Why colonize Mars and not the Moon?

[stefan r]

Nitrogen is the most common element in the atmosphere of Earth, it also exist in Mars' atmosphere in useful amounts.
It isn't a by-product of something else, Nitrogen is Nitrogen, unless talking about fusion reactions inside stars.

There are many major companies selling products made from air. One of them is called "Air Products" and has annual revenues around $10 billion. One of their customers, NASA, bought oxygen from them for rocket launches. Oxygen is oxygen and is a product usually produced on Earth through liquefaction and distillation of air. Nitrogen is nitrogen and is a by-product of oxygen production on earth. Liquid nitrogen frequently gets used for cooling and for purge gas.
Water is also a major industry in the United States.

 

[sophiecentaur]

Going back to a state of the past is fairly opposite of going where no one has ever been.

No one has ever been to a state of 'not in Europe any more'; that's pretty radical. The consequences have not been thought out by many of the Brexiteers - most of them will probably have been hoping for a pre 1970s situation but that is unreal.

 

[mheslep]

Nitrogen will be much more expensive on Mars.

2.5% of Martian atmosphere.

 

[mheslep]

No one has ever been to a state of 'not in Europe any more'; that's pretty radical...

Radical? More like more of the same. How many countries split from the British empire which spanned the globe a century ago? I suppose King George III called the colonists radical. This time at least Juncker won't be able to send the Dragoons to attemt to hang the Brexit leaders.

 

[stefan r]

2.5% of Martian atmosphere.

wikipedia says 1.9%.
The cost of nitrogen production involves removal of either 97.5% of the components or 98.1% of the components. In either case it is much more expensive than Earth where you have reasonably high purity nitrogen left over from oxygen production. On Earth's economy nitrogen is free once you subtract the cost of refrigeration in the case of liquid N₂ or subtract cost of bottling in the case of pressurized gas.

 

[mheslep]

The process of N2 production would be that same on Mars as on Earth, refrigeration to liquefy out the desired gas. ThE difference would be in energy, so the cost difference depends on energy cost.

 

[nikkkom]

wikipedia says 1.9%.
The cost of nitrogen production involves removal of either 97.5% of the components or 98.1% of the components.

CO2 "removal" will actually be the crucial step in atmospheric processing on Mars: you need carbon for all kinds of organics (plastics and more) and oxygen for breathing, rocket oxidizer and many industrial uses.

In general, CO2, H2O, N2 and noble gases extracted from Martian "air" are all quite useful.

 

[sophiecentaur]

2.5% of Martian atmosphere.

When you consider that the atmosphere is at very low pressure, compared with Earth's atmosphere, that could be an added hurdle for the Haber Process (talking as a not-industrial chemist) if it's needed for agriculture etc. (But I guess that, eventually, within a biome, N₂ would end up at higher concentration for recycling)

 

[mheslep]

When you consider that the atmosphere is at very low pressure, compared with Earth's atmosphere, that could be an added hurdle for the Haber Process (talking as a not-industrial chemist) if it's needed for agriculture etc. (But I guess that, eventually, within a biome, N₂ would end up at higher concentration for recycling)

Im not a chemist either, but a change in pressure doesn't not necessarily effect Haber; it effects power needs, as compressing the Mars atmosphere 170X in the front end produces Earth like conditions for whatever chemical process may follow (not that this is necessarily the best approach).

 

[mheslep]

CO2, H2O, N2

Water is only trace in that cold atmosphere, and that only near the poles. Maybe mine the soils for ice and/or recycle for human needs. BYO H2 for fuel, use local C and O, is the Mars Direct plan.

 

[stefan r]

CO2 "removal" will actually be the crucial step in atmospheric processing on Mars: you need carbon for all kinds of organics (plastics and more) and oxygen for breathing, rocket oxidizer and many industrial uses.

In general, CO2, H2O, N2 and noble gases extracted from Martian "air" are all quite useful.

