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General Discussion => Advanced Concepts => Topic started by: Robotbeat on 05/10/2010 05:53 pm

Title: Carbon Monoxide for fuel on Mars
Post by: Robotbeat on 05/10/2010 05:53 pm
A LOx/CO rocket has low Isp (~290s), but can be quite easily produced anywhere on Mars. Logistically, it's simple. But we have very little experience with carbon monoxide as a fuel.

(Yay for the NASA Technical Reports Server!)

What would be a good figure to use for the Isp of such a rocket? Is it feasible to produce a dual-fuel rocket, which uses a higher energy propellant for the trip down? (My guess is that it would be far simpler to just use one fuel.)

Also, what is the size/mass of a CO/O2 producing machine, and what sort of power requirements would it have and what sort of throughput and lifetime?
Title: Re: Carbon Monoxide for fuel on Mars
Post by: Robotbeat on 05/10/2010 06:04 pm
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.)

300s is nothing to sneeze at, especially since it enables potentially easy (and limitless) Martian ISRU. Lots of work, though, it seems.
Title: Re: Carbon Monoxide for fuel on Mars
Post by: Robotbeat on 05/10/2010 06:26 pm
The benefit over methane-based ISRU should be obvious: no need for bringing hydrogen from Earth and the long-term cryogenic storage thereof.

What would be used for pressurization? Is nitrogen or argon or carbon dioxide suitable, or should we just plan on bringing helium along with? Self-pressurization?

Another not-very-helpful point: for very low delta-v requirements, the lower the theoretical Isp, the lower the theoretical amount of energy needed for ISRU production of the fuel for a certain delta-v.

And, while we're using O2/CO for rocket fuel, what about for fuel for other vehicles?

If we had a magical gas-and-go VTVL Mars lander capable of about 4.1km/s delta-v, that should be enough for just about global access for point-to-point access between Martian bases that have the infrastructure for O2/CO production. Might be a good way to leverage hardware from past missions in case of emergencies, even if placed far away from later missions. It may also allow multiple trips to-and-from places on Mars inaccessible via wheeled vehicles, if you have plenty of O2/CO production to spare for such excursions. (This paragraph is pretty unrealistic, but awesome ;).)
Title: Re: Carbon Monoxide for fuel on Mars
Post by: A_M_Swallow on 05/10/2010 06:33 pm
There was a thread about this a few years ago.

Aircraft on Mars can burn atmospheric CO2 + alkaline metal or magnesium.

Using a Stirling converter as an electrical generator ISRU magnesium could power a Rover.

Splitting of CO2 to give ISRU CO + LOX can be performed using solar or nuclear power.

ISRU Argon can be extracted from Mars's atmosphere by refrigeration.
Title: Re: Carbon Monoxide for fuel on Mars
Post by: Robotbeat on 05/10/2010 07:04 pm
Also, here's an interesting proposal from Zubrin, et al, of a mixed methane/CO/O2 propellant Martian ISRU rocket system, which benefits from the added density of CO but retains most of the Isp of methane while also making the production equipment easier and smaller and more productive for a certain energy input, and Methane/CO/O2 all are storable at the same temperature, making common-bulkheads easier:

http://www.techbriefs.com/component/content/article/3365
http://hdl.handle.net/2060/20080047195
Mars Rocket Propulsion System (published November, 2008)

Sounds like a total win, except you still have to have more development of rockets using such a propellant combination (EDIT: And, you still will likely need to bring hydrogen from Earth).
Title: Re: Carbon Monoxide for fuel on Mars
Post by: Robotbeat on 05/10/2010 07:23 pm
What might be interesting is a "flex fuel" lander which can use varying amounts of methane or carbon monoxide for fuel. You'd likely want pure methane for initial descent propellant (because it has to be transported from Earth), and varying amounts of carbon monoxide depending on what payload capacity or delta-v you need and how much hydrogen is available (either from Earth or from Mars), but capable of operation to orbit on pure methane or pure carbon monoxide if needed.

Probably possible, don't know how feasible.
Title: Re: Carbon Monoxide for fuel on Mars
Post by: Robotbeat on 05/11/2010 02:10 am
It should be noted that the research done for ISRU on Mars led to the fuel cell promoted by the "Bloom Energy" start-up company (obviously, operated in reverse). If we assume those things are a good starting point for how much a Martian ISRU device would weigh (not including the separation and compression equipment or the power source), then the ISRU device should be quite light.

The large stationary devices that they sell (or plan to sell) have a specific power of over 10W/kg. Probably could be SUBSTANTIALLY increased for mobile applications, and I'm sure the weight could be halved, and probably made even only 10% for the same power output (this would be roughly the same for hydrogen fuel cells, the stationary versions of which are like 10 times heavier per watt than the mobile ones). So, let's guess that it'd be about 40W/kg. I think the notoriously stealthy Bloom Energy company is probably much of the reason many of recent the documents on the zirconia electrolysis process on the NASA Technical Reports server have "no digital copy." Maybe I'm just imagining things, though.

This website: http://ares.jsc.nasa.gov/HumanExplore/Exploration/EXLibrary/docs/ISRU/08Atmos.htm

...is a pretty comprehensible summary. If we believe its numbers (12 kW produces 1000kg of oxygen per month), then less than 300W is needed per crew member (at 1kg of O2/day). To provide 20 tons of propellant, that 12kW should be able to produce it in about 7 months, since it should produce roughly 2 tons of CO for every 1 ton of oxygen. Of course, there's probably significant power necessary for liquefying the CO (should be about the same as required for Nitrogen, though at a little higher temperature, since N2 and CO are very similar). But it's probably less than 20% of the power required to produce them (actually, for efficient compressors it should be less than 10%). Perhaps you could even integrate the ISRU fuel producer into each lander?

12kW is pretty minimal, as far as power goes. Much less than ISS, and typical for a comm sat. It could be produced by multiple, highly efficient Advanced "RTG"s (which could be either Sterling or thermophotovoltaic), though we'd need to produce more Pu-238 if we were to go that route. Also, 12kW could be produced, obviously, with solar panels, though they'd be no more than one fourth as efficient as at Earth, and may well be far less efficient because of pointing requirements, dust storms, etc. I'm a fan of just using advanced RTGs, since they seem to be less hassle than solar panels and last longer, cost less for development, and be safer than a fission power source, though a ground-based fission power source is in many ways easier than a free-space-based fission generator used for propulsion.

300W is also minimal, though not if you carry it on your back! I guesstimate, though, that it's possible to shrink a highly efficient "RTG" and one of these zirconia electrolysis devices into a portable life-support pack weighing no more than 100kg. Perhaps it could be shrunk even smaller, allowing unlimited oxygen for years integrated into a spacesuit. The same thing could be had much easier, though, by putting it on wheels (thus not requiring the astronaut to always be next to a radiation source, as safe as a purely alpha-emitter is).


(I put RTG in quotes because the most efficient ones being developed don't use the thermoelectric effect, but instead use a sterling engine or the thermophotovoltaic effect.)
Title: Re: Carbon Monoxide for fuel on Mars
Post by: Robotbeat on 05/11/2010 05:21 pm
(Sorry about that last long post... I had a lot of ideas that I had to put down so I could get them out of my head)

A single-stage lunar lander capable of EML1/2 rendezvous with methane/LOX (~5km/s delta-v and 360s Isp means wet:dry ratio of about 4.15... maybe a bridge too far) would be easily capable of reaching low Mars orbit from Mars's surface if fueled with CO/LOX (4.4km/s delta-v with 300s Isp, though with about 1.106 times the bulk density of methane/LOx, where 4.1km/s is minimum necessary for reaching low Mars orbit).
Title: Re: Carbon Monoxide for fuel on Mars
Post by: Robotbeat on 05/12/2010 12:48 am
A very small Advanced Sterling Radioisotope Generator has a specific power of roughly 8.4W/kg. "Ultraflex" panels are capable of at least 175W/kg. So even at only 10% Earth orbit efficiency, ultraflex panels (like used on the Phoenix lander) offer lower greater power per kilogram. Ultraflex solar panels can also deploy under one-gee, BTW.

Anyways, the 8.4W/kg figure probably can be greatly improved upon. These ASRGs convert thermal energy to electrical energy at about 32% efficiency, which is pretty impressive (compared to conventional RTGs).


Anyway, so:

12,000W/(8.4W/kg)=~1430kilograms. The power source would weigh about a ton and a half. Not too bad. We could probably land that in one shot via an improved skycrane descent stage and a EELV heavy with a guppy fairing for the big heatshield (I guesstimate that about 3 tons could be landed via this method). 12kW is enough for ISRU production of Carbon Monoxide and Oxygen for propellant, almost 20 tons worth in 6 months. For a smaller 750 kg ASRG which could be landed with roughly a stock Skycrane system, it'd take about a year for 20 tons of propellant. 750kg worth of Ultraflex panels should be enough power to produce 20 tons of propellant in 6 months, if not too much dust accumulates (and they aren't blown away because they're like giant sails, in spite of the thin martian air).
Title: Re: Carbon Monoxide for fuel on Mars
Post by: MickQ on 05/12/2010 07:01 am
Chris.

Ever get the feeling that you are talking to yourself ???

Mick.
Title: Re: Carbon Monoxide for fuel on Mars
Post by: Robotbeat on 05/12/2010 01:21 pm
Chris.

Ever get the feeling that you are talking to yourself ???

Mick.
:)
Title: Re: Carbon Monoxide for fuel on Mars
Post by: mmeijeri on 05/12/2010 01:26 pm
Zubrin has proposed using CO or CO2 NTR for a Mars RLV. Isp and T/W wouldn't be spectacular, but with the shallower gravity well of Mars and with plentiful local CO2 that wouldn't be a problem.
Title: Re: Carbon Monoxide for fuel on Mars
Post by: Robotbeat on 05/12/2010 02:00 pm
Zubrin has proposed using CO or CO2 NTR for a Mars RLV. Isp and T/W wouldn't be spectacular, but with the shallower gravity well of Mars and with plentiful local CO2 that wouldn't be a problem.
I think a NTR shouldn't be used because of this minimum size issues (I.e. Shielding mass stays roughly constant as power increases), unless you've demonstrated a NTR in space already and are impressed with its performance. However, a NTR lander could have enough delta-v to enable new mission modes, like turning a Mars flyby mission into one where you speed ahead of your MTV, land, do your mission, then launch again quickly to catch up with your MTV after it does a flyby of Mars. It wouldn't even need to do ISRU.

CO isn't as bad Isp as I initially thought: about 300s is feasible for a pump-fed engine running at Mars sea-level (which is basically vacuum). And you have to do CO synthesis anyway to produce O2 from CO2, only now you skip the steps of combining it with hydrogen you've lugged from Earth (and had to keep cold and liquid the whole way) and carefully filtering and purifying the methane of any CO (Zubrin proposes skipping the filtering/purifying step and using a CH4/CO mix, which would have greater density than just CH4 anyway while preserving most of the Isp). All that stuff is heavy, though the actual CO/O2 producing electrolysis cell can be rather small and lightweight.
Title: Re: Carbon Monoxide for fuel on Mars
Post by: A_M_Swallow on 05/12/2010 04:21 pm
Solar dynamic is another possibility.  A Mars generator would need bigger mirrors that the Earth version.
Title: Re: Carbon Monoxide for fuel on Mars
Post by: Robotbeat on 05/12/2010 04:50 pm
Solar dynamic is another possibility.  A Mars generator would need bigger mirrors that the Earth version.
...And during a dust-storm, would produce exactly zero power, but a photovoltaic array would still produce power.

