On Mon, Jul 07, 2003 at 04:06:48PM +0000, Robert J. Chassell wrote: > Erik Reuter <[EMAIL PROTECTED]> > > The only way I know of to get a simple equation is to make a > couple approximations: > > (1) The temperature of all the air is the same, 300K > (2) The air all rotates with the endcaps, speed proportional to > radial distance from center > > The second approximation, or assumption, makes good sense. But the > first begs the question. Is the air temperature the same throughout > the spinning space habitat?
Probably not. As I said, I didn't make the assumptions because I thought they were the best model of the habitat, I made them because they were the minimum assumptions I could make that allowed me to come up with a simple formula. In defense of the assumption, the same assumptions produces a model of Earth's pressure that is quite accurate (better than 5%) over a large altitutde range (10's of kms). So, that assumption probably does not result in total nonsense. > Erik Reuter goes on to say: > > Here is the corrected formula for the pressure in the habitat as a > function of height h: > > P/P0 = exp[ - ( h / R )^2 / ( 2 k T / ( m g R ) ) ] > = exp[ - ( h / R )^2 / 3.45 ] > > Incidentally, according to Erik's formula, the pressure at the center > of a spinning space habitat with a radius 8 km, like Rama, would be > nearly 0.9 of the pressure at the rim. No, don't think so. Where did you get 0.9? Note that the 3.45 number has a 1/R factor in it. If R goes from 5km to 8km, then 3.45 goes to 2.16. Then, exp[- 1/2.16] is 0.63. The larger the radius, the lower the pressure at the center. > But I still wonder what the standard temperature is? What is the > lapse rate? How much does temperature drop per kilometer of increased > altitude? How much does dew point drop? Those questions are well beyond my calculation abilities. If you are interested in doing a simulation, I'd be willing to work with you, but I'd have to do some reading on how to deal with the moisture and air currents and so on. I'm certain there won't be an accurate closed form solution. At best we will probably start with some boundary conditions and grid up the air in the habitat and then run the formulas. -- "Erik Reuter" <[EMAIL PROTECTED]> http://www.erikreuter.net/ _______________________________________________ http://www.mccmedia.com/mailman/listinfo/brin-l
