6 ms·
The ISS uses rechargeable zeolite beds for CO2 scrubbing, they don't need a new one frequently, and the fact that we shipped a new one is coincidence. Zeolite
by gpm 5y ago
The ISS uses rechargeable zeolite beds for CO2 scrubbing, they don't need a new one frequently, and the fact that we shipped a new one is coincidence.
Zeolite is a mineral, you get a bunch of small pellets of it in a bed, and run air over it while cooling it. The CO2 (and H2O) stick to it while everything else goes over it. Once you're at capacity you vent it to space and heat it, the CO2 (and H2O) leave the bed (into space) and recharge it for the next cycle. Repeat forever.
The consumables here are the small amount of gasses sent overboard, and energy, nothing else.
(And you use multiple of these beds because capturing CO2 is exothermic, and venting CO2 is endothermic, so you want to run a heat exchanger between the two beds in opposite cycles to minimize energy usage)
- dexwiz 5y agoIf both operations are exothermic, why the heat exchanger? I would assume one process would need to be endothermic.
- rolleiflex 5y agoIf they’re not recycling CO2 into O2 and instead venting CO2 to space, does that mean ISS is constantly losing gas and it needs an ongoing resupply of oxygen all the time? I thought oxygen was used fast enough to make resupply impractical, but perhaps there are in fact gigantic tanks of O2 under immense pressure somewhere aboard the ISS.
- mzs 5y agohttps://en.wikipedia.org/wiki/ISS_ECLSS#Oxygen_generating_system https://en.wikipedia.org/wiki/ISS_ECLSS#Oxygen_generating_sy...
- gpm 5y agoYes, and sort of. The ISS is constantly losing gas, I believe that the primary source of new O2 is actually electrolysis of water, not pressurized tanks, but that they do also have pressurized tanks as a backup. A person breathes out roughly 1kg of CO2/day, and it follows you breathe in about the same amount of O2, not an impossible amount of mass to resupply.
- azernik 5y agoAnd, to complete the equation: that carbon comes up in the form of food.
- fho 5y ago> 1kg of CO2/day which is crazy low if you put it in perspective and see that (gas powered) cars release about 0.2 kg of CO2 ... per kilometer.
- makeitrain 5y agoThat's insane, I didn't realize it was that much. If we could see cars drop carbon turds on the road instead of venting it invisibly in the air we'd all be freaking out right now.
- NickNameNick 5y agoWell, we used to have horses... There's a reason all the old buildings in big cities are elevated a few steps above street level...
- arethuza 5y agoWhere I used to live in the New Town of Edinburgh each house had a boot scraper fixed next to the step to the front door.
- fho 5y agoYep ... that's about two chocolate bars every kilometer ... and that has not really changed too much with newer motor generations as it is mostly a function of how much gas is used.
- rtkwe 5y agoThe new scrubber sounds like it's not using the old zeolite bed system but one based on molecular sieves. But you're otherwise right that they're not really turning that CO2 into anything on the regular beyond the limited ISRU experiment(s).
- gpm 5y agoZeolite is a molecular sieve. That's just a fancy word for "material that selectively holds on to some types of gasses" (CO2 and H2O in the case of zeolite). I haven't followed the new bed system though, I'd be very interested to know if it was using a different molecular sieve (and somewhat surprised if they are).
- rtkwe 5y agoAh yeah reading a bit closer further down they mention it's a 4 bed system and this is largely an iterative improvement instead of a new system entirely.
- lizknope 5y agoI don't disagree with anything you said but the article claims they are turning CO2 into fuel which the ISS is NOT doing.
- __MatrixMan__ 5y agoAgreed. Reaction mass != Fuel