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#51 2016-07-11 17:09:32

SpaceNut
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From: New Hampshire
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Posts: 10,650

Re: Combustion engines ... - ... on Titan and Mars

So all that is needed is a few pumps, filters and a building or large chamber to smelt the iron within when we are ready plus an energy source electrical or via fuels......
This smelting gives the materials to machine into the engine for mars use.....

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#52 2016-07-12 10:22:10

GW Johnson
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From: McGregor, Texas USA
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Re: Combustion engines ... - ... on Titan and Mars

Making steel,  you'll need enormous amounts of electricity.  This is not something solar PV will be able to do.  Take a look at videos of what goes on inside a steel mill,  and you'll see what I mean. 

GW


GW Johnson
McGregor,  Texas

"There is nothing as expensive as a dead crew,  especially one dead from a bad management decision"

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#53 2016-07-12 13:43:27

RobertDyck
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From: Winnipeg, Canada
Registered: 2002-08-20
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Re: Combustion engines ... - ... on Titan and Mars

I have argued for the "Direct Iron" method of smelting. It uses less energy, works at lower temperature (but still +900°C or slightly higher), when used on Earth it consumes less coal, produces fewer carbon emissions. Business uses it because it's lower cost, not for environmental reasons. Environmentalists should like it because it produces fewer emissions, but they never seem to like anything. On Mars it's useful because temperature is below that to melt stainless steel, so you can use the heat of a nuclear reactor directly. If you have to convert heat of a reactor to electricity, then use electricity in the smelter, it's very inefficient. It's far more efficient to use the heat directly. The catch is this method only works with very high grade ore. The good news is "hematite concretions" are very high grade ore.

But you will still need a lot of electricity. Carbon content in steel can be so excessive that it makes the steel brittle. The "Direct Iron" method uses a combination of CO and H2 to smelt. More H2 and less CO means less carbon in finished steel. H2 combines with oxygen from ore to form water, and CO becomes CO2. Use RWCS to recycle: CO2 + H2 → CO + H2O. Water is recycled via electrolysis to become H2. That means a lot of electrolysis, so a lot of electricity.

So you'll need a nuclear reactor for heat as well as electric production. Again, I suggest a thorium reactor because MGS identified thorium deposits on Mars. Produce nuclear fuel locally.

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#54 2016-07-13 05:28:48

Antius
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From: Cumbria, UK
Registered: 2007-05-22
Posts: 974

Re: Combustion engines ... - ... on Titan and Mars

RobertDyck wrote:

I have argued for the "Direct Iron" method of smelting. It uses less energy, works at lower temperature (but still +900°C or slightly higher), when used on Earth it consumes less coal, produces fewer carbon emissions. Business uses it because it's lower cost, not for environmental reasons. Environmentalists should like it because it produces fewer emissions, but they never seem to like anything. On Mars it's useful because temperature is below that to melt stainless steel, so you can use the heat of a nuclear reactor directly. If you have to convert heat of a reactor to electricity, then use electricity in the smelter, it's very inefficient. It's far more efficient to use the heat directly. The catch is this method only works with very high grade ore. The good news is "hematite concretions" are very high grade ore.

But you will still need a lot of electricity. Carbon content in steel can be so excessive that it makes the steel brittle. The "Direct Iron" method uses a combination of CO and H2 to smelt. More H2 and less CO means less carbon in finished steel. H2 combines with oxygen from ore to form water, and CO becomes CO2. Use RWCS to recycle: CO2 + H2 → CO + H2O. Water is recycled via electrolysis to become H2. That means a lot of electrolysis, so a lot of electricity.

So you'll need a nuclear reactor for heat as well as electric production. Again, I suggest a thorium reactor because MGS identified thorium deposits on Mars. Produce nuclear fuel locally.

I would agree that steel production on Mars would benefit from a nuclear heat source.  But the thorium reactor is unlikely, as there are too many uncertainties in long-term materials behaviour.  Stainless steels and nickel alloys are both susceptible to stress corrosion cracking and in a molten salt reactor, you have a high temperature mix of literally hundreds of fission product compounds, many of which will migrate along the grain boundaries.  On the plus side, it isn't pressurised.  But engineering a container that will survive for decades will be a very difficult challenge.

