From: utzoo!decvax!cca!REM@MIT-MC@sri-unix Newsgroups: net.space Title: solar power on the moon Article-I.D.: sri-unix.3371 Posted: Mon Sep 20 16:44:20 1982 Received: Tue Sep 21 09:45:30 1982 From: Robert Elton MaasDate: 18 Sep 1982 1825-EDT From: Margot Flowers If solar energy sufficient for the needs of the dark half could be generated at the poles (which would always recieve sunlight that is not greatly diminshed by atmosphere as it is on the earth), That's wrong. The Moon tips north and south with respect to the sun, just like the Earth does (Summer and Winter), although not the same amount. The effect is similar. Half the year the north pole is in darkness and half the year the south pole is in darkness, with some grazing lighting during the boundary region (Spring and Autumn equinox). A high tower might get light a little more than half the time at either pole, whereas a ground-based station might get light a little less than half the time. Two high towers are need for coverage all the time (except during eclipses). then the farthest transmission lines would have to reach would be to the moon's equator, at most "only" one quarter the diameter of the moon (still a somewhat long distance). Your geometrical terminology is lacking. The distance around the moon is called the "circumference", not the "diameter". You're off by a factor of PI (3.1415926535...). But because each pole gets light only half the time, there's an additional factor of two, because worst case is supplying the south pole from the north pole during southern Winter and vice versa during northern Winter. Thus you're really off by a factor of 6. I propose three stations on the equator separated by one third of the circumference. That way each supplies energy for a little less than half, and their less-than-halves overlap allowing smooth transition from one to the next, avoiding power glitches as current in cables is reversed gradually between the two sites. Except for the master trunk that girdles the Moon at the equator, worst case is quarter circumference. (That proposal is in the context of centralized production. Acutally I prefer distributed production whereby each station has its own solar energy, with computer making it track the sun, and decreasing level of activity each night to conserve limited energy storage. At least in the forseeable future, say 50 years.)