Dyson Dots: Changing the solar constant to a variable with photovoltaic lightsails
Highlights
► Maunder Minimum, ∼1580–1850, cut solar output ∼0.25%, avg Euro temp by −1.5 C. ► Same mag, but opposite sign, as global warming forecast in IPCC's 3rd Report. ► Giant “Dyson Dot” parasol in light-levitated orbit inside L1 can shade Earth 0.25%. ► Covered w/PV it can generate 10+ TW, more than global electricity demand by 2050. ► Geoengineering costs less than climate damage+new grid; bootstraps spacefaring civ.
Introduction
Water means life, and we live on a water world. Ultimately, climate change is about water also: too much water where it is not supposed to be or when; not enough water where or when it is supposed to be; plus drying soils, changing habitats and ocean currents, and rising sea levels over the next century. Warm air holds much more water than cool air, and when it is released, weather events tend to be much more violent and concentrated toward the extreme ends of the probability distribution. Agricultural practices and our few staple crops (not to mention the wider ecosystem) are adapted to long term averages with predictable error bars. But as the old saying goes, climate is the weather one expects, while weather is the precipitation one gets, therefore climate change means getting the unexpected. Since the IPCC's Fourth Report in 2007, it has become clear that a certain amount of global warming is already “dialed in” [1]. Therefore, coping with climate change means managing the unavoidable, while avoiding the unmanageable [2].
There are three elements to global warming: The first, which most people think of, is greenhouse gases (GHG) in the atmosphere, e.g., water vapor (H2O), carbon dioxide (CO2), methane (CH4), plus other minor ones. The second element is heat and light continuously coming in from the Sun, also known as “the radiative forcing function”. The third is how much incoming energy is immediately reflected, or albedo. Dark surfaces (e.g., water) absorb energy; light ones (e.g., ice) reflect it. Sunlight directly warms our planet because our atmosphere is transparent to the predominant wavelengths of solar radiation: visible light. But GHGs in our air partly block the IR re-radiating from the warmed surface, trapping some heat. This greenhouse effect keeps the overall planet warm (even at night) making it possible for life to exist. Without a blanket of GHGs, plus lots of that truly amazing substance, liquid water, to moderate temperature extremes, Earth would be a cold, inhospitable place.
Humanity's efforts are currently focused (unsuccessfully) on reducing the GHGs (principally CO2) being emitted to the atmosphere, mainly via (ineffective) top-down attempts to limit the consumption of carbonaceous fossil fuels. Conservation, recycling, more efficiency, altered lifestyles, and new low-carbon sources of energy are all needed to reduce our GHG emissions. But so far, all that these tactics have achieved is reducing the rate of emission growth, and not even that in most places. Absolute consumption of fuel, and concomitant emissions and concentration [CO2] in the atmosphere, continues to rise dramatically. To avoid the worst effects of climate change, humanity needs to do more than merely reduce growth; we must bring down the absolute amount of these gases in the atmosphere to levels below those of the last century. However, with more people (numbers, N) entering the global middle class (affluence, A) with commensurate use of more energy per capita yet nearly flat energy intensity (I) in the developing world, it does not seem we will be able to reduce the footprint of the gross energy product, E=N×A×I, and stop global warming. We certainly will not be able to conserve our way to pre-20th-century GHG concentrations—not without falling back to pre-20th-century living standards at any rate. Who would willingly accept that? Who would enforce it?
Traditional risk analysis fails in such situations because Black Swans [3] are more common than people living comfortable lives in the developed world realize, while traditional economic analysis fails because typical discount rates diminish the present value of a benefit beyond a generation in the future to virtually nothing, and because survival considerations trump the ordinary calculus of decision-making. (Hence the aphorism, “National security has no price.”) If we cannot eliminate the causes of climate change, then is there anything we can do to mitigate it? What if existing and expected cash flows were harnessed to meet this challenge? What if the answer to the problem directly and organically paid for itself in near-real time? What if we could reduce the overall amount of sunlight hitting Earth so that global atmospheric temperatures and weather patterns can return to what we consider normal? What if we were to build a large sunshade in space allowing Earth to cool off, thus buying time to do the really hard thing: changing our behavior and attitudes?
Section snippets
Geoengineering, or, A Modest Proposal
Planetary engineering, or geoengineering (as coined by Marchetti [4] in the context of terrestrial carbon sequestration), is now understood to be the application of technology, either ground- or space-based, for the purpose of influencing the properties of a planet on a global scale [5], [6]. No study of coping with climate change is complete without considering it [7]. Terrestrial approaches suggested recently include modifying Earth's albedo or increasing carbon sequestration, e.g., injecting
Why the Sun–Earth Lagrangian-1 point?
