f beaming solar power to the earth by way of the moon sounds like lunacy, consider this : It is a non-polluting and renewable source of energy. And it could supply adequate electric power for everyone on the planet in less than 50 years, believes Mr. David R. Criswell, a physicist and Space Age veteran.

"We think of beaming power from the moon as exotic, but it has been done for at least 15 years." Says Mr Criswell, director of the Institute for Space Systems Operations at the University of Houston. "Power beaming is like using a big radar."

Mr Criswell proposes a Lunar Solar Power System, which would put the moon in service as a ready-made satellite. Lunar power bases, built primarily from materials on the moon, would capture sunlight and convert it into microwaves, which would be transported, come rain or come shine on earth, to several thousand receivers around the globe. The microwaves would then be fed as electricity into local power grids.

A demonstration project could deliver commercial power within 10 years of start-up, he predicts in the current issue of the Industrial Physicts. Mr Criswell, who has pondered lunar based power systems for more than 20 years, contends the technology has been available since the 1970s. he began championing the possibilities of moon power at a Nasa symposium in 1984.

Earth-moon power beams are not science fiction, he emphasises. He points to the radio telescope at the Arecibo Observatory in Puerto Rico, which transmits images of the moon with a radar beam.

But don't expect moon beams to be available at the flick of a switch anytime soon, warn other Space Age veterans, including former Sen. John Glenn, the first American to orbit the earth. Moon power doesn't come cheap. Mr Criswell estimates that the price tag on his demonstration would be about $60 billion.

"In principle, it is perfectly feasible, but the problem is cost," believes Mr paul D. Lowman Jr., a Nasa geophysicist and the first geologist hired by the space agency in 1959. He helped plan the Apollo missions that sent men to the moon and brought back soil samples that scientists have been analysing for years. The last lunar landing was 30 years ago. Building a lunar power station would require another manned mission, but nobody plans a return trip anytime soon.

"As far a Nasa's concerned, the moon has been scratched off. Scientists' interests have shifted to astrobiology," Mr Lowman said.

Sen. John Glenn, who volunteered on a Space Shuttle mission in 1998, has little hope that money will be found for the project.

"Right now we have trouble funding the International Space Station with all of its important research projects. To go back to the moon, establish and keep viable bases for power generation would be a very, very expensive operation," he said.

Mr Criswell, who has written nearly 200 articles supporting moon power, isn't deterred by funding or challenges in transporting staff and materials.

"We are not talking about taking a GM factory to the moon," he said. "We are talking about machinery more on the scale of road building equipment - roughly 10 to 20 times the size of the Lunar Rover."

One of his University of Houston colleagues is already designing moon machines to be shipped from earth, but he stresses the 20 to 40 lunar power bases would be built primarily from materials widely available on the moon. Silicon, aluminum and iron could be chemically extracted from lunar soil to make the solar cells, he said "The cost and the rate of growth of the LSP System are limited only by how clever we are in applying our industrial skills, not by the cost of transporting materials to the moon," he contends.

Mr Martin Hoffert, a New York University physics professor who has written about how satellites can collect solar energy, suggests that the pressing energy needs of the 21 st century may make Mr Criswell's project worth considering. "Between 30 and 40 per cent of people on the planet are not connected to a power grid." Mr Hoffert said. "Beaming energy from satellites or the moon to people in developing countries could be a way of jump starting power distribution."