There is a certain principle known as the conservation of angular momentum. A ship approaching a planet has always some velocity relative to the planet's surface. Within a wide range of speeds, that angular velocity will make a ship take up an orbit at a distance appropriate to its speed. The greater the speed, the lower the orbit. It is like a weight on a string, twirled around one's finger. As the string winds up, the weight spins faster. It is like a figure skater spinning in one spot on the ice with arms outstretched, who spins more and more rapidly as he brings his arms closer to his body. The Aesclipus Twenty had such orbital, angular momentum. It could not descend vertically without losing its velocity. If it was to land safely, it would have to lose its velocity and at the moment it touched ground it must have exactly the motion of the ground it touched, for exactly the same reason that one stops a ground-car before stepping out of it.
But a grid field could only push or pull in one direction at a time. To land a ship it must cease to pull planetward from time to time, and push the ship sidewise to match its speed to that of the ground. If it didn't, the ship would go on beyond the horizon—or seem to.
So Calhoun waited. Grimly. The ship, plunging vertically, still retained its lateral speed. That speed drove it toward the horizon. It was necessary to pull it back to pull it down. So the bearded man, cursing as the ship swung away from the vertical, fumbled to pull it back.
An extremely skilled operator might well have done so, even against Calhoun's resistance. The shift of directional pull—or thrust—could have been made so swiftly that the ship would be actually free of all fields for less than the hundredth of a second. However, such fine work required practice.
Calhoun felt the ship shiver for the fraction of an instant. For that minute portion of a heartbeat, the downward pull had to be cut off so the sidewise push could be applied. But in that instant Calhoun jammed down the emergency rockets' control to maximum possible thrust. He was flung back into the pilot's chair. The weight of his chest forced air explosively out of his lungs. Murgatroyd went skittering across the floor. He caught an anchored chair leg with a wide sweep of his spidery arms and clung there desperately, gasping.
Three. Four. Five seconds. Calhoun swung the ship's nose and went on. Seven. Eight. Nine. Ten.
He cut the rocket-blast at the last instant before he would have blacked out. He panted. Murgatroyd said indignantly, "Chee! Chee! Chee!"
Calhoun said with some difficulty, "Right! I did you a dirty trick, but it had to be done! Now if we can keep him from getting his field locked on us—again . . ."
He sat alertly in the pilot's chair, recovering from the strain of such violent acceleration for even so brief a period. A long time later there was a faint, fumbling sensation as if a force field, groping, touched the ship. He blasted off at an angle at high acceleration again.
Then the ship was clear. It reached a spot where the landing grid, on the curved surface of Kryder II, was below the horizon. The Med Ship had orbital velocity. Calhoun made certain of it when he looked at the nearest-object indicator. He was then very close to atmosphere but the planet now below him curved downward and away from his line of flight. The ship was actually rising from the planetary surface. Calhoun had escaped a collision with Kryder II by speeding up across its face. One can sometimes avoid a collision in traffic by speeding up, but it is not the safest thing for either ground-cars or spaceships to do.
Murgatroyd made querulous noises to himself. Calhoun got out the data on the planet Kryder II. There were continents and highways and mountain ranges and cities. He studied the maps and a view of the actual surface beneath him. The communicator screen was blank, and had been since the horizon rose between the grid and the fleeing ship. He flipped it off. At the sunset line there was a city. He located himself.
Murgatroyd said "Chee!" in an apprehensive tone as the emergency rockets roared again.
"No," said Calhoun. "No more full-force rocketeering, Murgatroyd. And I'm not going to take the chance of being outwitted again. I've been fooled twice by not knowing how a murderer's mind works. I'm going to operate out of contact with such characters for a while. I'm going to land and do a burglary and get back out to space again."
He checked on maps. He glanced frequently at the nearest-object dial. He swung the ship and blasted his rockets again, and watched the dial, and used the rockets still again. The Med Ship was slowing. It curved downward. Presently, the needle of the nearest-object dial quivered. The Med Ship, still out of atmosphere, was passing above mountains.
"Now, if we can land beyond, here . . ." said Calhoun.
Murgatroyd was not reassured. He watched. He grew uneasy as Calhoun went through the elaborate, tricky and definitely dangerous operation of landing the Med Ship in the dark, on unknown terrain, and by instruments only except for the last few minutes. During those last few minutes the screens showed forests below the hovering Med Ship, lighted in unearthly fashion by the rocket flames. With that improbable light he finished the landing. He remained alert until sure that the ship was steady on her landing-fins. He cut off the rockets. He listened to the outside microphones' report. There were only the night sounds of a long colonized planet, where a Terran ecological system had been established and there were birds and insects of totally familiar varieties.
He nodded to himself. He turned on the planetary communications receiver. He listened for a long time. He heard news broadcasts. There was no mention of the Med Ship reported as arriving. There was resolutely hopeful news of the plague. It had broken out in a new area, but there was great hope that it could be contained. The use of combined antibiotics seemed to promise much. The death rate was said to be down slightly. There was no mention of the fact that the real percentage of deaths might be obscured by a large increase of new patients who wouldn't normally die just yet.
Calhoun listened. At last, he stirred. His eyes fell upon the small computer which had searched in the ship's microfiles for data on compounds with boiling points below such-and-such, with absorption coefficients in certain ranges, which had an inhibitive effect upon the formation of certain other substances. It was waiting to give him the information he'd asked for. He read it. He looked pleased.
"Not bad," he told Murgatroyd. "The broadcasts say the plague is prevalent in this area, and this says we want some groceries and ditch water. I've the crudes to make up these prescriptions."
He made ready to go aground. He was armed. He took a compass. He took certain highly odorous pellets. Murgatroyd zestfully made ready to accompany him.
"No," said Calhoun. "Not this time, Murgatroyd! You have many gifts, but burglary isn't one of them. I couldn't even depend on you to be a properly suspicious lookout."
Murgatroyd could not understand. He was bewildered when Calhoun left him in the Med Ship with water and food at hand. When Calhoun closed the inner air-lock door, he could still hear Murgatroyd arguing desperately, "Chee! Chee-chee!"
Calhoun dropped an odorous pellet on the ground and moved away on a compass course. He had a hand lamp, which he used sparingly. There were tree trunks to run into and roots to stumble over and much brushwood to be thrust through. Ultimately he came upon a highway. He deposited a pellet. With his hand lamp off, he searched as much of the sky as he could. He concluded that there was a faint glow in the sky to southward. He set out along the highway toward it.
It was not less than four miles away, and then there was a small town, and it seemed lifeless. Street lights burned, but there were no lighted windows anywhere. There was no motion.