THIN EDGE

BY JOHNATHAN
BLAKE MAC KENZIE

ILLUSTRATED BY JOHN SCHOENHERR

I

"Beep!" said the radio smugly. "Beep! Beep! Beep!"

"There's one," said the man at the pickup controls of tugship 431. He checked the numbers on the various dials of his instruments. Then he carefully marked down in his log book the facts that the radio finder was radiating its beep on such-and-such a frequency and that that frequency and that rate-of-beep indicated that the asteroid had been found and set with anchor by a Captain Jules St. Simon. The direction and distance were duly noted.

That information on direction and distance had already been transmitted to the instruments of the tugship's pilot. "Jazzy-o!" said the pilot. "Got 'im."

He swiveled his ship around until the nose was in line with the beep and then jammed down on the forward accelerator for a few seconds. Then he took his foot off it and waited while the ship approached the asteroid.

In the darkness of space, only points of light were visible. Off to the left, the sun was a small, glaring spot of whiteness that couldn't be looked at directly. Even out here in the Belt, between the orbits of Mars and Jupiter, that massive stellar engine blasted out enough energy to make it uncomfortable to look at with the naked eye. But it could illuminate matter only; the hard vacuum of space remained dark. The pilot could have located the planets easily, without looking around. He knew where each and every one of them were. He had to.

A man can navigate in space by instrument, and he can take the time to figure out where every planet ought to be. But if he does, he won't really be able to navigate in the Asteroid Belt.

In the Nineteenth Century, Mark Twain pointed out that a steamboat pilot who navigated a ship up and down the Mississippi had to be able to identify every landmark and every changing sandbar along the river before he would be allowed to take charge of the wheel. He not only had to memorize the whole river, but be able to predict the changes in its course and the variations in its eddies. He had to be able to know exactly where he was at every moment, even in the blackest of moonless nights, simply by glancing around him.

An asteroid man has to be able to do the same thing. The human mind is capable of it, and one thing that the men and women of the Belt Cities had learned was to use the human mind.

"Looks like a big 'un, Jack," said the instrument man. His eyes were on the radar screen. It not only gave him a picture of the body of the slowly spinning mountain, but the distance and the angular and radial velocities. A duplicate of the instrument gave the same information to the pilot.

The asteroid was fairly large as such planetary debris went—some five hundred meters in diameter, with a mass of around one hundred seventy-four million metric tons.

Within twenty meters of the surface of the great mountain of stone, the pilot brought the ship to a dead stop in relation to that surface.

"Looks like she's got a nice spin on her," he said. "We'll see."

He waited for what he knew would appear somewhere near the equator of the slowly revolving mass. It did. A silvery splash of paint that had originally been squirted on by the anchor man who had first spotted the asteroid in order to check the rotational velocity.

The pilot of the space tug waited until the blotch was centered in the crosshairs of his peeper and then punched the timer. When it came around again, he would be able to compute the angular momentum of the gigantic rock.

"Where's he got his anchor set?" the pilot asked his instrument man.

"The beep's from the North Pole," the instrument man reported instantly. "How's her spin?"

"Wait a bit. The spot hasn't come round again yet. Looks like we'll have some fun with her, though." He kept three stars fixed carefully in his spotters to make sure he didn't drift enough to throw his calculations off. And waited.

Meanwhile, the instrument man abandoned his radar panel and turned to the locker where his vacuum suit waited at the ready. By the time the pilot had seen the splotch of silver come round again and timed it, the instrument man was ready in his vacuum suit.

"Sixteen minutes, forty seconds," the pilot reported. "Angular momentum one point one times ten to the twenty-first gram centimeters squared per second."

"So we play Ride 'Em Cowboy," the instrument man said "I'm evacuating. Tell me when." He had already poised his finger over the switch that would pull the air from his compartments, which had been sealed off from the pilot's compartment when the timing had started.

"Start the pump," said the pilot.

The switch was pressed, and the pumps began to evacuate the air from the compartment. At the same time, the pilot jockeyed the ship to a position over the north pole of the asteroid.

"Over" isn't quite the right word. "Next to" is not much better, but at least it has no implied up-and-down orientation. The surface gravity of the asteroid was only two millionths of a Standard Gee, which is hardly enough to give any noticeable impression to the human nervous system.

"Surface at two meters," said the pilot. "Holding."

The instrument man opened the outer door and saw the surface of the gigantic rock a couple of yards in front of him. And projecting from that surface was the eye of an eyebolt that had been firmly anchored in the depths of the asteroid, a nickel-steel shaft thirty feet long and eight inches in diameter, of which only the eye at the end showed.

The instrument man checked to make sure that his safety line was firmly anchored and then pushed himself across the intervening space to grasp the eye with a space-gloved hand.

This was the anchor.

Moving a nickel-iron asteroid across space to nearest processing plant is a relatively simple job. You slap a powerful electromagnet on her, pour on the juice, and off you go.

The stony asteroids are a different matter. You have to have something to latch on to, and that's where the anchor-setter comes in. His job is to put that anchor in there. That's the first space job a man can get in the Belt, the only way to get space experience. Working by himself, a man learns to preserve his own life out there.

Operating a space tug, on the other hand, is a two-man job because a man cannot both be on the surface of the asteroid and in his ship at the same time. But every space tug man has had long experience as an anchor setter before he's allowed to be in a position where he is capable of killing someone besides himself if he makes a stupid mistake in that deadly vacuum.

"On contact, Jack," the instrument man said as soon as he had a firm grip on the anchor. "Release safety line."

"Safety line released, Harry," Jack's voice said in his earphones.

Jack had pressed a switch that released the ship's end of the safety line so that it now floated free. Harry pulled it towards himself and attached the free end to the eye of the anchor bolt, on a loop of nickel-steel that had been placed there for that purpose. "Safety line secured," he reported. "Ready for tug line."

In the pilot's