Where Can I Buy Model Rocket Engines
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Though each model rocket engine lasts for just one flight, the rockets themselves may be flown over and over again. You simply replace the used engine with a fresh one. Model rockets typically carry a parachute, streamer, or other recovery device that returns them to Earth gently for repeated flights.
Engines and wadding can be used only once, but your rocket can be flown repeatedly. Each model rocket kit includes a list of recommended engines to guide you when buying additional engines. At Tower Hobbies, we carry a selection of Estes rockets, engines, and wadding to meet your needs.
When launched, a model rocket accelerates to speeds of several hundred miles per hour. It can fly from several hundred feet to more than 1,000 feet high. Therefore, you need a clear, unobstructed site to launch your models.
Flying model rockets is a relativelysafeand inexpensive way for studentsto learn the basics of forces andthe response of vehicles to external forces.Like an airplane, a model rocket issubjected to theforces of weight,thrust, and aerodynamicsduring itsflight.The weight and aerodynamics are determined by the design of themodel rocket components.The thrust is provided by a replaceablesolid rocket enginewhich can be purchased at local hobby or toy stores.
Model rocket performance (how far,how high,how fast) depends a greatdeal on the rocketengine performance.There are several different ways tocharacterize rocket engine performance. Model rocket engines come in a varietyof sizes and weights, with different amounts of propellant, withdifferent burn patterns which effects the thrust profile, and withdifferent values of the delay time.
At the top of the page we show typical performance curves for several differentrocket engines. We plot the thrust versus the timefollowing ignition for each engine with solid lines. You will notice that when comparingengines, there is a great difference between the levels and shapes of theplots. For any single engine, the thrust changes with time.We can specify a time-averaged thrust of the engine byadding up the product of the thrust over some small time increment timesthe amount of the time increment and then dividing by the total time.The result of this averaging is shown by the dashed lines on the plot.
When purchasing model rocket engines, you will notice a label on each enginein the format; letter number - number. On the figure, we show a C6-4.The first number indicates the average thrust in Newtons.A C6-4 has an average thrust of 6 Newtons. The average thrust times theburn time of the engine is called thetotal impulseof the engine.The letter gives the maximum total impulse of thatclass of engine. An \"A\" engine has a maximum impulse of 2.5 Newton-seconds,a \"1/2A\" has 1.25 N-sec, a \"B\" has 5.0 N-sec, a \"C\"has 10.0 N-sec, and a \"D\" has 20.0 N-sec. If we compare the curves for B6 andthe C6, we find that both engines have the same average thrust (6 Newtons),but the \"C\" engine burns almost twice as long for double the total impulse.The second number indicates the length of the delay time inseconds.A C6-4 has a delay time of 4 seconds between the engine cutoff and the firingof the ejection charge.The delay time determines the length of thecoasting phase of the flight.If the delay time is too short relative to the optimum coast of the vehicle, the parachutedeploys on the way up and stops the flight. If the delay time is too long, the vehiclemight hit the ground before the parachute deploys.
The engine designer can affect the thrust and the totalimpulse of an engine by changing the diameter of the propellant (and casing).Typical \"1/2A\" engines are 13 mm in diameter, typical \"A\", \"B\" and \"C\" enginesare 18 mm in diameter, and typical \"D\" engines are 24 mm in diameter. This isimportant to remember because a model rocket designed for a \"B\" engine willnot accept a \"1/2A\" or a \"D\". The engines will not fit into thefixed engine mountof the rocket.
Flying model rockets is a relatively safe and inexpensive way for studentsto learn the basics of forces andthe response of vehicles to external forces.Like an airplane, a model rocket issubjected to theforces of weight,thrust, and aerodynamicsduring itsflight.The thrust force is supplied by a small solid rocket engine.
