"Hold it!"
He pointed to the airlock. Both doors were open. The young man at the control-board flushed vividly. One of the others closed and dogged the doors.
The ship lifted. Calhoun watched with seeming negligence. But he found occasion for a dozen corrections of procedure. This was presumably a training voyage of his own suggestion. Therefore when the blueskin pilot would have flung the Med Ship into undirected overdrive, Calhoun grew stern. He insisted on a destination. He suggested Weald. The young men glanced at each other and accepted the suggestion. He made the acting pilot look up the intrinsic business of its sun and measure its apparent brightness from just off Dara. He made him estimate the change in brightness to be expected after so many hours in overdrive, if one broke out to measure.
The first blueskin student pilot ended a Calhoun-determined tour of duty with rather more of respect for Calhoun than he'd had at the beginning. The second was anxious to show up better than the first. Calhoun drilled him in the use of brightness-charts, by which the changes in apparent brightness of stars between overdrive hops could be correlated with angular changes to give a three-dimensional picture of the nearer heavens. It was a highly necessary art which had not been worked out on Dara, and the prospective astrogators became absorbed in this and other fine points of space-piloting. They'd done enough, in a few trips to Orede, to realize that they needed to know more. Calhoun showed them.
Calhoun did not try to make things easy for them. He was hungry and easily annoyed. It was sound training tactics to be severe, and to phrase all suggestions as commands. He put the four young men in command of the ship in turn, under his direction. He continued to use Weald as a destination, but he set up problems in which the Med Ship came out of overdrive pointing in an unknown direction and with a precessory motion. He made the third of his students identify Weald in the celestial globe containing hundreds of millions of stars, and get on course in overdrive toward it. The fourth was suddenly required to compute the distance to Weald from such data as he could get from observation, without reference to any records.
By this time the first man was chafing to take a second turn. Calhoun gave each of them a second gruelling lesson. He gave them, in fact, a highly condensed but very sound course in the art of travel in space. His young students took command in four-hour watches, with at least one breakout from overdrive in each watch. He built up enthusiasm in them. They ignored the discomfort of being hungry, though there had been no reason for them to stint on food in Orede—in growing pride in what they came to know.
When Weald was a first-magnitude star, the four were not highly qualified astrogators, to be sure, but they were vastly better spacemen than at the beginning. Inevitably, their attitude toward Calhoun was respectful. He'd been irritable and right. To the young, the combination is impressive.
Maril had served as passenger only. In theory she was to compare Calhoun's lessons with his practise when alone. But he did nothing on this journey which—teaching considered—was different from the two interstellar journeys Maril had made with him. She occupied the sleeping-cabin during two of the six watches of each ship-day. She operated the food-readier, which was almost completely emptied of its original store of food;—confiscated by the government of Dara. That amount of food would make no difference to the planet, but it was wise for everyone on Dara to be equally ill-fed.
On the sixth day out from Dara, the sun of Weald had a magnitude of minus five-tenths.[A] The electron telescope could detect its larger planets, especially a gas-giant fifth-orbit world of high albedo. Calhoun had his four students estimate its distance again, pointing out the difference that could be made in breakout position if the Med Ship were mis-aimed by as much as one second of arc.