Come sail awayPart Two
By Rod Myers, Naturalist
Later this summer, the Planetary Society will launch its Cosmos I solar sail. It will hitch a ride on a Russian launch vehicle. At about 500 miles altitude, the sail will open and then start to change its orbit, thanks to the subtle pressure of sunlight. The sunlight at this low altitude from Earth will not be sufficient enough to get Cosmos I where it needs to be to test its speed. However, it will get added help from a microwave beam that will hit the sail, exerting electromagnetic pressure. The microwaves origin will be the Goldstone 70-meter antenna, the largest in the Deep Space Network (DSN) of communication antennae.
This will be the first known attempt to thrust forces on a spacecraft in space where the forces are emitted from Earth using purely electromagnetic beams. The microwave beam will reflect on the mylar-like aluminized skin on the sail, but only 1,700 watts will hit the sail. The microwave beams will spread broader as it propagates like a flashlight beam does. The waves will spread out much wider than the 30-meter sail diameter. The effect, though, will be small compared with the suns push, which at perpendicularity nears 1,370 watts per square meter. But this much sun power cannot be used when the sail is close to Earth. The Cosmos I projects main purpose is to illustrate future possibilities, and many people representing many interests will be watching.
The basic idea of creating a beam of energy to propel a sail dates back to 1966, when a scientist named G. Marx proposed using lasers. But lasers cost a million dollars a minute to fire, while microwave beams cost a few hundred dollars a minute and are conveniently created by NASAs Deep Space Network antennae. Microwave development has been around a lot longer than laser technology; therefore, it is cheaper.
Lasers can damage sails while microwaves do not, and microwaves dont refract; that is, the waves will not deviate from course when passing from one medium to another while on the way to the sails surface. The expensive part of the microwave beamer system is the beamer itself. Once its complete, which the DSN is, the network is like railroad tracks. Many sails could travel on the tracks and in space, like the American West was opened up for travel.
Spacecraft launched from Earth must fight to escape Earths gravity, but a craft still in Earths pull returns to an elliptical orbit. If an energy supply microwaver is put into orbit, then the sailcraft need only get aligned in orbit with the energy source to get another push, thus ending up farther out in space, where the sun will eventually take over the job of pushing the sail. This scenario is ideal for quick trips to Mars, where future manned outposts would need supplies post haste. It appears that when machines break the bonds of Earth, they work more efficiently, but the future will be a balance between Earth-bound and space-occupied technology. Smart sails and smart beamers will be the future, and they, at least on the drawing boards, are rising to the horizon quickly. One concept is the long-envisioned orbital sunlight-collecting platform that could beam microwaves to electrical power grids on Earth. This would make powering sails as inexpensive and easy as 1, 2, 3, or would it be 3, 2, 1, lift-off?
Combustion jet propulsion started our journey into space, but its time is fleeting, and fresh approaches are needed. As railroads gave way to automobiles and airplanes, jet propulsion will give way to sails. The next time you see a majestic sail, think of the possibilities.
Rod Myers is a local resident with an interest in the environment and disability issues. He has an associates degree in science and a bachelors in fine arts. Rod is a member of the Audubon Society, the Wild Ones Natural Landscapers and Rockford Amateur Astronomers, Inc.