22 ms·
> If each Starship manages 300 flights per year, each carrying 150 T of cargo, then we are talking a yearly incremental cargo capacity growth of 22 million tonn
by avmich 7y ago
> If each Starship manages 300 flights per year, each carrying 150 T of cargo, then we are talking a yearly incremental cargo capacity growth of 22 million tonnes to orbit.
https://en.wikipedia.org/wiki/Space_sunshade https://en.wikipedia.org/wiki/Space_sunshade
> One proposed sunshade would be composed of 16 trillion small disks at the Sun-Earth L1 Lagrangian point, 1.5 million kilometers above Earth. Each disk is proposed to have a 0.6-meter diameter and a thickness of about 5 micrometers. The mass of each disk would be about a gram, adding up to a total of almost 20 million tonnes.[3] Such a group of small sunshades that blocks 2% of the sunlight, deflecting it off into space, would be enough to halt global warming, giving us ample time to cut our emissions back on earth.
- deleted 7y ago[deleted]
- 7777fps 7y agoAnd if that works, and we restore a more normal cycle, how do we avert the next ice-age with all that space junk?
- xur17 7y agoWe remove it?
- _ph_ 7y agoIf it isn't automatic the case, the material for the discs could be designed such that it dissolves in the normal solar radiation after a decade or so.
- beerandt 7y agoCan't dissolve without a solvent.
- avmich 7y agoDo you know what happened to USA flags which astronauts installed on the Moon?
- beerandt 7y agoI don't- but if it "disappeared" it would likely be disintegration and dispersal, or possibly sublimation. But it certainly didn't dissolve.
- _ph_ 7y agoSorry, that is nonsense. You are over-interpreting a term. Put a plastic bag into the sun for some months and it will break into tiny pieces on the slightest touch. The radiation outside the earth atmosphere is way more dissolving than the sun shine on the ground. So a material could be chosen so that it desintegrates, if you don't like the term "dissolve", in a certain timespan in space. Actually, it will be a challenge to make sure that those disks hold up long enough.
- beerandt 7y agoSorry, I thought we were having a science based discussion where words have meanings... We're talking about retrieval difficulty in a worst case scenario. Even if it disintegrates, you've left a cloud of particulate matter that's going to create even more unintended consequences and is more difficult to collect / move / mitigate.
- _ph_ 7y agoI think it was plenty clear what I was trying to say. I am not a native English speaker, but in German, the term "auflösen" literally means to dissolve in a solution, yet, no one would have misunderstood it in the context of space. For most people it is quite obvious, there is no solvant in space. So if you feel the need to correct my use language, please do it in a constructive manner.
- wolfram74 7y agoLots of objects in space are designed using origami, so if we have a motor or little piezo-electric strip to apply tension, we could reverse the folding process and have them go from max size to minimum size on signal.
- GuB-42 7y agoL1 is unstable, and the disks will be pushed away by the solar wind, so I suppose theses disks will disperse eventually.
- beerandt 7y agoI think some amount of clumping might be expected before dispersal, depending on material properties.
- eloff 7y agoThat's got to be the cheapest solution to global warming I've heard of. I wonder what problems there are with it. The nice thing about it is if things start getting chilly (as we move into another glacial period one day) we can simply remove some of the shades again. The increased CO2 means more vegetation growth, which is nice. The only real problem at that point is ocean acidification, which I think won't be reversed by cooling things down again. I wonder if we will one day regulate our climate on earth by shading hot areas and pointing mirrors at cold ones. There are all kinds of knock on effects of doing that, but it seems like a human thing to do. Modify the environment instead of adapting to it. That's kind of our thing.
- ansible 7y ago> The only real problem at that point is ocean acidification, which I think won't be reversed by cooling things down again. From what I understand, it will help... eventually. If ambient temperatures come back to normal, then the ocean won't absorb as much CO2.
- eloff 7y agoYes, I think so. I wonder by how much.
- beerandt 7y agoThe bigger issue is the large amount of co2 that the ocean will quickly release back into the atmosphere as temperature and partial-pressure drop. It would be better if we could come up with a way to neutralize / sequester the co2 already in the ocean.
- DuskStar 7y agoThat's Project Vesta: https://projectvesta.org/ https://projectvesta.org/ Basically, artificial green-sand beaches which absorb CO2 as they weather.
