ALl youd really need to to do to make it work would be a large laser
collimator in the L1 lagrange point, in front of the moon, so to speak
which would illuminate whatever messages you wish to make, using the
moon as a projection screen. Youd probably get the best effect using the
dark side of the moon (in the wane-new-waxing phases). THis way you
could use the moon as a billborad during the day, and leave it "pure" or
undisturbed at night, or what the hell screw the romantics. TO power the
laser system, you'd need to project enough light to equal the 2 kW/m^2
flux of the sun on the lunar surface, and approximately double this if
you wished to use the sun illuminated areas. With a 1500 mile diameter,
thats 10.8 x 10^6 m^2, not counting the diffractive effects of
tangential areas. You then would need to determine the resolution you
wished to project, as well as the refresh rate of your pictures.
Basically, the amount of the lunar surface you want to illuminate at any
given time determines the amount of solar collectors you would need,
minus the efficiency of solar cells in space, about 33%, so if you
wanted to illuminate the whole face, you'd need collector area equal to
3 times the 10.8 billion square meters of lunar surface you wished to
illuminate. A daunting task. Of course, you could simply build a
reflector system, or possibly a fresnel lense system of equal area which
would orbit in retrograde around the moon in a period eaual to the lunar
28 day cycle around the earth, so it would always be between the moon
and the sun, and you could use the suns illumination of the moon to
illuminate a "slide" of the graphic motif you wished to project onto its
surface. By being of equal area as the lunar cross section, you would
get a neat eclipse effect which would illuminate a circular frame around
the edge of the moon, which would aid people in spotting this aetheral
sign. Damn, I like the fresnel idea, I wonder if the the the counter
periodic lunar orbit is possible?
Lessee, a 1/6th gravity equates to a 1/6th orbital velocity, or
approximately 3000 mph or less. Using a 28 day period, that equals an
orbital circumference of 2,016,000 miles, which is an altitude of 800
miles? My orbital velocity must be off, as the 17,800 mph for earth is
assuming an earth diameter planet to avoid. HMMMMM Given lunar GM equals
.0049, and a period of 2419200 seconds, to find the orbital velocity at
a 28 day period, we need the cube root of 0.0307876 / 2419200. To
calculate orbital radius from the moons center (remember its surface is
at approximately 750 miles), you need the cube root of 726408010.2949 to
get it in km x 10^2, which should be approximately 90,000 km out.
Given this, the projector station would be able to project an image
across the entire surface with a 28 day period in a retrograde orbit
about the moon. Of course, being almost 40% of the distance to the earth
at periapsis would have some significant tidal effects on the structure,
which could be countered with either solar wind, magsail, or ion thrust
(or Lorrey Drive) augmentation. If you were not in a retrograde orbit,
you would be in the Lagrange point between the Earth and Moon.
Of course if you came up with a novel energy source, you could have a
relativley small laser projeciton station that could pump to your hearts
content. Lessee, a singularity would be a decent source of power for
such an endeavor, which would also be usefull for generating antimatter
for spacecraft fuel, and being at the L1 lagrange point would be the
optimum place to have a fuel station anyhow. So lets key in a
singularity as a key economic asset for any lunar economy. The L1 point
would be the prime way point for any trade in this solar system, given
its advantageous position between the moon and earth.
Here's a twist on that idea: Suppose you develop a good sized lunar
colony system, and have a hundred million people on the moon, at least.
You could use lasers to trigger aurora effects on earth to create neon
signs visible to lunar inhabitants. how much do you think the nuts on
earth would howl at that concept? Given this, L1 station will become the
Madison Avenue of the 21st century. It will be come THE hot piece of
commercial real estate. Unfortunately, with toroidal habitat structures,
there would be no hope of getting a corner office! ;( AWWWWWW!
-- TANSTAAFL!!!Michael Lorrey --------------------------------------------------------- President retroman@tpk.net Northstar Technologies Agent Lorrey@ThePentagon.com Inventor of the Lorrey Drive Silo_1013@ThePentagon.com http://www.tpk.net/~retroman/ --------------------------------------------------------- Inventor, Webmaster, Ski Guide, Entrepreneur, Artist, Outdoorsman, Libertarian, Certified Genius.