Aggregate is useful. By weight one of the most used materials in civilization. I recently bought aggregate in urban eastern Pennsylvania. I made a small section of sidewalk. There is a rock dealership in-between my house and my in-laws. They offered 50lb bags of crushed limestone for $6 each or 1/4 ton for $8. When they realized I was loading into a Honda Accord they decided not to weigh at all and told me to take as much as I could. I checked the shocks (distance between tires and wheel well) with my hand as I shoveled to avoid damage. No one involved acted like the material had value. Less labor and lower liability had value to them and my car had value to me.

If you get truckloads of "earth" delivered in the Northern USA you will likely find that topsoil is slightly more expensive than aggregate which is slightly more than subsoil. Sometimes crushed aggregate is a bit more if you specify grading. Some stone types can get expensive depending on your location (diamond extreme example). The price of "fill" is an anomaly. Cubic yards of fill delivered are likely to be a little more than half the cost of delivering your aggregates or top soil. Looking at the chemical composition and relative abundance on Earth will not explain the prices. The low cost of "fill" occurs because the company selling it is also selling a contract to remove it and they are avoiding a charge for dumping it.

If we look at a product on mars, say polypropylene grocery bag. You could say that the carbon came from our valuable carbon dioxide atmosphere. Or we could say that the difficulty purifying 96% CO₂ into 99.999 CO₂ is very easy compared to the energy cost of reducing the the carbon. So easy that the price can be ignored. The value of hydrogen on Mars will be so much higher than the cost of reducing CO₂ that we could almost disregard that too. By weight finished plastic goods may be cheaper than saturated hydrocarbons(diesel, natural gas etc) because the hydrogen content is lower.

On the moon you get odd ideas like using aluminum regolith instead of portland cement to make lunacrete. link. Portland cement concrete uses a lot of water.

 

[Wastrophysicist]

Why? To prove we can. There are literally hundreds of reasons why, but this one is worth enough to colonize whatever you want to.
I mean, for example, AI is just to prove that we can do it. We, human species, want to show ourselves that we can push the boundaries of what it was assumed to be the limit and feel like we're super smart. Why did we go to the Moon? Why do we deal with Astrophysics, the Big Bang, Quantum Theory and such stuff that probably won't be useful in our life (at least in the next 100 years)? Curiosity, sure, but the main is self-centeredness.

 

[mheslep]

Why do we deal with Astrophysics, the Big Bang, Quantum Theory and such stuff that probably won't be useful in our life (at least in the next 100 years)?

Those don't cost $30B a shot and the risk is entirely different. Space travel has very high likelihood of killing people, maybe everyone involved for a Mars mission.

 

[stefan r]

Why? To prove we can. There are literally hundreds of reasons why, but this one is worth enough to colonize whatever you want to.
I mean, for example, AI is just to prove that we can do it. We, human species, want to show ourselves that we can push the boundaries of what it was assumed to be the limit and feel like we're super smart. Why did we go to the Moon? Why do we deal with Astrophysics, the Big Bang, Quantum Theory and such stuff that probably won't be useful in our life (at least in the next 100 years)? Curiosity, sure, but the main is self-centeredness.

Why not colonize both the Moon and Mars? Why neglect Oberon and the Kuiper belt? Alpha Centari is only a few light years. Building a Dyson Sphere might prove something.

In high school I read a book called "the Tao of Pooh". I remember the saying "a thousand mile journey begins with one step". The debate is which step is the next one. There is more than one path available.

 

[mfb]

Space travel has very high likelihood of killing people, maybe everyone involved for a Mars mission.

The risk is tiny for everyone involved apart from the few astronauts that would go to Mars. Space missions are not just the astronauts.

 

[nikkkom]

Water is only trace in that cold atmosphere, and that only near the poles. Maybe mine the soils for ice and/or recycle for human needs.

Mining requires a lot of additional equipment. Additional equipment needs to be designed and built or imported, and needs additional maintenance. Mining can't be done just in any location - you need to actually have the desired material at the mining location (as opposed to air which is everywhere).

Instead of messing with all that, if you already have air processing plant which produces some H2O anyway, it may make sense to use _it_ to get H2O.

Mars colony is likely to have closed-loop life support systems (developed from space station technology) and need not that much water to top up losses.

 

[nikkkom]

Why not colonize both the Moon and Mars?

Sure, I agree.
The discussion exists because the $$$ available for space programs is limited. Thus, the question is more like "which colony - Moon or Mars - should be prioritized?"

