The nickel-iron asteroids were necessary. They supplied the building material and the major export of the Belt cities. They averaged around eighty to ninety per cent iron, anywhere from five to twenty per cent nickel, and perhaps half a per cent cobalt, with smatterings of phosphorous, sulfur, carbon, copper, and chromium. Necessary—but not sufficient.
The silicate rocks ran only about twenty-five per cent iron—in the form of nonmagnetic compounds. They averaged eighteen per cent silicon, fourteen per cent magnesium, between one and one point five per cent each of aluminum, nickel, and calcium, and good-sized dollops of sodium, chromium, phosphorous, manganese, cobalt, potassium, and titanium.
But more important than these, as far as the immediate needs of the Belt cities were concerned, was a big, whopping thirty-six per cent oxygen. In the Belt cities, they had soon learned that, physically speaking, the stuff of life was not bread. And no matter how carefully oxygen is conserved, no process is one hundred per cent efficient. There will be leakage into space, and that which is lost must be replaced.
There is plenty of oxygen locked up in those silicates; the problem is towing them to the processing plants where the stuff can be extracted.
Captain St. Simon's job was simple. All he had to do was sink an anchor into the asteroid so that the space tugs could get a grip on it. Once he had done that, the rest of the job was up to the tug crew.
He crawled across the face of the floating mountain. At the spot where the North Pole was, he braced himself and then took a quick look around at the Nancy Bell. She wasn't moving very fast, he had plenty of time. He took a steel piton out of his tool pack, transferred it to his left hand, and took out a hammer. Then, working carefully, he hammered the piton into a narrow cleft in the rock. Three more of the steel spikes were hammered into the surface, forming a rough quadrilateral around the Pole.
"That looks good enough to me, Jules," he said when he had finished. "Now that we have our little anchors, we can put the monster in."
Then he grabbed his safety line, and pulled himself back to the Nancy Bell.
The small craft had floated away from the asteroid a little, but not much. He repositioned it after he got the rocket drill out of the storage compartment.
"Make way for the stovepipe!" he said as he pushed the drill ahead of him, out the door. This time, he pulled himself back to his drilling site by means of a cable which he had attached to one of the pitons.