Author Topic: Carbon Monoxide for fuel on Mars  (Read 60685 times)

Offline Robotbeat

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Carbon Monoxide for fuel on Mars
« 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?
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Offline Robotbeat

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Re: Carbon Monoxide for fuel on Mars
« Reply #1 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.
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Offline Robotbeat

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Re: Carbon Monoxide for fuel on Mars
« Reply #2 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 ;).)
« Last Edit: 05/10/2010 06:36 pm by Robotbeat »
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Offline A_M_Swallow

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Re: Carbon Monoxide for fuel on Mars
« Reply #3 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.

Offline Robotbeat

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Re: Carbon Monoxide for fuel on Mars
« Reply #4 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).
« Last Edit: 05/10/2010 07:12 pm by Robotbeat »
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Offline Robotbeat

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Re: Carbon Monoxide for fuel on Mars
« Reply #5 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.
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Offline Robotbeat

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Re: Carbon Monoxide for fuel on Mars
« Reply #6 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.)
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Offline Robotbeat

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Re: Carbon Monoxide for fuel on Mars
« Reply #7 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).
« Last Edit: 05/11/2010 05:22 pm by Robotbeat »
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Offline Robotbeat

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Re: Carbon Monoxide for fuel on Mars
« Reply #8 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).
Chris  Whoever loves correction loves knowledge, but he who hates reproof is stupid.

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Offline MickQ

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Re: Carbon Monoxide for fuel on Mars
« Reply #9 on: 05/12/2010 07:01 am »
Chris.

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

Mick.

Offline Robotbeat

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Re: Carbon Monoxide for fuel on Mars
« Reply #10 on: 05/12/2010 01:21 pm »
Chris.

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

Mick.
:)
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Offline mmeijeri

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Re: Carbon Monoxide for fuel on Mars
« Reply #11 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.
Pro-tip: you don't have to be a jerk if someone doesn't agree with your theories

Offline Robotbeat

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Re: Carbon Monoxide for fuel on Mars
« Reply #12 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.
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Offline A_M_Swallow

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Re: Carbon Monoxide for fuel on Mars
« Reply #13 on: 05/12/2010 04:21 pm »
Solar dynamic is another possibility.  A Mars generator would need bigger mirrors that the Earth version.

Offline Robotbeat

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Re: Carbon Monoxide for fuel on Mars
« Reply #14 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?
« Last Edit: 05/12/2010 05:24 pm by Robotbeat »
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Offline Robotbeat

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Re: Carbon Monoxide for fuel on Mars
« Reply #15 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?
« Last Edit: 05/12/2010 10:01 pm by Robotbeat »
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Offline Robotbeat

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Re: Carbon Monoxide for fuel on Mars
« Reply #16 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! ;)
Chris  Whoever loves correction loves knowledge, but he who hates reproof is stupid.

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Offline Swaggasorusrex

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Re: Carbon Monoxide for fuel on Mars
« Reply #17 on: 09/26/2012 01:00 am »
Robotbeat, why would you still have the need to bring hydrogen from Earth still?

Offline RocketmanUS

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Re: Carbon Monoxide for fuel on Mars
« Reply #18 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.

Offline douglas100

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Re: Carbon Monoxide for fuel on Mars
« Reply #19 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.
Douglas Clark

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