From the Earth to the Moon (8 page)

“So 2,400 feet per second is the highest velocity reached so far?” asked Barbicane.

“Yes,” replied Morgan.

“I
will
say, however,” remarked J. T. Maston, “that if my mortar hadn’t burst …”

“Yes, but it did burst,” Barbicane said with a benevolent
gesture. “Now, let’s take that velocity of 2,400 feet per second as our starting point. We’ll have to increase it fifteenfold. I’ll postpone discussing the means of achieving that velocity until another meeting! For the moment, I’d like to call your attention to the dimensions that the projectile will have to have. As you can well imagine, we won’t be dealing with a little bullet weighing no more than half a ton!”

“Why not?” asked Major Elphiston.

“Because our projectile,” J. T. Maston said quickly, “must be big enough to attract the attention of the inhabitants of the moon, if there are any.”

“Yes,” said Barbicane, “and also for an even more important reason.”

“What do you mean?” asked the major.

“I mean that it’s not enough to send off a projectile and then forget about it: we must be able to watch it until it reaches its destination.”

“What!” exclaimed the general and the major, somewhat startled by this idea.

“If we can’t watch it,” Barbicane said with self-assurance, “our experiment will be inconclusive.”

“Then you must be planning to make a projectile of colossal size!” said the major.

“No. Listen carefully. As you know, optical instruments have been highly developed. There are telescopes capable of magnifying objects six thousand times, and bringing the moon to an apparent distance of forty miles. At that distance, objects sixty feet wide are clearly visible. The reason why telescopes haven’t been made any more powerful is that their clarity decreases as their power increases, and the moon, which is only a reflecting mirror, doesn’t give off enough light to make it desirable to increase magnification beyond that point.”

“Then what will you do?” asked the general. “Give your projectile a diameter of sixty feet?”

“No.”

“Well, then, do you intend to make the moon brighter?”

“Yes, I do.”

“You can’t be serious!” cried J. T. Maston.

“It’s really quite simple,” said Barbicane. “If I succeed in diminishing the density of the atmosphere the moon’s light travels through, haven’t I, in effect, made its light brighter?”

“Of course.”

“Very well: to obtain that result, all that’s necessary is to place a telescope on a high mountain, and that’s what we’ll do.”

“I surrender!” said the major. “You have a way of simplifying things … And what magnification do you expect to get that way?”

“Forty-eight thousand. That will bring the moon to within five miles, and objects only nine feet wide will be visible.”

“Wonderful!” said J. T. Maston. “So our projectile will have a diameter of nine feet!”

“Exactly.”

“Allow me to point out, however,” said Major Elphiston, “that it will be so heavy that …”

“Before we discuss its weight, Major,” said Barbicane, “let me tell you that our ancestors performed wonders in that domain. Far be it from me to say that the science of ballistics hasn’t made progress, but we ought to realize that amazing results were obtained as long ago as the Middle Ages. I might even say that they were more amazing than ours.”

“That’s unbelievable!” said Morgan.

“Can you justify what you’ve said?” J. T. Maston asked sharply.

“Certainly,” replied Barbicane. “I have examples to support it. During the siege of Constantinople by Mohammed II, in 1543, stone projectiles were used that weighed 1,900 pounds and must have had impressive dimensions.”

“Ah,” said the major, “1,900 pounds is a good weight!”

“At Malta, in the days of the knights, a cannon in Fort St. Elmo shot projectiles weighing 2,500 pounds.”

“Incredible!”

“Finally, according to a French historian, in the reign of Louis XI a mortar shot a bombshell that weighed only five hundred pounds, but that bombshell went from the Bastille, a place where the insane imprisoned the sane, to Charenton, where the sane imprisoned the insane.”

“Very good!” said J. T. Maston.

“Since then, what have we done, really? The Armstrong cannon shoots a five-hundred-pound ball, the Rodman Columbiad a projectile weighing half a ton. It seems that what projectiles have gained in range, they’ve lost in weight. If we turn our efforts in that direction, we should be able, with the progress of science, to make cannon balls ten times as heavy as those of Mohammed II and the Knights of Malta.”

“That’s obvious,” said the major. “But what metal do you intend to use for our projectile?”

“Ordinary cast iron,” said General Morgan.

“Cast iron?” J. T. Maston said scornfully. “That’s too common for a projectile that’s going to the moon!”

“Let’s not exaggerate,” said Morgan. “Cast iron will be good enough.”

“Well, then,” said Major Elphiston, “since its weight
will be proportional to its volume, a cast-iron ball nine feet in diameter will be fantastically heavy!”

“If it’s solid, yes; but not if it’s hollow,” said Barbicane.

“Hollow! Is it going to be a shell, rather than a ball?”

“We can put messages in it,” said J. T. Maston, “and samples of our production here on earth.”

“Yes, it will be a shell,” said Barbicane. “It must be; a nine-foot solid ball would weigh more than 200,000 pounds, and that’s obviously much too heavy. However, since the projectile must have a certain stability, I propose to give it a weight of 20,000 pounds.”

“How thick will its walls be?” asked the major.

“If we use standard proportions,” said Morgan, “a nine-foot diameter will require walls at least two feet thick.”

“That would be much too heavy,” said Barbicane. “You must bear in mind that we’re not designing a shell to pierce armor plate. Its walls need only be thick enough to withstand the pressure of the powder gases in the bore. So our problem is this: how thick must the walls of a cast-iron shell be if it’s to weigh only 20,000 pounds? I’m sure our skilled calculator, Mr. Maston, can tell us that immediately.”

“I’ll be glad to,” replied the honorable secretary of the committee.

