Author Topic: Carbon Monoxide for fuel on Mars  (Read 66745 times)

Offline Proponent

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Re: Carbon Monoxide for fuel on Mars
« Reply #100 on: 08/19/2016 03:56 pm »
The calculation does not tell you much about payload.  All it does is tell you what fraction of the burn-out mass is not taken up by tanks, fluids and engines, the idea being that the larger this "available" mass is, the easier it would be build the vehicle with a positive payload.  The implicit assumption here is that most of the other non-payload mass would be independent of propellant mass, though that is no doubt only approximately true at best.

To calculate any quantity that's expressed per tonne of payload, we would need to guestimate an aggregate mass for all of the other stuff -- non-tank structures, landing gear, avionics, etc., to be subtracted from the available mass (mAvail) to get the payload mass.  Suppose you had the technology to build and Earth-to-LEO SSTO with payload being 1% of GLOM.  Looking back at the calculations I did for a delta-V of 10 km/s and Earth conditions, mAvail was about 0.553 for lox-ethylene, one of the better-performing propellant mixtures.  Propellant mass is 16.8 times the burn-out mass, so GLOM is 17.8.  If payload is 1% of GLOM, it's 0.178.  Since mAvail is 0.553, the other vehicle mass must be 1 - 0.553 - 0.178 = 0.269.

If we can apply the same "other" mass to our 4-km/s Martian SSTO, then the payload mass for the lox-CO case is 0.918 - 0.269 = 0.649.  The propellant mass is 3.63, so the propellant-to-payload ratio is 3.63 / 0.649 = 5.6.  At 20.2 MJ/kg for CO production, the electrical energy per unit mass of payload is 110 MJ/kg.

For lox-methane, the payload is 0.950 - 0.269 = 0.681.  The propellant mass is 2.20, so the propellant-to-payload ratio is 3.2.  At 142 MJ/kg for methane production (though what about the oxygen?), that's 460 MJ/kg.

Because of the way I've backed into the "other" mass, this is a pretty hokey calculation.  But maybe the fact that CO seems the more energy-efficient fuel by such a large margin is nonetheless indicative.  I do suspect that this model over-values propellant density, i.e., under-weights the knock-on effects of propellant mass, in part because the outputs seem pretty harsh on the some of the more popular SSTO propellant combinations.  But still, CO's advantage in energy efficiency over methane seems pretty big.

Where is the oxygen coming from for lox-methane?  Wouldn't producing it add to the energy budget, making lox-methane still less attractive?

Offline Robotbeat

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Re: Carbon Monoxide for fuel on Mars
« Reply #101 on: 08/19/2016 04:26 pm »
Oxygen comes for "free" by the electrolysis of water.
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Offline Robotbeat

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Re: Carbon Monoxide for fuel on Mars
« Reply #102 on: 06/10/2019 03:30 am »
I still think this is a good idea. And, kind of ironically, if high altitude water vapor from rocket exhaust becomes a global warming concern, a carbon monoxide rocket might be almost our only option on Earth, too. Because while CO2 is responsible for the bulk of anthropogenic global warming, ironically it's far less than water vapor at very high altitudes (since water's residency time up there is long).

Not a concern at present launch rates, or even an order of magnitude higher (although sooty kerosene WOULD be a concern, clean-burning methane perhaps not), but if you start launching a megaton of material to orbit or for hypersonic point-to-point, it's now a significant fraction of global aviation emissions (by global warming potential).
« Last Edit: 06/10/2019 03:34 am by Robotbeat »
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Offline speedevil

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Re: Carbon Monoxide for fuel on Mars
« Reply #103 on: 06/10/2019 09:59 am »
I still think this is a good idea. And, kind of ironically, if high altitude water vapor from rocket exhaust becomes a global warming concern, a carbon monoxide rocket might be almost our only option on Earth, too.
If a methane rocket uses half the fuel of a CO/O based one to get to near escape, the methane one wins, because you can make methane from electricity +CO2+water  at 50% efficiency even using todays technology.

