"She is pretty large, I'll grant you—about four hundred and thirty meters long, and the habitat ring is almost three hundred meters across. But the diameter of that habitat ring is necessary."
"Why?"
Glendale wondered if McNeil was really that ignorant of basic scientific concepts. But whether or not he was, the question served nicely to make an explanation to the general public that wouldn't sound patronizing.
"You all understand, I'm sure, that we can't send people on such a months-long voyage through space under weightlessness." He waited just long enough for a little wave of nods from about half the reporters present. "People did not evolve in null-gravity or micro-gravity conditions. We need a certain amount of gravity to keep our bone structure from deteriorating, and prevent all the other problems that years of research on microgravity have shown us turn up in people who spend too much time weightless. And, alas"—here he smiled wryly—"we do not have any of the methods of generating artificial gravity that the movie industry does. So, the only method we can use is to spin the ship and substitute centrifugal force for gravity."
"I understand all that," McNeil said impatiently. "All the more reason, it seems to me, to use a small ship. It'd be easier to spin."
Glendale gave him that long, level stare that he'd perfected over the decades. First, on bumptious grad students; later, on even more bumptious reporters. It was a stare that managed to convey, without being precisely rude, that Glendale was momentarily stumped because the question was so inane that he had to grope to remember the answer. As if someone had asked him, Dr. Glendale, how should one tie one's shoes?
"Indeed." He cleared his throat. "Let me respond with a question of my own—addressed everyone here. How many of you like going to amusement parks?"
Hesitantly, there was a show of hands.
"Any of you dislike the rides? Like the teacup ones, or the rotor, or other spinning ones? Any of you really hate them?"
A number of the hands stayed up. Glendale nodded. "That's a pretty typical response. As it turns out, there's a sizable percentage of the human race that will get quite disoriented in something that spins faster than, oh, about two or three times a minute—let alone once every second or two. Now, as anyone who's been on those rides knows, how much force spin puts on you is directly related to how fast the thing spins and how far out from the center you are. If you want to have a given centrifugal force—say, equivalent to Mars' gravity of about one-third Earth's—and you want to rotate slowly—less than three times a minute—you have to be a very considerable distance out from the center. About one hundred and forty-six meters out, to be reasonably exact. If you wanted Earth-level gravity, well, you do the math. A lot farther out, meaning a lot larger ring. Luckily for us, experiments indicate that one-third gravity should be enough to prevent the problems."
"But even granting that width as necessary, what about the rest of the ship?" asked another reporter.
"Well, a good deal of the interior of the main body is fuel storage. Remember, there are no filling stations along the way. Nike has an unfueled weight of almost two thousand tons—but she'll weigh almost eight thousand tons when we top off her tanks. The rest of the main body will have some considerable extra space, but who knows what she might be asked to carry once she reaches Phobos? And she will, of course, be carrying provisions for each person on board— which is quite a few tons per person, if you calculate it out. Not to mention scientific equipment of virtually every possible description, an SSTO lander—"
"A what lander?" That came from someone who was obviously not one of the regular correspondents.
"Sorry. 'SSTO' stands for 'single stage to orbit.' It refers to a lander that will be able to land on Mars with a mostly unpowered approach, and then take off back to orbit on its own, without needing a base station. Then, we have to carry construction equipment and supplies for making base areas on Phobos itself. And so on and so on and so on. You always need to remember that when you're a hundred million miles from Earth, you can't just send someone out to the nearest hardware store to get you that screwdriver you forgot to bring along. And these people will be out there for a year, at least, before they rotate back to Earth."
He fielded another question, from someone else.
After the reporter was done, Glendale shook his head. "Calling it a 'translation' is too strong a term. Our linguists are still not able to decipher the actual words of the alien language. But they are making progress in grasping how they wrote their language and some of its basic structure. To put it another way, they don't understand what the words mean, but they can now tell what's a word in the first place. According to Dr. Mayhew . . ."