To produce the sort of temperatures you are talking about is very difficult, as the outlet coolant temperature is always lower than cladding temperature, which again, is always lower than peak fuel temperature.  Liquid metal cooled reactors have a relatively low film temperature drop, due to excellent thermal conductivity.  But they lose that advantage in their heat exchangers.  Gas reactors using SS cladding only work for coolant temperatures up to about 700C, after which mechanical strength declines to the point where clad thickness and neutron losses become excessive.  Pebble-bed designs are reported to be capable of 900C outlet temperatures, but they have low power density largely resulting from the poor thermal conductivity of the pebble.  And fuel burn-up tends to be quite low.  Maybe not so bad for something you can build on Mars and never really have to decommission, but not good if you need to ship it from Earth.  On the plus side, Mars has lots of CO2 that can be used as coolant.

A nuclear assisted process is achievable, with nuclear heat providing the first 700C of temperature rise and electric heating the remaining 250C.

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#55 2016-07-13 05:44:04

Antius
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From: Cumbria, UK
Registered: 2007-05-22
Posts: 974

Re: Combustion engines ... - ... on Titan and Mars

One interest way of boosting coolant outlet temperatures - the vortex tube.

https://en.wikipedia.org/wiki/Vortex_tube

Put CO2 into the middle of the tube at say 20bar and 700C.  At the hot end, a fraction of the flow emerges at 900C.  At the cold end, the bulk of the coolant emerges at ~650C and is cycled back into the reactor.  The hot CO2 can provide heat through a heat exchanger or can be input directly into a nickel catalyst bed where it decomposes into CO and O2.  Power can be recovered from waste heat.

Not sure how you could separate CO from O2.  That's a question for an industrial chemist.  Maybe produce hydrogen through steam reforming and draw it off through a permeable membrane.

Last edited by Antius (2016-07-13 05:46:27)

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#56 2016-07-14 03:53:16

elderflower
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Re: Combustion engines ... - ... on Titan and Mars

You need to provide a lot of energy in the form of pressure drop to make a vortex tube work.

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#57 2016-07-14 04:47:35

RobertDyck
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From: Winnipeg, Canada
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Re: Combustion engines ... - ... on Titan and Mars

Antius wrote:

Not sure how you could separate CO from O2.  That's a question for an industrial chemist.  Maybe produce hydrogen through steam reforming and draw it off through a permeable membrane.

Direct CO2 electrolysis. It uses a thin wall ceramic tube, made of a special catalyst. It operates at the same temperature as a smelter using the direct iron method, so you can't reduce temperature if you want to do that. Direct CO2 electrolysis requires electricity in addition to heat; electricity causes oxygen ions to pass through the catalyst to the outside of the tube, while CO2 and CO remain inside.

This is only useful because the smelter requires CO. So this is an efficient means to produce one of the inputs to the process. It still requires a lot of electricity, and no net energy gain from the output heat.

You could use the heat to boil water, steam could drive a turbine which could turn a generator. Or a Peltier device: one end hot, the other cold. Heat flow from the hot end to cold is what generates electricity.

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#58 2016-07-19 17:35:08

Antius
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From: Cumbria, UK
Registered: 2007-05-22
Posts: 974

Re: Combustion engines ... - ... on Titan and Mars

RobertDyck wrote:
Antius wrote:

Not sure how you could separate CO from O2.  That's a question for an industrial chemist.  Maybe produce hydrogen through steam reforming and draw it off through a permeable membrane.

Direct CO2 electrolysis. It uses a thin wall ceramic tube, made of a special catalyst. It operates at the same temperature as a smelter using the direct iron method, so you can't reduce temperature if you want to do that. Direct CO2 electrolysis requires electricity in addition to heat; electricity causes oxygen ions to pass through the catalyst to the outside of the tube, while CO2 and CO remain inside.

This is only useful because the smelter requires CO. So this is an efficient means to produce one of the inputs to the process. It still requires a lot of electricity, and no net energy gain from the output heat.

