Talk:Space sunshade

Old talk
For the archived deletion debate for this article see Talk:Sunshade/delete -- Graham &#9786; | Talk 22:17, 17 Jul 2004 (UTC)

How about calling it a solar shade? (c.o. Alpha Centauri, the computer game). It sounds a bit more spacy, and less like a parasol or sunglasses.Bibble 20:08, 12 Jul 2004 (UTC)

insulation vs. insolation
While Venus's atmosphere probably is a better insulator than earth's, isn't the more relevant fact that Venus receives more insolation (incoming solar radiation) than earth? I did not change the page myself because I thought I might have misunderstood the writer's point.

Definition
Shouldn't the article start with a definition ("A sunshade is ...")? HistoryBA 00:46, 16 November 2005 (UTC)

Re Writing
I have re writen most of the article, making more clear what it is and what it does, I have also provided some more information about how it works, as well as a picture.

Title
The present title is rather confusing since most folks would regard a sunshade as being another name for a parasol. I suggest moving the page to Space sunshade as being more descriptive. Bridgeplayer 15:51, 13 May 2007 (UTC)


 * I'd agree with that - to me, a sunshade is something you put inside the car windscreen to stop it getting too hot. Although it would mean creating a disambig from the town, I think there ought to be a redirect from Soletta as well, given that that's the name Kim Stanley Robinson uses, which is where I suspect most people would have come across the concept —  irides cent   (talk to me!)  19:27, 13 May 2007 (UTC)

Sun-Earth L1 Distances
The distances from earth used in this article appear to be incorrect. They place the objects inside the orbit of the moon. The Sun-Earth L1 is about 150,000,000 km according to the Lagrangian_point article. This is my first post to a discussion section, so I hope I got it right. Jason3777 16:35, 19 May 2007 (UTC)


 * Extremely good point - the 24000km in the article is below geostationary orbit let alone the L1 point. Angel's original paper talks about having it at 1.5 Gm (1.5 million km), don't know where the error crept in. Have corrected it —  irides cent   (talk to me!)  16:59, 19 May 2007 (UTC)


 * 150,000,000 km distance to Earth-Sun L1 can't be right because Earth's semi-major axis is 149,598,261 km. According to http://orbitsimulator.com/formulas/LagrangePointFinder.html, ES-L1 is about 1,491,502 km distant from Earth's center of mass.Nydoc1 (talk) 02:13, 12 February 2013 (UTC)Nydoc1

Number of Sunshades required for 2% reduction
The article states that “In theory it would have a diameter of 210 kilometers.” This diameter represents an area of 34,636 sq km. The earth has a radius of 6,378.140 km [Peterson Field Guide₢ - Stars and Planets  p. 534, ISBN 0-395-93431-1] which represents a planar area of 127,802,093 sq km. Even at L1 where I believe the radius required to eclipse the entire earth completely would be 6,316 km, this small of a radius (105 km) would require a lot of Sunshades to reduce the light from the sun by 2%, as shown in the picture. I think the text needs to be updated to make clear that there would need to be many Sunshades of 210 km diameter to produce the 2% reduction in the sun’s light hitting the earth. Jason3777 21:55, 19 May 2007 (UTC)


 * In fact the area to totally eclipse the Earth gets larger, not smaller, the closer you get to the sun -- since, surprise, the sun is somewhat larger. However, you certainly are correct — the radius should be more like 900km for 2% coverage, which is still a whole damn lot of mirrors. smurfix 17:37, 9 August 2007 (UTC)


 * Roger Angel's research paper mentions 100,000 km radius, which is - um - a slight difference. I'll guess the 210km figure is left over from the old Kim Stanley Robinson-style geostationary shade proposal —  irides cent   (talk to me!)  22:32, 19 May 2007 (UTC)

FYI - Sources available
http://en.wikipedia.org/w/index.php?title=Solar_shade&oldid=260927355 The edit after this killed a related article that contained numerous sources that could be used to shore up this piece. Hope this helps, MrZaius  talk  13:16, 27 January 2009 (UTC)

Unrelated External Sources
The one external link is completely unrelated to the topic of the article. That article discusses how launching sulfur particles into the atmosphere in order to mimic volcanic eruptions could cool the Earth, but cause drought. But it's attached to the bottom of this page, which is about a solar shield at L1. I think that external link should be removed, or at least moved to some other article where it is actually relevant. 150.182.161.253 (talk) 22:22, 5 April 2009 (UTC)

Why disperse, when you could block sun with foil?
It would be easier and more effective to use a smaller area of aluminium foil to block large areas of sunlight instead of fraigle lenses.

It would be affected by solar wind, but so would all the billions of lenses, but they only disperse sun.