There are two main categories of rocket engines; liquid rockets andsolid rockets. In aliquid rocket,the fuel and the source ofoxygen (oxidizer) necessary forcombustionare stored separately and pumped into the combustion chamber of thenozzlewhere burning occurs.In asolid rocket,the fuel and oxidizer are mixed together into a solid propellantwhich is packed into a solid cylinder. Under normal temperature conditions,the propellant does not burn; but the propellant will burn when exposed toan external source of heat.Some type of igniter is used to initiate the burningof a solid rocket motor at the end of the propellant facing the nozzle.As the propellant burns, hot exhaust gas isproduced which is used to propel the rocket, and a\"flame front\" is produced which moves into the propellant.Once the burning starts,it will proceed until all the propellant is burned.With a liquid rocket, you can stop the thrust by turning off the flow offuel or oxidizer; but with a solid rocket, you must destroy the casing to stopthe engine. Liquid rockets tend to be heavier and morecomplex because of the pumps used to move the fuel and oxidizer,and you usually load the fuel and oxidizer into the rocket justbefore launch. A solid rocket is much easier to handle and can sit for yearsbefore firing.
The relativesafetyof building and flying model rockets is the result ofthe production and availability of pre-packaged solid model rocketengines. The engines are produced by several manufacturers andare available in a variety of sizes with a range ofengine performance.The engines can be bought at most hobby stores and some toy stores fora modest price (average current price is 3 engines for $5). The enginesare used once and discarded; a new engine is inserted into therocket for the next flight. Before theseengines became available, many young rocket builders lost limbs or life inthe process of mixing rocket fuels. With these engines, you can stillhave the fun of building and flying rockets, learn the fundamentals, and thenmove on to the more dangerous and complex problems of propulsion.
On this slide we show a drawing of the parts of a model rocket engineso that you can learn how it works.We have laid the engine on its side,and \"cut\" the engine in half so that we can see what is inside.Never disturb, cut, or modify a real model rocket engine. The propellantcan ignite at any time if there is a source of heat.The engine is installed in a rocket shown by the dashed lines on the figure.The engine casing is a cylinder made of heavy cardboard which containsthe nozzle, propellants, and other explosive charges.At the right side of the engine is thenozzle, a relativelysimple device used to accelerate hot gases and produce thrust. Model rocketnozzles are usually made of clays or ceramics because of the hightemperature of the exhaust. The hot gasesfor a model rocket are produced by the solid propellant, shown ingreen. An electric igniter is used to launch a model rocket.As the flame burns through the propellant, the rocket experiencespowered flight.When the flame front reaches the far left of the propellant, thrustgoes to zero, and a delay charge, colored blue, begins to burn.During thedelay, no thrust is produced and the rocketcoasts up to its maximum altitude.The length of the delay varies between engines from 2 to 8 seconds and theamount of the delay is listed on the engine casing.When the delay charge is completely burned through, the ejection charge,shown in red, is ignited. This produces a small explosion which ejectshot gas out the front of the engine through the engine mount, ejectsthe nose cone, and deploys the parachute for a saferecovery.
Just an unsolicited expression of appreciation for Robert and BuyRocketMotors - I've now placed several orders with BRM (not official, just my abbreviation :-), and I have been impressed and satisfied with each experience. Robert is incredibly responsive, communicative and helpful - he is a genuine pleasure to deal with. Every item I have ordered has been in stock, as shown on the website, and has shipped out the next (or on one case, the same) business day that it was placed. The prices are lower than anywhere else I've found, as well. (and I have looked around extensively!) Bottom line, this is a great place to purchase rocketry supplies and especially motors. I will keep coming back for all of the reasons I've described. THANK YOU for being such a great business!!
In California, to purchase model rocket engines through size \"D\", one must be at least 14 years of age. To purchase larger model rocket engines, one must be 18 years of age. When finding locations to fly, permission of the landowner or local fire marshal may be required. Additionally, many areas have pre-approved launch sites and times. Children, age 12, may receive and use model rocket engines under adult supervision. 59ce067264
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