 

[sophiecentaur]

Im not a chemist either, but a change in pressure doesn't not necessarily effect Haber;

I thought that Haber was all about the appropriate working pressures. Perhaps we'd only be talking about a few more Watts of compressor on low pressure atmospheric N on `Mars. Probably not the biggest problem up there.

 

[mfb]

The Haber process needs the right pressure range, but once you have purified the inputs (probably via distillation), you are decoupled from the atmospheric pressure anyway.

 

[stefan r]

Mining requires a lot of additional equipment. Additional equipment needs to be designed and built or imported, and needs additional maintenance. Mining can't be done just in any location - you need to actually have the desired material at the mining location (as opposed to air which is everywhere).

Instead of messing with all that, if you already have air processing plant which produces some H2O anyway, it may make sense to use _it_ to get H2O.

Mars colony is likely to have closed-loop life support systems (developed from space station technology) and need not that much water to top up losses.

I think they will hauling/piping water from the polar caps. At least until Ceres gets their elevator and mass driver built.
For colony #1 they are likely to drop the lander directly on the water deposit. http://www.space.com/31143-manned-mars-landing-sites-workshop.html

They will need to top up water much more than they will need nitrogen or argon. Data from viking mission has nitrogen 2.7% and water at 0.03%. Distillation would give you a cheap run separating CO₂ from the Ar/N₂. The water would be bound up in the dry ice at a little over 315 ppm. I suspect using a molecular sieve would be easier than distilling. Gypsum might be much more available than molecular sieves.
Maybe bulldoze the gypsum into a large solar bake oven or use nuclear waste heat oven. After extracting the water spread the gypsum out and let it pick up trace water for a few years. Maybe pile it on the habitats for extra radiation shielding. Helps if any water leaked reacts on location. then throw it back in the heat oven.

 

[mfb]

They found vast amounts of water ice at intermediate latitudes on Mars, just a few meters below the ground. A small digging or drilling tool can deliver as much as water as necessary. Digging gives water, the atmosphere provides CO2 and a bit of nitrogen. Water and CO2 are needed both for the station and to produce rocket fuel (and potentially as emergency energy storage), while nitrogen is only needed to cover losses in the station ecosystem.

 

[sophiecentaur]

The Haber process needs the right pressure range, but once you have purified the inputs (probably via distillation), you are decoupled from the atmospheric pressure anyway.

OK That's a reasonable reply, thanks. Nitrogen will just be a bit more expensive - fair enough as everything else would be the same. There is always the possibility that mineral Nitrate deposits exist, from a time when there was more of an atmosphere.
[Edit: it looks like they would have to be of biological origin so that's a non starter . . . . . unless. . . .]

 

[nikkkom]

Water and CO2 are needed both for the station and to produce rocket fuel (and potentially as emergency energy storage), while nitrogen is only needed to cover losses in the station ecosystem.

CO/O2 is a good fuel/oxidizer pair too, and this pair can be made from only CO2.
Nitrogen also is needed for plastics.

 

[mfb]

CO/O2 would give a bad I_sp. Wikipedia mentions 250 s without reference, that is at the level of bad solid rocket fuels. The Raptor engine using methane and oxygen has 380 s.

With 380 s, you can go from the Martian surface to Earth with a single stage easily (mass ratio ~5-6).
With 250 s, you probably want a second stage (mass ratio ~12-14). What do you do with the first stage then? And how do you get the now much larger and more complex rocket to Mars?

 

[nikkkom]

CO/O2 would give a bad I_sp. Wikipedia mentions 250 s without reference, that is at the level of bad solid rocket fuels. The Raptor engine using methane and oxygen has 380 s.
With 380 s, you can go from the Martian surface to Earth with a single stage easily.

Fuel is useful not only for rockets. It might be the way how to store PV-generated energy for night consumption. Also, vehicles.

You don't have to go from Mars surface to Earth using a single rocket. A developed colony can have dedicated LVs for ferrying cargo and people to low Mars orbit. Earthbound passengers then change the ship. CO/O2 is adequate for LMO launch vehicle.