BTW, the 1.2 square meter arrays on the MERs produce roughly .6 kWh per day, or about 25 Watts. I assume these are roughly 25% efficient arrays(EDIT: They are 27.5% efficient beginning-of-life), maybe a little more. If pointed directly at the Sun at 1AU from the Sun (i.e. Earth), they would produce roughly 451 Watts. At 1.52 AU (Mars), about 195Watts. Including the day/night cycle, half that again at about 97.6 Watts. The rest of the inefficiency is due to lack of pointing and dust accumulation (though I don't think this is included too much when calculating .6kWh/day) and atmospheric opacity.

That means that a flat solar panel on the surface of Mars experiences about 5.55% of the insolation of full illumination at Earth's orbit.

So, if I have a solar array which is capable of 175W/kg at Earth's orbit (like UltraFlex arrays are capable of) and I lay it flat on Mars, it will produce ~9.7W/kg (and sometimes less because of dust accumulation), which is comparable to an advanced Sterling Radioisotope Generator at ~8.4W/kg (which needs expensive Pu-238, but we should restart full production anyway if we plan on continued deep space missions).

BTW, are RTGs affected by dust accumulation, too? Wouldn't dust accumulation affect heat rejection?
Title: Re: Carbon Monoxide for fuel on Mars
Post by: Robotbeat on 05/12/2010 09:59 pm
Could the RL-10 or "CECE" engine be modified to run on Carbon Monoxide or a CO/Methane mix?
How much did it cost to modify the RL-10 to run on Methane?
Title: Re: Carbon Monoxide for fuel on Mars
Post by: Robotbeat on 05/13/2010 03:44 am
A Carbon Monoxide rocket engine on Mars with an Isp of 300s at Martian "sea level" is far better than any other sea-level (first-stage) rocket engine that was available during Apollo, etc. Also, on Mars, the T/W is tripled! ;)
Title: Re: Carbon Monoxide for fuel on Mars
Post by: Swaggasorusrex on 09/26/2012 01:00 am
Robotbeat, why would you still have the need to bring hydrogen from Earth still?
Title: Re: Carbon Monoxide for fuel on Mars
Post by: RocketmanUS on 09/26/2012 01:35 am
Mars atmosphere has .013% O2 and .08% CO.
So is there an efficient scrubber for O2 and another for CO?

If so separate the O2/CO out of the air.
Title: Re: Carbon Monoxide for fuel on Mars
Post by: douglas100 on 09/26/2012 08:07 am
Mars atmosphere has .013% O2 and .08% CO.
So is there an efficient scrubber for O2 and another for CO?

If so separate the O2/CO out of the air.

You would need a very large throughput of atmospheric gas to get a usable amount of propellant. From the energy standpoint I think it would be better to crack CO2 down to CO and O2.
Title: Re: Carbon Monoxide for fuel on Mars
Post by: sfuerst on 09/26/2012 06:21 pm
Another option might be Ethylenetetracarboxylic dianhydride, (C6O6).  It's a stable higher oxocarbon.  However, I haven't seen its chemical stats, so it may have an unsuitable melting/boiling point.  Making it might also be a challenge, something more for an advanced Mars base rather than a first try at ISU.
Title: Re: Carbon Monoxide for fuel on Mars
Post by: Robotbeat on 09/26/2012 06:31 pm
Robotbeat, why would you still have the need to bring hydrogen from Earth still?

Extracting water is a lot harder, since it's only a tiny, tiny portion of the atmosphere and processing any kind of solids requires a lot more hardware. I'm certainly not saying it can't be done, but probably isn't feasible until a base is set up.

A CO/O2 production facility would be a piece of cake in comparison, and would require less power and a HECK of a lot less cryogenic refrigeration equipment. You could build a demo of such a device that could be easily landed as a secondary payload using existing Mars EDL techniques (even Viking-era EDL would be more than sufficient). Not only that, but you don't have to worry about setting down someplace that has water... EVERY part of the surface of Mars has easy access to unlimited CO2.

If you brought a little bit of hydrogen from Earth, however, you could use the same CO/O2 process and make methane/LOx which is more commonly used for rocket fuel than CO/02 is (though the production would be a little harder)... without having to extract water from the soil.
Title: Re: Carbon Monoxide for fuel on Mars
Post by: Prober on 09/26/2012 11:19 pm
how much Methane is available on Mars?   

focus on what can be converted from the Methane & Carbon Monoxide and you have your answers.

Title: Re: Carbon Monoxide for fuel on Mars
Post by: RocketmanUS on 09/26/2012 11:26 pm
how much Methane is available on Mars?   

focus on what can be converted from the Methane & Carbon Monoxide and you have your answers.


10ppb methane in the Mars atmosphere.

Use the water in the Mars top soil and or air for the hydrogen needed with the CO2 in the Mars atmosphere to make the CH4.

Title: Re: Carbon Monoxide for fuel on Mars
Post by: Prober on 09/27/2012 12:02 am
how much Methane is available on Mars?   

focus on what can be converted from the Methane & Carbon Monoxide and you have your answers.


10ppb methane in the Mars atmosphere.

Use the water in the Mars top soil and or air for the hydrogen needed with the CO2 in the Mars atmosphere to make the CH4.



when I get some extra time can look into a simple cheap way to do something.  Got an idea coming out of the automotive tech.   Basic idea is that the catalytic converter is the model.

"it converts the three main pollutants in automobile exhaust: an oxidizing reaction converts carbon monoxide (CO) and unburned hydrocarbons (HC), and a reduction reaction converts oxides of nitrogen (NOx) to produce carbon dioxide (CO2), nitrogen (N2), and water (H2O)."

this could be a decent cheap model to start from.



Title: Re: Carbon Monoxide for fuel on Mars
Post by: Prober on 09/30/2012 04:04 pm
ahhh found this again..

Bioengineered bacteria could produce fuel from CO2
http://www.gizmag.com/bacteria-co2-isobutanol-biofuel/23880/

Title: Re: Carbon Monoxide for fuel on Mars
Post by: simonbp on 10/01/2012 02:59 pm
ahhh found this again..

Bioengineered bacteria could produce fuel from CO2
http://www.gizmag.com/bacteria-co2-isobutanol-biofuel/23880/

Yeah, no way in hell that's going to happen. The entire goal of at least the first several Mars landings will be the search for life. Dropping down a lander full of culturable microorganisms down is just asking for trouble. It may be an option much, much further down the line (i.e. massive Mars settlement), but not anytime soon.

Also, while they get carbon from the atmosphere in a way that may make sense on Earth, where it's easy to ship in nutrient media, on Mars providing all other needed nutrients (water, fixed nitrogen, iron, etc) is a problem. Again, a solvable one for a large Mars colony, but not a little ISRU rover.
Title: Re: Carbon Monoxide for fuel on Mars
Post by: Prober on 10/01/2012 03:12 pm
ahhh found this again..

Bioengineered bacteria could produce fuel from CO2
http://www.gizmag.com/bacteria-co2-isobutanol-biofuel/23880/

Yeah, no way in hell that's going to happen. The entire goal of at least the first several Mars landings will be the search for life. Dropping down a lander full of culturable microorganisms down is just asking for trouble. It may be an option much, much further down the line (i.e. massive Mars settlement), but not anytime soon.


ok, you wish to search for life, I prefer to prepare an area that is more comfortable to human life.   Thinking of a paper on Gale as a future 1st human landing site.

Might be better locations, but this one will be studied to death.
Title: Re: Carbon Monoxide for fuel on Mars
Post by: mmeijeri on 10/13/2012 10:58 am
Robotbeat, I really like the idea of ISRU based exclusively on atmospheric gases.
Title: Re: Carbon Monoxide for fuel on Mars
Post by: douglas100 on 10/13/2012 11:03 am
Yes, you're not tied to a specific location for your ISRU plant.
Title: Re: Carbon Monoxide for fuel on Mars
Post by: mmeijeri on 10/13/2012 12:58 pm
Not just that, it's also a much smaller technical challenge.
Title: Re: Carbon Monoxide for fuel on Mars
Post by: KelvinZero on 10/13/2012 02:16 pm
+1. This is exactly the sort of technical challenge NASA could and should do. A breathtaking step forward into a new paradigm yet unlike so many aborted HSF architectures, totally affordable.
Title: Re: Carbon Monoxide for fuel on Mars
Post by: Robotbeat on 10/13/2012 10:08 pm
Not only that, but if you also have a small fully reusable single-stage Mars lander, you could stock-pile the CO/O2 in orbit in a fully automated fashion, with just one propellant production station landed fully integrated... Mars makes this easier since the atmosphere is great enough to allow you to aerobrake most of your descent delta-v but low enough to allow essentially vacuum Isp and VERY low aero losses on the way up (which allows you to use a smaller-scale launch vehicle). I have a concept for one of these automated propellant production and transport facilities in my head... Not enough time to draw it out.


Robotbeat, I really like the idea of ISRU based exclusively on atmospheric gases.
Totally, totally agreed.
Title: Re: Carbon Monoxide for fuel on Mars
Post by: RocketmanUS on 10/14/2012 04:10 am
Not only that, but if you also have a small fully reusable single-stage Mars lander, you could stock-pile the CO/O2 in orbit in a fully automated fashion, with just one propellant production station landed fully integrated... Mars makes this easier since the atmosphere is great enough to allow you to aerobrake most of your descent delta-v but low enough to allow essentially vacuum Isp and VERY low aero losses on the way up (which allows you to use a smaller-scale launch vehicle). I have a concept for one of these automated propellant production and transport facilities in my head... Not enough time to draw it out.


Robotbeat, I really like the idea of ISRU based exclusively on atmospheric gases.
Totally, totally agreed.
Crew will need water. Water can be made in to LH2/LOX as we all know.

However-
If CO/O2 from CO2 can be a rocket fuel with enough performance it could be a good propellent for a reusable lander for cargo before crew ever lands on Mars. Would need a delivery system for cargo to be put into Mars orbit or SML-1.
Title: Re: Carbon Monoxide for fuel on Mars
Post by: Robotbeat on 10/14/2012 04:22 am
Water can be recycled, and rockets are thirstier than astronauts. Propellant is important. Also, co/o2 can be used in a reversible fuel cell with lower cryogenic requirements than liquid hydrogen, which can give pressurized rovers an excellent highly power dense energy source.

Water should be available on parts of mars, but never as easily available as carbon dioxide is.
Title: Re: Carbon Monoxide for fuel on Mars
Post by: quanthasaquality on 10/14/2012 10:13 am
I think CO gas spontaneously degrades into carbon and CO2, but don't know how fast it happens.
Title: Re: Carbon Monoxide for fuel on Mars
Post by: mmeijeri on 10/14/2012 11:55 am
Interesting paper on all this:

A CHEMICAL APPROACH TO CARBON DIOXIDE UTILIZATION ON MARS (http://www.uapress.arizona.edu/onlinebks/ResourcesNearEarthSpace/resources28.pdf)
Title: Re: Carbon Monoxide for fuel on Mars
Post by: RocketmanUS on 10/15/2012 05:46 am
Water can be recycled, and rockets are thirstier than astronauts. Propellant is important. Also, co/o2 can be used in a reversible fuel cell with lower cryogenic requirements than liquid hydrogen, which can give pressurized rovers an excellent highly power dense energy source.

