NASA's Oxygen-Generating Experiment Moxie Completes Mars Mission | Hacker News Reader

NASA's Oxygen-Generating Experiment Moxie Completes Mars Mission

mars.nasa.gov

49 pointssohkamyung26 comments

This works (and works well enough) because the atmosphere on Mars is 95% CO2.

On Earth, CO2 concentration is around 425 ppm (parts per million). On Mars, it is ~953,200 ppm!

If we had the same CO2 concentration on Earth, atmospheric carbon dioxide scrubbers and CO2 sequestration solutions would be many orders of magnitude more efficient (and therefore more feasible - enough to actually clean up the mess we’ve made of things, even). But we’d all be dead.

There's actually only about 15 times higher partial pressure of carbon dioxide on Mars because the atmosphere is so much thinner.

Good point. But a compressor pre-stage is still a lot cheaper and more scalable than actually filtering through that many particles to get at each gram of CO2, no?

>> the instrument proved far more successful than its creators ... expected

Always good to see that kind of result! And with technology that is cool and would be workable at a genuinely useful scale, not merely an interesting curiosity

Congrats to the team!

Takes CO2 and extracts one oxygen molecule. Really neat they can do that with Mars' thin atmosphere .

Does anyone know if there is a similar process that can separate both oxygen molecules and the carbon molecule? Then use the C to 3d print things and the oxygen to breathe/fuel/etc? Probably energy limited?

More details from https://en.wikipedia.org/wiki/Mars_Oxygen_ISRU_Experiment the reaction is

2 CO2 + heat --> 2 CO + O2

CO is a gas, so they let it escape. (It's toxic for mammals (in particular humans), but there is no one around to worry about. It will get transformed back to CO2 in the atmosphere when we react with something else that has an oxygen to steal. And in extremely low concentrations it's not a problem. So it's safe to let it escape for now.)

It's energy limited. You need heat to make the transformation.,

Hum... There are plenty of ways to turn that CO into plastics, like the GP wants (but all will require even more energy).

If you go to pure C, you get a solid that's hard to work with. So you stay with the CO which is a gas, you add H2 to get syngas, and then you can Fischer-Tropsch your way into ethylene and propylene, which is your feedstock for polyethylene (as in HDPE) and polypropylene (PP).

On Mars its really all about energy. We have plenty of C and O and if we get water, you can already make so many different things already.

We desperately need to develop a big surface nuclear reactor that fits on a Starship. Without that Mars just isn't gone work. Laying out 100s of football fields of solar panels is just stupid in comparison.

sure in comparison, but we have the existing technology, and capability to lay out 100 football fields of solar on Mars if we wanted to, today. it may cost a metric ton, but we.could do it.

we straight up don't have the ability to build a big surface buclear reactor on Mars. we probably could develop that capability, but until then, it isn't stupid to brute force a large solar installation until something better comes along.

solar likely would be used along side things like kilo power and maybe traditional generators slightly modified until that day comes. it's not stupid do do inefficient thing now, when you don't have a real alternative.

> existing technology, and capability to lay out 100 football fields of solar on Mars if we wanted to, today

No we don't actually. Not in a ready state to deploy to Mars and maintain and set up automatically.

I would say deploying small submarine navy reactors is closer to being a real thing.

> we straight up don't have the ability to build a big surface buclear reactor on Mars

I didn't say 'build it on Mars'. I said, put in on Starship and land it on Mars.

> it isn't stupid to brute force a large solar installation until something better comes along.

Technology doesn't magically fall from the sky. 'Something better' doesn't magically show up one day saying 'Hi, I'm ready'.

NASA does targeted development investment and spending to get the capabilities they need.

Everybody interested in Space has for 50 years known that space nuclear is a necessary part of the future and because of dumb politics NASA has done almost nothing.

> it's not stupid do do inefficient thing now

We are not flying to Mars right now ...

> when you don't have a real alternative.

If you refuse to develop an alternative your not gone have one.

