7 ms·

Can we discuss space sunshades? Assuming the cost of getting freight to orbit goes down substantially as companies like SpaceX ramp up launches, what's the limi

• kanzure 8y ago
  My personal preference is an inflatable sun shield method like these 10,000 kilometer-wide objects: "Self-deployed, extremely large low mass space structures" http://diyhpl.us/~bryan/papers2/space/Self-deployed%20extremely%20large%20low%20mass%20space%20structures%20-%202007.pdf http://diyhpl.us/~bryan/papers2/space/Self-deployed%20extrem... I don't think people realize how a lot of these problems are solvable for only a few billion dollars... It's an engineering problem, mainly. Someone just spends the money and goes and fixes the problem.
  • jpfed 8y ago
    That's one great thing about sunshades- they can be implemented by just convincing a spacefaring billionaire or two instead of having to change policy / steer nation-states.
    • ryandrake 8y ago
      Unfortunately, you still need to convince the billionaire that the project will make him into a 10-billionaire, otherwise he’ll just keep it in the bank, or bathe in it or whatever rich people do with all the vast piles of money they are sitting on.
      • makerofspoons 8y ago
        Perhaps there's the chance that they're interested in their legacy being saving the human race. There will probably be statues of them, schools named after them, and who knows what else if the plan succeeded.
  • throwaway5752 8y ago
    How would this affect plant life and agriculture?
    • zspade 8y ago
      Since this would be over the poles, agriculture would not be impacted. There would likely be a substantial impact to ecology of these regions, depending on size of the shade of course.
  • ergothus 8y ago
    I'm skeptical - You've shown a proposal, not a reality. (and the proposal didn't even mention a "shield" that I saw, but I may have skimmed past it). I didn't see a price tag, nor a timeline. Money can boost research speed, but not remove the need entirely. Second, If the cross section of the earth is 1.2x10^14 m^2, one of these would...well, we don't know, because the link mentioned volumes and length (the 10k km is a potential "span length" and wasn't tied to being "one" of anything). I failed to find the cargo volume for a Falcon 9 or other rocket (everything is in mass) but I think it's safe to say that you're talking a lot of launches which clearly aren't trivial to do. Third, and most importantly, you've just decreased the amount of energy coming to earth. You've not solved the problem, you've changed it. I love tech, but I think it's worth noticing the ratio of times someone says "It's [just] an engineering problem" versus the number of issues that have been actually been solved in this way (seeing the problem, spending a boatload of money, seeing problem solved). Most of our industries are based on the fact that we KNOW they can grow into more, but figuring out how and the complications thereof are literally the work of countless lifetimes.
    • Tuna-Fish 8y ago
      > Third, and most importantly, you've just decreased the amount of energy coming to earth. You've not solved the problem, you've changed it. Probably the most important advantage sunshades have over other kinds of geoengineering megaprojects is that they can be trivially (compared to their construction costs, that is...) turned off. If they turn out to be very harmful in some previously unforeseen way, we can choose to not have them anymore. That is not so for, for example, seeding lots of nutrients for algae over the continental shelf.
      • philipkglass 8y ago
        As others have noted, solar radiation management doesn't do anything to counteract ocean acidification. I still think that SRM of some sort may be necessary to stop runaway feedback loops like loss of soil carbon from thawing permafrost. The sunshade approach to SRM looks like it may have been devised like other big speculative space projects: "start by assuming that big projects in space are the solution, then find a problem to motivate that solution." (See also: mining helium 3 from the Moon.) Solar radiation management with reflective aerosols instead of space sunshades looks simpler and easier to me. Most importantly, SRM based on aerosols is incrementally scalable from small low initial investment/scope. The sunshade approach, like many envisioned large space projects, appears to require large "lumpy" investments before delivering any detectable benefit.
