06-09-2012, 04:11 PM
EARTH RINGS FOR PLANETARY ENVIRONMENT CONTROL
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ABSTRACT
This paper examines the creation of an artificial planetary ring about the Earth to shade it and reduce global warming. The ring could be composed of passive particles or controlled spacecraft with extended parasols. Using material from dangerous asteroids might also lessen the threat of asteroid impacts. A ring at 1.2-1.6 Earth radii would shade mainly the tropics, moderating climate extremes, and could counteract global warming, while making dangerous asteroids useful. It would also reduce the intensity of the radiation belts. A preliminary design of the ring is developed, and a one-dimensional climate model is used to evaluate its performance. Earth, lunar, and asteroidal material sources are compared to determine the costs of the particle ring and the spacecraft ring. Environmental concerns and effects on existing satellites in various Earth orbits are addressed. The particle ring endangers LEO satellites, is limited to cooling only, and lights the night many times as bright as the full moon. It would cost an estimated $6-200 trillion. The ring of controlled satellites with reflectors has other attractive uses, and would cost an estimated $125-500 billion
INTRODUCTION
For 95% of its past, the Earth’s climate has been warmer than it is now, with high sea levels and no glaciers (Butzer, 1989). This warmer environment was interrupted 570, 280, and 3 million years ago with periods of glaciation that covered temperate regions with thick ice for millions of years. At the end of the current ice age, a warmer climate could flood coastal cities, even without human-caused global warming. In addition, asteroids bombard the Earth periodically, with impacts large enough to destroy most life on Earth. A recent world concern is the effect of industrial greenhouse gases in raising the overall global temperature, melting the polar caps, and raising sea level. Govindasamy et al., (2000) estimated that the expected doubling of CO2 in the atmosphere over the next century will warm the Earth by about 1-4 kelvins and raise sea level by about 1 meter. Not all scientists are convinced of human-caused global warming.
ARTIFICIAL EARTH RINGS
This paper proposes to create an artificial ring about the Earth to reduce solar insolation. An equatorial ring location was chosen from the standpoint of stability and reduced perturbations. We describe two different options: a ring of passive particles, derived from the Earth, moon, or asteroids, and a ring of attitude-controlled spacecraft with large, thin-film reflectors. The optimum ring size, location, and material properties are addressed, using a climate model to determine the desired reduction in insolation. Ring materials and cost of emplacement are evaluated, and methods are discussed for controlling ring deterioration from particle loss due to air drag and ring spreading or from satellite malfunctions.
Earth Ring Concept
Our baseline concept is to create an Earth ring in equatorial orbit, similar to Saturn’s B ring, but closer. The concept is shown in Figure 1. We looked at radii between 1.2 and 1.8 Re. The ring can be composed of particles or of individual spacecraft, and is characterized by its radial extent and by its density, or opacity. This low-altitude ring shades the tropics primarily.