Here is a thread about CO/O2 fuel in NS forum - https://forum.nasaspaceflight.com/index.php?topic=21544.0
A few snippets:

"""
Here's a few technical reports:
Experimental evaluation of the ignition process of carbon monoxide and oxygen in a rocket engine
http://hdl.handle.net/2060/19960045922

Carbon monoxide and oxygen combustion experiments: A demonstration of Mars in situ propellants
http://hdl.handle.net/2060/19910014990
(This one says that 260-280s is a realistic Isp for a pressure-fed engine, while 290-300s is realistic for a pump-fed engine.)
"""
Use the right tool for the right job. The low Isp of the CO/O2 propellant combo is actually optimal from an energy standpoint (presuming you get really good mass fraction), which is relevant if you have to produce all that propellant from local power sources.
"""

 

[stefan r]

CO/O2 would give a bad I_sp. Wikipedia mentions 250 s without reference, that is at the level of bad solid rocket fuels. The Raptor engine using methane and oxygen has 380 s.

With 380 s, you can go from the Martian surface to Earth with a single stage easily (mass ratio ~5-6).
With 250 s, you probably want a second stage (mass ratio ~12-14). What do you do with the first stage then? And how do you get the now much larger and more complex rocket to Mars?

Colony #1 uses the same rocket. Earth to LEO with methane is much harder than Mars to MEO using CO. That would not work with H₂/O₂ engines.
ISP measurements vary depending on liquid vs gas going into the engine and the atmospheric pressure outside of the rocket nozzle. Wikipedia lists ISP 369 and ISP 309 for methane on the same chart.

You can do a single stage to orbit CO/O₂ rocket on Mars ISP 250 is enough. But you can make engines that burn both methane and CO. So launch with CO to haul CH₄ and Oxygen to the orbiting station and return using CH₄. You can switch tanks fuel tanks mid flight while using one LOx tank and one rocket. Would not be 2 stages but similar effect. Elon Musk said something about using natural gas instead of pure methane to further cut costs for launch from earth. That opens up options for CO mixed into CH₄ and/or mixtures with C₂H₄ and C₂H₂.

 

[mfb]

Use the right tool for the right job. The low Isp of the CO/O2 propellant combo is actually optimal from an energy standpoint (presuming you get really good mass fraction), which is relevant if you have to produce all that propellant from local power sources.

Let's calculate. For fuel that combust to CO2 and H2O, the reaction releases as much energy as we put in. Then, neglecting efficiency issues, the energy we need scales with $(\mathrm{mass factor} - 1) I_{sp}^2$ where $\mathrm{mass factor} = \exp(\Delta v / (g\cdot I_{sp}))$. For every $\Delta v$, this leads to a curve with a minimum at $g I_{sp} = 0.628 \Delta v$.

For Mars orbit, 3.5 km/s, the most energy-efficient I_sp is 225 s. If you get fuel from Earth in Mars orbit, then a low energy density can be an advantage. For return to Earth, 6 km/s, the most energy-efficient I_sp is 385 s, and CO/O₂ is significantly worse due to the staging issue.
This is neglecting gravity losses, which favor higher I_sp. It is also neglecting that a lower I_sp will need a larger rocket, again favoring higher I_sp. CO has a higher density than methane, but we need more of it compared to methane, the effective density is similar. CO has a lower boiling point, making cooling more difficult.

You don't have to go from Mars surface to Earth using a single rocket. A developed colony can have dedicated LVs for ferrying cargo and people to low Mars orbit. Earthbound passengers then change the ship. CO/O2 is adequate for LMO launch vehicle.

Why would a developed colony want to rely on fuel sent from Earth? Or do you suggest electric propulsion or something similar to leave Mars orbit? Or multiple fuel launches as pseudo-second stage? All that increases the complexity. With methalox you can launch from Earth, land on Mars, refuel, and fly back in the next launch window.. You don't need a rocket infrastructure on Mars.

Earth to LEO with methane is much harder than Mars to MEO using CO.

Yes, but you have to get to LEO, and Earth to LEO with CO is not going to happen. With methalox you can use the same engines to get to Mars and to get back.

But you can make engines that burn both methane and CO.