- cptskippy 7y agoSo our solution to polluting our planet is to pollute the space around our planet as well? What happens when those space shades get hit by micro meteorites causing them to alter or de orbit?
- willis936 7y agoA sunshade seems like a horrible idea. There are obvious implications from the increased motivation to use fossil fuels. Biodiversity will continue to plummet until there is an ecological collapse. The people with the keys to enable or disable the shade will be influenced by short term profit. Then once fossil fuels are gone there will be a giant energy crisis. Buying time is good only if that time is properly paid for. And there is the risk of unintended consequences. https://en.wikipedia.org/wiki/Unintended_consequences https://en.wikipedia.org/wiki/Unintended_consequences
- Dumblydorr 7y agoEven if we stopped fossil far faster than the most optimistic estimates, sunshade is still a great idea. There is a ridiculous amount of upside to not burying 250 M people in water by 2100. Further, have you thought about how we get off fossil for steel, concrete, plastics, hell even natural gas power plants? Climate change is the most important issue right now and even so, we are undeniably a fossil society. We need everything we can muster, and sunshade should be part of our tool kit to help the transition.
- thatcherc 7y ago> have you thought about how we get off fossil for steel, concrete, plastics, hell even natural gas power plants? Lots of people are thinking about these questions! Still early research phase, but the chemistry works out. Steel -https://www.technologyreview.com/s/611961/this-mit-spinout-could-finally-clean-up-steel-one-of-the-globes-biggest-climate-polluters/ https://www.technologyreview.com/s/611961/this-mit-spinout-c... Concrete - http://news.mit.edu/2019/carbon-dioxide-emissions-free-cement-0916 http://news.mit.edu/2019/carbon-dioxide-emissions-free-cemen... Plastics - no carbon emitted as long as you don't burn your plastics. Could also capture emissions from a plastic incinerator if you really want to burn trash Natural gas power plants - replace with solar/wind + batteries?
- willis936 7y agoIf we had an order of magnitude more electrical power and no greenhouse emissions from it we could do quite a lot. Desalination is a really big one. Chemical batteries won’t get us there, but pumped storage is an interesting avenue. I personally am a fan of fusion. The numbers check out with first gen power plants costing about 50% more per energy unit than fission/fossil.
- madaxe_again 7y agoThis reminded me of Kim Stanley Robinson’s Mars trilogy - an awful lot of it is about the technical processes and political issues presented by terraforming, and one of the techniques explored is the use of giant space-borne mirrors, both for shading and increased insolation, depending on the target body.
- gbrown 7y agoWouldn't solar radiation pressure blow them all over the place?
- raducu 7y agoThere would be a "unnatural" orbit where solar radiation pressure would cancel the mismatched orbit, I think. So the shades would stay in equilibrium in a bit higher solar orbit than their velocity would permit without the light pressure.
- gbrown 7y agoI'm having trouble visualizing how this would be stable - from their reference frame (orbiting a Lagrange point), the pressure is coming unidirectionally. They'd be accelerated in one direction constantly, which seems like it couldn't possibly be stable.
- raducu 7y agoActually, you are right, I was talking as if the shades are just orbiting the Sun. L1 orbits do require station keeping. Perhaps you could cheat a bit by making the shades black or oscilating/slanting them a bit forward/rearwards as to do the station keeping with very little fuel? Or shaping them like a lense to direct most light away from Earth, but not to experience too much net force? Or they are just designed to be expendable?
- gpm 7y agoFor what it's worth, Wikipedia suggests making them shaped like a lens.
- jagger27 7y agoYes. They need serious stationkeeping.
- CydeWeys 7y ago
- beerandt 7y agoUnintended consequences are a bitch. How can people smart enough to "design" these types of projects be so arrogant? Even removing the co2 that we've added to the atmosphere and sequestering it may not be free of negative consequences. That is the magnitude of uncertainty we need to be discussing and debating. At this point, blocking the sun is just crazy, and not because of feasibility, constructibility, or cost. Edit: Look at the disaster of updating the Washington DC water system for a supposed "fully understood" lead mitigation project that went unbelievably wrong, because of bad assumptions and factors not initially considered to relevant (unknown unknowns). And there was no controversy over such a conservative "fix" (other than maybe cost given necessity). https://en.m.wikipedia.org/wiki/Lead_contamination_in_Washington,_D.C._drinking_water https://en.m.wikipedia.org/wiki/Lead_contamination_in_Washin...
