Defending Meteors

Space-minded strategists, some of them official, have plugged for satellites as orbiting dugouts from which operations might be conducted against the earth below. A relatively minor experiment that the Air Force told about last week showed that satellite-based aggression may not be so easy as it sounds. On the night of Oct. 16 a standard Aerobee research rocket was fired at Holloman Air Force Base, N. Mex. At 35 miles altitude the nose separated from the rest of the rocket and coasted up to 55 miles. Then the nose exploded, but in no ordinary way. Inside its aluminum skin it carried three 2-to 5-lb. "shaped charges" of explosive designed and fitted by Astronomer Fritz Zwicky of CalTech.

A shaped charge is a mass of explosive with a carefully calculated cavity that focuses the force of the explosion in a desired direction. If the cavity is a conical depression, the explosion shoots out a spike of flame with enormous speed and power. Wartime bazookas carried shaped charges that punched neat holes in the armored sides of tanks.

Escape Velocity. When the Aerobee's nose exploded 55 miles up, the focused force of the shaped charges made three jets of aluminum pellets shoot into the near-vacuum like shot from three shotguns. The Air Force announcement is none too clear about what happened, but Maurice Dubin, physicist in charge of the project, thinks that some of the pellets reached the speed of 40,000 m.p.h. A photograph taken of the explosion showed meteorlike trails whose speed could be measured by a fast-moving shutter on the camera.

Since the particles started their flights at an altitude where there is still a little air, they were probably slowed down considerably by it. But Dubin thinks that some of them may have reached outer space while still moving about 30,000 m.p.h. This exceeds the escape velocity (25,000 m.p.h.) that is necessary to carry an object beyond the pull of the earth's gravitation. Any particles that did escape moved into the sun's gravitational jurisdiction. They will either 1) be swallowed by the sun, or 2) move around it on elliptical, cometlike orbits.

Sitting Satellite. The scientists of the Air Force Cambridge Research Center who conducted the experiment say that their purpose was to study the high atmosphere by injecting artificial meteors into it and observing their behavior and the light generated by them. This explanation has its elements of truth, but the experiment demonstrated in addition how easy it would be to fill a selected patch of space with deadly, speeding particles.

In spite of its speed (18,000 m.p.h.) a satellite is a sitting duck. Its motion on its orbit can be predicted precisely, days in advance if necessary. So if any kind of satellite makes itself objectionable to a nation that it passes over, a defending rocket can be shot up 'to meet it. A direct hit by the rocket would not be necessary. When it reaches the satellite's orbit, its warhead could explode into thousands or hundreds of thousands of tiny artificial meteors, any one of which packs enough energy to do a job on the satellite.

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