Model rocket

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 and High powered rocketry are 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-usable 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 initiated 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, multistage rockets 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 in (75 mm) tall models in the baseball field, to teams of adults launching 200 pound (100 kg) behemoths to the fringes of space. Model rocketry is often credited as the most significant source of inspiration for children who eventually become scientists and engineers. 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 .

Both amateur and model rocketry have come under controversy in the United States following the terrorist attacks on New York and Washington D.C., as federal and state authorities allege that model rockets can be modified to act as weapons used to shoot down aircraft within the United States. Authorities argue that all members of the hobby should have to be licensed and their purchases recorded and reported to federal agencies. Critics of such policies, particularly those involved in the hobby itself, including several ex-military members now involved in rocketry, argue that while building model rockets capable of going great distances is a relatively simple feat, guidance systems are exceedingly difficult to design—requiring an extensive educational and technical background—rendering the likelihood of anyone being capable of designing a guidance system for homing in on an aircraft extremely low.

The propellant used by most small model rocket moters (1/4A through F) is black powder. The propellant used by most higher power rocket moters is a fast-burning composite of varying chemical formulas. The standard propellant used is ammonium perchlorate composite propellant, or APCP, which is classified by the government as a low explosive. Following President Bush's signing of the Safe Explosives Act in 2002, hobbyists who had routinely purchased engines and APCP for years had to be fingerprinted, submit to background checks, and allow local and federal investigators at any time into their homes for inspections to ensure proper storage of the propellant.

The amount of APCP regulated is 62.5 grams and above, estimated to be about enough for a motor five or six inches (125 to 150 mm) long, one inch (25 mm) in diameter, and with a thrust of ten pounds force (44 N) for two seconds (88 newton-seconds impulse). This is a "G engine", which cannot exceed 160 newton-seconds impulse and are the largest rocket engines allowed for model rocketry. An "O engine", which cannot exceed 40960 newton-seconds impulse are the largest rocket engines allowed for high powered rocketry, which already requires certification.

According to the "Wall Street Journal," regulations on the transport of rocket fuel across state lines have been in place for many years but were not widely enforced until after the terrorist attacks on America, at which point authorities clamped down on regulations and added many new ones. Thereafter, amateur rocket enthusiasts have made use of a little-known law allowing the manufacturing of low explosives for personal purposes, initially intended for farmers who mixed fertilizer with fuel oil to create explosives to blast their own irrigation ditches. Amateur hobbyists use this law to justify "cooking parties," at which many gather and mix their own fuel legally and anonymously.

See also

• Water rocket

External links

• Joe's Rocket Page
• United States Spacemodeling Team Web Site