A Trip to Venus: A Novel by John Munro (best books for 7th graders .TXT) 📖

[2] Engineering, January 13th, 1893.

G. "Your spit-fire mode of progression is well enough in theory, but it strikes me as just a little complicated and risky. I, for one, shouldn't care to emulate Elijah and shoot up to Heaven in that style."

I. "If it be all right in theory, it will be all right in practice. However, instead of explosives we might employ compressed air to get the required velocity. In the air-gun or cannon, as you probably know, a quantity of air, compressed within a chamber of the breech, is allowed suddenly to expand behind the bullet and eject it from the barrel. Now, one might manage with a simple gun of this sort, provided it had a very long barrel, and a series of air chambers at intervals from the breech to the muzzle. Each of these chambers, beginning at the breech, could be opened in turn as the bullet passed along the barrel, so that every escaping jet of gas would give it an additional impulse."

G. (with growing interest). "That sounds neater. You might work the chambers by electricity."

I. "We could even have an electric gun. Conceive a bobbin wound with insulated wire in lieu of thread, and having the usual hole through the axis of the frame. If a current of electricity be sent through the wire, the bobbin will become a hollow magnet or 'solenoid,' and a plug of soft iron placed at one end will be sucked into the hole. In this experiment we have the germ of a solenoid cannon. The bobbin stands for the gun-barrel, the plug for the bullet-car, and the magnetism for the ejecting force. We can arrange the wire and current so as to draw the plug or car right through the hole or barrel, and if we have a series of solenoids end to end in one straight line, we can switch the current through each in succession, and send the projectile with gathering velocity through the interior of them all. In practice the barrel would consist of a long straight tube, wide and strong enough to contain the bullet-car without flexure, and begirt with giant solenoids at intervals. Each of the solenoids would be excited by a powerful current, one after the other, so as to urge the projectile with accelerating speed along the tube, and launch it into the vast."

G. "That looks still better than the pneumatic gun."

I. "A magnetic gun would have several advantages. For instance, the currents can be sent through the solenoids in turn as quickly as we desire by means of a commutator in a convenient spot, for instance, at the butt end of the gun, so as to follow up the bullet with ease, and give it a planetary flight. By a proper adjustment of the solenoids and currents, this could be done so gradually as to prevent a starting shock to the occupants of the car. The velocity attained by the car would, of course, depend on the number and power of the solenoids. If, for example, each solenoid communicated to the car a velocity of nine yards per second, a thousand solenoids, each magnetically stronger than another in going from breech to muzzle, would be required to give a final velocity of five miles a second. In such a case, the length of the barrel would be at least 1,000 yards. Economy and safety would determine the best proportions for the gun, but we are now considering the feasibility of the project, not its cost. With regard to position and supports, the gun might be constructed along the slope of a hill or mound steep enough to give it the angle or elevation due to the aim. As the barrel would not have to resist an explosive force, it should not be difficult to make, and the inside could be lubricated to diminish the friction of the projectile in passing through it. Moreover, it is conceivable that the car need never touch the sides, for by a proper adjustment of the magnetism of the solenoids we might suspend it in mid-air like Mahomet's coffin, and make it glide along the magnetic axis of the tube."

G. "It seems a promising idea for an actual gun, or an electric despatch and parcel post, or even a railway. The bullet, I suppose, would be of iron."

I. "Probably; but aluminium is magnetic in a lower degree than iron, and its greater lightness might prove in its favour. We might also magnetise the car, say by surrounding it with a coil of wire excited from an accumulator on board. The car, of course, would be hermetically sealed, but it would have doors and windows which could be opened at pleasure. In open space it would be warmed and lighted by the sun, and in the shadow of a planet, if need were, by coal-gas and electricity. In either case, to temper the extremes of heat or cold, the interior could be lined with a non-conductor. Liquefied oxygen or air for breathing, and condensed fare would sustain the inmates; and on the whole they might enjoy a comfortable passage through the void, taking scientific observations, and talking over their experiences."

G. "It would be a novel observatory, quite free from atmospheric troubles. They might be able to make some astronomical discoveries."

