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Model Rockets

Model Rockets are smaller (1-3 feet) rockets that are launched to 300-1500 feet in the air using rocket motors filled with black powder. They usually deploy a parachute to fall back to earth safely.

Below is a terrific introductory article where you can learn the basics and how to get started. You can help grow our learning community by contributing your knowledge to the article. Just click on the edit tab in the wiki article below.

Use the white subtabs above to navigate the other Model Rockets resources. We have a Model Rockets forum where you can get your questions & doubts answered, a page with Model Rockets how-to videos, a page with the best handpicked links to other sites, and a page with the best Model Rockets books and products.

Good Luck and Have Fun!
Duncan Davis

 

Introduction


Many modeling kits will involve bringing out the detail of a vehicle that the model was based on. There are working versions of those models, but those don’t focus on the physics involved like the model rocket.




Model rocketry does not involve detailed paint jobs or even hours of construction time. In practice, building a model rocket is a fairly straight forward process. Well, straight forward for those who have an idea what they’re doing. When it comes to this hobby three steps take place.




The first step is assembling the rocket correctly. Second, you must find a place to safely launch the rocket. And third, you will launch and retrieve the rocket.




Parts of the rocket


Instead of a wide array of tools and small parts to glue together, a rocket follows a very basic design. Remember, the functionality of the rocket is more important than the detail that goes into a rocket.




No matter the size, the principles of rocketry hold true. It’s learning how to apply those principles properly that is the trick. The following is a breakdown of a rocket then more specifically its engine. We’ll look at each piece and talk about what purpose it serves. Afterwards, you should get a good sense that a rocket uses no extra parts. It is straight forward in its design and functionality.


 



The Rocket


The top of a rocket should be the nose cone. This piece is responsible for reducing aerodynamic resistance on the rocket. This resistance is referred to as drag or aerodynamic drag. Some people may decorate this piece, but that is not necessary.




The next piece along the body of the rocket is called the payload. This is what houses the cargo of the rocket. In model rockets this is often where the retrieval unit is stored.




The last part of the rocket’s body is called the body tube. This portion of the rocket holds the engine and gives a mounting surface for the fins. Other smaller parts can be found in here. Those pieces will be indicated later.




Moving to the inside of the rocket, you have the engine. This is not like a typical vehicle engine. Rather, it is a propulsion unit that drives the rocket forward. It is located inside the body tube.




Next to the engine you’ll have the thrust ring. This piece keeps the engine from shooting through the rocket itself. Consider it as a type of bracing that the rocket has against the engine. It is also located inside the body tube.




Moving towards the nose, you’ll have the wadding. This is a protective material that keeps the engine from burning the retrieval unit. As seen later, the retrieval unit is very often flammable so requires this protection.




This brings us to the retrieval unit. There are a wide variety of types of retrieval units. They could involve gliding wings, helicopter style propellers, streamers, etc. The most commonly known retrieval unit is a small parachute. Most of these units will be deployed when the rocket splits in half.




To accomplish this, an ejection charge is used. This provides the proper deployment of the retrieval device. This is actually part of the engine.




Connecting the retrieval unit to the rocket are the shroud lines. These lines are typically packed in with the retrieval unit.




Since a sudden deployment of a retrieval unit would most likely destroy a rocket, there needs to be something that absorbs the shock of the impact. For this purpose, there is the shock chord. The shock chord connects the cone to the body and anchors the shroud lines.




The rocket will also have a small tube called a launch lug. This serves to guide the rocket at launch. It works by fitting over a launch rod. The launch rod is not part of the rocket. The rod is approximately thirty six inches long and can be used to point the rocket in a direction. The launch lug provides this important guidance that the rocket needs.




Finally, there are the fins. Once the rocket reaches proper speed and wind resistance, these are the only thing that keep its trajectory. The proper speed is roughly thirty miles an hour. This speed needs to be attained before the rocket the end of the launch rod. If not, the fins may not have enough influence over the rocket to guide it. This is why they don’t recommend modifying a rocket kit since all the specifics have been worked out. Tampering with the rocket may result in an unexpected result.


 



The engine


The engine or motor of a rocket is the most important element of a rocket. It provides the thrust needed to achieve launch which is the main goal behind building one of these kits. Because of this fact, extra details about the engine are presented here.




The ejection charge as stated before releases the retrieval unit through the proper apogee. The apogee is the opening designed to open to release or eject something specifically. In this case, it will release the retrieval device like a parachute.




Since the ejection charge is a substance rather than a piece or part, it requires a container to hold it. This container is called a retainer cap in a rocket. Its only function is to hold the charge while it waits to be ignited.




Because you don’t want the retrieval device to deploy as the rocket launches, an element is needed to prevent immediate ignition of the ejection element. This element is called the delay element. Not only does it act like a time delay fuse, but it also provides a smoke trail for your eyes to follow.




Now we move onto the propellant. This is the chemical compound that will provide thrust to your engine. When it burns it creates a gas exhaust that takes up more room than the space it’s in. Therefore, it must find a way out. This force that seeks release gives the rocket its thrust.




Thrust alone will launch the rocket a short ways up. In order to intensify the thrust model rockets come with a ceramic disk with a hole in it. This piece is called the nozzle. By forcing escaping exhaust gasses through a much smaller hole, the speed at which the gas escapes needs to increase. Remember, it still needs to displace the same volume of material. Therefore, you have a chain reaction.




To better understand how this works, let’s use the example of a water hose. When you turn it on water begins pouring out. Consider the water thrust provided by the propellant. Now put your hand over the end of the hose. As you can tell, you can’t really stop the water from coming out. So it tries to escape through any small opening your hand might provide. Since the same amount of water needs to come out the end result is stronger streams of water. This is how a nozzle works.




The last part of the rocket’s engine is the mechanism used to ignite the propellant. Since it’s very dangerous to use hand held ignition devices igniter wires are provided for this purpose. This will allow remote launching of your rocket.




What you need


Very little time and energy is needed to build the model. Beginners may take some time with their first rocket though. The real challenge for many is in finding a safe and open area to launch your rocket.




Sure there are a few things you can do to point the rocket in a direction you want to go, but there can be factors that change its course. Wind speed can play a major factor in disrupting a straight trajectory for your craft. It also can play havoc on how the retrieval unit will function.




When selecting a suitable place, follow all the guidelines that are outlined in the paperwork included with the rocket. Due to the potentially dangerous elements that go into a rocket make sure you follow the instructions on properly storing it if you don’t plan to put it together right away.




Many times hobby stores will recommend a smaller rocket for those just getting into the hobby. This is good advice to follow. For one it is a more affordable option especially if you end up making mistakes.




Warning


It is highly stressed that if you are interested in rocketry to purchase and use kits. Home made rockets tend to lack the fundamental elements that make a rocket work. Those who try have a long trial and error phase that they go through to figure the process out.




This phase may involve serious injury and damage. In addition, it will often turn out to be ten times more expensive than if you had just bought a kit. If you do wish to make personalized rocket, it’s recommended you seek an educational background to help you in this endeavor.




Conclusion


Model rocketry is a dynamic hobby that doesn’t require the amount of patience that other model kits need in abundance. Since they do have dangerous elements to them, it’s recommended that you make sure to follow every safety instruction that comes with the kit.




More advanced practitioners of the hobby can always find bigger rockets to launch. However, many times bigger rockets will require licenses to own and operate. This is also a hobby you can share with others. People of all ages love to see the grace and power displayed when science is at work.