He wrote a few algebraic formulas on a sheet of paper. Here and there he wrote a π or an
x
²
.
He even appeared to extract a certain cube root with the greatest of ease. Finally he said:

“The walls could be no more than two inches thick.”

“Would that be enough?” the major asked doubtfully.

“No, of course not,” replied Barbicane.

“Then what shall we do?” the major asked with a puzzled look.

“We’ll have to use some other metal than cast iron.”

“Copper?”

“No, that’s also too heavy. I have something better to suggest.”

“What is it?”

“Aluminum,” said Barbicane.

“Aluminum!” exclaimed his three colleagues.

“That’s right, my friends. As you know, in 1854 a famous French chemist, Henri Sainte-Claire-Deville, succeeded in obtaining aluminum in a compact mass. That precious metal is as white as silver, as unchanging as gold, as tough as iron, as fusible as copper, and as light as glass. It’s easily worked, it’s extremely widespread in nature, since alumina forms the base of most rocks, it has only a third of the weight of iron, and it seems to have been created for the specific purpose of providing us with material for our projectile!”

“Hurrah for aluminum!” cried J. T. Maston, who was always very noisy in his moments of enthusiasm.

“But isn’t aluminum very expensive to produce?” asked the major.

“It used to be,” replied Barbicane. “When it was first discovered, it cost somewhere between $260 and $280 a pound, then it dropped to $27, and now it’s down to $9.”

“But $9 a pound,” said the major, who did not give up easily, “is still an enormous price!”

“Enormous but not prohibitive.”

“How much will the projectile weigh?” asked Morgan.

“Here are the results of my calculations,” answered Barbicane. “A shell with a diameter of nine feet and walls a foot thick would weigh 67,440 pounds if it were made of cast iron. Made of aluminum, it will weigh only 19,250 pounds.”

“Excellent!” said J. T. Maston. “That will fit into our project beautifully!”

“Excellent! Excellent!” repeated the major. “But do you realize that, at $9 a pound, the projectile will cost …”

“It will cost $173,250, yes, I’m aware of that; but don’t worry, my friends: I assure you that our project won’t be short of money.”

“We’ll be flooded with money!” said J. T. Maston.

“Well, what do you think of aluminum?” asked Barbicane.

“Motion carried!” replied the three other members of the committee.

“As for the shape of the shell,” said Barbicane, “it’s not important, because once the shell has gone through the earth’s atmosphere it will be in a vacuum. So I propose a round ball; it can revolve if it wants to, and behave however it likes.”

Thus ended the first meeting of the committee. The question of the projectile was settled, and J. T. Maston was delighted with the thought of sending an aluminum shell to the inhabitants of the moon: “It will give them an impressive idea of what we’re like!”

T
HE DECISIONS
made at this meeting produced a great effect in the outside world. A few timorous people were alarmed by the idea of a 20,000-pound shell being shot into space. Everyone wondered what kind of a cannon would ever be able to give enough initial velocity to such a mass. These questions were to be triumphantly answered by the minutes of the committee’s second meeting.

On the evening following the first meeting the four members of the committee sat down before new mountains of sandwiches and a veritable ocean of tea. The discussion was immediately resumed, this time without preliminaries.

“Gentlemen,” said Barbicane, “we’re now going to take up the question of the cannon that must be built: its length, shape, material, and weight. We’ll probably give it gigantic dimensions, but no matter how great the difficulties, our industrial genius will easily overcome them. So please listen to me and don’t hesitate to make blunt objections. I’m not afraid of them!”

This statement was greeted with a grunt of approval.

“Let me remind you,” he went on, “where our discussion led us yesterday. We agreed that the problem is to give an initial velocity of 36,000 feet per second to a
shell with a diameter of nine feet and a weight of 20,000 pounds.”

“Yes, that’s the problem,” said Major Elphiston.

“I’ll continue from there,” said Barbicane. “When a projectile is launched into space, what happens? It’s acted on by three independent forces: air resistance, the pull of the earth’s gravity, and the propulsive force that’s been applied to it. Let’s examine these three forces. Air resistance will be unimportant. The earth’s atmosphere is only forty miles thick. At a speed of 36,000 feet per second, the shell will go through it in five seconds, and that time is so short that we can regard air resistance as insignificant. Next, let’s consider the pull of the earth’s gravity, in other words the shell’s weight. We know that its weight will diminish in inverse ratio to the square of its distance from the earth. Here’s what physics tells us: when a body is dropped near the surface of the earth, it falls fifteen feet in the first second, but if it were as far away from the earth as the moon is—257,542 miles—it would fall only a twentieth of an inch in the first second; in short, it would remain almost motionless. So we must progressively conquer the force of gravity. How will we do it? By the propulsive force we’ll use.”

“That’s the difficulty,” said the major.

“Yes, it is, but we’ll overcome it, because the propulsive force we need will result from the length of the cannon and the amount of powder used. This amount will be limited only by the strength of the cannon. We must now decide on the dimensions of the cannon. Practically speaking, we can make it as strong as we like, because it won’t have to be moved.”

“That’s all obvious,” said General Morgan.

“So far the longest cannons made, our enormous
Columbiads, have had a length of only twenty-five feet, so we’re going to surprise many people by the size we’ll have to adopt.”

“I’m sure we will!” said J. T. Maston. “I think we ought to make our cannon at least half a mile long!”

“Half a mile!” exclaimed the major and the general.

“Yes, half a mile, and it still won’t be half long enough.”

“Come, come, Maston,” said Morgan, “you’re exaggerating.”

“I am not!” retorted the fiery secretary. “I don’t know how you can say a thing like that!”

“I said it because you’re going too far.”

“Sir,” J. T. Maston said loftily, “you’d do well to remember that an artilleryman is like a cannon ball: he can never go too far!”