I. "A novel laboratory as well, for in space beyond the attraction of the earth there would be no gravity. The travellers would not feel a sense of weight, but as the change would be gradual they would get accustomed to it, and suffer no inconvenience."

G. "They would keep their gravity in losing it."

I. "The car, meeting with practically no resistance in the ether, would tend to move in the same direction with the same velocity, and anything put overboard would neither fall nor rise, but simply float alongside. When the car came within the sensible attraction of the moon, its velocity would gradually increase as they approached each other."

G. "Always supposing the aim of the gun to have been exact. You might hit the moon, with its large disc and comparatively short range, provided no wandering meteorite diverted the bullet from its course; but it would be impossible to hit a planet, such as Venus or Mars, a mere point of light, and thirty or forty million miles away, especially as both the earth and planet are in rapid motion. A flying rifle-shot from a lightning express at a distant swallow would have more chance of success. If you missed the mark, the projectile would wheel round the planet, and either become its satellite or return towards the earth like that of Jules Verne in his fascinating romance."

I. "Jules Verne, and other writers on this subject, appear to have assumed that all the initial effort should come from the cannon. Perhaps it did not suit his literary purpose to employ any other driving force. At all events he possessed one in the rockets of Michel Ardan, the genial Frenchman of the party, which were intended to break the fall of the projectile on the moon."

G. "If I recollect, they were actually fired to give the car a fillip when it reached the dead-point on its way back to the earth."

I. "Even in a vacuum, where an ordinary propeller could not act, the bullet may become a prime mover, and co-operate with the gun. A rocket can burn without an atmosphere, and the recoil of the rushing fumes will impel the car onwards."

G. "Do you think a rocket would have sufficient power to be of any service?"

I. "Ten or twelve large rockets, capable of exerting a united back pressure of one and a half tons during five or six minutes on a car of that weight at the earth's surface, would give it in free space a velocity of two miles a second, which, of course, would not be lost by friction."

G. "So that it would not be absolutely necessary to give the projectile an initial velocity of five miles a second."

I. "No; and, besides, we are not solely dependent on the rocket. A jet of gas, at a very high pressure, escaping from an orifice into the vacuum or ether, would give us a very high propelling force. By compressing air, oxygen, or coal-gas (useful otherwise) in iron cylinders with closed vents, which could be opened, we should have a store of energy serviceable at any time to drive the car. In this way a pressure or thrust of several tons on the square inch might be applied to the car as long as we had gas to push it forwards."

G. "Certainly, and by applying the pressure, whether from the rocket or the gas, to the front and sides, as well as to the rear of the car, you would be able to regulate the speed, and direct the car wherever you wanted to go."

I. "Moreover, beyond the range of gravitation, we could steer and travel by pumping out the respired air, or occasionally projecting a pebble from the car through a stuffing box in the wall, or else by firing a shot from a pistol."

G. "You might even have a battery of machine guns on board, and decimate the hosts of heaven."

I. "Our bullets would fly straight enough, anyhow, and I suppose they would hit something in course of time."

G. "If they struck the earth they would be solemnly registered as falling stars."

I. "Certainly they would be burnt up in passing through the atmosphere of a planet and do no harm to its inhabitants."

G. "Well, now, granting that you could propel the car, and that although your gun was badly aimed you could steer towards a planet, how long would the journey take?"

I. "The self-movement of the car would enable us to save time, which is a matter of the first importance on such a trip. In the plan of Jules Verne, the bullet derives all its motion from the initial effort, and consequently slows down as it rises against the earth's attraction, until it begins again to quicken under the gravitation of the moon. Hence his voyage to our satellite occupied four days. As we could maintain the velocity of the car, however, we should accomplish the distance in thirteen hours at a speed of five miles a second, and more or less in proportion."

G. "About as long as the journey from London to Aberdeen by rail. What about Mars or Venus?"

I. "At the same speed we should cover the 36,000,000 miles to these planets in 2,000 hours, or 84 days, that is, about three months. With a speed of ten miles a second, which is not impossible, we could reach them in six weeks."

G. "One could scarcely go round the world in the same time. But, having got to a planet, how are you going to land on it? Are you not afraid you will be dissipated like a meteorite by the intense heat of friction with the planet's atmosphere, or else be smashed