Model rocketry is a hobby similar to model airplanes. In the contemporary U.S., there are two distinct types of rocket hobbyist.
Amateur rocketry hobbyists experiment with fuels and make their own rocket motors, often launching rockets hundreds of miles into the ocean. Amateur rockets can be dangerous because noncommercial rocket motors fail more often than commercial rocket motors.
Model rocketry is different because these hobbyists purchase professionally-manufactured solid-fuel or hybrid liquid/solid fuel rocket motors. Since they are professionally designed and constructed, they are far safer. The motors also are tested and approved by The National Association of Rocketry or The Tripoli Rocketry Association and come in standard sizes and powers. The motors can range from the small single use variety that have cardboard bodies, and lightweight molded ceramic nozzles to re-useable casings that are re-loaded with propellent and used over and over again. The top of the rocket motor is designed to burn through, and emit a small pulse of hot gas. This is used to initiate recovery (usually, push out a parachute), or ignite the next stage of rocket motor. Recovery and second stage ignition may also be intitated by small flight control computers. Motors are electrically ignited with a short length of nichrome wire pushed into the propellant and tamped with cotton or toilet paper. After a motor is used, it is thrown away.
Model rockets are designed to use these standard motors. The rocketeers experiment with rocket sizes, shapes, payloads, multistagerocketsrockets and recovery methods. Some rocketeers even build models of larger rockets.
Model rocketry is enjoyed by many different levels of hobbyist, from grade-school children launching 3" tall models in the baseball field, to teams of adults launching 200-pound behemoths to the fringes of space. For educational and smaller model rocketry information, see National Association of Rocketry. For information on larger rockets, also known as high-powered rocketry (as distinct from amateur rocketry) see Tripoli Rocketry Association.