Water should be available on parts of mars, but never as easily available as carbon dioxide is.
True also.

If CO can be stored for a given amount of time, then it could also be a means to power a base if the solar power were off line due to a dust storm.

So how long can CO be stored on Earth, in orbit?
If it can be stored for a reasonable amount of time then we would need to design an engine that with run on CO/O2. Then all the other parts that are needed too. So how could this be done commercially?
Title: Re: Carbon Monoxide for fuel on Mars
Post by: john smith 19 on 10/15/2012 06:37 am
As regards the thread title CO/O2 looks like a very usable system for work *on* Mars and acceptable performance for ascent *from* Mars.

But slightly off topic does it also make a viable fuel for return *from* Mars?

LH2/LO2 is the obvious propellant for the EDS but would it be a serious hit in tank size and payload to go with a return propellant *solely* mfg on Mars? Once  you've *got* a capability like ISRU does it make sense to use it as much as possible or does LH2 win hands down?

Obvious downsides are developing a CO cooled *large* engine (200Klbs? Bigger) CO engine. Alternatively NASA could just bite the bullet and start developing LO2 cooled engines and halve their development problems. They've known LO2 is not the monster they thought it was since the early 80's
Title: Re: Carbon Monoxide for fuel on Mars
Post by: guckyfan on 10/15/2012 09:11 am
But slightly off topic does it also make a viable fuel for return *from* Mars?

The problem would be to get it from the surface to Mars orbit. You would need a reusable one stage to orbit and back to the surface vehicle capable of a significant number of flights to do that.
Title: Re: Carbon Monoxide for fuel on Mars
Post by: john smith 19 on 10/15/2012 09:18 am
Interesting paper on all this:

A CHEMICAL APPROACH TO CARBON DIOXIDE UTILIZATION ON MARS (http://www.uapress.arizona.edu/onlinebks/ResourcesNearEarthSpace/resources28.pdf)
*Very* nice paper. Thanks for the reference. The mass reduction for even the Earth return stage looks very good. I'd thought CO/O2 was only *really* viable to get back to Mars orbit but that does not appear to be the case.

My only quibble is the authors go after Ethyne (Acetylene) instead of Propyne which is a known industrial fuel and AFAIK has none of the explosion hazard of Acetylene and would not need dilution. I guess its chemistry is not as well known.
Title: Re: Carbon Monoxide for fuel on Mars
Post by: A_M_Swallow on 10/15/2012 10:45 am
As regards the thread title CO/O2 looks like a very usable system for work *on* Mars and acceptable performance for ascent *from* Mars.

But slightly off topic does it also make a viable fuel for return *from* Mars?
{snip}

If the transfer vehicles uses Solar Electric Propulsion (SEP) there is plenty of Argon in Mars's atmosphere.  Concentrated Argon is a waste product when extracting the CO2.
Title: Re: Carbon Monoxide for fuel on Mars
Post by: mmeijeri on 10/15/2012 03:42 pm
LH2/LO2 is the obvious propellant for the EDS but would it be a serious hit in tank size and payload to go with a return propellant *solely* mfg on Mars?

You mean for return to Earth? I think LOX/LH2 is far from obvious for that, with hypergolics being the clear favourite, followed by LOX / methane produced from Martian carbon dioxide with hydrogen / water brought from Earth.
Title: Re: Carbon Monoxide for fuel on Mars
Post by: cordor on 10/15/2012 06:05 pm
Also, here's an interesting proposal from Zubrin, et al, of a mixed methane/CO/O2 propellant Martian ISRU rocket system, which benefits from the added density of CO but retains most of the Isp of methane while also making the production equipment easier and smaller and more productive for a certain energy input, and Methane/CO/O2 all are storable at the same temperature, making common-bulkheads easier:

http://www.techbriefs.com/component/content/article/3365
http://hdl.handle.net/2060/20080047195
Mars Rocket Propulsion System (published November, 2008)

Sounds like a total win, except you still have to have more development of rockets using such a propellant combination (EDIT: And, you still will likely need to bring hydrogen from Earth).

It sounds complicated and less reliable. Don't think you can mix liquid CO and liquid methane. If not, then you need 3 tanks for pressure fed system, or 3 pumps for gas generator cycle. on top of that, where do you generate methane? on mars? you need to bring hydrogen, equitment to make methane, and extra set of tool to make CO.

How about,  producing biogas(methane) while your astronauts are on the way to mars, at the same time you have a robot producing CO on mars surface. In stead of mixing methane and CO, the lander use methane for descent, and the same lander same engine same tank use CO to ascent.
Title: Re: Carbon Monoxide for fuel on Mars
Post by: john smith 19 on 10/15/2012 06:34 pm
You mean for return to Earth? I think LOX/LH2 is far from obvious for that, with hypergolics being the clear favourite, followed by LOX / methane produced from Martian carbon dioxide with hydrogen / water brought from Earth.
The report you cited helps answer that question. I thought of LOX/LH2 because NASA is very fond of this combination for "high energy" missions and that seems to be the lead option for their architecture.

Given the cited report on the *very* positive effect of using ISRU on the mass you have to put into LEO that would seem to open up the field quite a lot, at the expense of multiple rendezvous, docking and propellant transfers, which seems like a fair trade to me.

The tradeoff between water and LH2/LO2 looks quite interesting. If you have a use for the oxygen in water My BOTE suggest that you can deal with 2 m^3 of LO2 and LH2 or 630l of water. 

Title: Re: Carbon Monoxide for fuel on Mars
Post by: Robotbeat on 10/15/2012 07:22 pm
Also, here's an interesting proposal from Zubrin, et al, of a mixed methane/CO/O2 propellant Martian ISRU rocket system, which benefits from the added density of CO but retains most of the Isp of methane while also making the production equipment easier and smaller and more productive for a certain energy input, and Methane/CO/O2 all are storable at the same temperature, making common-bulkheads easier:

http://www.techbriefs.com/component/content/article/3365
http://hdl.handle.net/2060/20080047195
Mars Rocket Propulsion System (published November, 2008)

Sounds like a total win, except you still have to have more development of rockets using such a propellant combination (EDIT: And, you still will likely need to bring hydrogen from Earth).

It sounds complicated and less reliable. Don't think you can mix liquid CO and liquid methane. If not, then you need 3 tanks for pressure fed system, or 3 pumps for gas generator cycle. on top of that, where do you generate methane? on mars? you need to bring hydrogen, equitment to make methane, and extra set of tool to make CO.

How about,  producing biogas(methane) while your astronauts are on the way to mars, at the same time you have a robot producing CO on mars surface. In stead of mixing methane and CO, the lander use methane for descent, and the same lander same engine same tank use CO to ascent.

I'm fairly confident you CAN mix methane and carbon monoxide... both are miscible in liquid oxygen (which can be... interesting).

And NO, you do NOT need an extra set of tools to make CO. Making CO is done automatically when you make oxygen from carbon dioxide, and you use CO to produce methane. This method actually simplifies the process since you can skip the step of separating the CO from the methane (which you normally have to do if you want to ONLY use methane).


If you're making oxygen from the Martian air, you're already making carbon monoxide by default. The question is whether or not you're going to do anything with it. That is why the Zubrin proposal is interesting...

Also, if you do have a rocket that runs on CO/O2 or a mixture of CH4/CO and O2, then the question may come up on whether you could switch fuels... A good point, cordor (although producing biogas is a non-starter... except for bad jokes ;) ).
Title: Re: Carbon Monoxide for fuel on Mars
Post by: cordor on 10/15/2012 10:22 pm
carbon monoxide boils at −191.5 C, methane melts at -182 C. When you have liquid CO, does methane supposed to be ice?
Title: Re: Carbon Monoxide for fuel on Mars
Post by: Robotbeat on 10/15/2012 11:45 pm
carbon monoxide boils at −191.5 C, methane melts at -182 C. When you have liquid CO, does methane supposed to be ice?
...maybe at STP. But you're going to have to pressurize those tanks, anyway. But at a reasonable ullage pressure (say, 36psi), the liquid phases of methane and carbon monoxide overlap. Besides, mixing two liquids often changes their freezing/boiling points.
Title: Re: Carbon Monoxide for fuel on Mars
Post by: cordor on 10/16/2012 01:31 am
I still don't see how "Zubrin proposal" is interesting. If you make CO and O2 on mars surface, you don't need to bring any raw material, as long as your solar panel and equitment whatever work, it keeps making propellant.

On the other hand, you want extra methane, you need to bring hydrogen, that's logistic problem, worst case you need to launch from earth all the way to mars.

Is it really worth that extra performance? you know 290s isp is not so bad, F-1 only has 263s.  I was thinking you can use robot craft to bring extra CO+O2 propellant store on orbit, for return flight or lander. If you don't have to carry return propellant or fuel for landing, that's interesting. the  Zubrin proposal just bust my dream. 



Title: Re: Carbon Monoxide for fuel on Mars
Post by: RocketmanUS on 10/16/2012 02:03 am
I still don't see how "Zubrin proposal" is interesting. If you make CO and O2 on mars surface, you don't need to bring any raw material, as long as your solar panel and equitment whatever work, it keeps making propellant.

On the other hand, you want extra methane, you need to bring hydrogen, that's logistic problem, worst case you need to launch from earth all the way to mars.

Is it really worth that extra performance? you know 290s isp is not so bad, F-1 only has 263s.  I was thinking you can use robot craft to bring extra CO+O2 fuel up to mars orbit for return flight propellant back to earth, that  Zubrin proposal just bust my dream. 




There is water on Mars already, in the soil and air. No need to bring the hydrogen to Mars. As Mars needs to be a long term project, no flag and foot step, it is better to send the needed equipment to extract the water for our needs. If you bring the hydrogen from Earth and it leaks out ( our other loss ), it is better to have the ability to get hydrogen from were you are than not have enough from Earth.

That said, a commercial developed reusable lander using CO/O2, even with it's lower ISP over other options could be the better choose for surface to orbit.

Having that and adding a CO/O2 powered OTV ( orbital transfer vehicle ) between a Mars orbit gateway station and a SML-1 gateway station were a SEP powered trans hab would be stationed to take the crew back to Earth by way of an EML-2 gateway station.
Title: Re: Carbon Monoxide for fuel on Mars
Post by: RocketmanUS on 10/22/2012 03:24 am
Are there other ways to split CO2 to make CO/O2?

Can it be done with Sun light with a way to separate the two before they would recombine?
Title: Re: Carbon Monoxide for fuel on Mars
Post by: Joel on 11/02/2012 12:05 am
The Martian atmosphere has 3 % nitrogen. How feasible is it to extract this and produce nitrogen tetroxide (NTO)? Might be much easier to handle than LOX on Mars, since it does not need to be kept cool for 2+ years and could easily be stored as a liquid or even as a solid.

