Basic information about various hobby and craft topics.

Friday, September 21, 2012

Model Rocket Parts And What They Do

Model Rocket Parts And What They Do

Building and flying model rockets is a fun and exciting hobby. Many kid’s organizations like 4-H and Scouts have rocketry as part of their programs. Many schools build rockets as class projects to learn about space and rocketry.

Rocketry is easy to learn. The model rocket parts are pretty basic and consist of the body tube, nose cone, engine mount, launch lug, parachute, fins, and shroud line. The body tube makes up the main body of the rocket. It is made of a lightweight material, like cardboard, is hollow. In flight, it contains the parachute, recovery wadding, engine.

The nose cone attaches to the body tube at the apex of the rocket. It helps lower air resistance to the rockets flight. It comes off with the ejection charge to allow the recovery system to deploy.

The engine mount is installed at the bottom of the rocket, and holds the rocket engine in place during the flight.

The launch lug attaches to the side of the body tube. It holds the rocket securely to the launch rod on the launch pad while launch arrangements are being made.

The parachute is packed inside the body tube before flight, and is attached to the body tube with the shroud line. The parachute is deployed when the ejection charge is fired, bringing the rocket safely back to earth.

The fins are attached to the bottom of the body tube. They give the rocket stability during flight.

Rockets may be flown on as small as a 1/4 acre. Field size is determined by the size of the rocket and size of the engine used. The smallest engines - 1/2A - will fly a rocket up to 200 feet in altitude, and will require an altitude of about fifty feet by fifty feet. A engines will achieve about 400 foot altitude and need about 100 feet by 100 feet area. B engines will fly approximately 800 feet high and need about 200 feet on each side - this is about an acre. C engines will achieve about 1600 feet in altitude and need about 400 feet on each side. This is about 2 acres. D engines push a rocket up to about 1800 feet and need about 500 feet on each side.

The rocket engine casing is composed of paper and clay materials, and are pre-loaded with non-toxic, bio-degradable materials. The engine is used once, and discarded. The rocket engine’s attributes are communicated by a simple to understand code stamped on its side, and on the package. A8-3 would be an example of this code. The A designates the total thrust of the engine expressed in Newtonian seconds. Their are four letter grades - A, B, C, and D. Each letter grade is twice as powerful as the one preceding it. The first number is the average thrust of the engine expressed in Newton’s. The last number in the code tells you number of seconds from engine shutdown until the ejection charge fires. The longer this interval is, the higher the rocket will go, as it will drift upward until the parachute deploys.

The igniter is the next thing we well talk about. It is, quite simply, a wire made from an electrically resistant material. When electricity from the launch controller is applied, the igniter heats up, igniting the propellant in the rocket engine. The igniter installs in the dimple like depression in the bottom of the rocket engine. Be careful with the igniter, as it is quite brittle and easily broken. Make sure the igniter is firmly seated and making good contact with the propellant in the engine. Improper igniter installation is the number one cause of launch failure.

Now we get to the launch controller. This is a device about the size and shape of a candy bar, and is used to control the launch of the rocket. There is a push button and an indicator light. The indicator light verifies when the rocket is ready to launch. This is when the safety key is inserted in the little hole at the top of the controller. The button is pushed to activate the igniter when all launch preparations are complete.

The safety key is a little round key attached to the safety cap. The safety cap is placed on top of the launch rod after the rocket is placed on the launch pad. The controller will not launch the rocket as long as the key is not in the hole in the controller. The safety cap blunts the end of the launch rod during launch preparation, preventing accidents. A seventeen foot wire leads from the controller to the rocket. The wire has alligator clips which attach to the igniter wire after it is installed in the engine.

The launch pad consists of the launch rod, blast plate, and three legs. The rocket is installed on the launch pad by slipping it into the launch lug on the side of the rocket body. It fits loosely enough to allow the rocket to escape easily during launch. The blast plate protects the area directly under the rocket from escaping gasses from the engine at ignition.

Once the rocket is built, follow these steps to launch and retrieve your rocket. Place it on the launch pad, threading the launch rod through the launch lug on the side of the rocket. There may be two launch lugs on taller rockets. Insert the rocket engine in the engine mount at the bottom of the rocket, securing with the engine clip. Insert the igniter wire, making sure there is good contact with the propellant of the engine. Place the safety cap with the key attached to the top of the launch rod. Attach the alligator clips to the leads of the igniter wire. Uncoil the wire from the launch controller to its full length. Make sure all bystanders are at least fifteen feet from the rocket, and make sure they stay there. Remove the safety cap from the top of the launch rod, and place key in hole indicated on controller.

Countdown and ignition!

The rocket will literally leap from the launch pad at speeds approaching 200 MPH. It will continue to gain altitude until the engine shut down. The rocket will track slightly into the wind. During this phase, the engine will emit tracking smoke to allow you to see the rockets progress. At peak altitude the ejection charge will fire, ejecting the recovery system - parachute or streamers. The rocket will descend to the ground, where you can retrieve it for another launch. As the rocket descends, watch an object in the distance directly behind it. When rocket hits the ground, walk directly towards the object, and you should easily find your rocket.

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© 2012 Hobby Hobnob

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