Given that all else fails to stop global warming, and action is taken soon enough that a 10 percent reduction in the solar insolation factor over the EM band around 10^-6 m, from latitudes 50 to -50, then the following is suggested as a rough first estimate of how this might be done.
The objective might be met by dispersing orbiting aluminum nanopowder from latitudes 50 to -50, at, say, an altitude of about 800 km. This might be accomplished by deploying a ring of satellites that orbit between those latitudes, and then firing rockets in a direction normal to the direction of travel and a radial line through the earths center and such a satellite. The rocket firing would thus not change the orbit altitude, only the poles of the orbit. During the firing the nanopowder would be deployed, possibly into the exhaust. It might be possible to design an electric rocket that uses the nanopowder as a reaction mass, and which runs on solar power. It is presently possible to obtain metal nanopowders of dimension 8 nm. These then have volume of (8x10^9 m)^3 = 5.12x10^-22 m^3/particle, or 1.95x10^21 particles/m^3 of, say, aluminum. Aluminum weighs 2.70 g/cm^2 = 2700 kg/m^3. There is thus (1.95x10^21 particles/m^3)/(2700 kg/m^3) = 7.22x10^17 particles/kg. If we assume that one such particle can reflect incoming photons of about 10^-6 m wavelength about 10 percent of the time within a radius of 10^-6 m, then each nanoparticle has the required coverage of Pi*(10^-6 m)^2 = 3.14x10^-12 m^2. This gives a coverage of (7.22x10^17 particle/kg)(3.14x10^-12 m^2/particle) = 2.98x10^6 m^2/kg. The radius of the earth is 6.38x10^6 m, and if we deploy at 800 km then the effective radius of our deployment sphere is 7.18x10^6 m. Given that the area of the zone of a sphere is 2 Pi R h, the total deployment area is 2*Pi*(7.18x10^6 m)*((7.18x10^6 m)*sin(50 deg.)) = 2*Pi*(7.18x10^6 m)^2*(.766) = 4.96x10^14 m^2. The total deployed mass is thus (4.96x10^14 m^2)/(2.98 m^2/kg) = 1.66x10^8 kg, or 166,000 metric tons. Assuming the deployment of this amount of payload can get the price down to $10,000/kg, the cost of deployment is (1.66x10^8 kg)($10,000/kg) = $1.66x10^12. The price of, for a limited time, saving the earth when it is at the defined point of stress is about 1.7 trillion dollars. The worst assumption in this rough first estimate is probably the assumption that an 8 nanometer particle can provide 10 percent reflection back into space of low infrared to visible radiation, radiation averaging about 10^-6 m wavelength, over an area about (10^-6 m)^2. Ultimately the nanopowder will reenter the earth's atmosphere, but before doing so, might tend to form an equatorial ring, which will continue to give partial shelter from solar heating during both winter and summer, but not during the solstices. Hopefully such a dispersal will be planned to occur at sufficient altitude that it will last long enough for us, or subsequent generations, to solve the global warming problem. This is really a last ditch effort, and may be totally unnecessary. There is enough methane hydrate in the Northern hemisphere to meet all our needs for generations, probably well over 1x10^14 CF. If that gas can be produced and converted to hydrogen, without burning the carbon in the process, and all the carbon in the gas is converted to construction materials, the carbon dioxide in the earth's atmosphere hopefully would diminish at a sufficient rate to avoid runaway warming. I hope I got this all right. It's late. Regards, Horace Heffner