I don't know if NTO can be used as an oxidizer for CO or CH4, but if you bring hydrogen with you, you could produce hydrazine. NTO+Aerozine-50 (1.93 O/F ratio) is storable, well known as a rocket fuel and just 5 % hydrogen by weight.

EDIT: Corrected numbers
Title: Re: Carbon Monoxide for fuel on Mars
Post by: Warren Platts on 11/02/2012 12:19 am
You can use CO2 itself as an oxidizer if you use magnesium for the fuel...
Title: Re: Carbon Monoxide for fuel on Mars
Post by: cleonard on 11/02/2012 01:42 am
The Martian atmosphere has 3 % nitrogen. How feasible is it to extract this and produce nitrogen tetroxide (NTO)? Might be much easier to handle than LOX on Mars, since it does not need to be kept cool for 2+ years and could easily be stored as a liquid or even as a solid.

I don't know if NTO can be used as an oxidizer for CO or CH4, but if you bring hydrogen with you, you could produce hydrazine. NTO+Aerozine-50 (1.93 O/F ratio) is storable, well known as a rocket fuel and just 5 % hydrogen by weight.

EDIT: Corrected numbers

Making N2O4 is not easy.  You need hydrogen.  First you use the Haber process to make ammonia.  Then you use part of the Ostwald process where you basically burn the ammonia with oxygen resulting in NO2. 

The thing that carbon monoxide has going for it is that it is a single process.  Simplicity is important for an application like this.
Title: Re: Carbon Monoxide for fuel on Mars
Post by: Robotbeat on 04/27/2016 02:43 pm
Necrobumping this thread, but...

I recently saw a presentation by Geoffrey Landis, and he said that the optimal exhaust velocity from an energy standpoint is equal to about 2/3rds of your mission delta-v (exhaust velocity equal to current velocity is actually the most efficient as it leaves the exhaust with exactly zero kinetic energy relative to the rest frame, but requires you to adjust your exhaust velocity continuously, and also requires ridiculously big tanks at the beginning). The very minimum effective delta-v (ignoring gravity drag, but including gravitational energy and ignoring aerodynamics and including the benefit from Mars' rotation) is 3.4km/s. Let's say we get really good thrust/weight ratio and low drag, then perhaps the real-world delta-v could be about 4km/s.

2/3rds of 4km/s is 2.7km/s. That is doable by CO/O2. Thus from an energy perspective, CO/O2 may actually be more efficient from an energy perspective than other propellant combos (unless you "cut" them down by adding CO2 or something to the propellant), plus is ubiquitous on Mars and very dense. It's almost like Mars is telling us to use CO/O2...

...if only CO/O2 weren't so dangerous to test on Earth. Still, we use hydrazine which is pretty fantastically horrible, so I don't think CO/O2 would be impossible.
Title: Re: Carbon Monoxide for fuel on Mars
Post by: A_M_Swallow on 04/27/2016 03:27 pm
Carbon monoxide detectors are cheap and can be purchased at good hardware stores.
https://www.amazon.co.uk/Monitor-Sensor-Carbon-Monoxide-Detectors/dp/B00DKXHHJ6 (https://www.amazon.co.uk/Monitor-Sensor-Carbon-Monoxide-Detectors/dp/B00DKXHHJ6)

Build the lab and launch pad to burn off any CO that escapes. Consider issuing breathing apparatus to people handling the propellant.
Title: Re: Carbon Monoxide for fuel on Mars
Post by: Tetrakis on 04/27/2016 03:44 pm
We use CO all the time in organometallic chemistry. To answer some practical questions:

1. It is not a liquid in pressurized tanks at room temperature.

2. It does not spontaneously decompose at room temperature.

3. It would be energy efficient to recover from the Martian atmosphere via pressure-swing gas adsorption separation technologies. O2 and CO are fairly reactive gases which makes them especially susceptible to this sort of thing. You would need to liquefy the CO and O2 at the end anyway, so dual-purposing the cryogenic equipment for cryogenic distillation is another easy option.

Now a question from me:

can Mars landers use nickel? I didn't realize Mars' atmosphere contained so much CO. CO will spontaneously react with nickel to form nickel tetracarbonyl, perhaps one of the most toxic substances known to man. In a laboratory setting nickel is rigorously excluded from CO applications.
Title: Re: Carbon Monoxide for fuel on Mars
Post by: Proponent on 04/27/2016 04:09 pm
Necrobumping this thread, but...

I recently saw a presentation by Geoffrey Landis, and he said that the optimal exhaust velocity from an energy standpoint is equal to about 2/3rds of your mission delta-v (exhaust velocity equal to current velocity is actually the most efficient as it leaves the exhaust with exactly zero kinetic energy relative to the rest frame, but requires you to adjust your exhaust velocity continuously, and also requires ridiculously big tanks at the beginning). The very minimum effective delta-v (ignoring gravity drag, but including gravitational energy and ignoring aerodynamics and including the benefit from Mars' rotation) is 3.4km/s. Let's say we get really good thrust/weight ratio and low drag, then perhaps the real-world delta-v could be about 4km/s.

2/3rds of 4km/s is 2.7km/s. That is doable by CO/O2. Thus from an energy perspective, CO/O2 may actually be more efficient from an energy perspective than other propellant combos (unless you "cut" them down by adding CO2 or something to the propellant), plus is ubiquitous on Mars and very dense. It's almost like Mars is telling us to use CO/O2...

...if only CO/O2 weren't so dangerous to test on Earth. Still, we use hydrazine which is pretty fantastically horrible, so I don't think CO/O2 would be impossible.

I wanted to include CO/O2 in playing with the trade between specific impulse and density (http://forum.nasaspaceflight.com/index.php?topic=31040.msg1518743#msg1518743), and I've got CO's fluid properties from NIST.  Unfortunately, RPA Lite does not have CO in its database.  I have not taken the time to figure out how to get CO into RPA Lite, nor have I figured out how to get CEA to do batch runs (I need an Isp curve as a function of mixture ratio; hints, anybody?).  But otherwise I'm all set to compare CO/O2 against other combinations for a delta-V of 4 km/s and can optimize the mixture-ratio program.
Title: Re: Carbon Monoxide for fuel on Mars
Post by: sevenperforce on 04/27/2016 06:51 pm
It would be amusing if flying to Mars, landing, cracking CO2 into CO and LOX, then launching, flying back to LEO, and refueling an Earth LEO propellant depot proved cheaper than refueling a propellant depot from Earth.
Title: Re: Carbon Monoxide for fuel on Mars
Post by: A_M_Swallow on 04/27/2016 07:47 pm
It would be amusing if flying to Mars, landing, cracking CO2 into CO and LOX, then launching, flying back to LEO, and refueling an Earth LEO propellant depot proved cheaper than refueling a propellant depot from Earth.

One off certainly. Multiple journeys may have a different result.

Mars has a very thin atmosphere so ordinary planes will have big problems. Point to point sub orbital flights using CO/LOX rocket engines may work. The break even point for sub orbital may be where the mass of fuel used is at least twice the mass of the 2CO2 to CO + O2 cracker.
Title: Re: Carbon Monoxide for fuel on Mars
Post by: sevenperforce on 04/27/2016 08:24 pm
It would be amusing if flying to Mars, landing, cracking CO2 into CO and LOX, then launching, flying back to LEO, and refueling an Earth LEO propellant depot proved cheaper than refueling a propellant depot from Earth.

One off certainly. Multiple journeys may have a different result.

Mars has a very thin atmosphere so ordinary planes will have big problems. Point to point sub orbital flights using CO/LOX rocket engines may work. The break even point for sub orbital may be where the mass of fuel used is at least twice the mass of the 2CO2 to CO + O2 cracker.
I can't imagine a one-off mission would prove cheaper.

But a fully-reusable, autonomous spacecraft designed to collect propellant from the Martian atmosphere and return it to an LEO refueling depot could actually be cheaper in the long run than trying to refuel the LEO depot with repeated launches from Earth, simply because the dV from Mars to Martian orbit is so much lower than the dV from Earth to LEO.
Title: Re: Carbon Monoxide for fuel on Mars
Post by: Robotbeat on 04/27/2016 08:38 pm
It would be amusing if flying to Mars, landing, cracking CO2 into CO and LOX, then launching, flying back to LEO, and refueling an Earth LEO propellant depot proved cheaper than refueling a propellant depot from Earth.
It may, if you had a HUGE tank of the stuff, used efficient trajectories and low-Isp SEP. Might make sense to transport water instead, though, since it's stabler (I think?) and has higher value once electrolyzed than CO/O2 does, and space-based solar power near Earth would be cheaper than surface power is likely to be at Mars.

Small, ultra-high-flightrate CO/O2 Mars RLV that launches Mars water to a huge tank in orbit.
Title: Re: Carbon Monoxide for fuel on Mars
Post by: virnin on 04/30/2016 12:37 am
It would be amusing if flying to Mars, landing, cracking CO2 into CO and LOX, then launching, flying back to LEO, and refueling an Earth LEO propellant depot proved cheaper than refueling a propellant depot from Earth.
It may, if you had a HUGE tank of the stuff, used efficient trajectories and low-Isp SEP. Might make sense to transport water instead, though, since it's stabler (I think?) and has higher value once electrolyzed than CO/O2 does, and space-based solar power near Earth would be cheaper than surface power is likely to be at Mars.

Small, ultra-high-flightrate CO/O2 Mars RLV that launches Mars water to a huge tank in orbit.

I'm thinking that mining from icy asteroids might be cheaper than lifting (relatively scarce) water up the Mars gravity well.  Use that high-flightrate RLV to replenish the orbital filling station with CO/O2 for the asteroid tug.
Title: Re: Carbon Monoxide for fuel on Mars
Post by: Robotbeat on 04/30/2016 01:34 am
It would be amusing if flying to Mars, landing, cracking CO2 into CO and LOX, then launching, flying back to LEO, and refueling an Earth LEO propellant depot proved cheaper than refueling a propellant depot from Earth.
It may, if you had a HUGE tank of the stuff, used efficient trajectories and low-Isp SEP. Might make sense to transport water instead, though, since it's stabler (I think?) and has higher value once electrolyzed than CO/O2 does, and space-based solar power near Earth would be cheaper than surface power is likely to be at Mars.

Small, ultra-high-flightrate CO/O2 Mars RLV that launches Mars water to a huge tank in orbit.

I'm thinking that mining from icy asteroids might be cheaper than lifting (relatively scarce) water up the Mars gravity well.  Use that high-flightrate RLV to replenish the orbital filling station with CO/O2 for the asteroid tug.
Water is not scarce on Mars. There's something like 5 Petatons of water there that we've been able to measure so far. Fly 1000 tons of water out of Mars every SECOND for a thousand years and it wouldn't make a dent. And that's just the water that we know about. There's much more subsurface water that's even deeper than we can measure.
Title: Re: Carbon Monoxide for fuel on Mars
Post by: Nilof on 05/02/2016 11:21 am
It would be amusing if flying to Mars, landing, cracking CO2 into CO and LOX, then launching, flying back to LEO, and refueling an Earth LEO propellant depot proved cheaper than refueling a propellant depot from Earth.
It may, if you had a HUGE tank of the stuff, used efficient trajectories and low-Isp SEP. Might make sense to transport water instead, though, since it's stabler (I think?) and has higher value once electrolyzed than CO/O2 does, and space-based solar power near Earth would be cheaper than surface power is likely to be at Mars.

