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Variant, v. 1, issue 3, September 1947
Page 38
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[[illustration text]] TO FUEL TO OXYGEN ATOMIZER COMBUSTION CHAMBER NOZZLE EXHAUST FIGURE 4 [[end illustration text]] machine we make must push against something. In short, this means that no matter how we slice it, any kind of space drive we can conceive of making at the present time must be a rocket in one disguise or another. And so many further discussion about space travel must center around the subject of rockets. To begin with, we must clarify this idea of "pushing against something." It used to be that whenever you said something about space ships, people would inquire in a plaintive tone of voice,' "But how can a rocket work in a vacuum when there's nothing there to push against? " But I think that today, now that nearly everybody has gone through the experience of having his shoulder jarred by the kickback from a 30 calibre rifle, this question is less likely to be asked. For it's clear that a rifle is going to kick back just as hard whether or not you fire it in a vacuum. The enormous recoil absorbers on a 155 mm. cannon are not going to be rendered unnecessary just because of a little thing like lack of an atmosphere. A rocket is a machine designed to expel large quantities of gas as quickly as possible. (See figure 5) (The PSFS, nevertheless, is not a rocket.) The important thing to keep in mind is the fact that this gas being expelled has mass, and the force which the rocket exerts to shoot the gas in one direction results in a force that drives the rocket in the other direction. The amount of the force on the rocket depends on the mass of the exhaust gas, and upon the velocity with which it is ejected. The thing that makes the rocket so interesting and useful is the fact that it doesn't push against the ground, the air, or any other stationary object. It pushes against its own exhaust, and that means that no matter how fast it is moving, it is going to keep on picking up speed as long as it doesn't run out of fuel. The fuel problem, of course, is one of the two tough problems involved in making rockets work. The other problem is making a motor that won't melt while it's working. The reason for high temperatures is to get a high exhaust velocity. The faster you can eject the fuel the more force the motor will exert, and the less fuel you will need to reach a given velocity. However, to attain these high exhaust velocities requires fuels of high energy content, resulting in high temperatures within the motor. The standard fuel at present is alcohol and liquid oxygen. Also being used extensively is aniline and concentrated nitric acid in which is dissolved nitric oxide. This, while horrible stuff to handle, has the advantage of burning spontaneously when mixed in the motor, thus making unnecessary a device to start the burning, which is usually a tricky business. Naturally the thought in everybody's mind is how to use atomic energy in a rocket. So early in the game, all that can be done, is to make theoretical calculations as to what can be done, and I understand that a paper is to appear in the next American Journal of Physics on this subject. There is much more that can be said about rockets in detail, but that had best be saved for another paper, this one being already sufficiently long. (38)
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[[illustration text]] TO FUEL TO OXYGEN ATOMIZER COMBUSTION CHAMBER NOZZLE EXHAUST FIGURE 4 [[end illustration text]] machine we make must push against something. In short, this means that no matter how we slice it, any kind of space drive we can conceive of making at the present time must be a rocket in one disguise or another. And so many further discussion about space travel must center around the subject of rockets. To begin with, we must clarify this idea of "pushing against something." It used to be that whenever you said something about space ships, people would inquire in a plaintive tone of voice,' "But how can a rocket work in a vacuum when there's nothing there to push against? " But I think that today, now that nearly everybody has gone through the experience of having his shoulder jarred by the kickback from a 30 calibre rifle, this question is less likely to be asked. For it's clear that a rifle is going to kick back just as hard whether or not you fire it in a vacuum. The enormous recoil absorbers on a 155 mm. cannon are not going to be rendered unnecessary just because of a little thing like lack of an atmosphere. A rocket is a machine designed to expel large quantities of gas as quickly as possible. (See figure 5) (The PSFS, nevertheless, is not a rocket.) The important thing to keep in mind is the fact that this gas being expelled has mass, and the force which the rocket exerts to shoot the gas in one direction results in a force that drives the rocket in the other direction. The amount of the force on the rocket depends on the mass of the exhaust gas, and upon the velocity with which it is ejected. The thing that makes the rocket so interesting and useful is the fact that it doesn't push against the ground, the air, or any other stationary object. It pushes against its own exhaust, and that means that no matter how fast it is moving, it is going to keep on picking up speed as long as it doesn't run out of fuel. The fuel problem, of course, is one of the two tough problems involved in making rockets work. The other problem is making a motor that won't melt while it's working. The reason for high temperatures is to get a high exhaust velocity. The faster you can eject the fuel the more force the motor will exert, and the less fuel you will need to reach a given velocity. However, to attain these high exhaust velocities requires fuels of high energy content, resulting in high temperatures within the motor. The standard fuel at present is alcohol and liquid oxygen. Also being used extensively is aniline and concentrated nitric acid in which is dissolved nitric oxide. This, while horrible stuff to handle, has the advantage of burning spontaneously when mixed in the motor, thus making unnecessary a device to start the burning, which is usually a tricky business. Naturally the thought in everybody's mind is how to use atomic energy in a rocket. So early in the game, all that can be done, is to make theoretical calculations as to what can be done, and I understand that a paper is to appear in the next American Journal of Physics on this subject. There is much more that can be said about rockets in detail, but that had best be saved for another paper, this one being already sufficiently long. (38)
Hevelin Fanzines
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