For this rocket project we have the option to use black powder which is already made, or sugar fuel which you have to make yourself. Before choosing what kind of fuel to use we have to find out a little bit about of them, to make sure we make the best decision for our rocket motor.
Black Powder: Black powder is motor fuel that is commonly used in smaller rockets, it consists of three ingredients, Sulfur, Charcoal, and Potassium Nitrate (KNO3). Black powder usually has a fast burn rate, but if any other ingredients are added it can hinder that, and will slow it down. Also it can be used as a propellant instead of using zinc-sulfur, because it has more consistency. Sugar Rocket Fuel: Sugar fuel isn't used as often but that doesn't mean it's hard to make, there are only three ingredients needed and they each play a key role for the motor. The first ingredient is Sorbitol is the fuel which can be found in fruits because it's the sugar in them, Potassium Nitrate the oxidizer, and Red Iron Oxide is a catalyst so it increases the rate of the thrust, and enhances burn rate.
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Core Burner: A rocket motor with a core is the traditional motor to use, it has a hollow section going up through the nozzle, and for the rocket to gain distance into the fuel grain as well. When the core burner is lit inside a hollow core, and when this happens it burns inside out and also from both ends . Core burners have a higher surface area when burned which affects its thrust greatly. The length of the core plays a very important role in how your rocket will perform, if your core is too short your rocket won't perform as well. If your core is too long, there is a higher chance that your motor will Cato because the chamber pressure limit will have been exceeded. The good thing about core burners is that there is a coating of propellant that hasn't been burned, and it separates the casing wall and the flame, which insulates the heat from the flame up until the final moments of the burn. Motors with short cores and small nozzles their maximums are reached at burnout because the thrust and chamber pressure start out slow. Initial values are higher for motors with longer cores and bigger nozzles. If your motors have very long cores and very big nozzles the thrust can exceed 50% of its maximum because of the starting thrust and pressure. End Burner: A rocket with an end burner isn't something you see very often, and the reason for that is because end burners get a substantially lower level of thrust, but the level stays constant. End burners also have a longer burn time, but since the casings inside wall is exposed to the flame there is a good chance you'll burn through the wall if not made perfectly. This is because the casing is almost always made out of paper, so during the time span of the burn the paper is in contact with open flame, which makes it very easy to burn through. In order for the thrust and chamber pressure to stay consistent, it is absolutely necessary that the propellant burn keeps a steady rate. When an end burner is lit the flame moves in a straight line, the flame starts at the point of ignition and eventually makes its way to the forward bulkhead. Right after the motor is ignited there is a dome-shaped flame front that forms, this produces a rush of high thrust and high pressure. The thrust and the chamber pressure are reduced when the dome starts forming a shallow cup shape, then after that the thrust and chamber pressure stay constant. Above there are different types of cored rocket motors. Above is an end burner, and the process that happens when it's lit. * Pictures and information is all from: http://what-when-how.com/rocket-motor/cylindrical-core-burners-rocket-motor/ *
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December 2015
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