Small, ultra-high-flightrate CO/O2 Mars RLV that launches Mars water to a huge tank in orbit.

I'm thinking that mining from icy asteroids might be cheaper than lifting (relatively scarce) water up the Mars gravity well.  Use that high-flightrate RLV to replenish the orbital filling station with CO/O2 for the asteroid tug.
Water is not scarce on Mars. There's something like 5 Petatons of water there that we've been able to measure so far. Fly 1000 tons of water out of Mars every SECOND for a thousand years and it wouldn't make a dent. And that's just the water that we know about. There's much more subsurface water that's even deeper than we can measure.

It is abundant, but it is not close to LEO in delta-v or in delta-t. Even for a LMO depot Martian volatiles may have difficulty competing with Phobos ISRU once that gets going.
Title: Re: Carbon Monoxide for fuel on Mars
Post by: Rei on 05/04/2016 02:33 pm
Water on Mars is, of course, something that has to be...

1) Mined from a permafrost full likewise of rocks and gravel,
2) With mining equipment, which is no insignificant engineering cost given the low TRL and high needs
3) With maintenance, and with operators being either A) high latency/low labor cost (aka, from Earth), low latency / very high labor cost (aka, from Mars), or C) autonomous (high development / higher risk of needing a rescue / accidentally damaging something).
4) Requiring filtering
5) Requiring distillation to remove the (fairly significant, fairly corrosive) salts
6) Work with materials whose properties are less well known than the atmosphere, and much more variable.

It's no surprise that the main area of focus for O2 production has been from CO2, not water electrolysis.  It's a lot simpler and more reliable to work with gases.

LOX/CO is an interesting concept I hadn't thought much of.  I don't have data on-hand on CO/CH4 mixture densities, but I happen to have the molar density data on a variety of pure gases with respect to temperature and pressure here.  My lowest pressure datapoint for CO is 17,5kPa, so higher than Mars, but the boiling point there is 68,9K.  That's pretty low, even colder than oxygen, which is 76,2K at those pressures.  Methane by contrast is 93,9K at those pressures.

Balloon tanks are commonly ~35kPa overpressure so let's see, my datapoint for 37kPa here is a boiling point of 73,7K for CO... still not great.   100kPa = 81,52.. hmm, you know, it's looking like the best bet is just to have the rocket be self-pressurizing... so if we want say 300kPa feeding the turbos then you can have the CO at 92,6K.  By contrast methane would be 126,7K and oxygen 102,0K at those pressures.  The molar densities at those temperatures and pressures (in mol/m) for O2, CH4 and CO are respectively 33753, 24894 and 28337.  So in kg/m3, that's 1080, 400, and 793 respectively.

(Note: I haven't checked whether these density figures are for liquid or solid)

Basically, you're dealing low ISP and high tank masses, which isn't good.  But then again, the delta-V needed for Mars operations isn't huge.  And with self-pressurization you certainly gain in terms of simplicity.  And CO's nearly double density in comparison to CH4 is going to be a big mass advantage.  It's also closer in temperature to O2, simplifying the bulkhead.  Likewise, the propellant production too is much simpler, just CO2 through a SOFC .  And simplicity doesn't also just mean reliability, it also means big savings in the development phase.  Which might justify having to send heavier flight hardware and more power generation.

All around, a interesting notion.  But yes, CO/CH4 eutectics would also bear attention  :)  Hmm, I may actually have some data on them somewhere around here, I was researching it shortly after the Pluto flyby....

Hmm, thought, has anyone checked the materials compatibility for CO?  Is CO compatible with composite or aluminum tanks?
Title: Re: Carbon Monoxide for fuel on Mars
Post by: john smith 19 on 05/04/2016 10:40 pm
There is a higher performance fuel you can make out of the Martian atmosphere.

It's called Cyanogen.

It is however very toxic to handle.  :(
Title: Re: Carbon Monoxide for fuel on Mars
Post by: Dalhousie on 05/04/2016 11:10 pm
We use CO all the time in organometallic chemistry. To answer some practical questions:

1. It is not a liquid in pressurized tanks at room temperature.

2. It does not spontaneously decompose at room temperature.

It also used large scale in the industry as a fuel, partly via production from coke (water gas reaction, where it's mixed with hydrogen).  During WWII and after many countries used charcoal gas in cars instead of petrol.  This was mostly CO.

Quote
can Mars landers use nickel? I didn't realize Mars' atmosphere contained so much CO. CO will spontaneously react with nickel to form nickel tetracarbonyl, perhaps one of the most toxic substances known to man. In a laboratory setting nickel is rigorously excluded from CO applications.

I wouldn't have called 0.0557% CO "a lot" - that 3.3 x 10e-7 millibars partial pressure at datum altitude, or a third of the partial pressure on Earth in clean air.

There were a number of papers on CO as a fuel in the early case for Mars conferences.  Not only can it be used in rockets, it can be used for gas turbines, diesel engines, and fuel cells.  I can dig the papers out if need be.
Title: Re: Carbon Monoxide for fuel on Mars
Post by: Rei on 05/04/2016 11:47 pm
The issue is not that Mars's atmosphere contains lots of carbon monoxide - it's that the currently most favored process for producing oxygen on Mars (solid state electrolysis of carbon dioxide - slated for testing on Mars 2020) produces carbon monoxide as a byproduct.  You have a single, already-extant, already-slated-for-actual-testing-on-Mars system that produces both your fuel and oxidizer.

Toxicity of propellants isn't of particular relevance on Mars where anyone working outside has to be in a space suit regardless and any leaked gases will diffuse extremely rapidly.  Unless there's a risk of them somehow pooling from the rocket into its capsule, which would be kind of odd because there would be no plumbling connections between them.  And clearly you wouldn't produce or store dangerous chemicals of any kind in the habitat.

Honestly, I've never put much thought into cyanogen as a propellant.  What's the proposed production route and expected ISP?

ED: I just ran it through CEA2.  I got a vacuum ISP of 352 sec burning it with O2 at an optimal ratio under the same conditions that stoichiometric methane combustion yielded a vacuum ISP of 369 sec.  But, cyanogen is a lot more dense and its boiling point isn't much less than room temperature, so it's probably a better performer overall.

I'm not seeing any simple routes to production though... but this one doesn't look too bad:

1.0 Air -> 0.9597 CO2 + 0.0189 N2 + misc.
CO2 + 4 H2 → CH4 + 2 H2O (Sabatier process)
8 CH4 + 3 O2 → 4 C2H2 + 6 H2O (Partial combustion)
N2 + C2H2 → (CN)2 + H2 (Reaction in spark discharge)

That is, it's two processes on top of that needed for methane production.  Note that I'm being careful to write "processes", not "steps", as each of these involves many steps.... if only chemistry would do precisely what you wanted of it and nothing else, with no complications  ;)

Honestly, I'm kind of liking this propellant, as far as in-situ needs go.  Burns hot, though.
Title: Re: Carbon Monoxide for fuel on Mars
Post by: john smith 19 on 05/05/2016 01:56 am
Honestly, I've never put much thought into cyanogen as a propellant.  What's the proposed production route and expected ISP?
No idea. it was mentioned in passing as part of REL's presentation on their Project Troy Mars feasibility study. Their point was there are alternatives beyond the obvious of CO/O2 without needing to bring Hydrogen to Mars. I never read their report in detail so I'm not sure how much more work they did on it.
Quote
ED: I just ran it through CEA2.  I got a vacuum ISP of 352 sec burning it with O2 at an optimal ratio under the same conditions that stoichiometric methane combustion yielded a vacuum ISP of 369 sec.  But, cyanogen is a lot more dense and its boiling point isn't much less than room temperature, so it's probably a better performer overall.
That's sort of a mixed blessing. Sounds like an insulated bulkhead tank is pretty much mandatory due to the temperature differential.
Quote
I'm not seeing any simple routes to production though... but this one doesn't look too bad:

1.0 Air -> 0.9597 CO2 + 0.0189 N2 + misc.
CO2 + 4 H2 → CH4 + 2 H2O (Sabatier process)
2 CH4 + O2 → C2H2 + 2 H2O (Partial combustion)
N2 + 2 CH4 → (CN)2 + 4 H2 (Reaction in spark discharge)

That is, it's two processes on top of that needed for methane production.  Note that I'm being careful to write "processes", not "steps", as each of these involves many steps.... if only chemistry would do precisely what you wanted of it and nothing else, with no complications  ;)

Honestly, I'm kind of liking this propellant, as far as in-situ needs go.  Burns hot, though.
True. Even hotter than LO2/LH2 (I didn't know there was such a thing  :o ). IIRC it was used in heat shield testing.

it's attraction of course is you don't have to bring LH2. Obviously the discovery of Martian water makes that less of an issue but as you point out no one really knows what form that water is in. Might be a nice clean ice layer, might be frozen mud with a bunch of chemicals hostile to mining machinery. There's no real way to know.

Naturally as rocket engines usually optimize for Isp, not complete combustion it will normally run a bit cooler as the engine will be run fuel rich.
Title: Re: Carbon Monoxide for fuel on Mars
Post by: Dalhousie on 05/05/2016 03:15 am
For those interested in digging into the historic literature, the relevant Case for Mars papers are:

CFM 2

S Welch "Mission strategy and spacecraft design for a Mars base program" (AAS-84-69)

J. R. French "The impact of martian propellant manufacturing on early manned exploration" (AAS-84-178)

CFM 3

W. M. Clapp and M. P. Scardera "Applications of in-situ carbon-monoxide oxygen propellant production at Mars" (AAS-87-212)

J. R. French "An overview of Mars surface mobility justification and options" (AAS-87-220)

CFM 6

M. R. Grover et al.  "Ares Explore: a study of human Mars exploration alternatives using in situ propellant production and current technology" (AAS-96-332)


Title: Re: Carbon Monoxide for fuel on Mars
Post by: cleonard on 05/05/2016 04:22 am
Using the Carbon Monoxide and Oxygen fuel cycle seems like a no brainer.  Simple one step production process and you need this process anyway to get O2 to breathe.  I just don't think there is an easier method to get these two very important resources.

However, there are significant issues. 

There is not much study of an engine using this set of propellants.  While carbon Monoxide it toxic, it is at least 10x less toxic than Hydrazine.  We test plenty of engines using Hydrazine, so testing using Carbon Monoxide should not be too hard.

One problem with this selection is the high temperature of the combustion coupled with the somewhat poor cooling properties of the propellants.  There is a reason that LOX is not used to cool combustion chambers, but in this case I think both will need to be used.   Simple you say, use one of those super alloys that can take the heat.  Well most of those have a lot of Nickel and Carbon Monoxide reacts with Nickel at room temperature producing Nickel Carbonyl.  It is extremely toxic.  As little at 5 ppm kills in minutes.  Carbon Monoxide also causes problems with a lot of different metals if teh temperatures are high enough.

I don't think that these are insurmountable issues.  They just need engineering to solve the issues.

