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Making a rocket stable is very simple, but making it stable and lightweight is more difficult. A stable rocket is one that will continue to travel forward once the thrust from the motor(s) has ended. Once the rocket is stable, it is guaranteed to travel in a given direction until it loses most of its speed. There are two major factors that determine the stability of a rocket: center of drag (also center of pressure CP) and center of gravity (CG). A stable rocket has its CP towards the rear, and its CG close to the nose. The closer to the top that the center of balance is, the more stable the rocket is. The more lateral resistance there is in the rear, the more stable it is. The best way to get lateral resistance in the rear is to attach fins to the rocket. To get the CG closer to the front, weight must be added to the nose of the rocket. There is a simple way of testing whether or not the rocket is stable. First find the center of gravity by balancing it on a string, so that it doesn’t lean to one side. Then swing it around in a circle, if the nose points forward, the rocket is stable. For this test to be accurate, the rocket must be in the same state as when it is launched (with the engine, recovery system, etc.). A stable rocket generally has the following appearance:
It can be difficult to make a stable rocket so that it’s also lightweight. The easiest way to do this is to make the rocket no heavier than it must be, and try to put everything that must be on the rocket towards the nose, like the recovery system and altimeter, but not the motor. The shorter the rocket the more weight must be added the nose to pull the CG in front of the CP. For example, a rocket which has fins that almost touch the nosecone will have a CP at about the middle of the rocket, and since there is not much body length to bring the CG forward of the CP, a great deal of weight must be added to the nose. Another way to keep it light is to make the body diameter as small as possible, so that it is light and it has little lateral resistance, keeping the CP more near the fins. The recent launch of Mini Blue proved to be very stable, but also too heavy. The rocket didn’t reach its desired altitude because the body of the rocket was made of a heavy plastic material, and it was too short, and had too great a diameter, so a great deal of nose weights were added to bring the CG in front of the CP. Always be sure to make the body of the rocket out of a light cardboard or plastic material, and as they get bigger, fiberglass. This is how to make your rocket stable and lightweight, to achieve the greatest altitude.
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Welcome to Rocketss. The site is divided into two main sections, the Water Rockets section and the Pyro Rockets section.
In each section you will find tutorials, links, and and a project registry. Because this site is always being updated with the latest information, please check back.
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