Offline Robotbeat

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Re: Carbon Monoxide for fuel on Mars
« Reply #104 on: 06/10/2019 10:32 am »
I still think this is a good idea. And, kind of ironically, if high altitude water vapor from rocket exhaust becomes a global warming concern, a carbon monoxide rocket might be almost our only option on Earth, too.
If a methane rocket uses half the fuel of a CO/O based one to get to near escape, the methane one wins, because you can make methane from electricity +CO2+water  at 50% efficiency even using todays technology.
Water vapor is something like 40 times worse than CO2 at those altitudes, so no, the CO/O2 rocket is still easily the winner.
« Last Edit: 06/10/2019 10:42 am by Robotbeat »
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Offline rakaydos

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Re: Carbon Monoxide for fuel on Mars
« Reply #105 on: 06/10/2019 11:59 am »
I still think this is a good idea. And, kind of ironically, if high altitude water vapor from rocket exhaust becomes a global warming concern, a carbon monoxide rocket might be almost our only option on Earth, too. Because while CO2 is responsible for the bulk of anthropogenic global warming, ironically it's far less than water vapor at very high altitudes (since water's residency time up there is long).

Not a concern at present launch rates, or even an order of magnitude higher (although sooty kerosene WOULD be a concern, clean-burning methane perhaps not), but if you start launching a megaton of material to orbit or for hypersonic point-to-point, it's now a significant fraction of global aviation emissions (by global warming potential).
Soot in the upper atmosphere actually opposes global worming, increasing planetary albedo and keeping energy from ever reaching earth to be stuck behind CO2.

It also weakens solar power, starves plants, and smells horrible. But it slows global warming.

Offline Robotbeat

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Re: Carbon Monoxide for fuel on Mars
« Reply #106 on: 06/10/2019 12:47 pm »
I still think this is a good idea. And, kind of ironically, if high altitude water vapor from rocket exhaust becomes a global warming concern, a carbon monoxide rocket might be almost our only option on Earth, too. Because while CO2 is responsible for the bulk of anthropogenic global warming, ironically it's far less than water vapor at very high altitudes (since water's residency time up there is long).

Not a concern at present launch rates, or even an order of magnitude higher (although sooty kerosene WOULD be a concern, clean-burning methane perhaps not), but if you start launching a megaton of material to orbit or for hypersonic point-to-point, it's now a significant fraction of global aviation emissions (by global warming potential).
Soot in the upper atmosphere actually opposes global worming, increasing planetary albedo and keeping energy from ever reaching earth to be stuck behind CO2.

It also weakens solar power, starves plants, and smells horrible. But it slows global warming.
It also destroys the ozone layer, and if it settles to the ground makes global warming worse and accelerated melting of glaciers in particular. It won’t be allowed at high flight rates.
« Last Edit: 06/10/2019 12:56 pm by Robotbeat »
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Offline rakaydos

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Re: Carbon Monoxide for fuel on Mars
« Reply #107 on: 06/10/2019 02:08 pm »
I still think this is a good idea. And, kind of ironically, if high altitude water vapor from rocket exhaust becomes a global warming concern, a carbon monoxide rocket might be almost our only option on Earth, too. Because while CO2 is responsible for the bulk of anthropogenic global warming, ironically it's far less than water vapor at very high altitudes (since water's residency time up there is long).

Not a concern at present launch rates, or even an order of magnitude higher (although sooty kerosene WOULD be a concern, clean-burning methane perhaps not), but if you start launching a megaton of material to orbit or for hypersonic point-to-point, it's now a significant fraction of global aviation emissions (by global warming potential).
Soot in the upper atmosphere actually opposes global worming, increasing planetary albedo and keeping energy from ever reaching earth to be stuck behind CO2.

It also weakens solar power, starves plants, and smells horrible. But it slows global warming.
It also destroys the ozone layer, and if it settles to the ground makes global warming worse and accelerated melting of glaciers in particular. It won’t be allowed at high flight rates.
I think you'd be surprised what would be permitted. Or rather, what does not require permitting. I know I am.

