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#26 2020-01-28 22:20:00

kbd512
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Registered: 2015-01-02
Posts: 3,175

Re: Carbon Monoxide - a way to power Mars?

Even if the rockets end up being heavier as a result, from an energy input perspective LOX/LCO still looks like a much better deal to me if energy and resource input per unit of output thrust produced is taken into consideration.  We already know that we can obtain as much CO2 as we need and this propellant combination is very simple to make, requiring no new technology development.  Unless humans will be breathing the atmosphere outside the rocket without pressure suits, which will never happen, or the propellant lines intrude into the pressurized compartment of the vehicle, which shouldn't happen given proper design, then this is also one of the most benign realistic propellant combinations available.

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#27 2020-01-29 04:03:32

Calliban
Member
From: Northern England, UK
Registered: 2019-08-18
Posts: 309

Re: Carbon Monoxide - a way to power Mars?

kbd512 wrote:

Even if the rockets end up being heavier as a result, from an energy input perspective LOX/LCO still looks like a much better deal to me if energy and resource input per unit of output thrust produced is taken into consideration.  We already know that we can obtain as much CO2 as we need and this propellant combination is very simple to make, requiring no new technology development.  Unless humans will be breathing the atmosphere outside the rocket without pressure suits, which will never happen, or the propellant lines intrude into the pressurized compartment of the vehicle, which shouldn't happen given proper design, then this is also one of the most benign realistic propellant combinations available.

Agreed.  If the production can be carried out thermochemically, using nuclear or solar heat, then LOX/LCO becomes even more attractive as a propellant.

https://www.frontiersin.org/articles/10 … 00601/full

It would be difficult to develop nuclear fuel with an operating temperature of 1500C.  A pebble bed could probably reach those temperatures and could run on natural uranium.  Maybe a pressurised sodium reactor using unclad UO2 fuel.  Now there's a scary thought :-)

Last edited by Calliban (2020-01-29 04:20:37)


Interested in space science, engineering and technology.

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#28 2020-01-29 08:25:57

tahanson43206
Member
Registered: 2018-04-27
Posts: 1,819

Re: Carbon Monoxide - a way to power Mars?

For Calliban re #27

Thanks for the link to the paper about use of Cerium to facilitate production of Carbon Monoxide.  I didn't read every word, but I read enough to understand that this was a significant effort by a number of researchers with a considerable financial investment.  Along the way I picked up the mention of the use of electric furnace technology to provide the needed temperatures.

Your suggestion of a fission power plant as the underlying mechanism to produce CO on Mars, and the normal operating temperature well under what is required, leads me to wonder if the existing temperature can be used to generate electricity in sufficient quantity and force to yield a useful amount of CO for propulsion.

I understand that efficiency falls with each stage of energy conversion, but I'd like to point out that Uranium decaying naturally has an efficiency of zero.

If humans can achieve a net efficiency of 5%, given a resource that would otherwise go to waste, I would count that as a good day, on Earth or Mars.

Can you (would you) estimate the net efficiency achievable by using a practical nuclear fission plant to create CO?

A related question is what size of fission plant is needed to produce enough CO to lift a reasonable payload to Mars Low Orbit?

NASA is contemplating a sample return mission from Mars.  They'll need a way to lift the sample from the surface.  The vehicle to achieve that might be worth considering for the estimate.   

Google found a question/answer pair about decomposition of CO2.  The first discovery (for me) was that the ration of CO2 to CO2 changes over a wide range of temperatures.  There was a StackExchange answer with plenty of math for those who might be interested.

The math answer included a branch to this link: https://chemistry.stackexchange.com/que … down-to-co

Heating CO2 at atmospheric pressure:
At 1000K it is still essentially all CO2.
At 2000K: 98% CO2, 1.4% CO, 0.7% O2
At 3000K: 44% CO2, 36% CO, 16% O2, 4% O
At 5000K: 50% CO, 50% O
only at even higher temperature does significant atomic C appear (9% at 6000K).

The "atmospheric pressure" is most likely to be Earth sea level.

From the point of view of how production of CO would actually work in an industrial setting, I'm wondering how the CO would be separated from the mixture.

Now I'll have to go back to the Cerium paper to see what temperatures they were using. 

Edit #2 ... the answer appears to be that at 1500 C, the Cerium material is able to deliver CO as a part of the gas flow.

Edit #3 ... from https://www.theunitconverter.com/celsiu … elvin.html

1500 Celsius (°C) = 1773.15 Kelvin (K)

If I am following the discussion correctly, at 1773 Kelvin, there would be (about) 1% free CO in a mixture which began as all CO2.

(th)

Last edited by tahanson43206 (2020-01-29 13:12:48)

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#29 2020-01-29 19:48:25

kbd512
Moderator
Registered: 2015-01-02
Posts: 3,175

Re: Carbon Monoxide - a way to power Mars?

tahanson43206,

CO would probably be separated from other gases the way we've been doing it:

Molecular Sieve 5A and 13X - Packed GC Columns for Permanent Gas Separations

Edit:

However, this also looks very promising because the researchers were able to accurately predict CO output using a mathematical model:

Converting carbon dioxide to carbon monoxide using water, electricity

Last edited by kbd512 (2020-01-29 20:04:43)

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#30 2020-01-29 21:22:04

SpaceNut
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From: New Hampshire
Registered: 2004-07-22
Posts: 17,766

Re: Carbon Monoxide - a way to power Mars?

Other gasses would be cooled out of the mixture as we compress the air into a chamber for use.
If you have co2 we can use the system which is going to be fully tested in mars conditions.
I got thinking about using o3 with the co with regards to temperature of reaction and then what we would get from the reaction.

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#31 2020-01-29 21:36:14

tahanson43206
Member
Registered: 2018-04-27
Posts: 1,819

Re: Carbon Monoxide - a way to power Mars?

For kbd512 re #29

Thank you for those two links!

The first seems applicable when CO is already present.  I'm certainly open to correction on that point.

The second is (as you say, very promising) because it is able to make CO, and (as nearly as I can tell) it does so at modest temperatures.

The ceramic method found by Calliban seems appropriate for an industrial scale CO manufacturing operation, such as would (presumably) be needed for creating large quantities of fuel and oxidizer for Mars launches.  Calliban appeared (as I read the post) to be leaning toward using nuclear fission as a reliable source of power to drive the process.  My impression is that an electric furnace would be needed to achieve the temperatures where CO is freed up by thermal activity, so the nuclear plant would create the electric current through a heat-to-mechanical-energy process of some kind.  NASA is working on the Stirling engine method for their low power reactor, but I'm not sure how scalable that approach would be.

On the other hand, if the catalyst mediated conversion process can be scaled up, perhaps electricity from a fission reactor can deliver needed quantities of CO and oxygen without the high temperatures of the ceramic process.

(th)

Last edited by tahanson43206 (2020-01-29 21:40:01)

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#32 2020-02-11 11:42:28

elderflower
Member
Registered: 2016-06-19
Posts: 1,159

Re: Carbon Monoxide - a way to power Mars?

CO is a cryogenic gas with physical properties similar to O2 or N2. Storage is therefore not very difficult. It is a usable fuel gas with O2. Specific impulse in a rocket is limited because of its relatively low heat of combustion (2CO +O2 >2CO2) but could be a useful energy source for surface equipment or for a hopper or flying machine on Mars.

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