9 votes

A program to reduce Earth's heat capture by injecting aerosols into the atmosphere from high-altitude aircraft is possible, but unreasonably costly with current technology.

8 comments

  1. [8]
    spctrvl
    Link
    Oddly, the article made that claim, but then never went on to support it. Apparently the problem is that you'd need to have custom built planes to fly at the appropriate altitudes for the...

    Oddly, the article made that claim, but then never went on to support it. Apparently the problem is that you'd need to have custom built planes to fly at the appropriate altitudes for the appropriate durations, but the development costs aren't estimated to be particularly staggering. Per the article:

    The team estimated the total development costs at less than $2 billion for the airframe, and a further $350 million for modifying existing low-bypass engines.

    Although, with an estimated per-year cost of $2Bn for the program, it might be better to build a solar shade out in L1 for about $10-20Bn, which has the advantage of being easy to shut down should the reduced sunlight have unforeseen climatic side effects.

    2 votes
    1. [7]
      Neverland
      Link Parent
      I am a fan of the solar shade. May I ask where you got the cost from? When I calculated the mass required from earth to L1 my cost got much higher, using falcon heavy.

      I am a fan of the solar shade. May I ask where you got the cost from? When I calculated the mass required from earth to L1 my cost got much higher, using falcon heavy.

      2 votes
      1. [6]
        spctrvl
        Link Parent
        That was the figure given by Gregory Benford for his proposed giant Fresnel lens. But one of the citation links is dead and the other is just a repetition of the idea, so his analysis can't really...

        That was the figure given by Gregory Benford for his proposed giant Fresnel lens. But one of the citation links is dead and the other is just a repetition of the idea, so his analysis can't really be fact checked. Which is pretty unfortunate, since a lot of older space project proposals made some big assumptions regarding the shuttle's future launch costs and having an industrial base in space.

        What's your projected cost and mass?

        1 vote
        1. [5]
          Amarok
          Link Parent
          Given reusable rockets are a reality now, I'd expect that to revise any past launch costs downward, and possibly quite a bit. It makes me batty that more people aren't talking about the solar...

          Given reusable rockets are a reality now, I'd expect that to revise any past launch costs downward, and possibly quite a bit. It makes me batty that more people aren't talking about the solar shade. It's still the best solution I've seen. I am curious though how we 'shut it down' easily. Most of the models I've seen are based on a dust cloud doing the shading, and that seems like it'd be challenging to clear out of L1 in a hurry if we changed our minds - or miscalculated and put too much shade material up there. Maybe we could park a big ass nuke in the middle of the cloud, and just remotely detonate it if we wanted to disperse the material?

          2 votes
          1. [4]
            spctrvl
            Link Parent
            The model I'm talking about is a single large lens to dissapate light.

            The model I'm talking about is a single large lens to dissapate light.

            1. [3]
              Amarok
              Link Parent
              Isn't building a 'structure' of any kind there a lot more expensive than just creating a cloud of sand/dust? I mean, it'd be ideal to actually have a long-term mechanism there rather than a cloud,...

              Isn't building a 'structure' of any kind there a lot more expensive than just creating a cloud of sand/dust? I mean, it'd be ideal to actually have a long-term mechanism there rather than a cloud, but I thought that was a major factor in the cost. Granted most of the stuff I've read on this is rather old (90s).

              2 votes
              1. [2]
                spctrvl
                Link Parent
                The model I'm talking about is the one linked in the earlier comment, a single large fresnel lens. Benford claims that it should be possible to build it for around $10Bn, but the Wikipedia...

                The model I'm talking about is the one linked in the earlier comment, a single large fresnel lens. Benford claims that it should be possible to build it for around $10Bn, but the Wikipedia citation doesn't link to an in depth analysis and I've yet to be able to find one.

                1. Amarok
                  (edited )
                  Link Parent
                  I just spent a couple hours digging into all of it again. Last couple of years have seen quite a renewal of interest in the topic, but actual scientific papers are hard as hell to find - I can't...

                  I just spent a couple hours digging into all of it again. Last couple of years have seen quite a renewal of interest in the topic, but actual scientific papers are hard as hell to find - I can't find anything like a concrete launch cost for the various models myself, but most papers seem to be in agreement it's going to run in the low single digit trillions range, and that rockets, even reusable ones, are not a feasible way to get that much material up there. It's mass drivers or orbital rings or we're not going there. Rings have an almost infinite array of other benefits, but given how long they take to build I doubt we have that luxury.

                  Trillions we can afford - it's still just one Iraq War Unit, and I am done listening to people bitch about the 'costs' of things that make the world better - if it's one Iraq War Unit or less, we do it, and government/industry/markets can shut the fuck up and deal with it.

                  It's the scale that's the issue. This project would employ a significant chunk of the human race for decades, and we've never done any projects on this scale before. The logistics might be harder than the costs. :P

                  This seems to be the most modern, well-thought out proposal for a solar shade, and it's one from 2015 I've never seen before, trading the single large lens for a system of two smaller lenses that offers some interesting advantages (and cost reductions) over the single large lens.

                  The version I remember reading was the dust cloud variant. It's a lot cheaper than the cloud of spaceships model. It turns out that L1 is a bitch to maintain year-over-year, so dust is better than tons of small spacecraft - why bother making them into spacecraft when they are just going to get pushed out anyway? We're going to be firing replacements up there every week for centuries, may as well just use the dust.

                  That's also why the single and dual lens models are better - the large lenses are the only way to easily maintain an L1 orbit over long periods of time. You can't apply thrust effectively on millions of tiny spacecraft but you can apply thrust with great efficiency on a large lens.

                  So, call it $5 trillion at the outside and between one and two decades of steady work to get our lenses up there, and then a cost of a quarter billion or so to maintain it every single year of it's lifespan. That's the ballpark, far as I can tell.

                  Still costs less than moving New York City to a new not-underwater location... and that's just one city, most of them will end up underwater if the climate keeps going this way. It's a cheap solution in the context of the expense of the problem.

                  Edit: This sounds like a great project to use to develop our robotic manufacturing economy. Those trillions could be used to advance a host of technologies we can use for other purposes, so it's not a waste, it's an opportunity.

                  Edit2: This Dyson Dots paper paints a rosier picture - only blocking a quarter of one percent of sunlight (because that's all we need to buy time) using a solar sail array about the size of Texas, which is a lot smaller than the proposed lens solutions. It has an incremental implementation plan that's much less difficult. They even claim to know how to make it self-sustainable and provide us with a ton of solar energy back here on Earth - though how they plan to get those ten terawatts of power back here safely is a mystery. Since it's behind a paywall, I can't get all the details. From the abstract, though, this does sound like the least expensive/most profitable/most feasible proposal out there.