I think that other exotics like Acetylene and Cyanogen are true non starters.  Hard to make on Mars and even hotter burning.  If I remember correctly Cyanogen Oxygen burns at just under 5000K.  That's hot, real freaking hot.  The SSME ran at a comparatively cool 3350K.
Title: Re: Carbon Monoxide for fuel on Mars
Post by: Rei on 05/05/2016 01:54 pm
The period of time in which CO would be in contact with the combustion chamber before dissociating from the heat is measured in milliseconds at best - and the toxicity of the plume is irrelevant, as nobody breathes it, or any other air on Mars, and Mars is already toxic to begin with (hexavalant chromium, perchlorates, carbon monoxide levels that would be highly deadly at Earthlike atmospheric pressures, etc).  The question is, how corrosive would it be to the combustion chamber versus other alternatives?  That I can't answer - but a lot of propellant combinations in use today are already pretty corrosive.

The heat of combustion of propellants like cyanogen can be dropped by diluting with other fuels.  There's also ceramic combustion chambers, which - according to Akatsuki - work fine..... so long as you run your engine within the engineered operating parameters  ;)
Title: Re: Carbon Monoxide for fuel on Mars
Post by: A_M_Swallow on 05/05/2016 07:14 pm
For simplicity a base will want to use the same fuel for its rockets and for generation of electricity. Various types of engines can work at these combustion temperatures but their heat exchangers and pipes will also need to take the pressure. Such equipment will need building and testing.
Title: Re: Carbon Monoxide for fuel on Mars
Post by: Rei on 05/05/2016 08:51 pm
For simplicity a base will want to use the same fuel for its rockets and for generation of electricity. Various types of engines can work at these combustion temperatures but their heat exchangers and pipes will also need to take the pressure. Such equipment will need building and testing.

Fuel... for the generation of electricity?
 : ???
Title: Re: Carbon Monoxide for fuel on Mars
Post by: Dalhousie on 05/05/2016 09:02 pm
The period of time in which CO would be in contact with the combustion chamber before dissociating from the heat is measured in milliseconds at best - and the toxicity of the plume is irrelevant, as nobody breathes it, or any other air on Mars, and Mars is already toxic to begin with (hexavalant chromium, perchlorates, carbon monoxide levels that would be highly deadly at Earthlike atmospheric pressures, etc).

Hexavalent chromium, if present at all (it was a made up hazard based on zero evidence) would be in the soil, not the atmosphere,  Perchlorate is not particularly toxic and it too is in the soil.  Carbon monoxide is at a partial pressure well below unpolluted Earth atmosphere.  Even carbon dioxide partial pressure is below toxic levels. 
Title: Re: Carbon Monoxide for fuel on Mars
Post by: A_M_Swallow on 05/05/2016 09:35 pm
For simplicity a base will want to use the same fuel for its rockets and for generation of electricity. Various types of engines can work at these combustion temperatures but their heat exchangers and pipes will also need to take the pressure. Such equipment will need building and testing.

Fuel... for the generation of electricity?
 : ???

Solar panels only work during the day. The batteries needed to keep a base going during the night are enormous - possible on Mars but not at the Moon's equator. Carbon monoxide and liquid oxygen can be kept in tanks.

This applies double to rovers. In 2012 NASA tested running the MMSEV manned rover from a hydrogen fuel cell. A CO/LOX system may have to use a Stirling engine converter to generate the electricity.
http://www.lpi.usra.edu/meetings/lpsc2013/eposter/3097.pdf (http://www.lpi.usra.edu/meetings/lpsc2013/eposter/3097.pdf)
Title: Re: Carbon Monoxide for fuel on Mars
Post by: Robotbeat on 05/06/2016 04:39 am
Using the Carbon Monoxide and Oxygen fuel cycle seems like a no brainer.  Simple one step production process and you need this process anyway to get O2 to breathe.  I just don't think there is an easier method to get these two very important resources.

However, there are significant issues. 

There is not much study of an engine using this set of propellants.  While carbon Monoxide it toxic, it is at least 10x less toxic than Hydrazine.  We test plenty of engines using Hydrazine, so testing using Carbon Monoxide should not be too hard.

One problem with this selection is the high temperature of the combustion coupled with the somewhat poor cooling properties of the propellants.  There is a reason that LOX is not used to cool combustion chambers, but in this case I think both will need to be used.   Simple you say, use one of those super alloys that can take the heat.  Well most of those have a lot of Nickel and Carbon Monoxide reacts with Nickel at room temperature producing Nickel Carbonyl.  It is extremely toxic.  As little at 5 ppm kills in minutes.  Carbon Monoxide also causes problems with a lot of different metals if teh temperatures are high enough.

I don't think that these are insurmountable issues.  They just need engineering to solve the issues.

I think that other exotics like Acetylene and Cyanogen are true non starters.  Hard to make on Mars and even hotter burning.  If I remember correctly Cyanogen Oxygen burns at just under 5000K.  That's hot, real freaking hot.  The SSME ran at a comparatively cool 3350K.
People have used oxygen as a regen coolant before. Sometimes by accident...


Additionally, you could mix some liquid CO2 or argon or nitrogen in as a coolant to solve some of the issues. Annoying to have a third propellant, but could be done. Adjust the mixture ratio so you add less CO2 and less CO/O2 as time goes on (while reducing CO2 faster), so as to start with a lower Isp but higher thrust and ending with a higher Isp. This is the most energy efficient way to get to orbit, if you get very good mass fraction.
Title: Re: Carbon Monoxide for fuel on Mars
Post by: Dalhousie on 05/06/2016 06:13 am
Using the Carbon Monoxide and Oxygen fuel cycle seems like a no brainer.  Simple one step production process and you need this process anyway to get O2 to breathe.  I just don't think there is an easier method to get these two very important resources.

However, there are significant issues. 

There is not much study of an engine using this set of propellants.  While carbon Monoxide it toxic, it is at least 10x less toxic than Hydrazine.  We test plenty of engines using Hydrazine, so testing using Carbon Monoxide should not be too hard.

One problem with this selection is the high temperature of the combustion coupled with the somewhat poor cooling properties of the propellants.  There is a reason that LOX is not used to cool combustion chambers, but in this case I think both will need to be used.   Simple you say, use one of those super alloys that can take the heat.  Well most of those have a lot of Nickel and Carbon Monoxide reacts with Nickel at room temperature producing Nickel Carbonyl.  It is extremely toxic.  As little at 5 ppm kills in minutes.  Carbon Monoxide also causes problems with a lot of different metals if teh temperatures are high enough.

I don't think that these are insurmountable issues.  They just need engineering to solve the issues.

I think that other exotics like Acetylene and Cyanogen are true non starters.  Hard to make on Mars and even hotter burning.  If I remember correctly Cyanogen Oxygen burns at just under 5000K.  That's hot, real freaking hot.  The SSME ran at a comparatively cool 3350K.
People have used oxygen as a regen coolant before. Sometimes by accident...


Additionally, you could mix some liquid CO2 or argon or nitrogen in as a coolant to solve some of the issues. Annoying to have a third propellant, but could be done. Adjust the mixture ratio so you add less CO2 and less CO/O2 as time goes on (while reducing CO2 faster), so as to start with a lower Isp but higher thrust and ending with a higher Isp. This is the most energy efficient way to get to orbit, if you get very good mass fraction.

Why not use excess O2 or CO?
Title: Re: Carbon Monoxide for fuel on Mars
Post by: cleonard on 05/06/2016 06:53 am
Using the Carbon Monoxide and Oxygen fuel cycle seems like a no brainer.  Simple one step production process and you need this process anyway to get O2 to breathe.  I just don't think there is an easier method to get these two very important resources.

However, there are significant issues. 

There is not much study of an engine using this set of propellants.  While carbon Monoxide it toxic, it is at least 10x less toxic than Hydrazine.  We test plenty of engines using Hydrazine, so testing using Carbon Monoxide should not be too hard.

One problem with this selection is the high temperature of the combustion coupled with the somewhat poor cooling properties of the propellants.  There is a reason that LOX is not used to cool combustion chambers, but in this case I think both will need to be used.   Simple you say, use one of those super alloys that can take the heat.  Well most of those have a lot of Nickel and Carbon Monoxide reacts with Nickel at room temperature producing Nickel Carbonyl.  It is extremely toxic.  As little at 5 ppm kills in minutes.  Carbon Monoxide also causes problems with a lot of different metals if teh temperatures are high enough.

I don't think that these are insurmountable issues.  They just need engineering to solve the issues.

I think that other exotics like Acetylene and Cyanogen are true non starters.  Hard to make on Mars and even hotter burning.  If I remember correctly Cyanogen Oxygen burns at just under 5000K.  That's hot, real freaking hot.  The SSME ran at a comparatively cool 3350K.
People have used oxygen as a regen coolant before. Sometimes by accident...


Additionally, you could mix some liquid CO2 or argon or nitrogen in as a coolant to solve some of the issues. Annoying to have a third propellant, but could be done. Adjust the mixture ratio so you add less CO2 and less CO/O2 as time goes on (while reducing CO2 faster), so as to start with a lower Isp but higher thrust and ending with a higher Isp. This is the most energy efficient way to get to orbit, if you get very good mass fraction.

Why not use excess O2 or CO?


Due to the high temps both the CO and O2 will likely have to be used for cooling to the maximum extent possible.

The high temps are unavoidable as they are pretty critical to the resulting ISP.   More traditional rocket engine fuels contain Hydrogen in the fuel.  You can run those fuel rich and increase the amount hydrogen going out the nozzle.  ISP is the exhaust velocity and lower molecular weight exhaust means faster.  For example the high ISP SSME ran at a mass ratio of 6:1, but full combustion to H2O is 8:1.  Lowers combustion chamber temps with a still very respectable ISP.

This does not really apply to a CO and O2 fueled engine.  The molecular weights are high as CO2 is 44 and the fuels are 28 and 32.  Fuel rich is not going to help as the CO is the strongest chemical bond.  Oxidizer rich might give some free O weight 16 radicals in the exhaust but free O atoms tend to eat everything like walls of combustion chambers. Running slightly fuel rich might be a good idea just to prevent those free Oxygen radicals.


The only way to maximize the exhaust velocity is to burn near stoichiometric and have the exhaust at the highest possible temperature.  Adding inerts like CO2 or Argon will only cool the process and result in considerably lower exhaust velocity.  Actually, water would probably be better.

I think that the issues will yield to engineering, it's just not been done yet.  The TRL for this fuel cycle is low compared to more conventional fuels.
Title: Re: Carbon Monoxide for fuel on Mars
Post by: Dalhousie on 05/06/2016 07:03 am
Thanks!
Title: Re: Carbon Monoxide for fuel on Mars
Post by: Rei on 05/06/2016 10:25 am
For simplicity a base will want to use the same fuel for its rockets and for generation of electricity. Various types of engines can work at these combustion temperatures but their heat exchangers and pipes will also need to take the pressure. Such equipment will need building and testing.

Fuel... for the generation of electricity?
 : ???

Solar panels only work during the day. The batteries needed to keep a base going during the night are enormous - possible on Mars but not at the Moon's equator. Carbon monoxide and liquid oxygen can be kept in tanks. ...  A CO/LOX system may have to use a Stirling engine converter to generate the electricity.

