The earth absorbs sunlight with a cross section of 2*pi*R^2, and reradiates it as a sphere, with area 4*pi*R^2. This gives an area advantage of a factor of 2. A cylinder, side-on to the sun, would absorb as 2*r*length, and reradiate as 2*pi*r*length, giving an area advantage of a factor of pi/2. Since the radiation goes like T^4, I don't see why the temperature of a cylinder would be much higher than that of the earth, about 300 K. Although the theoretical temperature of the atmosphere (gas) near the "top" is quite high, the density is so low that little heat is available, is my understanding. Bill C. -----Original Message----- From: math-fun-bounces+cordwell=sandia.gov@mailman.xmission.com [mailto:math-fun-bounces+cordwell=sandia.gov@mailman.xmission.com] On Behalf Of Henry Baker Sent: Tuesday, August 01, 2006 1:30 PM To: Eugene Salamin Cc: math-fun Subject: Re: [math-fun] A modest proposal for carbon sequestration in space True, but I'm not saying that you don't have to pump. Furthermore, in order to "sequester" the CO2, we only have to get it into orbit, so we don't have to send it any further than geosynchronous orbit. The pressure in the pipe goes down exponentially with height, and the molecules at the top are going extremely fast. If they bounce off the inside of the pipe without losing energy (not a good assumption), then they should come flying out the end. The failure mode is probably that the temperature gets so hot above the "atmosphere", that it melts the carbon tube. Even if the tube doesn't melt, it may radiate away an enormous amount of the energy which we would rather be used to propel the molecules _up_ the tube. So the pressure & density at high altitudes inside the tube would be much higher than the pressure & density outside the tube, so my assumptions about the density inside & outside would no longer hold. So, ideally, we might rather have a true "nanotube" in which the CO2 molecule travels as if in a waveguide, rather than ballistically. Then we would need an enormous number of them in parallel to carry a substantial amount of gas. Launching the molecules into such a waveguide might then be problematic. BTW, I understand that we actually _do_ lose H2 into space all the time, but probably not at an appreciable rate. At 12:00 PM 8/1/2006, Eugene Salamin wrote:
--- Henry Baker <hbaker1@pipeline.com> wrote:
Eugene:
My intuition is that CO2 is only modestly heavier than N2+O2, so you only have to lift the _difference_ between the weight of the CO2 and the atmospheric pressure due to N2+O2.
Then it should take no energy to dispose of the atmosphere into space.
Gene
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