I'm wondering, I know that Earth originally went through an atmospheric change process by bacteria that changed a previously toxic (to us) process into a fully breathable atmosphere...

considering that, wouldn't it be feasible to bring closed containers full of said bacteria (I assume one that does that might still exist) to mars and have them transform CO2 into oxygen in a closed environment?

you pull CO2 into the place with the bacteria then when it's purified into oxygen you pull it into the base.

Of course there's always the risk your bacteria somehow die but still

Cyanobacteria. Those morons almost killed everyone. They are still floating around https://en.wikipedia.org/wiki/Cyanobacteria I think the total weight of Cyanobacteria is bigger than the total weight of Humanity, but I can't find hard numbers.

I guess it's possible to send a container with them to Mars. The biggest problem would be to get enough water so they don't disécate. Also preventing them freezing may be difficult, but I guess it's possible.

Anyway, for now people is trying to not send bacterias to Mars, just in case there are some bacteria-like things living there. It would be very interesting to have a second independent example of life to investigate and compare.

The amazing part to me is that the experiment required more than the available power, and they made it work anyway, with some clever engineering.

So MOXIEs would inject O2 to a martian habitat, CO2 scrubbers would remove exhaled CO2 from the habitat. I suppose Nitrogen would be initially fed into the system, but then would be unconsumed.

I wonder what the power budget to run a MOXIE per astronaut would be.

If you are gone produce your fuel on Mars, the power budget to actual make the fuel is gigantic. The power need to produce enough for a human in comparison isn't very much.

Someday there might be a permanent presence on Mars, where the fuel budget is not the primary concern.

A nuclear power plant would almost certainly be required. All plans that only use solar plans are overly optimistic.

They say oxygen with 98% purity. What's the other 2%?

I’m guessing CO2 that didn’t undergo conversion? Or the non-CO2 gases (comprising ~5% of the Martian atmosphere) that made it into the system and thus weren’t affected? Or the CO byproduct that wasn’t expelled separately?

Edit: thinking about the numbers some, I think non-CO2 (Martian!) atmospheric gases is a good guess for the bulk because they’re 5% of the atmosphere and the conversion input is two CO2 for one O2 out, so at the 2:1 ratio with 0.95 of the input converted you end up with 98.96% converted to either O2 or CO, and the rest is whatever else you had mixed in there, if I did the math right. Depending on how the O2 and CO are separated, the non-CO2 gases not affected by the conversion/reaction could plausibly end up all with the O2, all with the CO, or some mix of the two (probably by weight?). Add in a few ppm of CO2 that slipped through the process unconverted and Bob’s your uncle. Maybe.

Hum... If you don't expel the CO separately, you will very soon get all of your CO2 back and have no CO.

Obviously the bulk of it is expelled separately - I’m just saying it could be an imperfect process.

Probably CO2, as it's the main gas in the atmosphere there.

The wikipedia page on the mission has more information, including that they managed to get up to 99.6% purity. That later number makes the resulting atmosphere not toxic anymore (assuming the impurity is CO2). But it still doesn't specify the impurity.

I came to a different conclusion (see sibling comment to yours) in part because I don’t believe the 98% O2 solution was toxic (and it would be if the other 2% were CO2, no?). I don’t have hard evidence for that belief, but I just expect that if it were toxic it would have been mentioned and NASA wouldn’t have been celebrating. (My guess was non-CO2 atmospheric gases.)

AFAIK, a 2% CO2 concentration is just toxic enough to cause long term health issues, and people can deal with it for months without a lot of problems. (And that's at sea level pressure, at a 0.3 atm O2-only atmosphere, I have no idea.)

NASA may quite well consider it livable. I have no idea what kinds of missions they have in mind. (But there are some low confidence studies claiming it makes people stupid.)

Anyway, the wikipedia page's language implies the CO2 is purified before going into the Moxie. And from what I can tell, you can't reach even 94% purity without that step, so I assume it's there.

> NASA's Oxygen-Generating Experiment Moxie Completes Mars Mission

Total Recall is becoming reality. /s

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