Offline guru

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Re: Carbon Monoxide for fuel on Mars
« Reply #108 on: 06/21/2020 07:18 pm »
I read a paper a long time ago about an industrial scale system to extract trace gases from Mars' atmosphere for use as rocket propellant.  Carbon monoxide and oxygen were specifically mentioned, but carbon dioxide, nitrogen, argon, and  water (when present) would also be produced for other uses.  The tagline on the associated presentation was something like "Fish don't electrolyze water to get oxygen, so why should rocket scientists", in reference to the fact that fish have gills which are used to gather oxygen already absorbed in the water.  Since electrolysis and adsorption have already been mentioned, I though this thread would be a good place to add this.

This setup would probably need to be placed in a well established settlement, but the described process would work as follows:

Atmospheric gases would be compressed to the point that the carbon dioxide liquifies at ambient Martian temperatures.  (I imagine water would be removed beforehand using either a desiccant/zeolite material, or just in an intermediate compression step at a lower pressure that would allow the water to fall out as a liquid, since the compression would clearly raise the temperature enough to allow for liquid water to exist.)  The remaining gases would be siphoned off and run through additional cooling / distillation processes to isolate each substance.

Here's the important part.  The stored liquid CO2 (which makes up 96% of the gas compressed) would be expanded through a turbine, which would in turn be connected to the primary compressor.   This step would recover a significant amount (how much I don't recall) of the energy used in the original compression process.  This would reduce the amount of added energy required for subsequent compression operations and improve the overall efficiency of the system considerably.

A diagram seemed to show the various compressors and refrigerators connected by a system of pulleys to transfer the mechanical power from the turbine, but there may be a more elegant way to do that.  There were probably also some electric motors to bootstrap the facility's startup and make up for energy lost in the various processes.

[By the way, if anyone happens to know where this paper or presentation is available, I would love to find out.  It seems to have disappeared from the internet.]

So, yes, a carbon monoxide / oxygen rocket does have certain advantages, one notably being that the propellants are floating around freely in the air.

Offline guru

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Re: Carbon Monoxide for fuel on Mars
« Reply #109 on: 12/16/2020 04:43 am »


By the way, if anyone happens to know where this paper or presentation is available, I would love to find out.  It seems to have disappeared from the internet.


Only took six months, but I just stumbled upon the associated paper, if not the PowerPoint presentation, I was referencing.

http://www.niac.usra.edu/files/studies/final_report/483England.pdf

This came out in 2001.

A follow up synopsis from 2004 (here: https://ntrs.nasa.gov/citations/20040196381) states:

" With single redundancy both for propellant and crew air, the oxygen requirement for the MRM is estimated at 5.8 kg/hr. The process thermal power needed is about 120 kW, which can be provided at 300-500 C. A lower-cost nuclear reactor made largely of stainless steel could serve as the heat source."

At 120 kW thermal, this scenario requires a reactor only 5% the size of the one base-lined in the original Mars Direct, which produced 2.4 MWt (for a 100 kW electric output).

Offline stefan r

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Re: Carbon Monoxide for fuel on Mars
« Reply #110 on: 12/16/2020 04:29 pm »

Here's the important part.  The stored liquid CO2 (which makes up 96% of the gas compressed) would be expanded through a turbine, which would in turn be connected to the primary compressor.   This step would recover a significant amount (how much I don't recall) of the energy used in the original compression process.  This would reduce the amount of added energy required for subsequent compression operations and improve the overall efficiency of the system considerably.

A diagram seemed to show the various compressors and refrigerators connected by a system of pulleys to transfer the mechanical power from the turbine, but there may be a more elegant way to do that.  There were probably also some electric motors to bootstrap the facility's startup and make up for energy lost in the various processes.

The colony needs a nuclear reactor (probably).  The nuclear reactor will have a turbine.  The working fluid goes to a cooling tower.  Carbon dioxide is a better working fluid than water.  There are proposals to use CO2 instead of water in power plants here on Earth. https://www.powermag.com/what-are-supercritical-co2-power-cycles/  The CO2 optimized turbines are more compact and efficient.  It is hard to compete with a working fluid that falls from the sky and then collects in rivers and lakes.  On Mars the situation will be reversed.  CO2 is readily available but water would have to be mined. 

CO2 separated from atmosphere can be fed into the reactor.  That recovers all of the energy you intended to recover. 

