5 ms·

Cool concept, though solid sheets of silica aerogel are very difficult to manufacture.. I wonder how well this concept holds up with leakage between panels, or

• samstave 7y ago
  We need a “foam” of areogel in a host substance to be viable. The odea being that we can host the aerogel in a substrate material which can withstand/accept the design limitations of the applicatioon environ and support the reasons why we want aerogel there... The surface area of aerogel foam is huge and its ability to absorb heavy toxic metals from water is also huge. I wonder if aerogel desalinization filters could be a thing.
• bayesian_horse 7y ago
  I guess there are a lot details not explained in the article and much of them have come up in the research. I would have liked a discussion over how this stuff could be produced on Mars, because no self-respecting rocket engineer would allow transplanetary shipping of a material largely composed of air.
  • russdill 7y ago
    The primary components of Mars's crust are silicon and oxygen. The components of Silica Aerogel are .... silicon and oxygen.
    • bayesian_horse 7y ago
      Thank you, I didn't know that. Though the next question is how much energy you need to part the silicon and the oxygen and bring them back together to form the aerogel.
      • jacobush 7y ago
        One nice thing which didn't automatically occur to me, is that a nuclear fission reactor on Mars would be comparatively cheap to build. You don't need any radiation shielding at all. Just walk away and turn it on. Have it produce methane and oxygen or electricity or both.
        • bayesian_horse 7y ago
          That would require really good automation. I think most nuclear reactors still require a lot of manual labor relatively close by. But yes, some kind of fission or fusion reactor would be on a colonization plan, if it is easier/cheaper than solar. One problem though would be getting fissile material. You can probably find some on Mars or its moons or some asteroids, but it would require lots of heavy industry to get enough of it for reactors. Bringing significant amounts of nuclear fuel from Earth would be really unpopular, what with the risk of rockets blowing up. That risk or fear is also what prohibits the use of nuclear propulsion for space travel...
          • jacobush 7y ago
            Yeah... politically it would be hard, I agree. But I don't think it would be a show stopper technically to bring fissile material from earth. For one, automated nuclear power plants are being designed for use on here on Earth. The fissile material itself does not weigh very much. It's also not (very) radioactive until you start the process. The bulk mass of a (normal) reactor is shielding and cooling plumbing. You don't need any shielding on Mars, and cooling could maybe (probably?) be some kind of radiator/convector to the surrounding air. Maybe you could even crack the CO2 with the heat directly? Fusion needs a lot plumbing and containment. Fission is just basically a pile of fissile material in proximity. Not very hard if you can skip on all the protection.
            • stefco_ 7y ago
              You still need a heat sink of some sort to extract usable energy from any reactor, nuclear or otherwise; this is a universal property of engines [1]. Radiators are very inefficient for this and would be far heavier than the equivalent water cooling method. Same for air-cooling (especially in mars's thinner atmosphere). The cooling systems are not just there to prevent meltdowns; you need heat to flow, in large quantities, from a hot place to a cool place in order to extract energy. You're right that, if you could find some useful endothermic reaction like vaporizing CO2, you could use it as a heat sink. The problem is that distributing heat to arbitrary places in the martian ground (remember, this CO2 is not magically flowing to you) requires an even more complex heat exchanger than that used by a simple earth-based reactor. Not to mention that having no shielding would be hell for your robots; radiation hardening of automated systems remains non-trivial. But the fundamental thermodynamics strike me as harder. Maybe there are niches where this would make sense, but the thermodynamics is the elephant in the room. [1] https://en.wikipedia.org/wiki/Thermal_efficiency https://en.wikipedia.org/wiki/Thermal_efficiency
  • memorysafety 7y ago
    If you ever heard of "liquid glass", or silica glue -- it's the same kind of material as in airogel, a mix of (hydrated) silicate minerals. The main trick in making aerogel is drying it out, in a way when the liquid doesn't collapse the porous structure by its surface tension. Peeps on youtube usually do this through a "supercritical CO₂" process -- which basically avoids having any liquid surface. That said, manufacturing aerogel on Mars seems way more feasible than transporting it.
• azernik 7y ago
  The full paper proposes using this for literal greenhouses - growing plants only. What matters there is partial pressures of CO2 (actually higher than on Earth), N2, and H2O. So the pressure differential would be relatively low, well within the structural limits of the aerogel as long as there's a sealant between sections. (They also ran tests on aerogel pebbles, but don't talk about sealing questions for that form.) https://www.nature.com/articles/s41550-019-0813-0 https://www.nature.com/articles/s41550-019-0813-0 "The higher carbon dioxide partial pressure on Mars versus Earth is favourable for plant growth, but the low total atmospheric pressure means that at temperatures of 273 K or higher, the undersides of silica aerogel greenhouse shields would need to remain slightly pressurized relative to the atmosphere to avoid loss of water vapour either vertically or laterally. This would place light demands on their structural properties, which could plausibly be met by interspersing the silica aerogel with thin layers of solid transparent material or via organic polymer reinforcement""
  • hyperpallium 7y ago
    I think parent means the layer of sand would block sunlight, thus negating the greenhouse effect.