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Check out this link:
[http://www.lanl.gov/projects/thermoacou … Wollan.pdf]http://www.lanl.gov/projects/thermoacou … Wollan.pdf
as well as other thermoacoustic devices describes at the Los Almos National Laboratory website:
[http://www.lanl.gov][http://www.lanl.gov]www.lanl.gov
They?ve built a device which can reduce gases to cryogenic liquids using no moving parts, without any inherent requirement for pressurization. It uses a heat source to power a sound source, but an electric transducer would serve for a smaller unit. Either method could be adapted to Martian conditions.
Because there are no moving parts, the mechanism required for gas extraction is much simpler than methods requiring compressors, has significantly higher reliability, and requires significantly less power input despite needing more energy over time.
I suspect that the possible power savings are sufficiently high that such a system could extract gases from the Martian atmosphere without need for a nuclear power source.
"We go big, or we don't go." - GCNRevenger
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The nuclear power source is mainly there because solar pannels 1: Don't work at night and 2: dust, not because the nuclear reactor makes loads more energy (though it is quite compact).
[i]"The power of accurate observation is often called cynicism by those that do not have it." - George Bernard Shaw[/i]
[i]The glass is at 50% of capacity[/i]
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Regardless of how we power it, can this device separate the various Martian gases by fractional cooling? (Is that the opposite of fractional distillation?)
That would seem very useful as a precursor to the Sabatier process or other chemical processing based on atmospheric raw materials.
I suppose you could freeze/liquefy a mixed sample and allow it to heat in a controlled manner, siphoning off each element as it evaporated.
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[...] can this device separate the various Martian gases by fractional cooling? [...]
Actually, thermoacoustics offers another technique besides fractionation by evaporation & condensation: thermoacoustic mixture separation (also being investigated by the folks at Los Alamos):
[http://www.eurekalert.org/features/doe/ … 092402.php]http://www.eurekalert.org/features/doe/ … 092402.php
Note that no physical state changes (or the energy needed for them) are required using this technique. Thermoacoustic separation is a new transport phenomenon (like diffusion or osmosis), discovered in 1998. It can be used for fractionation by producing a concentration difference between two ends of a tube containing a gas mixture. Given a long enough tube and a loud enough sound source, this difference in concentration can approach 100%. It requires no moving parts and is very forgiving in terms of temperature and pressure. The degree of temperature control necessary for fractional distillation in the Martian environment would not be necessary.
Thermoacoustic heat engines are quite versatile. It is even possible to set up a cycle in which they can act as continuous operation compressors, lacking any moving parts more complex than a backflow valve.
Long tube lengths for thermoacoustic separation and thermoacoustic heat engines don't take up excessive space, because the tubes can be coiled like the tubing of a tuba or french horn. The tubing can be made of plastic instead of the metal used by these researchers, which saves mass.
This looks like a very versatile technique.
One difficulty I've had with the Mars Direct scheme is the fact that, in the fuel production stage, no one has ever provided a satisfactory answer for how the carbon dioxide reactant will be separated from the atmospheric intake. Nor, apparently, has anyone taken the initial fuel production experiment to its logical conclusion and actually liquified the fuel gas generated by Dr. Zubrin's original Sabatier reactor experiment.
These folks at Los Alamos have provided us with two related technologies that can deal with both of those shortcomings.
CME
"We go big, or we don't go." - GCNRevenger
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What's the relative efficiency of thermoacoustic refrigeration these days? I was under the impression that is was significantly more power-hungry than a traditional refrigerant-based system.
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Thermoacoustic refrigeration is certainly less efficient, though perhaps "energy hungry" is a better description than "power hungry".
The refrigerator has to run longer if thermoacoustic, but can be powered by other sources than electricity. The gas liquifier in the article, for example, is thermally powered. Sound energy is required, not electric.
Thermally powered... hmm... I wonder if that would make a useful reactor cooling system?
"We go big, or we don't go." - GCNRevenger
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*bump*
There's a new method of thermoacoustic cooling being developed. Check out the You-tube video of this water hammer heat pump.
It's not clear whether the thermal cycle involved is a Sterling Cycle or Malone Cycle acoustic analog, but what is clear is that heat is being transferred from the rotor body (and the reservoir/room it's in) to the exhaust. The heat source is not friction. This thermal cycle can be used for refrigeration as well as heating.
An equally important observation is that the use of liquid cavitation as a sound source is more efficient and produces far more acoustic power than piezo-electric sources.
I think it's got potential.
"We go big, or we don't go." - GCNRevenger
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