Offline Robotbeat

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Re: Carbon Monoxide for fuel on Mars
« Reply #111 on: 12/19/2020 02:58 pm »
So, a lot of the worry about CO for fuel is that it's toxic. But ammonia is just as toxic (look up the LD50), and we used it as a fuel on the crewed reusable rocketplane X-15 on Earth! All humans will be in positive pressure suits or habitats, as Mars is a near-vacuum, so I don't see any particular reason why it'd be any significant problem at all for Mars.

I mean, farmers also spread anhydrous ammonia directly into their soil. Hydrazine is an order of magnitude more toxic (see LD50/LC50). I don't think CO, which is no more dangerous than ammonia, is any kind of real toxicity challenge. Yes, it's odorless, but we can just use CO sensors (which are cheap and ubiquitous).
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Offline Robotbeat

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Re: Carbon Monoxide for fuel on Mars
« Reply #112 on: 12/19/2020 04:16 pm »
For posterity, here is a Wayback Archive link to the pdf and a screenshot of the CO/O2 engine.
https://web.archive.org/web/20160313060635/http://www.reactionengines.co.uk/tech_docs/mars_troy.pdf
298s Isp.
Oxygen-rich preburner, LOx-cooled regen. Both would’ve seemed fairly exotic a decade or so ago, but now smallsat rocket companies have built some engines with these features.

Also possible to do electropump. May be easiest that way, shortening development time.

(I also attached the pdf in case it disappears.)
« Last Edit: 12/19/2020 06:33 pm by Robotbeat »
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Offline Proponent

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Re: Carbon Monoxide for fuel on Mars
« Reply #113 on: 12/20/2020 01:53 pm »
For that matter, there was a time when coal gas, one component of which is carbon monoxide, was widely used in homes where natural gas is used today. Natural gas is definitely safer, but it's not like people regularly died of CO poisoning.

I think the safety of CO use on Mars is a non-issue.  The hardly insurmountable problem I do see is the need for extra safety precautions when developing and testing the technology here on Earth.
« Last Edit: 12/20/2020 01:56 pm by Proponent »

Offline mmeijeri

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Re: Carbon Monoxide for fuel on Mars
« Reply #114 on: 12/20/2020 02:35 pm »
While we are thinking of exotic and toxic propellant combinations, here's another one. It turns out there exist other suboxides of carbon than carbon monoxide, such as tricarbon dioxide, which has a much higher normal boiling point (279.9 K) than CO (81.6 K). However, the boiling point of CO is close to that of LOX (90.2 K), so that may not be much of an advantage unless you are able to source a non-cryogenic oxidiser purely from the Martian atmosphere. NTO would be possible, but would also be much more expensive to produce than LOX.
« Last Edit: 12/20/2020 02:37 pm by mmeijeri »
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Offline john smith 19

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Re: Carbon Monoxide for fuel on Mars
« Reply #115 on: 12/20/2020 03:55 pm »
For that matter, there was a time when coal gas, one component of which is carbon monoxide, was widely used in homes where natural gas is used today. Natural gas is definitely safer, but it's not like people regularly died of CO poisoning.
Actually they did. Check the statistics for the 40's through to the 70's at least. It was also a popular choice for suicide. Each year a certain number of people die of badly adjusted or maintained gas furnaces generating CO. It's called "The silent killer" as it is odorless and tasteless.  :(
Quote from: Proponent
I think the safety of CO use on Mars is a non-issue.  The hardly insurmountable problem I do see is the need for extra safety precautions when developing and testing the technology here on Earth.
CO poisoning is now a much better recognized issue in gas combustion and various kinds of sensor exist, bot h chemical papers that change color and sensors.

But then REL looked at Cyanogen (CN)2 whose flame temperature at 4525c gives it substantially higher Isp. Along with substantially higher toxicity (it's basically 2 cyanide fragments stuck together. On earth you wouldn't want to be standing down wind of the exhaust.  :o )
MCT ITS BFR SS. The worlds first Methane fueled FFSC engined CFRP SS structure A380 sized aerospaceplane tail sitter capable of Earth & Mars atmospheric flight.First flight to Mars by end of 2022 TBC. T&C apply. Trust nothing. Run your own #s "Extraordinary claims require extraordinary proof" R. Simberg."Competitve" means cheaper ¬cheap SCramjet proposed 1956. First +ve thrust 2004. US R&D spend to date > $10Bn. #deployed designs. Zero.

