Photonics Spectra - September 2009

l

LETTERS

White Elephant in Space?

Many view the International Space Station (“Solar-powered space station,” Photonics Spectra, July, p. 36), as a $150 billion

“white elephant” in space that has sucked

resources from many other more worth-

while programs – construction that was

said to have been created in part to pro-

vide jobs for out-of-work ex-Soviet nu-

clear scientists so they would not run off

and give atom bombs to rogue states.

That it needs 32,800 solar cells is no

brag. The same job could have been done

with a plutonium energy cell the size of a

home computer box, and it would not be

relying on the sun to function.

Richard Anderson

Toronto

A solar fraud?

In the July issue of Photonics Spectra I

read “Solar from space” (page 35). This

concept is a complete fraud to get money

for nonsense.

First, why is it so necessary to send

power to Earth from space? Do we not

have enough from fossils or other sources?

One reason given is that it is often cloudy,

so solar power plants cannot generate

enough power.

If you look at pictures of the globe sent

from a Meteo geostationary satellite, you

can easily see that only about one-eighth

of the half-globe is covered by clouds.

This means that the remaining seven-

eighths has unlimited solar irradiation, and

we have terrestrial power networks to

transport the generated power around the

globe.

Next, consider that solar cells are quite

inefficient; today’s best are at about 15

percent, and they age in space. Satellite

designers know better. In my opinion,

heating water is more efficient, and it is

done in California, Arizona, Spain, Japan

and elsewhere without rocket technology.

Then there’s the issue of energy loss as

power is transmitted to Earth. Anyone

who has heard about electromagnetic

waves knows that the power decreases due

to propagation in proportion to inverse

square. In a power distribution, a “good”

efficiency is more than 80 percent. The

experts claim that the power will be fo-

cused and collected by huge antennas. A

typical good satellite antenna has about 50

percent efficiency. And the free-space

power loss at 2.45 GHz over 35,000 km is

~190 dB, otherwise 1020. What kind of

power efficiency can you expect?

Finally, I have asked some of the ex-

perts how to get those wonderful antennas

that amplify power. I would use them in

microwave and millimeter-wave commu-

nication systems. Nobody has responded.

All this is a hoax and pure fantasy, and

moreover not based on natural laws. Those

space solar concepts are pure nonsense.

Jiri Polivka Santa Barbara, Calif.

Editor’s response:

As a science writer, I cover subjects that I think will be of interest to our readers and make no claims as to the success of a technology or marketing concept. We do, however, appreciate readers keeping us informed of the many issues surrounding such a controversial topic.

Thin-film question

I read with great interest Caren B. Les’ article in the July issue on p. 28: “Image sensor market: Looking forward to better times.” I am curious about a statement in your article: “A third generation of devices based on polymeric thin films … also could be developed.”

Are there companies or start-ups in this space?

Erik Bodegom Professor of Physics

Chairman, Department of Physics Portland State University

Portland, Ore.

Response:

I’m not sure of any companies that might be involved, but think PARC [Palo Alto Research Center] and the University of California, Santa Barbara, might be working on polymer-based image sensors.