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Research Article

Feasibility of cooling the Earth with a cloud of small spacecraft near the inner Lagrange point (L1)

Roger Angel
PNAS November 14, 2006 103 (46) 17184-17189; https://doi.org/10.1073/pnas.0608163103
Roger Angel
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  • For correspondence: rangel@as.arizona.edu
  1. Contributed by Roger Angel, September 18, 2006

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Abstract

If it were to become apparent that dangerous changes in global climate were inevitable, despite greenhouse gas controls, active methods to cool the Earth on an emergency basis might be desirable. The concept considered here is to block 1.8% of the solar flux with a space sunshade orbited near the inner Lagrange point (L1), in-line between the Earth and sun. Following the work of J. Early [Early, JT (1989) J Br Interplanet Soc 42:567–569], transparent material would be used to deflect the sunlight, rather than to absorb it, to minimize the shift in balance out from L1 caused by radiation pressure. Three advances aimed at practical implementation are presented. First is an optical design for a very thin refractive screen with low reflectivity, leading to a total sunshade mass of ≈20 million tons. Second is a concept aimed at reducing transportation cost to $50/kg by using electromagnetic acceleration to escape Earth's gravity, followed by ion propulsion. Third is an implementation of the sunshade as a cloud of many spacecraft, autonomously stabilized by modulating solar radiation pressure. These meter-sized “flyers” would be assembled completely before launch, avoiding any need for construction or unfolding in space. They would weigh a gram each, be launched in stacks of 800,000, and remain for a projected lifetime of 50 years within a 100,000-km-long cloud. The concept builds on existing technologies. It seems feasible that it could be developed and deployed in ≈25 years at a cost of a few trillion dollars, <0.5% of world gross domestic product (GDP) over that time.

  • geoengineering
  • global warming
  • space sunshade

Footnotes

  • *E-mail: rangel{at}as.arizona.edu
  • Author contributions: R.A. wrote the paper.

  • The author declares no conflict of interest.

  • ↵ † Koppel, C. R., Marchandise, F., Estublier, D., Jolivet, L., 40th AIAA/ASME/SAE/ASEE Joint Propulsion Conference and Exhibit, Fort Lauderdale, FL, July 11–14, 2004, abstr. 3435.

  • ↵ ‡ Brophy, J. R., Marcucci, M. G., Ganapathi, G. B., Gates, J., Garner, C. E., Klatte, M., Lo, J., Nakazono, B., Pixler, G. (2005) 41st AIAA/ASME/SAE/ASEE Joint Propulsion Conference and Exhibit, Tucson, AZ, July 10–13, 2005, abstr. 4071.

  • ↵ § Dowdle, J. R., Throvaldsen, T. P., Kourepenis, A. S. (1997) AIAA Guidance, Navigation, and Control Conference, New Orleans, LA, August 11–13, 1997, abstr. 3694.

  • Abbreviations:
    L1,
    inner Lagrange point;
    Gm,
    million km.
  • © 2006 by The National Academy of Sciences of the USA
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Feasibility of cooling the Earth with a cloud of small spacecraft near the inner Lagrange point (L1)
Roger Angel
Proceedings of the National Academy of Sciences Nov 2006, 103 (46) 17184-17189; DOI: 10.1073/pnas.0608163103

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Feasibility of cooling the Earth with a cloud of small spacecraft near the inner Lagrange point (L1)
Roger Angel
Proceedings of the National Academy of Sciences Nov 2006, 103 (46) 17184-17189; DOI: 10.1073/pnas.0608163103
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Proceedings of the National Academy of Sciences: 103 (46)
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  • Article
    • Abstract
    • Shading Efficiency and Radiation Pressure
    • Optical Design to Minimize Mass and Reflectivity
    • From the Earth to L1
    • The Sunshade as a Cloud of Autonomous Spacecraft
    • Discussion
    • Acknowledgments
    • Footnotes
    • References
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  • Info & Metrics
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