Offline Robotbeat

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Re: Carbon Monoxide for fuel on Mars
« Reply #116 on: 12/20/2020 04:29 pm »
I think it's easy to forget how ubiquitous CO is. Do you have a natural gas fired water heater? central heat? dryer? fireplace, either gas or wood? The exhaust has lots of CO. Same even for a stove. Your car exhaust has massive CO output.

Every charcoal fire has MASSIVE amounts of CO, not a trace amount. The flames you sometimes see *after* all the lighter fluid has burned off is actually CO burning. It's a CO flame.

CO is no great toxicity hazard beyond what is encountered in almost every home. It's about an order of magnitude less toxic than hydrazine. I would say our brave Martian explorers will be at less risk of CO poisoning than your average car driver or household with a gas stove.

So let's not concern troll about it.
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Offline Robotbeat

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Re: Carbon Monoxide for fuel on Mars
« Reply #117 on: 12/20/2020 04:40 pm »
For that matter, there was a time when coal gas, one component of which is carbon monoxide, was widely used in homes where natural gas is used today. Natural gas is definitely safer, but it's not like people regularly died of CO poisoning.

I think the safety of CO use on Mars is a non-issue.  The hardly insurmountable problem I do see is the need for extra safety precautions when developing and testing the technology here on Earth.
Yup, and natural gas kitchen stoves can produce massive amounts of CO, hundreds of ppm of CO, particularly when you put a pot on it. This is *indoors*, too, in a residential space, and is really normal and often there isn't even a vent!

"CO fuel" sounds scary, but that ignores just how flippant we are with CO in reality, even if we don't realize it. If you have a gas stovetop, you're putting significant amounts of CO right into your face while you're cooking, not uncommonly 100ppm. In fact, the flue gases from a stovetop can be up to 800ppm before they're considered illegal.

A home with an unvented gas stove (which is a LOT of them) is a bigger hazard than these astronauts will ever face.
« Last Edit: 12/20/2020 04:57 pm by Robotbeat »
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Offline Genial Precis

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Re: Carbon Monoxide for fuel on Mars
« Reply #118 on: 12/20/2020 05:30 pm »
To be fair, in the ubiquitous CO-producing applications on Earth, "don't be in a confined space with the combustion" is still good advice. I'd suspect the main important safety measure would be for the CO tank to be normally unconnected to the people tank. Either isolation valves in the ventilation, airlocked compartment, or even outside the people tank altogether, something like that. Starting point isn't what people do when fresh air is everywhere, more like what people put up with on a ship or a submarine.

On the subject of propellants that can be made from martian atmosphere alone, has anyone seen calculations for CO+NO? Going by wikipedia data, std enthalpy of CO+1/2O2->CO2 is 284 kJ/mol or 6.45 kJ/g and CO+NO->CO2+1/2N2 is 375 kJ/mol or 6.45 kJ/g, but now the average molecular mass of the exhaust is lower and some of the products are diatomic. Seems like that implies better specific impulse, but I'm not set up to do rocket propellant calculations.

CO+O2 combination actually seems like an interesting possibility for grid energy storage on Earth.

Offline Robotbeat

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Re: Carbon Monoxide for fuel on Mars
« Reply #119 on: 12/20/2020 07:40 pm »
To be fair, in the ubiquitous CO-producing applications on Earth, "don't be in a confined space with the combustion" is still good advice. I'd suspect the main important safety measure would be for the CO tank to be normally unconnected to the people tank. Either isolation valves in the ventilation, airlocked compartment, or even outside the people tank altogether, something like that. Starting point isn't what people do when fresh air is everywhere, more like what people put up with on a ship or a submarine.
...
Mars is a near vacuum, and the propulsion systems will be outside the pressure vessels entirely. So this is actually safer than on Earth as all humans will be in positive-pressure habitats without possibility of any CO coming in.
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