Fredrik@fotogenisk.se —Preceding unsigned comment added by 95.209.137.71 (talk) 05:49, 27 November 2010 (UTC)


 * Interesting question. Maybe it's a question of mass?  Aluminum foil is around 0.1mm thick, with a density of 2.7g/cm3.  Someone (without citing any sources) asserted on this page that the proposed Fresnel lens would be 2 mm thick with a density of 1g/cm3.  If those figures are accurate, the aluminum would be much lighter.  Maybe it's a question of tensile strength?  Aluminum foil rips very easily.  On the other hand, the cost of manufacturing a precision lens 2mm thick are probably much higher than the cost of manufacturing aluminum foil!


 * Unfortunately, until some scientist or government agent or prominent figure proposes it publicly, we can't discuss this in the body of this article because of the WP:NOR rule. &mdash; Lawrence King ( talk ) 18:15, 27 November 2010 (UTC)


 * Where are we going to get a billion tons of plastic or billions of tons of glass to make this lens? How will we build a country-sized billion-section optical instrument? How will we launch it? Sagittarian Milky Way (talk) 19:21, 15 February 2012 (UTC)

Has any one calculated the cost for a 2mm glass lens thats 1000sq km? Because doing some rough math I priced it at 6.4+e17 USD based on mass of 2500kg per meter3 launching via Falcon heavy to GTO Even with an Orion booster I cannot fathom how he reached 10 billion price — Preceding unsigned comment added by 24.131.103.161 (talk) 17:11, 8 March 2014 (UTC)

This isn't a blog. It isn't a place to offer and discuss proposals. -- Jibal (talk) 21:17, 9 July 2021 (UTC)

Proposal to merge with Space mirror (anti-global warming measure)
This merge proposal makes a great deal of sense.

The current Space sunshade article has three subsections, each describing a different implementation of this general idea.

But before we can do the merge, we need to be sure of two things:
 * Does the current Space mirror (anti-global warming measure) article describe one of the three implementations in the Space sunshade article? Or is it a fourth possible implementation?  Or is it sufficiently vague that it can apply to any of them?
 * Do reliable sources prefer a specific term for this? If there is, we should use that for the title of the article.  If there is not, we should pick the most descriptive and simple term.  I have always been uneasy using the term "sunshade" to refer to "a cloud of small spacecraft near the L1 point", since the term "sunshade" to my mind conveys a single object.  On the other hand, the term "space mirror" seems even more dubious, because not all of these implementations reflect the light:  some absorb light, and others refract it.

What does everyone think? &mdash; Lawrence King ( talk ) 03:59, 26 March 2012 (UTC)


 * It's a fourth implementation as it uses mirrors rather than lenses, the light is reflected back rather than refracted. I'm not sure a merger is a good idea as it risks confusing the reader to discuss mirrors and lenses in the same article - unless it is done very carefully and the difference is explained clearly, if so it might be okay Robert Walker (talk) —Preceding undated comment added 13:54, 26 March 2012 (UTC).


 * Hi - I created Space mirror (anti-global warming measure). I have not responded up to now because I am honestly on the fence about this proposed merger. I created the article after noting persistent hijacking of the Space mirror DAB page, looking up what was referred to, and establishing that it was notable; but I do not have much education in the sciences, so this is the only science article I have started, and I don't feel very competent to judge whether they are in fact the same topic. The issue raised above by Robert Walker had occurred to me, but whereas this article uses scientific and technical sources, I wrote the other article from popular science and journalistic sources, and therefore the distinction may be partly an artefact of the differing terminologies and degrees of sophistication in the exposition. I do know the other article could use updating, and integration of specialist terminology that I'm not equipped to use. But I suspect I'm not a good judge of whether it merits its own article. I've asked friends for insights but not received any useful guidance. It looks as if by default it stays as it is, but I could be persuaded either way. Yngvadottir (talk) 21:05, 14 May 2012 (UTC)

Defunct Source Link
Hey, I was checking out the citations for this page, and I noticed that due to the fact that Nasa Earth Observatory no longer maintains its online Newsroom, the link for citation 7 is not usable. I searched for the article, by date and title, on their archives, which are linked to by the NASA page the link now goes to, but could not find it. If anyone else can provide help in finding this, it would be greatly appreciated. YoungScienceNerd (talk) 18:13, 8 May 2016 (UTC)

External links modified
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The 10 billion estimate of Fresnel lenses is dubious
The source seems to be a blog that doesn't cite any further sources. However, in a newspaper article Gregory Benford states in reply to a sunshield through many small flyers proposal: “This whole L1 idea is neat, but it’s going to cost trillions of dollars, we can’t do it right away, and it gets used to label the entire field of geoengineering as smoke and mirrors.” and continues to propose an aerosol solution (https://www.technologyreview.com/2007/02/13/130428/cooling-the-planet/). — Preceding unsigned comment added by 2003:6:2190:A558:8824:7415:896E:A3F0 (talk) 16:30, 3 December 2020 (UTC)

stub
This article should be considered a stub that only offers a tiny bit of information from a very limited POV. For instance, there is no mention of this NASA-sponsored 2006 paper https://www.pnas.org/content/103/46/17184 that notes "In conclusion, it must be stressed that the value of the space sunshade is its potential to avert dangerous abrupt climate change found to be imminent or in progress. It would make no sense to plan on building and replenishing ever larger space sunshades to counter continuing and increasing use of fossil fuel. The same massive level of technology innovation and financial investment needed for the sunshade could, if also applied to renewable energy, surely yield better and permanent solutions. A number of technologies hold great promise, given appropriate investment (3)." -- Jibal (talk) 21:14, 9 July 2021 (UTC)