You could use the heat to boil water, steam could drive a turbine which could turn a generator. Or a Peltier device: one end hot, the other cold. Heat flow from the hot end to cold is what generates electricity.

Here is an interesting but probably impracticable idea.  How about we build a nuclear reactor in which the fuel elements themselves are CO2 electrolysis tubes?  Include the nuclear fuel as solid 'raisins' within the catalyst tubes.  That way the fuel directly heats the catalyst by conduction which can get up to the temperatures required.  Does mean having both a combustible gas and oxidiser within the reactor pressure vessel.  That's the impractical part.  Explosion risk is eliminated if the concentration of both CO and O2 in the seperated streams is sufficiently low.  And CO2 is an excellent inerting gas due to its high density.

If the hot CO exhaust can be used to produce crude metallic iron, further processing can be achieved using an electric furnace.  This would remove any impurities and allow alloying elements to be added.

Last edited by Antius (2016-07-19 17:43:56)

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#59 2016-07-19 18:10:00

Antius
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From: Cumbria, UK
Registered: 2007-05-22
Posts: 974

Re: Combustion engines ... - ... on Titan and Mars

It turns out that the Martian atmosphere contains CO in concentrations of 0.0557%.  Oxygen is about 3 times more abundant.  How about we use Martian night temperatures and some compression to remove the CO2 from the air by liquefaction.  We then separate the CO2 and use stored solar or nuclear heat to expand the CO2 and recover the power needed to compress it.  What remains is 32% Argon, 60% N2, 6% O2 and 2% CO, all at Martian night time temperatures.  Argon and O2 are denser than CO and N2.  By cascading the air through a set of fractionating towers, CO and N2 will be progressively concentrated within the gas mix.  The output of the process would be a CO rich gas that can be pumped into an electric furness containing a mixture of iron and iron oxide.  More iron oxide can be added as pure iron is gradually taken off.

One could presumably use a gas centrifuge to achieve the same effect in a more compact geometry.  The atmospheric compressor, CO2 expander and centrifuge could all be placed on the same drive shaft.  One could also add a generator to the drive shaft.  So a Martian nuclear power plant could work as a hybrid, producing both electricity in the CO2 expansion cycle and CO rich gas from the centrifuge.  If friction is low, the production of CO would not appreciably reduce efficiency and is effectively a free resource.

The CO within the atmosphere is constantly regenerated through photochemical dissociation, so there is no problem with depleting the atmosphere.  And as natural abudance falls, the rate of natural removal is reduced, restoring the balance.  I have often wondered if it would be possible to actually generate power using the CO and O2 content of the Martian atmosphere.  It is an intriguing idea.  But the concentrations are low, so the power plant would suffer from low power density.  With a hybrid we can use low temperature gas-cooled reactors to concentrate the natural resource.

Last edited by Antius (2016-07-19 18:35:42)

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#60 2016-07-19 19:42:57

SpaceNut
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From: New Hampshire
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Re: Combustion engines ... - ... on Titan and Mars

http://descanso.jpl.nasa.gov/propagatio … b_sec4.pdf

Diurnal temperature range: 184 K to 242 K
Atmospheric composition (by volume):
Major:
carbon dioxide (CO2)  95.32%
nitrogen (N2)  2.7%
argon (Ar)  1.6%
oxygen (O2)  0.13%
carbon Monoxide (CO)  0.08%
Minor (units in parts per million [ppm]):
water vapor (H2O)  ~100–400 (variable)
nitrogen Oxide (NO)  100
neon (Ne)  2.5
hydrogen-deuterium-oxygen (HDO)  0.85
krypton (Kr)  0.3
xenon (Xe)  0.08
ozone (O3)  0.04–0.2.

https://en.wikipedia.org/wiki/Hellas_Planitia

The mars surface pressure is around 6 while the lowest depths of the Hellas_Plantia basin is near 11 so this would be the natural place to make a thermal cycle system to use the change in pressure, solar and the cooling of the night to make a Co2 engine.....

Still searching for the concentration of methane that has been detected in many places as another important gas to concentrate.
Ah finally found  "Curiosity found methane levels in the Martian atmosphere to be, on average, about 0.7 parts per billion with episodic increase of up to ten times this value during a period of sixty soles to about 7 ppvb.."