"At night" is a good clarification to your earlier statement  ;)  Still, I seriously doubt they're going to use combustion for the creation of energy at night.  Even assuming that power is non-nuclear.  Fuel cells are a possibility, but concerning combustion, I can't begin to imagine that they'd choose a system that throws out 2/3rds of the energy and involves extensive use of moving parts in a hostile environment as their energy storage means of choice.  Fuel cells for space applications are both a much higher TRL and significantly more efficient.

Assuming, again, that batteries aren't used, and that the power isn't nuclear.

What exactly was your link supposed to be about?
Title: Re: Carbon Monoxide for fuel on Mars
Post by: Vultur on 05/06/2016 09:58 pm
Does the process that will be used to make oxygen in the MOXIE experiment planned for the Mars 2020 rover produce CO as a byproduct?

EDIT: remove incorrect quote
Title: Re: Carbon Monoxide for fuel on Mars
Post by: john smith 19 on 05/06/2016 10:37 pm
Fuel cells are a possibility, but concerning combustion, I can't begin to imagine that they'd choose a system that throws out 2/3rds of the energy and involves extensive use of moving parts in a hostile environment as their energy storage means of choice. 
As always "it depends." Conversion of reactants to electricity, yes. But a settlement is a different issue. It's like IVF, where heat is a valuable 2nd product of the process. Mars is cold at night. Low convection thermal design will certainly help but Mars atmosphere is still substantially above a vacuum.
Quote
Fuel cells for space applications are both a much higher TRL and significantly more efficient.

Assuming, again, that batteries aren't used, and that the power isn't nuclear.
Only for the O2/H2 combination. AFAIK the materials are only really developed for conversion the other way 2 CO2 --> O2 + 2CO
Title: Re: Carbon Monoxide for fuel on Mars
Post by: Robotbeat on 05/07/2016 01:33 am
If you're making oxygen from the Martian air, you're already making carbon monoxide by default. The question is whether or not you're going to do anything with it.

So does the process that will be used to make oxygen in the MOXIE experiment planned for the Mars 2020 rover produce CO as a byproduct?
Yes, MOXIE produces both oxygen and carbon monoxide. BTW, you butchered your quote tags, I wasn't the one who said the above.
Title: Re: Carbon Monoxide for fuel on Mars
Post by: A_M_Swallow on 05/08/2016 02:25 pm
{snip}
Assuming, again, that batteries aren't used, and that the power isn't nuclear.

What exactly was your link supposed to be about?

We will not be using nuclear on man sized rovers. RTG do not produce sufficient power and full sized nuclear reactors are not moved once started.

The MMSEV is a prototype manned rover. The quote shows it being powered by a fuel cell.
2H2 + O2 = 2H2O

Repeat
Quote
This applies double to rovers. In 2012 NASA tested running the MMSEV manned rover from a hydrogen fuel cell. A CO/LOX system may have to use a Stirling engine converter to generate the electricity.
http://www.lpi.usra.edu/meetings/lpsc2013/eposter/3097.pdf
Title: Re: Carbon Monoxide for fuel on Mars
Post by: Vultur on 05/08/2016 06:14 pm
Yes, MOXIE produces both oxygen and carbon monoxide.

OK, cool! So that's an opportunity to test out the production pretty soon (2021 or so...)

When I first heard about this combination, I thought it was kind of silly/unnecessary since methane/LOX has way better Isp. But it could easily be a good choice early on, since the basic chemistry will already be tested out on Mars and it doesn't require either bringing hydrogen from Earth or getting it from Martian ice.

(I have a feeling SpaceX will still go the methalox route so they can use Raptor, though.)

Quote
BTW, you butchered your quote tags, I wasn't the one who said the above.

Oh, sorry  :-[ Fixed.
Title: Re: Carbon Monoxide for fuel on Mars
Post by: Proponent on 05/09/2016 03:56 am
For example the high ISP SSME ran at a mass ratio of 6:1, but full combustion to H2O is 8:1.  Lowers combustion chamber temps with a still very respectable ISP..

Not merely "still very respectable," but actually better (https://forum.nasaspaceflight.com/index.php?topic=31040.msg1518613#msg1518613).  The SSME ran leaner than most lox-hydrogen stages (O/F typically being 5-ish), and therefore suffered both lower Isp and higher chamber temperature:  the trade between Isp and bulk propellant density shifts toward density for ground-lit stages.
Title: Re: Carbon Monoxide for fuel on Mars
Post by: Tetrakis on 05/09/2016 04:38 am
There is a higher performance fuel you can make out of the Martian atmosphere.

It's called Cyanogen.

It is however very toxic to handle.  :(

Now this idea I rather like. What would be the performance of that, exactly?

I realize that cyanogen is toxic, but so is carbon monoxide. More importantly it is comparatively hard to synthesize, but still this is an intriguing idea since a closed cycle can be envisioned where no external hydrogen need be supplied for its preparation from the Martian atmosphere (although some would be needed in the system itself for the preparation of ammonia and hydrogen cyanide as intermediates, thermodynamic driving force comes from oxidation of these compounds by oxygen to make water, which can be split again to make oxygen and regenerate hydrogen for ammonia synthesis)

Also, for those interested in something a bit... spicier, theres always dicyanoacetylene.
Title: Re: Carbon Monoxide for fuel on Mars
Post by: Rei on 05/09/2016 10:06 am
Quote
Now this idea I rather like. What would be the performance of that, exactly?

See earlier in this thread where I ran it through CEA2.

And yes, there are definite advantages for Mars in a hydrogen-free cycle.  Even bigger for Venus.  Although high performance is even more critical there due to the Earthlike gravity, so hydrogen still may be the best option (even though it's harder to get).  Cyanogen is also nice and dense and doesn't require the sort of sub-LOX temperatures of carbon monoxide.  But it burns very, very hot.

Hmm. I wonder if CO and(CN)2 form a eutectic... that could be the best of both worlds.

Quote
Also, for those interested in something a bit... spicier, theres always dicyanoacetylene.

I could be mistaken, but I don't think people are generally fond of their propellants being explosive  ;)  Hehe

Title: Re: Carbon Monoxide for fuel on Mars
Post by: acsawdey on 05/09/2016 06:29 pm
I could be mistaken, but I don't think people are generally fond of their propellants being explosive  ;)  Hehe

That's what I always say about GPIM and its hydroxylammonium nitrate monopropellant --- the concept seems frightening, just put your fuel and oxidizer in an aqueous solution together, nothing could ever go wrong with that, right?
Title: Re: Carbon Monoxide for fuel on Mars
Post by: Rei on 05/10/2016 01:03 pm
We will not be using nuclear on man sized rovers.

So now we're talking about rovers?

Can we be clear about what is actually being discussed here before discussing it?  First it was "a base will use chemicals to power itself".  Then it was "a base will use chemicals for nightime power storage".  Now it's " a rover will be driven by chemicals".  It's hard to make statements when the topic keeps shifting.

Quote
The MMSEV is a prototype manned rover. The quote shows it being powered by a fuel cell.

And I wrote "Fuel cells are a possibility".  Whether they're "ideal" depends on the application, of course.  IMHO while H2+O2 is more widespread, H2+Cl2  is better suited for closed-cycle fuel-cell applications.  Efficiency and power are both better than H2+O2 and Cl2 can be liquefied with just pressure or moderately low temperatures, no sub-100K temperatures needed.  It also works well (unlike H2/O2 PEMFCs) for both electrolysis and galvanic operation in a single unit. 

We're still not very good at the anode side working with H2/O2, it involves significant overpotential (loss).
Title: Re: Carbon Monoxide for fuel on Mars
Post by: A_M_Swallow on 05/10/2016 06:10 pm

So now we're talking about rovers?

Can we be clear about what is actually being discussed here before discussing it?  First it was "a base will use chemicals to power itself".  Then it was "a base will use chemicals for nightime power storage".  Now it's " a rover will be driven by chemicals".  It's hard to make statements when the topic keeps shifting.
{snip}

In a well designed power system landers, habitats and rovers all work together.
Title: Re: Carbon Monoxide for fuel on Mars
Post by: Proponent on 05/12/2016 08:54 am
I've just run lox-carbon monoxide* and, as suggested by john smith 19, lox-cyanogen (https://forum.nasaspaceflight.com/index.php?topic=21544.msg1528705#msg1528705) through Whitehead's SSTO model, with the modifications described earlier (https://forum.nasaspaceflight.com/index.php?topic=31040.msg1518743#msg1518743).  The results are as tabulated below for a delta-V of 4 km/s, representative of a one-way trip from the surface of Mars to low Mars orbit.  The attached plot portrays the results (except for the hydrogen case) in the density-specific impulse plane, each curve representing the full range from maximum specific impulse to maximum impulse density.  The grey contours represent constant values of mAvail, as labeled.  The oxidizer is oxygen in all cases.  I've added a column MechEff,
which is the mechanical energy efficiency: the kinetic energy of the vehicle at burn-out divided by the mechanical energy of the jet (i.e., 0.5(propellant mass)(effective exhaust velocity)2).


           Fuel   O.F  RelMix Isp Dens Ctemp DenExp MechEff mProp   mEng  mTank  mFluid mAvail
         syntin 2.621   0.435 347 1043  3989  0.408   0.617  2.24 0.0106 0.0214 0.01118  0.957
        boctane 2.707   0.438 347 1036  3954  0.409   0.617  2.24 0.0107 0.0216 0.01120  0.956
          JP-10 2.718   0.418 340 1077  3911  0.401   0.621  2.32 0.0108 0.0215 0.01160  0.956
           JP-5 2.869   0.414 342 1032  3871  0.406   0.620  2.29 0.0111 0.0222 0.01147  0.955
           RP-1 2.891   0.425 342 1030  3864  0.406   0.620  2.30 0.0111 0.0223 0.01149  0.955
         octane 3.023   0.448 344  987  3841  0.412   0.618  2.27 0.0114 0.0230 0.01134  0.954
         hexane 3.065   0.447 345  966  3835  0.414   0.618  2.26 0.0116 0.0234 0.01131  0.954
       ethylene 2.817   0.410 354  902  3981  0.426   0.613  2.17 0.0118 0.0241 0.01085  0.953
      propylene 2.872   0.422 349  931  3931  0.420   0.616  2.22 0.0118 0.0239 0.01110  0.953
        pentane 3.097   0.436 345  949  3830  0.416   0.618  2.26 0.0118 0.0238 0.01128  0.953
         butane 3.142   0.443 346  938  3822  0.418   0.617  2.25 0.0119 0.0240 0.01125  0.953
        propane 3.207   0.440 347  928  3808  0.419   0.617  2.24 0.0120 0.0241 0.01120  0.953
         ethane 3.331   0.451 349  910  3785  0.422   0.616  2.22 0.0121 0.0244 0.01111  0.952
       cyanogen 0.918   0.377 331 1033  4506  0.400   0.625  2.43 0.0119 0.0235 0.01215  0.952
        methane 3.711   0.438 351  838  3711  0.431   0.615  2.20 0.0129 0.0262 0.01098  0.950
  cyanogen-lean 2.178  16.028 295 1073  3900  5.199   0.640  2.99 0.0150 0.0279 0.01496  0.942
       hydrogen 7.932   0.338 415  424  3738  0.518   0.578  1.67 0.0181 0.0395 0.00837  0.934
  cyanogen-rich 0.156 -23.192 271  972  3900 -4.628   0.646  3.51 0.0204 0.0361 0.01754  0.926
carbon monoxide 0.594   0.248 266  895  3543  0.367   0.647  3.63 0.0231 0.0405 0.01814  0.918


As before, mixture ratios are adjusted maximize the available mass fraction, mAvail.  You'll note, though, that there are three entries for cyanogen.  One corresponds to maximal mAvail.  As cleonard pointed out above (https://forum.nasaspaceflight.com/index.php?topic=21544.msg1528796#msg1528796), however,  cyanogen burns hotter 'n Georgia asphalt.  So, the other two points correspond to the rich and lean lox-cyanogen mixtures which burn at a more moderate 3900 K (these fall outside the usual density range and are represented by small red circles in the plot).  A lean cyanogen mixture burning at 3900 K actually performs quite well:  though it falls near the bottom of the table (which is sorted by mAvail), its mAvail isn't really much lower than those of the best fuels.  For that matter, rich-burning cyanogen at 3900 K and CO aren't awful either.


