Rapid Transit

The compass, the chronometer, the sextant gradually changed navigation from an art to a science, made mere curiosities of such seafaring geniuses as the early Polynesians--who, according to legend, could smell land far beyond the horizon and head their boats accordingly. In 1960, man's most accurate substitute for weather-dependent celestial navigation is World War II's loran (for long-range aid to navigation), a system of cross-monitored radio signals that is highly expensive and covers only the more frequently traveled parts of the earth. Last week loran seemed destined for obsolescence, as an experimental Navy satellite called Transit I-B blasted into space from Florida's Cape Canaveral.

Transit I-B (an attempt to send Transit I-A into orbit failed last September) is only the first basic step in a process that is expected to take two years to develop. Many of the first press stories excitedly treated it as though it were already an operational system. It is not--however dramatic its promise for the future.

By Doppler Effect. Lofted by an Air Force Thor-Able-Star rocket. Transit I-B slanted around the world from 51DEG N. to 51DEG S. and settled into an elliptical orbit (apogee, 475 miles; perigee, 235 miles), sending radio signals from the moment it left the pad. From Texas to Hampshire, England, tracking stations sent information to a computing center near Washington, D.C. In future models, orbit-predicting data will be quickly rebroadcast to the satellite, which will remember its daily itinerary on magnetic tape, constantly announce it from space (the day-to-day orbital variations are minuscule, but would be vital to navigators).

The key to the navigation system is a common phenomenon first articulated scientifically little more than 100 years ago, when Austrian Physicist Johann Christian Doppler noted that sound waves coming from a moving object increase in frequency as the source of the sound approaches an observer, decrease as it moves away. Thus, in what has become the standard example of the Doppler effect, a train whistle seems to rise and fall in pitch as the train goes by. Similarly, the signals from a satellite increase in frequency as they move nearer to a receiver on earth, diminish as they move on. By measuring the rate of change of these frequencies, a navigator can determine his exact distance from the satellite's path. And since Transit will also announce just where it will be on its path at any given moment, a computer on shipboard will be able to tell the navigator where he is.

Scrounged Parts. Only one satellite is needed for an accurate navigational fix, but when the Navy's system is operational in 1962, four satellites will crisscross in a synchronization planned to serve all quarters of the earth. The advantage to commercial shipping will be slight, since present methods are more than adequate. But the military significance is great, may solve the major problem of missile shots from submarines: determining the exact distance and direction from the sub to the target. Cruising underwater far off the beaten track and out of loran's range, a nuclear submarine will be able to poke a whip antenna above the surface, take a fix on the nearest Transit satellite, and blaze away with lethal accuracy.

The Transit project began as a hobby of Johns Hopkins Physicists George Weiffenbach, 39, and William Guier, 33. When Russia's Sputnik I went up in 1957, the two men stripped a hi-fi set, scrounged spare parts from a Hopkins lab, built a receiver to record the Soviet satellite's beeps. Charting the Doppler shifts, they tracked Sputnik with remarkable accuracy. A third colleague, Canadian-born Physicist Frank McGuire, suggested that if satellite positions could be plotted from earth, earth positions could be plotted by readings from a satellite. The three men took their idea to Richard B. Kershner, 47, head of the space development division of Hopkins' Applied Physics Laboratory and a longtime man-about-missiles (Terrier, Polaris). Kershner sold it to the Navy's Admiral Arleigh Burke.

Hob in the Ionosphere. The project's first tentative step aloft, Transit I-B is a sphere with a 36-in. diameter, has a spiraling stripe around its exterior. The stripe is actually a broad-band antenna capable of handling the four different frequencies on which the satellite broadcasts from its two transmitters. When the Transit quartet eventually go aloft, they will be more streamlined, each carrying two solar-powered transmitters (each broadcasting on one frequency) and weighing from 50 Ibs. to 100 Ibs. v. the present satellite's 265 Ibs. Cost estimates: $1,000,000 apiece to launch, plus $3,000,000 a year for maintenance.

By launching the satellite, the Navy and the Johns Hopkins scientists have begun to address themselves to a long set of problems. The computation of an exact orbital path is subject to unforeseen variants; Vanguard I, for example, was pushed slightly out of orbit by pressure of sunlight (TIME, March 28). The ionosphere plays hob with radio waves, could affect the navigators' Doppler measurements. The shape of the earth is still not precisely known, and its subtle variations could lead to serious navigational errors.

But even though the program still has a long way to go, it has already demonstrated one thing. The long sluggish U.S. space program has proved its recovery with a third straight success: last month's Pioneer V (TIME, March 21) has already probed more than 4,500,000 miles into space; and the weather satellite Tiros I (TIME, April 11) last week celebrated its tenth day in orbit by sending home a detailed picture of a cyclonic cloud formation 2,000 miles wide.

Moreover, in the headline news about Transit's potential for navigation, an ordinarily front-page achievement passed all but unnoticed: the second stage (Able-Star) of the rocket that took the satellite up from Canaveral fired, then shut off and coasted, then fired again. It was the first time a rocket engine had been restarted in space.

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