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#61 2016-07-20 19:26:33

knightdepaix
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Registered: 2014-07-07
Posts: 100

Re: Combustion engines ... - ... on Titan and Mars

SpaceNut wrote:

http://descanso.jpl.nasa.gov/propagatio … b_sec4.pdf

Diurnal temperature range: 184 K to 242 K
Atmospheric composition (by volume):
Major:
carbon dioxide (CO2)  95.32%
nitrogen (N2)  2.7%
argon (Ar)  1.6%
oxygen (O2)  0.13%
carbon Monoxide (CO)  0.08%
Minor (units in parts per million [ppm]):
water vapor (H2O)  ~100–400 (variable)
nitrogen Oxide (NO)  100
neon (Ne)  2.5
hydrogen-deuterium-oxygen (HDO)  0.85
krypton (Kr)  0.3
xenon (Xe)  0.08
ozone (O3)  0.04–0.2.

Regarding the use of CO, could metal carbonyl metallurgy be used. Zubrin wrote about that in his "the Case for Mars" but someone may say the idea was his or hers.

If import of Venusian sulfur and carbon dioxide is possible, sulfuric acid could be mass produced for electrosynthetic metallurgy: digest iron and metal oxides on Mars surface, reduce the sulfate solution to metals. The powdered metal go thru carbonyl metallurgy. Or the other direction: carbonyl metallurgy first, electroplating of each metal from sulfate solution to corresponding metal ingot on cathode.

At any rate, huge amount of electricity will be needed: nuclear energy is the feasible way at this time.
https://en.wikipedia.org/wiki/Helium-3
Hey HDO is available, could it be fused into helium-3; 2 helium-3s fuse into helium-4 and two protons which balance the electronic charge. This reaction series produces 18.534+3.268*2 MeV = 25.07 MeV for 4 molecules of HDO.
The helium-4 could be used as coolant or fused to nitrogen-14.

I see ozone. Exhausted oxygen from reducing metal oxides can become ozone molecules. Therefore as the metallurgical, chemical and nuclear industries progress, they contribute to the global warming effort of putting ozone into Martian atmosphere. Well known, ozone layer shields the Earth from harmful to human solar rays.

Just off the top of head, I encourage importing sulfur and other elements from inner planets and near-earth objects. In the end, Venus and Mercury are going to be cooked before Mars when the Sun is going to expand many many millennia from now, anyway.

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#62 2016-07-20 19:55:58

RobertDyck
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From: Winnipeg, Canada
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Re: Combustion engines ... - ... on Titan and Mars

knightdepaix wrote:

If import of Venusian sulfur and carbon dioxide is possible...

I thought of that when I was a teenager in the 1970s. Build an automated factory on the Moon that does nothing but build factories. The second tier factories would build gas transport tankers to carry atmosphere from Venus to Mars. All tankers reusable, making multiple trips between planets. The rate of gas transport would increase exponentially. All resources mined from lunar regolith. Waaaaaay overkill.

Mars has enough dry ice for a surface atmosphere with sufficient pressure for humans. It would be a CO2 atmosphere so you would need an oxygen mask, but that's far better than a spacesuit. The text book "Terraforming: Engineering Planetary Environments" has a comprehensive description of terraforming technologies. It quotes 2 papers that estimate Mars CO2; one estimates Mars surface pressure of 200 millibars, the other 300 millibars. Earth has 1013.25 millibars at sea level. For humans, 170 millibars is minimum and requires pure oxygen with a mask with high humidity. At 300 millibars, requires high oxygen but not 100%, and anyone can do it easily.

And that was before the ground penetrating radar of Europe's Mars Express orbiter found a large deposit of dry ice embedded within the water ice cap of the south pole. And there's enough water ice to fill the ancient ocean basin. Perhaps not to the same depth it once had, but enough to cover the floor of the ancient ocean basin and part way up the escarpment sides. So same area, just not as much depth.

Mars and Venus have opposite problems, but I don't think we have to transport massive quantities of materials between planets.