* The CEA thermodynamic database which RPA uses does not contain an entry for liquid CO.  Entering a substance requires calculating its enthalpy with respect to the chemical elements from which it is formed at STP (25 oC and 1 bar).  To do this, I started with the the CEA heat of formation for CO(g) at STP (-110.535 kJ/mol) then used NIST data to find the difference in enthalpies between CO(g) at STP and CO(l) at its boiling point of 81.6 K.  The result is -122.972 kJ/mol.

Just to check that my calculation was reasonable I applied the same technique to methane, a liquid-state enthalpy for which is contained in CEA.  The result was -89.200 kJ/mol, which differs by just 0.033 kJ/mol from the value -89.233 kJ/mol that is given.  A change of 0.04 kJ/mol in the enthalpy of CO(l) changes its specific impulse by only about 0.02 s.

EDIT:  Removed erroneous second apostrophe from colloquialism "hotter 'n Georgia asphalt."  Corrected table and plot to reflect a take-off thrust-to-weight ratio of 1.3 on Mars rather than Earth.  Added MechEff column and corresponding explanation.  Deleted oxidizer and engine T/W columns.
Title: Re: Carbon Monoxide for fuel on Mars
Post by: Proponent on 05/12/2016 09:21 am
Now let's look at a round trip from Mars to LMO and back.  Rei pointed out that the 8-km/s delta-V I previously assumed for this was probably rather harsh (https://forum.nasaspaceflight.com/index.php?topic=31040.msg1521191#msg1521191).  Let's suppose you can do it for 6 km/s, getting about 2 km/s of braking from the martian atmosphere.


           Fuel   O.F  RelMix Isp Dens Ctemp DenExp MechEff mProp   mEng  mTank mFluid mAvail
         syntin 2.608   0.347 347 1043  3988  0.323   0.644  4.82 0.0191 0.0462 0.0241  0.911
        boctane 2.692   0.347 347 1035  3953  0.323   0.644  4.83 0.0193 0.0467 0.0241  0.910
          JP-10 2.710   0.331 340 1077  3910  0.316   0.642  5.05 0.0197 0.0469 0.0253  0.908
           JP-5 2.856   0.327 342 1032  3871  0.321   0.642  4.98 0.0201 0.0482 0.0249  0.907
           RP-1 2.876   0.337 342 1029  3863  0.321   0.642  4.99 0.0202 0.0484 0.0249  0.906
         octane 3.002   0.358 345  986  3840  0.326   0.643  4.91 0.0207 0.0497 0.0245  0.905
       ethylene 2.783   0.338 354  901  3979  0.338   0.645  4.64 0.0210 0.0515 0.0232  0.904
         hexane 3.042   0.362 345  965  3834  0.328   0.643  4.89 0.0210 0.0506 0.0244  0.904
      propylene 2.843   0.341 349  930  3930  0.333   0.644  4.78 0.0212 0.0514 0.0239  0.904
        pentane 3.070   0.346 346  948  3829  0.329   0.643  4.87 0.0213 0.0514 0.0244  0.903
         butane 3.115   0.356 346  937  3821  0.331   0.643  4.86 0.0215 0.0518 0.0243  0.902
        propane 3.177   0.351 347  927  3807  0.332   0.644  4.83 0.0215 0.0521 0.0241  0.902
         ethane 3.298   0.364 349  909  3784  0.335   0.644  4.78 0.0217 0.0525 0.0239  0.902
       cyanogen 0.914   0.299 331 1033  4508  0.314   0.639  5.35 0.0221 0.0518 0.0268  0.899
        methane 3.668   0.356 351  836  3710  0.342   0.644  4.71 0.0231 0.0563 0.0235  0.897
       hydrogen 7.763   0.322 417  419  3738  0.426   0.645  3.34 0.0295 0.0796 0.0167  0.874
  cyanogen-lean 2.178  16.028 295 1073  3900  5.199   0.618  6.97 0.0300 0.0650 0.0349  0.870
  cyanogen-rich 0.156 -23.192 271  972  3900 -4.628   0.595  8.57 0.0432 0.0882 0.0429  0.826
carbon monoxide 0.578   0.166 266  893  3545  0.281   0.590  8.94 0.0497 0.1001 0.0447  0.805


By rank order, the results are pretty much the same as in the 4-km/s case.  However, carbon monoxide and fuel-rich low-temperature cyanogen now produce much lower available mass fractions than do other fuels.  Lean cyanogen might be the way to go as for as ISRU propellants are concerned.  Running lean (i.e., oxygen rich) might limit the lifetime of the propulsion system, though.

Lowering the combustion temperature by diluting cyanogen with CO might be a possibility, though CO's poor performance suggests to me that unless the density of the mixture is high (maybe if that eutectic that Rei mused (https://forum.nasaspaceflight.com/index.php?topic=21544.msg1531298#msg1531298) about exists, or if the solubility of solid cyanogen [which freezes at 245 K, far above CO's boiling point] in CO is high), CO-cyanogen mixtures will perform poorly.

I don't think the toxicities of carbon monoxide and cyanogen are much of an issue.  Nobody's going outside without the equivalent of a hazmat suit (i.e., a spacesuit) anyway.

EDIT:  Corrected T/W calculation to Mars and other miscellaneous changes as in previous post.
Title: Re: Carbon Monoxide for fuel on Mars
Post by: Rei on 05/12/2016 12:26 pm
Great work  :)  Just as a note: I know for a fact that CO/CH4 eutectics do exist. 

https://books.google.is/books?id=VC2mKJlHbokC&pg=PA344&lpg=PA344&dq=%22methane%22+%22carbon+monoxide%22+%22eutectic%22&source=bl&ots=Qfr8KT4KA7&sig=pBlLyoayaalBiZ-hUSByR1bjj3g&hl=is&sa=X&redir_esc=y#v=onepage&q=%22methane%22%20%22carbon%20monoxide%22%20%22eutectic%22&f=false

However, I don't know their densities.  As a general rule, the density of a eutectic is higher than the proportional mixture of the two densities.  They also tend to have a wider liquid-state temperature range.

(I would expect CO to be cosoluble with a wide range of hydrocarbons - supercritical CO2 is often used as a hydrocarbon solvent)

I know nothing about cyanogen eutectics.  Given that it's a pseudohalogen, however, I'd expect it to behave similar to halogens.
Title: Re: Carbon Monoxide for fuel on Mars
Post by: Robotbeat on 05/12/2016 02:27 pm
I was thinking CO-O2 would be an ideal propellant for a SSTO Mars RLV just shuttling cargo up to LMO and back. Not actually for leaving Mars.

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.

...but it likely would be a poor fuel for further destinations. Use a CO/O2 shuttle to transport water, hydrolox, or CH4/O2 propellant to orbit. That higher Isp for hydrogen and methane makes more sense the higher up the delta-v tree you get, plus it's not bad from a resource-acquisition standpoint since you'll need a lot less of it than you would for getting all that to LMO.

A CO/O2 SSTO RLV, with 2.5-2.6km/s exhaust velocity, perhaps with initial launch assisted by a rail (to like 0.3-1km/s), would be an incredibly efficient and inexpensive way to get payload to low Mars orbit and back.


...launching water is a good idea since solar power is more plentiful in orbit than on the Martian surface anyway and it is much denser than hydrolox plus much easier to store. Split the water in orbit like we do on ISS.
Title: Re: Carbon Monoxide for fuel on Mars
Post by: Robotbeat on 05/12/2016 02:30 pm
Proponent:
Try running the numbers for 4-4.2km/s delta-v. Include the energy needed to electrolyze the propellant (if you want, assume 50% electrolysis efficiency across the board as a simplifying assumption, so multiply the fuel specific energy by 2).
Title: Re: Carbon Monoxide for fuel on Mars
Post by: Proponent on 05/16/2016 03:56 pm
In my two preceding posts, I had mistakenly assumed Earth gravity in imposing a take-off thrust-to-weight ratio of 1.3.  I've now corrected the error.  The result is to improve performance, since engines can now be quite a bit lighter.  Although in the 4-km/s case the available mass fraction improves by only about 0.01 for the best-performing fuels, CO improves by about 0.04.

Try running the numbers for 4-4.2km/s delta-v. Include the energy needed to electrolyze the propellant (if you want, assume 50% electrolysis efficiency across the board as a simplifying assumption, so multiply the fuel specific energy by 2).

I'm afraid I don't understand.  Could you please spell out what you have in mind in a little more detail.

PS  I added back in to the tables above a column for mechanical efficiency.  It's the kinetic energy of the vehicle at burn-out, in the launch-site frame, divided by the kinetic energy of the jet, in the vehicle's frame.  You'll note that though CO is the lowest-performing fuel, it does have high (in fact, the highest) mechanical efficiency for 4 km/s, as you've been saying.
Title: Re: Carbon Monoxide for fuel on Mars
Post by: Robotbeat on 08/18/2016 09:53 pm
I mean:

Given really good tank and engine mass fraction (adjusted based on the density of the fuel, of course, but I'm assuming a really good effort is made to reduce tankage mass by using state of the art materials):

How much energy does it take to electrolyze the propellant needed to launch 1 ton of cargo into low Mars orbit?

Compare CO/O2 with CH4/O2.

Energy needed to electrolyze CO:
10.1MJ/kg, so double that to 20.2MJ/kg to account for 50% efficiency.

Energy needed to electrolyze CH4:
Hydrogen has 142MJ/kg, and it takes 0.5kg of hydrogen to produce 1kg of CH4 via Sabatier reaction, so 71MJ/kg, double that back to 142MJ/kg to account for 50% efficiency of electrolysis.

So, how much CO (in kg) does it take to put 1000 kg of payload through 4km/s? How much CH4 does it take to put 1000kg of payload through 4km/s?

Multiply that mass of fuel by 20.2MJ/kg and 142MJ/kg, respectively. Which number is the least?
Title: Re: Carbon Monoxide for fuel on Mars
Post by: Proponent 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 (http://forum.nasaspaceflight.com/index.php?topic=31040.msg1518743#msg1518743), 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 (http://forum.nasaspaceflight.com/index.php?topic=21544.msg1533154#msg1533154), 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?
Title: Re: Carbon Monoxide for fuel on Mars
Post by: Robotbeat on 08/19/2016 04:26 pm
Oxygen comes for "free" by the electrolysis of water.