Juno's Gold Cone

It was a clear, calm night at Cape Canaveral. The Army, making its first attempt to shoot the moon, had spent weeks fussing over the Juno II, a 60-ton Jupiter IRBM with a spike of high-speed rockets mounted on its nose. At twelve seconds after 12:45 a.m., almost exactly on schedule, Juno II took off. It climbed loudly but smoothly, arching slightly north of east. For about three minutes the first-stage rocket burned brightly, diminishing slowly with distance. Then its power shut off, and the upper stages coasted flameless for 55 seconds. About 110 miles up and 160 miles distant, the eleven solid-fuel rockets in the second stage ignited as scheduled. The third and fourth stages ignited too, and Pioneer III, Juno II's instrumented moon probe, was on its own.

The launch looked good. But lack of further reports made veteran "birdwatchers" sense that something had gone slightly wrong. Later that night came confirmation : Dr. Wernher von Braun, the Army's top space man, admitted that Juno II had missed perfection by a thin but sufficient hairbreadth. It was still climbing, but not climbing fast enough to get near the moon.

Too Fast, Too Soon. The failure was due to one of those technical minutiae that bedevil rocketeers. The Jupiter's reliable first stage had been modified for the occasion by elongating its tanks to give it more fuel capacity. This required a change in the complicated valve that controls the mixture of kerosene and liquid oxygen. Apparently the rejiggered valve did not work quite right. Either the kerosene or lox was used up too fast, and the flame went out 3.7 seconds sooner than it should have. The toolow boost of the first stage (plus a small aiming error) kept Pioneer III from reaching its intended speed.

Pioneer III was a 12.95-lb. Fiberglass cone. Its surface was washed thinly with gold to make it electrically conductive, and it was ingeniously utilized as an antenna for Pioneer's radio. Over the gold were stripes of black and white paint, designed to control heat from the sun's rays and thus to keep Pioneer III warmer than Pioneer I, whose interior became so cold that some instruments did not work.

Pioneer III was designed to attain a top speed of 24,486 m.p.h. This would have been enough to toss it free of the earth's gravitation and make it a satellite (or burned-up victim) of the sun. The actual speed attained, 23,606 m.p.h., was only enough to carry the gold cone 66,654 miles from the earth. It reached its high point in 20 hours of travel. Then it fell back. Gathering speed again in its long fall, it hit the earth about 20 hours later in a brief streak of flame in the night sky over Africa.

Yo-Yos for Spin. Since Pioneer III never approached the moon, not all its instruments came into play. The most novel one was an optical gadget designed to send a radio signal when it saw a bright object the size of the moon at a distance of 22,000 miles. The instrument was shielded from the sun, and it would have been activated by a timing device only after the receding earth looked smaller than the approaching moon.

All the upper stages of Juno II, including the gold cone, had been gyrostabilized by spinning at 400 r.p.m. This rapid motion would have kept the moonspotter from operating, so an ingenious system was devised to slow the spin. Two wires about 5 ft. long were wrapped around the base of the cone. On their ends were small (.2 oz.) weights, called "yo-yos'' by their designers. A timer was set to let the wires unwind about ten hours after launch. The yo-yos would swing outward, and the energy needed to make them swing in large circles would be taken from the spin of the cone, making it slow down to about 51 r.p.m.

The overall purpose of this intricate and spider-light gadgetry was to try out a way to trigger cameras and other viewing equipment on the more ambitious space probes of the future. But the moon's image did not grow big and near enough to work the trigger.

Two Geiger counters worked well, should enable scientists to chart more exactly the dangerous Van Allen Radiation Belt that surrounds the earth (TIME, Dec. 8). The core is believed to be about 5,000 miles up. The Explorer satellites have charted its lower levels. The instruments of the Air Force's Pioneer I, the only other object to climb to the belt's upper reaches, did not start working until they reached an altitude where the Van Allen radiation is fading out. If Pioneer III finds the core and ceiling of the radiation belt, its faltering pass at the moon will be rated a scientific triumph.

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