ESG7@DFVLROP1.BITNET (11/25/86)
I'm going to reduce my already tarnished credibility by describing how
one could construct a telescope for resolving an earth-like planet
orbiting Tau Ceti. Tau Ceti is a sun-like star that is 11.95 light
years from Earth. By Rayleigh's criterion (based on diffraction
considerations), one can resolve an earth-like world orbiting Tau Ceti
for light of 5500 Angstroms if the telescope mirror's diameter is 11.89
kilometers. One can construct such an enormous telescope in space only
if there are no gravity gradiants, and if the telescope is shielded
from the suns light. I propose building such a telescope by blowing
bubbles. In theory one could construct such a telescope by blowing a
bubble with a radius of 120 km. One could sliver a small section within
the bubble and place optics at the center to receive the incoming light.
The image would have to be corrected for spherical aberration. The
silvered section would have a radius of 11.89 km and have an f-number
of f/10. There are several problems with this approach: Most of
the material for the bubble would be useless. Manipulating the bubble
would be difficult. Also, maintaining the receiving station at the
center of the bubble without distorting the bubble's shape would be
difficult. A better approach would be to have a thin plastic hose
with a length of 37 km. Form this hose into a ring and pressurize it
with gas or a liquid like silicon oil. You now have a rigid ring. Now
blow a bubble with a 12 km diameter and touch this bubble onto the ring
such that the bubble collapses into a disc membrane supported by the
ring. Construct a second identical membrane disc using the same process.
On one disc, spray material onto the membrane to build up its thickness
and to stiffen it. Spray a thin layer of metal on one side of this
stiffened disc. With the other disc, the membrane is allowed to be
flexible. Spray a uniform, highly reflective surface on one side and on
the other side spray a honeycomb pattern of hexagons of conductive
metal which are separated by the noconductive plastic of the
membrane. Now attach the two membranes with struts that are 700 meters
long. The telescope is now a cylinder that looks like a Tom-Tom drum
that is 12 km in diameter and 700 meters long. Have the
conductive surface of the stiff membrane face the honeycomb
surface of the flexible membrane. Apply a uniform positive charge on
the stiff membrane's surface while providing selective negative charges
on the different hexagons of the flexible membrane. Now distort the
flexible membrane into a parabolic shape. At the focus, 120 km away
place the receiving station and position it with ion thrusters whose
beams do not intersect with the mirror. Raster scan the mirror with a
laser using a light wavelength which doesn't effect the telescope's
astronomy. Count fringe shifts of the laser beam as it scans the mirror
and use this information for positioning the receiving station and
adjusting the level of charge on the hexagonals of the flexible
membrane. Charge can be added or subtracted to the heagonals by using
electron guns mounted on the sides. Between the mirror and the sun
construct a larger third membrane and render this membrane opaque using
it as a sun screen. Have the whole affair in heliocentric space with an
orbital radius far enough away from the sun that its orbital motion
isn't a factor. I admit that this idea is crazy but at first glance it
seems workable.
Gary Allen