Down-to-Earth Satellite

Earth-orbiting communications satellites literally come too high for the strapped treasuries of developing countries. A typical example, the National Aeronautics and Space Administration's new Applications Technology Satellite, which was launched in May to beam educational TV programs to remote regions in the U.S. and elsewhere, cost a hefty $111 million. Now engineers of a Westinghouse subsidiary, TCOM (for Tethered Communications) Inc., have devised an inexpensive alternative: a tethered balloon, held at altitudes of two or three miles, that can perform many of a satellite's functions at a bargain-basement price.

The idea is based on the signal-relay balloons that were used to reach isolated U.S. outposts in the jungles of Viet Nam. Like the military's message bearers, TCOM's balloon, or aerostat (from the Greek words for "air" and "one that stops"), as its developers call it, is anchored by cable over a fixed spot on the ground. In a test now under way in the Bahamas, an aerostat floating 11,500 ft. over Grand Bahama Island is picking up TV signals from Miami 110 miles away and rebroadcasting them on a local channel--in effect, trebling the range of the Florida stations without resorting to a satellite, a boost in signal power, costly relay towers or cables.

With the stubby fins and tail of a World War II blimp, the 175-ft.-long aerostat has proved to have extraordinary stability; Hurricane Gilda's 100-m.p.h. winds last year barely nudged it. The helium inside the balloon's tough, eight-layer plastic skin provides enough lift to allow up to 4,000 lbs. of electronic gear to be packed into the gondola hanging from its underside. The equipment can receive and rebroadcast as many as four television channels, two commercial radio stations and the data from 5,000 to 10,000 microwave circuits. At present, the aerostat must be hauled down once a week to refuel the Wankel-powered electric generator; in the future, electric power may be sent up directly from the ground through the tether cable, allowing the balloon to be left aloft almost indefinitely.

The trial balloon in the Bahamas has been so impressive that South Korea and Iran have already placed orders for their own. Several other countries are seriously considering aerostats. At $5 million for a single-balloon system, they are not only cheaper than satellites, but also considerably less costly than ground-based microwave-relay communications systems. TCOM's president, Richard Cesaro, concedes that small modifications may be needed to meet local conditions. In regions inhabited by parrots, for instance, the balloon's tether may have to be made of a material other than the Dacron-like synthetic now used. Parrots, it seems, love to chew on the stuff.

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