Different temperature range, completely different fuel mixture ratios, different temperatures... I don't think that would lead to a good performance. Mixtures might work, but I don't see why CO should be in the mixture.

 

[mheslep]

The risk is tiny for everyone involved apart from the few astronauts that would go to Mars. Space missions are not just the astronauts.

Sure. ? And the topic is moot if the astronauts are removed from the mission. Unmanned missions continue as before, for a $billion per go, with no concern about flight time, radiation, return, and relatively little concern about failure.

 

[stefan r]

...Yes, but you have to get to LEO, and Earth to LEO with CO is not going to happen. With methalox you can use the same engines to get to Mars and to get back.
Different temperature range, completely different fuel mixture ratios, different temperatures... I don't think that would lead to a good performance. Mixtures might work, but I don't see why CO should be in the mixture.

CO should be in the mixture because it is excessively abundant. Splitting CO₂ to make O₂ creates CO. Using the CO means no added infrastructure.
It is certainly not going to be ideal performance. The question is how much performance is lost. The oxy-fuel mix is easy to adjust. The valves to control flow are already in the engine. I have never built a turbo-pump. If I was buying a pump for a lab I would likely use the same model on CO or CH₄.
I would worry about the engine getting hot enough to crack the CO. Would be easy to test for that.

 

[mfb]

For 1 liter of oxygen, you need 3.1 liters of CO, or 0.8 liters of methane. That is a factor 4 difference. An engine that can burn both needs horribly oversized fuel pumps and probably two separate injection systems. Not to mention the problem how to design the tank. Do you want to keep it 3/4 empty in methane operation? Or keep the oxygen tank 3/4 empty in CO operation?
The optimal chamber pressure and the optimal expansion ratio will be different for the two fuels, again you misdesign your engine for at least one of them. A thermal system good for CO is overdesigned for methane. You would need a gigantic benefit to outweigh all these disadvantages.

I'm sure it is possible to design a methalox engine to accept 1% CO or vice versa. But where is the point? You just add complexity for no reason.

 

[mheslep]

f you already have air processing plant which produces some H2O anyway

H20 is only trace in the air, except for small periods near the poles.

 

[mheslep]

I thought that Haber was all about the appropriate working pressures. Perhaps we'd only be talking about a few more Watts of compressor on low pressure atmospheric N on `Mars. Probably not the biggest problem up there.

Right, whatever Haber requires, additional power can make the conditions Earth like.

 

[rootone]

Right, what ever Haber requires, additional power can make the conditions Earth like.

In principle yes, but where is additional energy to come from?
With useable technology at present the only feasible option is to set up several fission power plants on Mars.
These will have to be shipped, installed, and maintained from Earth.
That seems unlikely at best.

 

[mheslep]

In principle yes, but where is additional energy to come from?
With useable technology at present the cheapest option is several fission plants set up on Mars.
These will have to be shipped, installed, and maintained from Earth.
That seems unlikely at best.

Any power source on Mars must be shipped from Earth, of course. Small nuclear power plants have been proposed for missions, both by in the Mars Direct proposal in NASA's "90 Days Study". Either radioisotope (already used multiple times in space missions) or fission are considered.

Immediately after landing, the propellant factory/ERV would deploy a robot “utility truck” rover carrying a 4.5-metric-ton SP-100 nuclear reactor. The rover, which would burn methane fuel and oxygen oxidizer, would carry the reactor a few hundred meters away and place it into a natural crater or one blasted “with the aid of a few sticks of dynamite.” The crater wall and rim would prevent the reactor from irradiating the landing area. Thermal radiators would deploy from the SP-100, then the rover would run a cable from the reactor back to the propellant factory/ERV.

The SP-100 would supply 100 kilowatts of electricity to compressors in the ERV. These would draw in martian air, which is mostly carbon dioxide. The carbon dioxide would be reacted in the presence of a catalyst with 5.8 metric tons of liquid hydrogen brought from Earth, yielding 37.7 metric tons of methane and water...

I believe the deployment of the reactor to make fuel in Mars Direct occurs before arrival of the manned mission, i.e. is all robotic.

 

[mfb]

Solar panels are considered as well. They have a nice power to mass ratio and space is not an issue.