- hoorayimhelping 7y agoA sunshade is not just a temporary band aid for global warming. It will likely be a necessary addition to our planet to manage the heat we will continue generating. Our energy consumption and production continues increasing as society keeps advancing, and it will continue to do so as we unlock more diverse ways of harvesting and storing energy and using it. A mark of a technological civilization is the conversion of starlight into heat energy - the civilization converts the energy from the star into useful work which produces heat. The heat has to go somewhere. Up until now, it's been fine just letting earth manage it (but we're obviously running into the limits of that with global warming), but as we start approaching planetary levels of energy consumption, we're going to start producing planetary levels of heat, and we're going to need to do something about it. The simplest and most straightforward way is by putting sunshades into orbit to limit the amount of sunlight that comes in to cool the planet. This works especially well if the sunshades are solar panes that can collect energy while they shield heat. It's attractive because it doesn't involve changing delicately balanced atmospheric composition, and they can be moved or rotated to adjust the amount of light coming in on demand.
- raducu 7y agoBut I think our energy consumption is miniscule on the scale of energy received from the Sun. I did the math once, and a square of 300x300km of solar panels in the Sahara would cover all the world electricity demands. The issue is with green house gases, cutting forests which alter the way Earth handles Sun's light, not out actual heat output which is minuscule compared to the heat of planet Earth.
- servercobra 7y agoI believe Elon came up with similar figures during his Powerwall presentation, along with how small of an area it would be to provide the batteries to complement the solar panels.
- UnFleshedOne 7y ago"300x300km of solar panels should be enough for everybody" Joking aside, much like with memory, bandwidth and storage, we'll invent ways to use (all of the) energy if it is cheap enough.
- DennisP 7y agoAt $35/kg, that would cost about $750 billion. More than Musk could do on his own anytime soon, but definitely feasible as a global effort. Each pound of methane would produce 2.75 pounds of CO2: https://www.engineeringtoolbox.com/co2-emission-fuels-d_1085.html https://www.engineeringtoolbox.com/co2-emission-fuels-d_1085... And each launch burns 240 tonnes of methane (launch mass minus rocket mass is 1200 but that's 4/5 oxygen): https://en.wikipedia.org/wiki/SpaceX_Starship https://en.wikipedia.org/wiki/SpaceX_Starship So that's 660 tonnes CO2 per launch times about 150,000 launches, or about a hundred megatons CO2. Given that we're emitting 36GT annually, that seems a good trade. That's just launch to LEO, we need extra delta-v to L1, but potentially that could be from a fleet of solar-powered ion drive tugs. My quick google didn't turn up Starship payload capacity to L1. If the shades can be manufactured on the moon from local materials, potentially this could be a lot cheaper, with almost zero emissions. It'd take longer to get started, but it'll take a long time before people agree on something like this anyway; if we're setting up lunar manufacturing anyway, this would be something to keep in mind.
- kijin 7y agoIf we could somehow capture the methane that's escaping from the clathrates under the sea and in the permafrost, it would be a net gain in terms of global warming to burn it up in a rocket engine and convert it to CO2. Methane has much more than 2.75 times the warming potential as the same mass of CO2.
- wang_li 7y ago16 trillion small, unsteerable, solar sails all sitting at the boundary between the Sun and Earth's gravitational influence. As light pressure pushes these things out of the L1 point they will all make their way to the Earth where they will enter the atmosphere and give up their gravitational potential as heat. Does their shading effect counter the fact that they will all give back some heat?
- pas 7y agoThe potential energy is close to the energy used during launch. And every time we launch a rocket/sat (and then it comes back eventually) we heat up the atmosphere a bit.
- beerandt 7y agoThe potential energy due to gravity is separate from the potential energy due to embedded chemical energy, which I suspect would be bigger for such a shape, given drag. (Since energy is proportional to velocity-squared.)
- markwkw 7y agoHow would one prevent the cloud of sunshades from clumping together due to gravitation? The effect on a single disk on the outskirt of the cloud should be equivalent to the attraction of a 16 million ton mass at the center of mass of the cloud. Would we need to spin the cloud? (perhaps forming a galaxy-like shape)
- DennisP 7y agoThe wiki page says they would need some stationkeeping, probably using small solar sails.