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#63 2016-07-20 20:15:15

SpaceNut
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From: New Hampshire
Registered: 2004-07-22
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Re: Combustion engines ... - ... on Titan and Mars

knightdepaix for sulfur on mars here are some of what we have found by the rovers of mars and orbiting satelite research.

http://ammin.geoscienceworld.org/content/101/6/1389

http://www.lpi.usra.edu/meetings/lpsc2010/pdf/2174.pdf

http://www.lpi.usra.edu/meetings/lpsc2013/pdf/1713.pdf

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#64 2016-07-21 10:59:45

Antius
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From: Cumbria, UK
Registered: 2007-05-22
Posts: 974

Re: Combustion engines ... - ... on Titan and Mars

RobertDyck wrote:
knightdepaix wrote:

If import of Venusian sulfur and carbon dioxide is possible...

I thought of that when I was a teenager in the 1970s. Build an automated factory on the Moon that does nothing but build factories. The second tier factories would build gas transport tankers to carry atmosphere from Venus to Mars. All tankers reusable, making multiple trips between planets. The rate of gas transport would increase exponentially. All resources mined from lunar regolith. Waaaaaay overkill.

Mars has enough dry ice for a surface atmosphere with sufficient pressure for humans. It would be a CO2 atmosphere so you would need an oxygen mask, but that's far better than a spacesuit. The text book "Terraforming: Engineering Planetary Environments" has a comprehensive description of terraforming technologies. It quotes 2 papers that estimate Mars CO2; one estimates Mars surface pressure of 200 millibars, the other 300 millibars. Earth has 1013.25 millibars at sea level. For humans, 170 millibars is minimum and requires pure oxygen with a mask with high humidity. At 300 millibars, requires high oxygen but not 100%, and anyone can do it easily.

And that was before the ground penetrating radar of Europe's Mars Express orbiter found a large deposit of dry ice embedded within the water ice cap of the south pole. And there's enough water ice to fill the ancient ocean basin. Perhaps not to the same depth it once had, but enough to cover the floor of the ancient ocean basin and part way up the escarpment sides. So same area, just not as much depth.

Mars and Venus have opposite problems, but I don't think we have to transport massive quantities of materials between planets.

It looks like the southern cap CO2 deposit may be a good place to build large nuclear power plants.  A S-CO2 gas cooled fast reactor could operate on an open cycle, with mined dry ice loaded into a boiler and injected as liquid into a recuperator, which would heat the liquid above super-critical temperature and inject it into the core.  By venting the output directly into the atmosphere, we avoid the need for condensers, heat exchangers and radiators which would otherwise dominate the mass of the system.  The CO2 passing through the reactor would be activated by neutron radiation, but half-lives of activated N16 is only 7 seconds, so will not contaminate the environment.  To avoid irradiating people in the vicinity, the exhaust could be discharged through a tall stack.

The outlet temperature of an S-CO2 Gas Cooled Fast Reactor is typically 650C.  This is limited by the excessive corrosivity of CO2 at higher temperatures.  The outlet CO2 could be vented into a CO2 electrolysis cell.  Resistance heating would provide the remaining 250C of heat needed to operate the cell.  Alternatively, the reactor could outlet into a vortex tube, which would separate the gas into colder and hotter streams.  The colder stream would enter a power generation cycle and then re-injected into the reactor, the hotter stream input to the electrolysis cell.

Hence, a nuclear powered electrolysis unit at the southern cap could produce CO that could then be directly input into a reduction furnace.  I would put a tenner on future Mars steel production being based around the power caps.

Last edited by Antius (2016-07-21 11:17:39)

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#65 2016-07-22 21:06:43

SpaceNut
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From: New Hampshire
Registered: 2004-07-22
Posts: 10,650

Re: Combustion engines ... - ... on Titan and Mars

Fuel cells need lots of energy to produce the fuels only to loss more in the conversion for use. The batteries are heavy with limited capacity and they loss more energy over time plus through conversion back to working energy for use in the engine of choice.

For the use of either the limitations of distance is the factor and time is the second for its use.
The thoughts of using Methane and oxygen is only viable for making use of the excess manufacturing of it otherwise its no better than any of the other choices that can be made.

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