.5 °C (-109.3 °F). |
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Would there not be an ideal zone somewhere on Mars that would let us use the sublimation of Carbon Dioxide to power generators? |
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I am trying to picture a sublimation engine driven by sunrise. I suppose a big chamber with a gradually rising piston as it fills with CO2, geared down to spin a generator? Then same thing in reverse as it condenses at night. |
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I do not have an intuitive feel for CO2. Or phase changes in general. For example - is the volume of gas in a cylinder greater than that volume of CO2 as a solid? I cannot imagine that would be allowed but maybe. |
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Would there be a Mars vapour nuclear engine for
Mercury? |
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From what I've read, pressurized CO2 (in proposed LFTR reactors) can approach the viscosity of water, making very small and efficient turbines possible. Since the atmosphere of Mars is CO2, maybe it would make sense to use it as a working fluid? |
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Of course, nuclear need not be the only option. Once we can make PV panels locally on Mars, or at least support structures for massive rolls of such brought from Earth, solar might be a better option. Mars only gets about 60% of the solar power we get, but perhaps the temperatures would help increase average efficiency, and networks of superconductive power transmission lines might actually be possible due to the much lower cooling effort required to reach superconductivity. |
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Sublimation engine: cool idea. Actually, it makes me wonder if a working fluid, like He, could be cooled enough during the night to freeze large quantities of CO2. The He would be circulated through a device that insulates it from surrounding IR, and allows heat to dissipate in the direction of space. The CO2 ice could then be used in a sublimation engine, drawing ambient heat from the atmosphere to change phase. I guess it's the opposite of solar power -- dark power. |
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