None of this, of course, applied to Astronomy 101.
There Dr. Vorhulst managed to make every session a pleasure. Like what happened when they were talking about terraforming—that is, reworking planetary surfaces so that human beings could live on them. And, if you were going to do that, how did you get there to do the terraforming?
Ranjit’s answer would have been “rocket ships.” His hand was already halfway toward the raised position so that he could offer that answer when the teacher froze it mid-motion. “You’re going to say ‘rocket ships,’ aren’t you?” Dr. Vorhulst asked, addressing the whole class and particularly the dozen or so who, like Ranjit, had been putting their hands up. “All right. Let’s think about that for a bit. Let’s suppose that we want to start terraforming Mars, but all we have to work with is an absolute minimum of heavy-duty earthmoving machinery. One very big backhoe, for instance. One bulldozer. A couple of medium-size dump trucks. Fuel enough to run them all for, let’s say, six months or so. Long enough to get the job started, anyway.” He paused, eyes on a hand from the second row that had just sprouted. “Yes, Janaka?”
The boy named Janaka eagerly shot to his feet. “But, Dr. Vorhulst, there’s a whole plan to make fuel from Martian resources that are already there!”
The professor beamed at him. “You’re absolutely right, Janaka. For instance, if there really is a large amount of methane under Mars’s permafrost, as many people think there is, then we could burn that for fuel, assuming we could find some oxygen to burn it with. Of course, to do that we’d really have to have a bunch more heavy machinery, which would need a bunch more fuel to run it until the extraction plants were working.” Vorhulst gave the boy a friendly smile. “So, Janaka,” he said, “I think that if you wanted to start any terraforming in the near future, probably you’d want to fly your fuel in after all. So let’s see.”
He turned to the whiteboard and began writing. “Say six or eight tons of fuel to start. The earthmoving machines themselves—what would you say, at least another twenty or thirty tons? Now to get those at least twenty-eight tons of cargo from low earth orbit, known as LEO, to Mars, we need to put them into some kind of spaceship. I don’t know what that would mass, but let’s say the ship itself would run fifty or sixty tons, plus the fuel to get it from LEO to Mars.” He stepped back to look at his figures on the board and frowned. “I’m afraid we have a problem,” he said to the class, addressing it over his shoulder. “All that stuff won’t start out in low earth orbit, will it? Before the ship can start heading for Mars, we have to get it into LEO. And I’m afraid that’s going to be expensive.”
He paused, looking with a sorrowful expression at his class. He was waiting for some student to rise to the occasion, and after a bit, one of the girls did. “That’s because it has to get out of the Earth’s gravity well, isn’t it, Dr. Vorhulst?”
He gave her a big smile. “Exactly right, Roshini,” he said, looking up at the class timer that had just turned amber. “So you see, it’s that first step that’s a killer. Is there anything we can do to make it easier? We’ll try to find out next time. But if any of you guys just can’t wait for the answer, hey, that’s what search engines are for.”
And then, as everybody began to rise, he said, “Oh, one more thing. You’re all invited to the end-of-term party at my house. Don’t dress any differently than you do for class, and don’t bring any house gifts but yourselves. But do come. You’ll hurt my mother’s feelings if you don’t.”
One of the things that Ranjit liked best about his astronomy teacher—apart from such unexpected surprising joys as end-of-term parties—was that Dr. Vorhulst didn’t actually spend a lot of time in the normal practice of teaching. When, at the end of each session, Dr. Vorhulst told the class what the next session was going to be about, Vorhulst knew perfectly well that his hundred eagerly motivated space-cadets would look all that material up long before the next session started. (The few who hadn’t started out all that motivated—the ones who had entertained the false hope of a snap course and an easy A—either soon dropped or were reformed by the enthusiasm of their fellows.) Thus, each time, Dr. Vorhulst had that next session to play.
This time, however, Ranjit couldn’t hit the search engines right away. He had other obligations. First there was the terminally tedious hour and fifty minutes of philosophy to get through. Then came the quick gulping of a detestable sandwich and a lukewarm bag of some anonymous variety of juice, which was lunch, all swallowed in a hurry so he could get to the two o’clock bus that would take him to the library.
But just outside the lunchroom his seatmate in Astronomy 101 was standing with a few of his fellows, and he had news for Ranjit. “You didn’t hear what Dr. Vorhulst had promised for our next session? I was just telling my friends the news about it. The Artsutanov project, you know. Vorhulst says we might get the project built right here! In Sri Lanka! Because the World Bank’s just announced that it has received a request for financing a study of a Sri Lankan terminal!”
Ranjit was just opening his mouth to ask what all that meant when one of the others said, “But you said it might not pass, Jude.”
Jude looked suddenly brought down. “Well, yes,” he admitted. “It’s the damn Americans and the damn Russians and the damn Chinese that have all the power—and all the money, too. They’re just as likely as not to hold it up, because once you’ve got an Artsutanov lifter going, any damn little pipsqueak country in the world can have a space program of its own. Even us! And there goes their monopoly! Don’t you think?”
Ranjit was saved the embarrassment of not having an answer for that—indeed, of not having any really good idea of what Jude was talking about in the first place—by the Sinhalese group’s growing hunger. And then in the library—search engines working—Ranjit was soaking up information at a high rate of knots. The more he learned, the more he shared Jude’s excitement. That tough first step of getting from Earth’s surface to LEO? With an Artsutanov skyhook it was no problem at all!
True, feasibility studies were a long way from an actual car that you could hop into and have drawn at high speed up to low earth orbit, no million-liter oceans of explosive liquid propellant required. But it might happen. Probably would happen, sooner or later, and then even Ranjit Subramanian might be one of those lucky ones who would circle the moon and cruise among Jupiter’s satellites and perhaps even walk across the hopelessly dry deserts of Mars.
According to what the search engines turned up for Ranjit, as far back as 1895 Russia’s first thinker on space travel, Konstantin Tsiolkovsky, got a look at Paris’s Eiffel Tower and then came up with his idea. A good way to get a spacecraft into orbit, he said, was to build a really tall tower with a built-in elevator and hike your ship up to the top before turning it loose to roam.
However, in 1960 a Leningrad engineer named Yuri Artsutanov read Tsiolkovsky’s book and quickly saw that the plan wouldn’t work. It was a lesson the ancient Egyptians had learned long ago—as had the Maya, a few thousand years later and on the other side of the world. The lesson was that there is a limit to how tall you can build a tower or a pyramid, and that limit is set by compression.
In a compression structure—which is to say, any structure that is built from the ground up—each level must support the weight of all the levels above it. That would be hundreds of kilometers of levels, to reach low earth orbit, and no imaginable structural material could support that weight without crumbling.