The ultimate regatta is taking shape - a race to the moon and Mars in 1992 by an international fleet of celestial sailing ships.

The unmanned, gossamer craft - some resembling huge square sails bigger than football fields - will be fashioned from polymers thinner than plastic wrap and coated to reflect the light. Wafted along by sunbeams instead of ocean breezes, they will reach speeds of more than 70,000 mph on their dash through the solar system.Called the Columbus 500 Space Sail Cup, the race - the first ever in space - is one of many spectacular events planned to commemorate the 500th anniversary of Christopher Columbus's historic sail. So far, solar sail entries are planned by Canada, France, Israel, Italy, Japan, the Soviet Union, Spain and the United States.

"We consider it an America's Cup kind of competition that features science and technology as well as sailing," says Klaus P. Heiss, a mathematical economist and space consultant who is coordinating the Mars race.

Rockets will put the sails into high Earth orbit, beyond the weight of the atmosphere, which could drag the wispy craft down. They will then unfurl from small canisters to catch the flow of photons, particles of light from the sun, that will propel them through space.

Sensors and other devices on board will maneuver the craft by changing their angle to the sun, just as sailing ships alter course by adjusting their sails to wind direction. Most will carry video cameras to record the progress.

But contestants must first overcome some difficult financial problems. Steve Horvath, leader of the Canadian Solar Sail Project, estimates that the effort will cost $15 million, $1.5 million for the craft and $13.5 million to launch it. "In the current economic climate, this is a tough project to pull off, but we're determined," he says.

The unusual Canadian entry features a small, rounded central core containing electronics, computers and control systems, circled by 30 long strips of ultrathin material resembling helicopter blades.

Designers of the United States' more traditional square sail hope to save on launch costs by piggybacking with two other similar entries - a joint French and Spanish sail and a Japanese one. An Ariane space rocket will probably carry all three up.

"We're budgeting about $6.5 million for our craft," says Emerson H. LaBombard, who is leading the U.S. effort, which is sponsored by the World Space Foundation, a non-profit scientific research corporation. "Since we'll be at the bottom of the stack, we'll use a small rocket motor to get our sail under way, after we eject from the big rocket."

Even with this assist, LaBombard has modest expectations. "Our 3,600-square-yard craft may be one of the poorest-performing devices," he says. "We've taken the attitude that we're interested in strength and reliability, and proving the technology rather than getting someplace before someone else.

"We don't even know if our vehicle will steer, much less get to Mars. Setting our sights on Mars would be like the Wright brothers planning to land in London when they took off on their first flight at Kitty Hawk."

No matter what happens to the entries, the solar race should rekindle interest in a technology that promises a breakthrough for a relatively inexpensive form of space transportation and research.

The upcoming race has given new hope to solar sail enthusiasts who see boundless possibilities for the craft. "They offer incredible time and monetary savings to those who want to explore and research the solar system," says Heiss.

Visionaries view the great sails as the clipper ships of the future, shuttling passengers and cargo between Earth, the moon and Mars. In the next century, a martian clipper hauling a passenger module could make the voyage from Earth to the red planet in nine months, about half the time required by today's spacecraft.