What Are Model Rockets

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The hobby of model rocketry got its start in the late 1950s at the beginning of the "space race". Many people, inspired by the fiery boosters carrying the first satellites into orbit tried to emulate that activity by making their own rockets. These amateur rockets tended to be made of steel pipes filled with explosive chemicals and were more likely to blow off a finger or hand than to fly. Anyone who has seen the movie October Sky has an idea of what amateur rocketry was like before the advent of model rocketry. If you have seen the movie, keep in mind, that is not model rocketry.

October Sky is not model rocketry!!!

Model rocketry was started as an alternative to this amateur rocketry, to give the enthusiastic amateurs a rocket they could fly that was not likely to kill them in the process.

Model rockets are light weight, rocket powered vehicles, made of paper, balsa wood and thin plastic castings. They use professionally manufactured, single use engines made of paper tubes with clay nozzles or plastic. These engines are less flammable than cans of model airplane fuel. A few newer, reusable engine casings are made of metal, but they are carefully constructed to blow out the end plugs instead of blowing off fingers.

The Estes Alpha shown here is a good example of a first model rocket. It is 12 inches tall, 1 inch in diameter and weighs 0.8 oz without an engine.

Model rockets all have a recovery system that changes the configuration of the rocket when it reaches the peak of its trajectory. The configuration is changed so that as the rocket returns to earth it does not do so as a ballistic vehicle. The configuration is changed by either making the rocket unstable (popping off the nose cone) so that it tumbles, using a parachute or streamer to slow it down, or by changing it into a glider.

This shows the basic design of a simple Estes rocket (from the Estes Model Rocketry Technical Manual).

The following image shows a standard flight profile for a typical model rocket that uses parachute recovery.

Model rocketry is actually broken down into two ranges.

Model Rocketry

High-Power Model Rocketry

The separation of Model Rocketry and High-Power Model rocketry is based on total weight, the total combined impulse of all the engines, the average thrust of a single motor, and the use of large amounts of metal in the airframe. Exceeding any of the following limits makes a flight high-power.

1,500 grams (53 ounces) liftoff weight.
A single motor with an impulse of 160 Newton-seconds (36 pound-seconds) (a low end H motor).
A combination of motors with a combined impulse of 320 Newton-seconds (71.9 pound-seconds) (three G motors).
A single motor with an average thrust of more than 80 Newtons (18 pounds).
The airframe includes any parts of ductile metal. This does not apply to metal clips and screws.

See the section on Rocket Motors for a description of total impulse and engine sizes. Most model rockets weigh considerably less than the limits, and are more in the range of 100 to 300 grams (5 to 10 oz) using engines with 5 to 20 Newton seconds (1.12 to 4.48 pound-seconds) of total impulse.

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Last modified on Tuesday, 31-Mar-2009 17:00:00 PDT