CHAPTER XVI.
Phobos.
“Deimos is exceedingly valuable also as a sort of stepping stone from which to get onto Phobos. Once on Deimos and it is as easy getting onto Phobos as to step from one car to another in a running train. Phobos is 5,807 miles from the center of Mars. When the three are in line it is 8,740 miles from Deimos. Deimos travels 3,016½ miles an hour, Phobos 4,777. A body thrown off from Deimos towards Mars will retain the velocity of Deimos and will acquire in falling that 8,740 miles an additional velocity enough to bring its speed up to that of Phobos. So our Lunarians by close calculation and timely departure from Deimos have had little or no trouble in lighting on Phobos without a perceptible jar and have conveyed by that route all the machinery and apparatus they needed in making their improvements there.”
“Was Phobos worth improving then?”
“No, its motive power was simply harnessed so as to be utilized on Mars. They did it in this way.
“A large number of powerful steel magnets were prepared on Mars together with the materials for a large basket or crate stout enough to hold them, also four cables made of wire, each two inches in diameter. These materials done up in proper shape were taken up the cable by repulsion to Deimos then again by repulsion cast off with a company of Lunarians in one of their cars to sail down to Phobos.”
“I should think that being encumbered with such a lot of stuff would have added greatly to the risk of the trip,” said I.
“Not at all, the more metal the better, since it can be made light or heavy at will and so kept under control while other materials could not be made light. It is always desirable to have more than half the weight of our outfit in iron or steel on that account. Well, they landed this material on Phobos and there put it together. The different parts were insulated from each other to provide for the use of repulsion or gravitation as the case might require.
“They staked off an exact square five and a half miles on each side, which was about as large a one as they could get on Phobos and at each corner they firmly anchored one end of one of the cables. At the center of the square Mars appeared directly overhead. At this point the crate was put together upside down and its load of magnets arranged inside of it also upside down. The cables 3,760 miles long were coiled in a pile each to itself and the end fastened to the corners of the crate. On Mars this outfit weighed many tons, but on Phobos it was so light that one man could lift it. Wires connected with a battery passed through the cables to regulate the weight of the concern. A small amount of repulsion raised it and carried it to the limit of the attraction of Phobos. The momentum taking it a little further, and within the dominance of that of Mars when light attraction was turned on and the crate rose or rather fell slowly toward Mars. When the cables were stretched out and the crate hung by them, it was within a few feet of the ground in some places, at others as much as one or two hundred. Its motion was from west to east at the incredible speed of 1,160 miles an hour. Its actual rate of travel is 1,681 miles per hour, but the revolution of Mars on its axis is at the rate 521 miles in the same direction, so the difference constitutes the apparent motion of the crate of Magnets. In order to get electric power from these it was only necessary to set up insulated slabs of soft iron along the route of the magnets in such position that they would pass close to them as they swept by. This was done at different places along the route, and covered altogether, distances aggregating more than three thousand miles. Of the remaining distance around the planet a part was over the sea and some over low land, where the scaffolding would be too high to pay. The electricity generated in these stationary armatures was run off to storage batteries wherever required in the equatorial regions of the planet. So, with the cable to Deimos and the big dynamo of Phobos. Mars is supplied with unlimited power at nominal cost.”
“But doesn’t the plant require renewal? I should think it would rust out after awhile.”
“Yes the cable has been renewed twice. The last one put up is 12 inches in diameter. It is easy now to put one up, with the one already up to steady and steer it. It only has to fall up as you might say, under the influence of repulsion. The occasion of putting up the last cable, however, was not rust, but a singular accident. During the winter there are generally only two or three men left at the pole to keep the shaft oiled and see that everything is all right. One winter the men left in charge undertook to move some heavy timbers and steel beams that had been left on the top of the mountain, and managed to get them into such a position that they were caught by the cable which slowly carried them around until they partly fell into a crevice and became immovable. The cable bent itself around the obstruction, and in doing so was thrown so far down over the edge of the mountain which as I told you had been turned off to resemble a capstan, that it began to be wound around it as if it were a great spool. The men telegraphed to the general manager who came up with a crowd of engineers and workmen, but they could not do a thing except to keep the cable raised by repulsion as much as possible to keep it from catching some obstruction on the ground. The cable made the complete circuit of the railway track in a trifle over 5½ days. The mountain stem had been whittled down to about a mile in diameter so that each revolution wound up a little over three miles of cable, which was at the rate of a little over half a mile a day.