Well, wasn’t that grand news? It was. And the only thing that slowed Ranjit’s quiet exultation was the fact that his father’s call needed to be returned.
The old man picked the phone up on its first ring. His voice was cheerful, too, as he said, “Ah, Ranjit”—affectionate, pleased—“why do you keep secrets from your father? You didn’t tell me that Gamini Bandara had gone to England!”
Though no one was there to see, Ranjit rolled his eyes. If he had failed to tell his father the news, it was almost entirely because he had been confident his father’s watchers would make sure it got to him. The only surprising thing was that it had taken so long. Ranjit considered for a moment whether or not to mention that Gamini would at least briefly be coming home, and decided not to do the dormitory staff’s work for them. He said guardedly, “Yes, he’s going to school there. London School of Economics. His father thinks it’s the best school in the world, I think.”
“And I’m sure it is,” his father agreed, “at least for certain kinds of studies. And I know you must miss him, Ranjit, but I have to say that it goes a long way toward solving a major problem for me. No one is going to be worrying about your closeness with a Sinhalese boy when there’s an ocean or two between you.”
Ranjit didn’t know what to say to that and sensibly said nothing. His father went on. “The thing is, I’ve missed you very much, Ranjit. Can you forgive me, Ranjit?”
Ranjit had no need to think over his answer to that. “I love you, Father,” he said at once, “and there is nothing to forgive. I understand why you had to do what you did.”
“Then,” his father said, “will you come and spend your summer holidays here in Trinco?”
Ranjit assured him he would like nothing better, but he was beginning to feel uneasy. The conversation was getting sticky. He was glad when he remembered the question his father might be able to answer. “Dad? There’s a man from Trinco who’s been arrested in Colombo, Kirthis Kanakaratnam, and I have a feeling I might have known him at some time. Do you know who he is?”
Ganesh Subramanian sighed deeply—whether because the question was troubling to him or because he, too, was grateful for the change of subject, Ranjit could not tell. “Yes, of course. Kirthis. Don’t you remember him, Ranjit? My tenant? The one with all those little children, and a wife in somewhat poor health? He usually worked as a coach driver for one of the hotels along the beach. His father used to do odd jobs around the temple until he died—”
“I remember now,” said Ranjit, and he did. The man they were talking about was short and as black as Ranjit himself. He had lived, family and all, in the tiny house at the edge of Ganesh Subramanian’s property: by the most optimistic count, three rooms all told, for two adults and four tiny kids, and no interior plumbing. Ranjit’s clearest memory was of the mother despondently washing children’s clothes in a huge tin tub…and the children whining around her feet as they assiduously dirtied more clothes, and themselves.
When Ranjit got off the phone, he readied himself for bed, feeling pretty good about the world. Things were going well. He had made up with his father. He was going to see Gamini, at least briefly. And that mystery concerning the identity of this Kirthis Kanakaratnam was solved, and he would never have to think of the man again, he thought.
Statistics wasn’t quite as boring as Ranjit had feared it might be. It wasn’t much fun, either. Long before Ranjit entered the class, he had a pretty good understanding of the differences between mean, median, and mode and knew what a standard deviation was, and it didn’t take him long to learn how to draw any kind of histogram the teacher wanted. But the teacher surprisingly turned out to have a sense of humor, and when she wasn’t teaching the class what stem-and-leaf and other statistical plots were, she was almost—well, sometimes she was almost—as entertaining to listen to as Joris Vorhulst himself.
But on second thought, Ranjit told himself, no. That was going too far. She was a nice enough person, but she just didn’t have the material of Astronomy 101 to work with. Such as the space elevator and its wondrous ways.
Even Artsutanov’s lift wasn’t the only game in town. What (asked one of the students one day in astronomy class) about something like the Lofstrom loop? For that you didn’t have to start by putting some humongous satellite into orbit because the thing just sat on Earth’s surface, from which it flung your space capsules into orbit.
But there Dr. Vorhulst began to rein in the class’s speculation. “Friction,” he said succinctly. “Don’t forget friction. Remember what reentry did to a lot of the early spacecraft. If you used a Lofstrom loop, you’d need to accelerate your capsule to that seven miles a second of escape velocity that I was talking about the other day before you let go of it, and then the air friction would burn it right up.”
He paused, eyes roving over his class, expression as good-natured as always but with a faint twinkle that made Ranjit expect some sort of surprise was coming. “So,” the teacher said sociably, “have any of you junior-grade astronauts figured out what kind of rocket drive your ship is going to have yet?”
Ranjit hadn’t thought of anything beyond the usual fuel-plus-oxidizer. He kept his mouth shut, though, because he knew, from the fact that the professor had raised the question in the first place, that Dr. Vorhulst had something else in mind.
So did his seatmate, but he responded in a different way. His hand went right up. “You’re not talking about a chemical rocket, are you, Dr. Vorhulst? So, then, what do you think? Maybe a nuclear-powered one?”
“Good guess,” the teacher said, “but, no, I don’t think a nuclear-powered rocket would be your best bet, at least not the kind of nuclear power you mean. Oh, there are designs around for rockets that were driven by exploding atom bombs, one after another. We can talk about them if you like, but for getting from LEO to Mars I think there are two much better possibilities. Both of them are tailor-made to be used with some kind of space elevator to boost them into low earth orbit because they’re both way too feeble to lift anything off Earth’s surface and into space. One is the solar sail. The other is the electric rocket.”
Ten minutes later Dr. Vorhulst had given short and convincing reasons for avoiding nuclear explosions as rocket propellants—the need for heavy shielding to protect astronauts from the deadly radiation, and anyway who wants to shoot a few hundred atomic bombs off into space? Solar sails had a lot to recommend them, he conceded, but they were dreadfully slow and not very maneuverable. However, the electric rocket, while also pretty slow to accelerate, required no fuel storage and produced no undesired byproducts. Where did the electricity come from? Perhaps from an onboard nuclear power plant, Vorhulst conceded, but just as easily from solar power—that is, from solar power in space, where there were no nights or cloudy weather, so that the sun always shone. “And what do you do with that electricity? You use it to ionize some working fluid—a gas like xenon, for instance—and the gas fires itself out of your rocket nozzles at very high velocity, and off you go.”
He paused for a breath. “All right,” he admitted, “an electric rocket would not accelerate very fast.” But it would keep right on accelerating as long as you liked, and the longer the acceleration, the greater its velocity would be. You could accelerate until you were halfway there. Then you could turn around and decelerate until you arrived. Did anyone see what that implied?
Vorhulst gave them a few moments to figure it out, but no one did. “It means,” he told them, “that the farther your trip, the faster the speed that you’ll attain. You wouldn’t want to use an electric rocket to go to the moon. Short trip; you don’t really have time to get going very fast. For Mars, though, it’s optimal. And for the outer planets, say Uranus or Neptune, why, that trip doesn’t take much longer than to Mars! And if you’re really going to go a far piece, say to the Oort cloud, you build up so much velocity with all that acceleration that that enormous journey in fact becomes feasible!”