Science: Satellites Aweigh

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President Eisenhower's announcement that the U.S. will build unmanned satellites to circle the earth (see NATIONAL AFFAIRS) was thrilling news for all space-flight enthusiasts—from space-minded kids to sobersided scientists. Besides appealing to the imagination, the satellite will have genuine scientific utility.

The far-cruising spaceships of science fiction are beyond present-day capabilities. Theoretically they are possible, but many layers of problems must be cleared away before they can set their courses for the moon or Mars. The most difficult problems are human: how to keep the crews alive in space and how to get them back to earth in reasonably good condition. Both problems are bypassed by making man's first step toward space a satellite that carries no crew and is not expected to return to earth.

Behind the wall of secrecy that surrounds the guided-missile program, rockets have been developing rapidly (TIME, May 30 et seq.). Scientists in a position to know believe that some of them are powerful enough to raise an object weighing 50 to 100 Ibs. above most of the atmosphere (about 200 miles up) and set it revolving around the earth at 18,000 m.p.h. Supported by this speed, it will not fall, any more than the moon does. It will circle the earth every 90 minutes, until the slight resistance of the fringe of the atmosphere makes it slow down. Then it will plunge into denser air and turn into incandescent particles.

Balloon or Cylinder. Before this fiery end, a satellite will serve its creators in many ways. One type (many different kinds can be shot into space) may be merely visible: a balloon that expands out of the nose of the final stage of a multistage rocket. It can be followed by telescope or perhaps by radar, and the path that it follows around the earth will give information about the density of the upper atmosphere. If big enough, this kind of satellite will appear at dusk as a bright and rapidly moving star that rises in the west.

More elaborate and more interesting satellites will be small spheres or cylinders packed with instruments. The best known of these is the MOUSE (Minimum Orbital Unmanned Satellite of the Earth), developed by Professor Fred Singer of the University of Maryland (see diagram). According to Singer, the Mouse will yield a large amount of valuable information. Even on the clearest day, the atmosphere is as opaque to many kinds of radiation as if it were an ocean of ink. But the satellite, soaring above the atmosphere, can measure all kinds of radiation, including the sun's ultraviolet and the primary cosmic rays. Its electrical eyes, looking downward, can scan the earth, following masses of cloud as they form and drift. Other instruments can measure the electrified particles that stream out of the sun.

Reports from the instruments can be sent to earth by radio telemetering. The transmitter may get its power from the fierce sunlight of space, perhaps using the silicon solar batteries perfected by Bell Telephone Laboratories (TIME, July 4).