Numbers should be consistent
In the same paragraph, we read about 16 trillion disks, a mass of "about a gram", and that the total mass would be 20 million tonnes. These numbers still make sense but the style is questionable - using "about a gram" here to go on quoting a number which implies a mass of 1.25 g per disk.

A more serious issue occurs later on: 20 years contain about 7300 days. Thus, in 20 years with 100 tonnes launched per day, we would have launched 730000 tonnes. And that, according to the text, would be to low earth orbit - we need to get it to L1, and we need 20 million tonnes! Not even accounting for additional structure that might be necessary for deployment. Icek~enwiki (talk) 18:39, 6 November 2021 (UTC)

Starship
Would be interesting to know if studies from the previous years have been redone on the basis of the availability of Starship. Hektor (talk) 18:15, 20 October 2022 (UTC)

Second merge proposal
Housekeeping: just to clarify what the proposal is: "merge Space mirror (climate engineering) into this article." EMsmile (talk) 09:11, 11 August 2023 (UTC)
 * The previous merge proposal (first raised 11 years ago) only appears to have been closed due to complete lack of interest from the editors over 4 years. Since then, both remain stuck with a rather low number of views, and continue to overlap greatly. The only apparent difference (mirror vs. lens, reflection vs. refraction) can be comfortably described within a single article. InformationToKnowledge (talk) 12:57, 16 July 2023 (UTC)
 * Support as per nominator's reasoning. EMsmile (talk) 08:14, 17 July 2023 (UTC)
 * Oppose, as they're completely different things. Redacted II (talk) 13:26, 27 July 2023 (UTC)
 * Are they?
 * Both are space-based interventions that are currently completely theoretical.
 * Both appear to trace their roots to the same physicist named Hermann Oberth, and both articles talk about him at length, with effectively total overlap.
 * In both articles, the bulk of the text is devoted to potentially applying the article's subject for solar geoengineering purposes. This particular article does have a brief and uninformative "Spacecraft sunshades" section which is at odds with the rest of the article, and appears to belong somewhere in spacecraft thermal control. The other article talks about Znamya, but that is also solar geoengineering, just intended for a different purpose (and effectively a footnote of a different era anyway.)
 * In all, the only real differences are on a technical level and not on the intent level. The two articles are describing different ways of achieving the same goal (countering climate change) by doing mostly the same thing - launching a whole lot of objects into orbit/L1 point. While they are split, they are not doing that very effectively, as the more clicks people need to see information, the less likely they are to actually do it, and pageview stats back this up. A merge would only help more people see the contents. InformationToKnowledge (talk) 14:06, 31 July 2023 (UTC)
 * "real differences are on a technical level"
 * Exactly! There are major differences in the design. It's like saying Staged Combustion and Pressure Fed are the same thing (same intent: to push fuel and oxidizer into the combustion chamber, but different means of achieving that goal).
 * Also, the # of page views is similar to some very important articles. Several of the articles I tend to check on get significantly less.
 * And, the intent is very different. Space Mirrors are designed solely for reducing sunlight hitting earth, while Space Sunshade is in regards to any object particularly spacecraft) Redacted II (talk) 14:52, 31 July 2023 (UTC)
 * If the same title can conceivably cover things as different as a continent-sized lens and a person-sized heat shield, then all it shows is that the article has a poorly defined scope, which is all the more reason for merging some of its content and splitting away the rest.
 * And bringing up a low-quality article with three citations is...not a winning argument. Pressure-fed engine is almost exactly the kind of article we would want to see less of.
 * "Similar to", "very important" and "significantly less" are all vague to the point of uselessness. InformationToKnowledge (talk) 15:16, 31 July 2023 (UTC)
 * I didn't check Pressure-fed engine before mentioning it. But my point was that the proposed merge would be similar to merging Pressure-fed engine with Staged Combustion. Both are of similar intent, but have differences that require separate articles.
 * While the quality of the Space Sunshade article is poor, that isn't necessarily cause to merge it with a different article. Instead, try to improve this one first. Redacted II (talk) 15:25, 31 July 2023 (UTC)
 * Support as the technology of large space mirrors is not developed enough to merit separate articles Chidgk1 (talk) 19:48, 6 August 2023 (UTC)

Relevant material
The solar shield concept: Current status and future possibilities (Science Direct). Mooonswimmer 03:17, 13 February 2024 (UTC)