Reaching for the Moon

The U.S. is about to try to send a rocket to the moon. This week or next, the Air Force will try the first of three lunar probes planned for August, September and October. The Army's rocket team will also get two chances. All five probes, billed as more scientific than military, are supposed to be complete by next March under the International Geophysical Year program. Any one of them could turn out to be that celestial coup, a voyage around the moon by a highly instrumented vehicle. But any probe that reaches a great altitude, even if far short of the moon, will radio back news of such interest that the try will be worthwhile.

The pioneer probe vehicle weighs about 60 Ibs., is shaped like a doughnut with a sausage through its middle. If all goes well at the Cape Canaveral launching pad, a three-stage Thor-Able rocket will shoot the probe into space at an initial speed of 23,827 m.p.h. After the third-stage rocket drops off at 200 miles beyond earth, the probe, still pulled by earth, will gradually slow down as it flies for almost three days.

The Unseen Face. The probe will be fired roughly eastward to get the added throw of earth's eastward spin, and its course will be an elongated S in the plane set by the moon's 27-day easterly revolution around the earth. The reverse in the curve will come when the probe nears a rendezvous in the moon's path and feels the moon's pull.

Ground controllers at the Space Technology Laboratory of Thompson Ramo Woolridge Corp. in Inglewood, Calif, will study the flight closely. At the proper instant, an Air Force tracking station in Honolulu will trigger the probe's own rocket, guiding it so that the moon sweeps it in. Then the probe can make a lazy, 50-hour pass around the moon, performing such chores as sending an electric-eye view of the moon's unseen face. Theoretically, the moon could sling the vehicle back to earth in a figure-eight-shaped voyage (TIME, June 23).

The odds against success are great.They begin on the ground, where the Thor rocket has yet to prove its reliability. The probe should be launched only during the four days of the month when the moon is in the best position for tracking; if the rocket fizzles on the launching pad, another attempt must await the same short period next month. Even if the probe does get off on schedule, the perils of imprecision mount as the vehicle soars closer to the moon. The margin for error at the rendezvous point is about 30 minutes, and the slightest miscalculation in the rocket's fuel mixture could ruin the whole attempt.

Stirring Snooper. But any probe that sails a respectable distance into space will repay the sweat and strain. If it soars just 2,500 miles above earth, it will top all artificial satellites, and its instruments will be snooping in regions unknown to man. A probe that got within 50,000 miles of the moon would be an enormous scientific success. Its instruments could record meteorite density, perhaps reveal whether the moon has an atmosphere. Even more important, it could tell some of the secrets of the source of earth's magnetism, and of the thickness of the radiation belt that earth satellites have already probed.

The earth's magnetic field is now known not to come from a permanent-magnet core. A probe may help confirm the current theory that the revolving earth and its molten metal interior form a giant dynamo, generating electric currents and thus magnetism. If the probe reports that the moon itself has no magnetic field, it will make the terrestrial-dynamo theory seem more credible.

Cosmic Counter. The degree of cosmic radiation in space is a bafflement that earth satellites have so far only deepened. Geiger counters aboard Explorers I and III were so swamped that they choked up. The new Explorer IV, equipped with more specialized counters, reports that radiation doubles for every 60 miles over a threshold 250 miles beyond earth.

Explorer IV spotted two other puzzles. Cosmic radiation measured close to earth is fairly weak near the geomagnetic equator (where magnetic deflection is greatest), and strongest near the magnetic poles. At 1,200 miles above South America, the radiation hit Explorer IV at a heavy ten roentgens an hour--enough to give the human space traveler his top weekly X-ray dosage in about two minutes. And one Geiger counter inside the satellite, though coated with lead 1/16 in. thick, recorded 60% as many impacts as its unshielded mate, which in turn reported radiation almost as intense as that reported by two scintillation counters outside the vehicle. Nobody knows where this radiation comes from or what gives it such high energy. One theory is that cosmic-ray protons are strengthened by interaction with vast magnetic fields wandering in space.

The best way to pierce these mysteries is to see how they affect the lunar probe. Such data alone will make the gadget a superb spy in space. It hardly matters whether it also becomes the greatest billiard shot in the history of man.

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