- gpm 7y agoThey'll need station keeping anyways [0], but is 16 million tons actually enough to create substantial gravitational force? Looks like the circle would be approximately 1100 kilometers in radius (per wikipedia), according to this random calculator [1] 20 million tons at 1100 km creates a force of 0.000000000001103 N/kg. I don't think gravity is likely to be the biggest problem. [0] Solar wind will push them, the lagrange point they would sit as is actually a "point" and anywhere nearby you slowly drift out of it [1] https://www.omnicalculator.com/physics/gravitational-force https://www.omnicalculator.com/physics/gravitational-force
- aeturnum 7y agoWouldn't this be basically the "scarring the sky" thing that the matrix used as a symbol of a desperate, foolish attempt to avoid the consequences for our mistakes? lol
- tomphoolery 7y agoThe idea of exploring and possibly colonizing other worlds has nothing to do with our ecology and everything to do with the fact that a comet could hit earth and destroy our entire species at any moment and we wouldn't really have enough time to react properly. Add planets to your species and you reduce the chances that your entire civilization could be gone in an instance.
- beerandt 7y agoThey both require certain degrees of geo-engineering, even if the scopes are entirely different. I find it amusing that people who think 2-4 degrees over decades is an insurmountable problem, but creating an entire hospitable atmosphere on another planet is doable.
- anovikov 7y agoBut it will consume several percents of world's total energy supply, in fuel. That is, burn more fuel than airlines do. Clearly not possible. Even 1/10 as much (which is still the scale of Berlin airlift) is problematic.
- Tuxer 7y agoFor what it's worth, there is a BIG difference between 22 million tons to orbit (LEO), and the Sun-Earth L1 point, in terms of delta-v.
- darzu 7y agoThis delta-v map suggests roughly 2x vs. LEO: https://www.reddit.com/r/space/comments/1ktjfi/deltav_map_of_the_solar_system/ https://www.reddit.com/r/space/comments/1ktjfi/deltav_map_of... Although it might be significantly easier with gravity assists.
- AtlasBarfed 7y agoGreat! Reduce plant growth and carbon sequestration by 2%! Reduce solar yield by 2% Then put up another shield. Drop yields more. Put up another shield. Wasteland.
- simonh 7y agoThe reflight turnaround time is off. SpaceX are aiming to turn around a vehicle from landing to launch readiness in 24 hours as a best case lower limit. It does not include payload integration. This also does not include the time it takes to wait for the launch window, launch, deploy a payload, de-orbit and land. Thats likely to be at least 24 hours, and often more. If operating beyond LEO a lot more. In practice I’d be surprised if the real cargo delivery rate was as much as a fifth of this. It’s still a staggering amount though.
- TearsInTheRain 7y agoWouldn't increasing cloud cover be the same solution and just like way easier?
- chipsa 7y agoSunshades are more persistent. The cloud I make will disappear after not very long, so I'd need to make more.
- pedalpete 7y agoI don't know much about sunshades, but it looks like the wikipedia article assumes the sunshade would block/filter light across the entire planet. Couldn't we have a significant effect by blocking a small percentage of light during the summer months toward the poles? If we can keep the poles cooler, we could increase the ice cap, reduce melt, and affect only a small number of living creatures. My initial searches have turned up nothing related to this, and I'm a total novice, so just asking the question.
- spiralx 7y ago> If we can keep the poles cooler, we could increase the ice cap, reduce melt, and affect only a small number of living creatures. And more ice means a higher albedo, so more sunlight is reflected back into space. But I see the challenges of partial blocking as a lot higher than in the general case - you need to keep two hemispheres in place and synchronise them with the tilt of the planet as it orbits the sun.
- namirez 7y agoDo you know the cost of putting only 1kg at the Sun-Earth L1 point? To give you an idea, the cost of putting a satellite in the geosynchronous orbit is about $30k/kg, and the geosynchronous orbit is only 36,000 km away. But let's assume somehow miraculously we find a way to put objects at L1 as cheaply as the geosynchronous orbit. Your proposal would still cost $66 trillion. That's roughly the entire world's gdp. Do you really think this is going to be cheaper than reducing carbon emission?