  • sandworm101 8y ago
    >> for only a few billion dollars. Really? This isn't just a matter of putting a big ball of tin foil out there letting it go. What about the station keeping? How is this big piece of tinfoil going to stay in place? At these sizes, solar pressure and the buildup of static charges become huge issues. It is going to drift. It will need engines, power and fuel. Ion thrust would seem an obvious answer, but electrical/static issues may make a web of ion drives difficult. It will need either new tech or, at least, extensive testing of current tech before any attempt. = a great many billions of dollars. I'd rather see that money spent on solar panels.
• natosaichek 8y ago
  Anything you can do in space would be cheaper on earth. So rather than shading the pole by spreading ~100,000 sq. km of material in orbit, instead ask why we wouldn't spread the same shade cloth / reflective mylar etc. on the surface of the earth. Then you realize how much of a colossal project it is and how completely impractical is is.
  • alkonaut 8y ago
    The easiest surfaces to make more reflecting should be the oceans. Some proposed carbon capture methods involve algae. Maybe algae could be synthesized that are white/reflective as well as capture carbon? Patches of algae can be huge without the need for any construction.
  • throwaway5752 8y ago
    Earth is a closed system, so the shade cloth on Earth would simply warm up and reradiate the absorbed energy as infrared. Reflective mylar would see a portion of the reflected sunlight (which would have warmed the atmosphere upon entry) trapped by the greenhouse effect.
    • wallace_f 8y ago
      This is not necessarily true as demonstrated by Steven Chu's 'Paint the Earth White' campaign.
    • coltonv 8y ago
      Earth is is not even close to a closed system. There's a giant thermonuclear explosion factory in space that pumps insane amounts of energy into our system. If earth was a closed system it could not harbor life as entropy increased.
      • deleted 8y ago
        [deleted]
  • kiba 8y ago
    That's why you set up orbital infrastructure so that you don't have to bring up everything from Earth and can just mine stuff in space.
• pasbesoin 8y ago
  Sunshades don't address other attendant issues stemming from increased CO2, such as ocean acidification. The ocean biosphere wholesale is threatened by acidification. (Among other things, bio-carbonate generation and stability are undermined. And thus, the entire food chain above organisms that depend upon this.)
• Retric 8y ago
  Because the earth is effectively a black body it cools down at T in kelvin^4. This means you need to block a huge amount of energy ~2% of the sun to get around global warming. Sticking something at L1 looks elegant, but you cant just toss junk there it needs serious station keeping making it far more expensive than many assume. PS: Unfortunately, as a side effect you reduce the energy of all plant life by ~2% solar panels would also be effected. While this is probably no where near as bad as global warming it is something to look into.
  • Symmetry 8y ago
    The launch volume looks infeasibly large in the foreseeable future, but I don't think the station keeping problem is that bad. Any sun shade is basically going to be a solar sail already and steering via LCD panels like IKAROS did should be sufficient. https://en.wikipedia.org/wiki/IKAROS https://en.wikipedia.org/wiki/IKAROS
    • Retric 8y ago
      The problem is you now need some actual structure rather than just some thin sheets / inflatable structure or whatever. Further applying even small amounts of force across huge sheets adds up while as you say it's acting like a solar sail. That is to say it's clearly still possible, just not as cheap as people are assuming.
      • Symmetry 8y ago
        IKAROS handled that by spinning very slowly to remain rigid with centrifugal force. To be practical you really can't have one single structure but a swarm of medium sized shades would work much better.
        • Retric 8y ago
          If by medium size your thinking ~1km^2 then sure. But, much smaller than that you you start talking about billions of these things. Keeping them properly aligned and not shading each other would be a non trivial challenge.
• mrec 8y ago
  How would you keep a sunshade over one pole? Keeping anything over a single spot requires a geostationary orbit, which by definition is only possible on the equator. I suppose you could have a bunch of shades in a geosynchronous polar orbit, but I suspect they'd still be more effective over the equator, just because it gets more sunlight.
  • emiliobumachar 8y ago
    Seconded. It would just fall down.
