Voice in Space

The world has a new scout in the space between the planets. Its paddle-shaped solar batteries wheeling in the glaring sunlight of airless space, Pioneer V, a 94.8-lb. sphere only 26 in. in diameter, was the first interplanetary traveler with a far-ranging and long-lasting voice. If all goes well, scientists will be hearing from Pioneer V steadily for the next five months, then sporadically for years to come, as it swings back within range.

At five seconds past 8 a.m. one morning last week, the Thor-Able rocket took off from its pad at Cape Canaveral with a symmetrical gush of flame and climbed into the morning sky. Above the clouds, the second-stage rocket, the Able part of the act, took over and burned as scheduled. Unseen in space, four paddle-batteries sprang into position. At an altitude of 300 miles, the solid-propellant third stage fired and pushed its speed to 24,869 m.p.h.

Across the Atlantic in Britain, a young (34) American electronics expert, Bill Young, sat in a gadget-packed trailer parked near Jodrell Bank's giant radio telescope. The 250-ft. dish picked up the "woo-woo" signal from Pioneer V's 5-watt transmitter on schedule and swung slowly to track it through the sky. Bill Young listened. Twenty-seven minutes after the launch, when the rocket was about 5,000 miles above the earth's surface, he pressed a button that sent a radio impulse to the telescope's big dish, and from there it was beamed into space. Pioneer V got the message. A switching device in its electronic insides shot an electric current through a fusible bolt. The bolt melted and released a spring. It pushed Pioneer V away from the third-stage rocket, whose burned-out carcass might otherwise interfere with efficient radio transmission.

Signal for Woo-Woo. Five minutes later, Bill Young sent another message, and Pioneer V obediently switched off its transmitter. Every hour on the half-hour Young turned the transmitter on and listened to its woo-woo sound for 15 minutes. Then he turned it off to permit the 4,800 silicon cells in Pioneer V's four "paddles" to recharge its storage batteries with solar-generated electricity. This routine was repeated successfully until the earth's rotation put Pioneer V below Jodrell Bank's horizon.

Pioneer V, part of a National Aeronautics and Space Administration experiment headed by rumpled, energetic Dr. Abe Silverstein, 51, was originally intended to send a probe to the close vicinity of Venus. The best time for the launch would have been last June. But the payload was not ready then, and a launch scheduled for December was canceled because of instrument failure. By March, Venus was far away, but NASA decided to shoot anyway. Though the Venus probe will never probe Venus intimately, it can (if all goes well) gather vital information about interplanetary space.

Slower Is Closer. To shoot at Venus or its orbit, a probe must be shot in the opposite direction to the motion of the earth on its orbit around the sun. Most of its speed will be expended in pulling away from the earth's gravitation. Any speed left over will be subtracted from the orbital speed (66,600 m.p.h.) that the probe had--as every mountain, building and man has--as part of the earth. Left behind in space with reduced speed, the probe will curve inward toward the sun.

As it falls, it will pick up speed from the sun's gravitational field and will creep ahead of the earth. After a while, it will be moving fast enough to stop falling and to maintain itself in an eccentric solar orbit. The more backward speed the probe has when it clears the earth, the slower it will be moving around the sun and the farther it will fall toward the sun before it goes into a solar orbit. To fall all the way to Venus, whose orbit is 25 million miles inside the earth's, a probe would have to escape from the earth with a backward velocity of 5,670 m.p.h.

Pioneer V did not attain quite this speed, missing it by about 150 m.p.h. So instead of intersecting the orbit of Venus, it will stay about 7,500,000 miles outside. During each of its trips around the sun, which will take 311 days, Pioneer V will swing outward toward the earth's orbit. But only very rarely will the earth be there to meet it. NASA scientists estimate that at least 100,000 years may have to pass before Pioneer V gets close enough to the earth to burn up in its atmosphere.

But it is impossible to predict to what extent the orbit of Pioneer V will be disturbed by the gravitational pull of the earth and Venus.

Five Months Away. As Pioneer V curved toward the sun, the 5-watt transmitter performed perfectly, delivering reports from its sensing instruments: two radiation counters, a magnetometer to feel for magnetic fields in space and a device to count micrometeorites. When Pioneer V recedes a few million miles from the earth, a 150-watt transmitter will take over. NASA scientists estimate that Jodrell Bank will be able to hear Pioneer V 50 million miles away. It will reach the limit of this range in about five months.

Two other space probes, one U.S. and the other Russian, have gone into solar orbits, but their radios went dead a few hundred thousand miles from the earth. Pioneer V's 150-watt transmitter is designed to work indefinitely. It will accumulate information in a recording device, send it in a five-minute burst, and then rest for five hours while the solar cells recharge its batteries. NASA scientists hope that it will still be transmitting in 1963 when Pioneer V will overtake the earth and again come within the 50 million-mile range.

Even if Pioneer V does not report except on its outward journey, it will yield information of great value. Many earth satellites have reported on conditions near the earth. Six shots toward the moon (three U.S., three Russian) have delivered data about space near the earth-moon system. But space far from any planet is still unexplored. This outer space is presumably traversed by vast clouds of material shot out of the sun, and they may behave differently when not near a planet. Cosmic rays and micrometeorites may behave differently, too. There may be stray magnetic fields wandering free through empty space. The information Pioneer V can report about all these things will be essential when, years hence, man himself ventures on voyages between the planets.

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