Gravity keeps our feet on the ground, satellites in orbit overhead, and Earth revolving around the Sun. The Sun's (shown as Primary in Fig. 6 below) immense mass pulls on Earth (depicted as Satellite below)—but for our motion in orbit around it, we would fall in. Earth likewise tugs on the Sun. There exists an orbiting point in space between the two bodies at which an interesting thing happens. It is called the Sun–Earth Lagrange-1 point (SEL1) and is much closer to us than the Sun, due to our
Parasols in space
If we want to cut down the amount of solar radiation hitting a planet with as little effort as possible, then the object must have maximum surface area for minimum mass. It must block a lot of light yet not be too heavy to launch. Fortunately, a technology exists today that should be up to the job: solar sails.
A historical coincidence
How much sunlight must be stopped to deal with climate change? This seemingly simple question does not have a simple answer. Early (1989) [28], and later McInnes (2002) [29] estimated that single sails on the order of 2000-km diameter at SEL1 would be necessary overcome a projected +2% increase in Earth's “radiative forcing function”. These estimates for the reduction in total insolation to achieve a designated temperature reduction were derived from a simple proportionality using the
Dyson dots and dinosaurs, or, asteroid defense with light
Since the discovery in the 1980s of the true cause of the dinosaurs' demise, humanity has been made increasingly aware of the chaotic and violent nature of the solar system. Distressingly meager resources are being devoted to the problem of surveying and characterizing the threat of bolides from space (both asteroids and comets) [42]. Much more is needed [6]. While solar sails such as the IKAROS launched by JAXA in 2010 [43], or the disk-mirror unfurled by the Progress resupply vehicle in 1993
The interstellar perspective
Imagine, in the interest of other worlds, other places, we wanted to reduce the solar radiation hitting our neighbor Venus to Earth-normal levels (as opposed to the venuforming of Terra which seems to be going on right now). We would need to block about half (48% exactly) of the incoming sunlight, which can be done using Dyson Dots located at the Sun–Venus L1 point. But that level of effort would be several orders greater than what's required to cope with global warming right here on terra firma
Conclusion—Dots' raison d'être, or the killer app
SEL1 is way up beyond this deep gravity well we live in, and our existing technology is grossly unequal to the task of lofting such large payloads into space. Chemical rockets are too expensive to implement this solution. At a current launch cost of $20,000/kg, the 300-megatonne Dot above would cost ∼$6000 trillion (6×1015 dollars, or gross planetary product of all goods and services for an entire century) just for the ride into LEO. Clearly, that absurd scenario will never come to pass.
Acknowledgments
The authors would like to acknowledge the following persons who contributed to, reviewed, or helped refine the “Mirrors & Smoke” concept (now known as Dyson Dots) over the years: B. Derk Bruins Ph.D.; Earl Crabb; Dwayne A. Day Ph.D.; Joe Falcon and ASME's National Energy Committee, Linda Fippin, D.R. Fudge; Giancarlo Genta Ph.D., Dick L. Henderson, H. Keith Henson; Bill Howe; Debbie Hughes; Eric Hughes; Akademik Yu.A. Izrael and the Organizing Committee of “Problems of Adaptation to Climate
References (48)
- IPCC, 2001: Climate Change 2001: Synthesis Report. A Contribution of Working Groups I, II, and III to the Third...
- R.M. Bierbaum, J.P. Holdren, M.C. , R.H. Moss, P.H. Raven (Eds.), Scientific Expert Group on Climate Change,...
The Black Swan: The Impact of the Highly Improbable
(2010)On Geoengineering and the CO2 Problem
(1976)- et al.
Advanced technology paths to global climate stability: energy for a greenhouse planet
Science
(2002) - Yuriy A. Izrael, G.L. Lioznov, A.A. Rasnovski, ⪡Потенциальные возможности и органичения истользоватия космонавтики в...
- Various, GAO, Climate Change: A Coordinated Strategy Could Focus Federal Geoengineering Research and Inform Governance...
- Various, Федеральной службы по гидрометеорологии и мониторингу окружающей среды (“Rosgidromet”) и Российской академии...
- Various, GAO, Climate Engineering: Technical Status, Future Directions, and Potential Responses, GAO-11-71, July...
- Various, United Nations, Convention on the Prohibition of Military or Any Other Hostile Use of Environmental...
Critical Path
Solar Power Satellites
Solar Sails: An Answer to Global Warming?
The Little Ice Age: How Climate Made History: 1300-1850
Solar Sailing: Technology, Dynamics and Mission Applications
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