  • T-A 8y ago
    https://en.wikipedia.org/wiki/Statite https://en.wikipedia.org/wiki/Statite
    • mrec 8y ago
      Interesting; I'd seen this before but forgotten about it. Don't think it works here though - if the pressure of reflected sunlight is counteracting gravity, then I don't see how the statite can be acting as a sunshade. If it were in position for that, the sunlight would be pushing it toward the Earth, no? If anything this sounds more like the reflectors often proposed for Martian terraforming, which are designed to heat the planet rather than cool it.
      • T-A 8y ago
        A very different mode of Statite system operation is possible that would allow the Statite to be placed at any point around the Earth, at all times of the year, even over the sunlit side, at the expense of slightly greater operating distance. Instead of the Statite being balanced by sunlight in the gravitational field of the Earth, the Statite would be placed in orbit around the Sun, at such a distance from the earth that the gravitational field of the Earth plus the moon is only a perturbation on the gravitational field of the Sun. [1] But in practice, I think you're right. Forward wrote a short story about such a "pole sitter" ("Race to the Pole"), and had one of the characters say this: The control problem of keeping the [statite] balanced over the pole is very tricky, especially during the summer season of that hemisphere when the polar axis is over on the sunlit side of the Earth. That’s why ‘pole-sitters’ have to be placed so far away from the Earth. If they get any closer than 250 Earth radii, they become unstable during the summer. [2] [1] https://patents.google.com/patent/US5183225A/en https://patents.google.com/patent/US5183225A/en [2] https://www.centauri-dreams.org/2010/07/29/statites-hovering-over-the-pole/ https://www.centauri-dreams.org/2010/07/29/statites-hovering...
• jimison 8y ago
  That falls under a number of strategies for Solar Radiation Management [https://en.wikipedia.org/wiki/Solar_radiation_management https://en.wikipedia.org/wiki/Solar_radiation_management], which, as you say, doesn't address the core CO2 concentration problem, but it might buy us time. Personally, I like the idea of Marine Cloud Brightening. Getting 1 or 2 thousand ships spraying seawater into the air seems tractable, if not trivial.
• afterburner 8y ago
  ...Mr. Burns?
• tribune 8y ago
  Wouldn't sun shades blocking any amount of sunlight have a negative effect on agriculture and endanger the food supply?
• LinuxBender 8y ago
  What impact would sun-shades have on agriculture?
• lchengify 8y ago
  I think Nathan Myhrvold [1] proposed something like this. There's a summary of it on one of the Freakonomics podcasts, but the summary is basically that it acts like an erupting volcano to cool the earth slightly. "MYHRVOLD: So, climate change is a 1-percent effect. Now all we have to do is make the sun 1 percent dimmer. Now I don’t literally mean changing the sun. But there are a variety of things that bounce sunlight back into space. Clouds are one of those things: white clouds bounce white light back up into space. It turns out that volcanoes throw ash and particles, if it’s a big volcano, very high in the atmosphere. That reflects some of that light. And in fact this happened in 1991 when Mount Pinatubo went off. It cooled worldwide temperatures by a degree, degree-and-a-half-Fahrenheit for 12 to 18 months. Well, my company has come up with some very practical and cost-effective ways of deliberately putting particles into the upper atmosphere. And on paper, it works out that you could nullify all of global warming that way." [2] [1] http://www.nathanmyhrvold.com/ http://www.nathanmyhrvold.com/ [2] http://freakonomics.com/podcast/save-the-planet/ http://freakonomics.com/podcast/save-the-planet/
  • beambot 8y ago
    "My company" referring to Intellectual Ventures, which has such an illustrious reputation with patents?
• aoner 8y ago
  I think geo-engineering will open Pandora's box. On one hand, we need to invest in geo-engineering as a last resort, on the other hand, if people see this as the last resort the problem of CO2 will seem less urgent. Very dangerous stuff.
  • Dumblydorr 8y ago
    People already don’t care about carbon emissions. Those on the right think it’s a hoax or humans aren’t causing climate change, those on the left largely pay lip service, but still do very little.