Model Rocketry and Siege Engine Glossary Letter A


Model Rocketry and Siege Engine Glossary Letter A

Glossary
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ARAMID
Aramid fiber is a fire-resistant and strong synthetic fiber. A shortened form of "aromatic polyamide"
Ablation
The flaking and vaporization of material undergoing severe heating due to aerodynamic drag.
In a model or high power rocket the only component that typically undergoes ablation is the motor nozzle. This is why, even with a reusable motor system, the nozzle is usually used only once
Abort
1) In an operational action, an instance of a rocket, missile, or vehicle failing to function effectively or to achieve the objective plotted for it 2) A rocket missile, or vehicle that so fails
Acceleration
The rate of increase in velocity. For example, increasing velocity from 20 to 50 feet per second in 1 second is an acceleration of 30 feet per second.
Accelerometer
An electronic device for detecting the presence of high acceleration. An accelerometer can be used for flight data gathering, or for controlling flight events.
For example, an accelerometer with a memory chip can record the strength and duration of a rocket’s acceleration. This data can be used by a computer to calculate the rocket’s approximate altitude at various points of its descent.
An accelerometer can also be combined with a timer to determine the proper time for a deployment charge or sustainer motor to be activated, by counting down a pre-set number of seconds after acceleration ceases (motor burn-out)
Acetate Dope
A liquid material made from cellulose and acetic acid that shrinks, waterproofs and protects flexible coverings such as tissue or silk
Acetone
An inflammable liquid used as a general solvent for dope, lacquers and epoxy.
Acrylic resin
A transparent, stiff thermoplastic resin sometimes used for body tubing
Actuator
A mechanical, electrical, or electronic device that sets a mechanism in operation or performs a specific action such as throwing a switch
Adapter
Part used in model rocketry to connect one part of an airframe to another allowing smooth airflow. Also called a Transition.
Additive
Substance added to another to modify its properties such as micro balloons added to epoxy.
Adhesive
A substance used to bond two components together.
Advanced Model Rocket
Model rockets constructed of either exotic materials and or designed to perform functions different from normal model rockets.
Aerial Photography
Covers the taking, study, and interpretation of photographs taken from the air.
Aerodynamics
That field of dynamics which treats of the motion of air and other gaseous fluids and of the forces acting on solids in motion relative to such fluids
Aerodynamic Heating
Heating of solid objects in an airflow caused by the friction of the air against the objects.
Aeronautics Act
Canadian law that regulates all use of airspace in Canada. Section 507 applies to hobby rocketry directly. Equivalent to FAR101
Aerosol
A mixture of fine liquid and/or solid particles suspended in a gas or air, such as paint from a spray can
Afterburning
The process of fuel injection and combustion in the exhaust jet of a turbo-jet engine (after the turbine
AGL - Above Ground Level.
The altitude a rocket attains above ground level altitude. The altitude a rocket attains, not counting the altitude of the launch site. In the United States, waivers are issued by the Federal Aviation Administration (FAA), limiting the maximum altitude permitted.
AHJ
See Authority Having Jurisdiction
Aileron
A hinged or movable surface on an airframe, the primary function of which is to induce a rolling moment on the airframe. On an airplane, it is part of the trailing edge of a wing
Aircraft Dope
Liquid material applied to model aircraft to strengthen and seal the covering material. Sometimes used with talcum powder to make a filler to seal balsa on a model rocket.
Air-Breathing Jet
A propulsion device which operates by taking in air and then ejecting it as a high-speed jet
Airflow
the motion of air past and around an object.
Airfoil
A part or surface, such as a wing, propeller blade, or rudder, whose shape and orientation control stability, direction, lift, thrust, or propulsion.
A streamlined shape given to fins or wings for maximum aerodynamic efficiency in flight. A conventional airfoil - optimized for subsonic flight - has a rounded leading edge tapering to a pointed trailing edge. See Cambered, Diamond, Symmetrical.
Airfoil Section
The cross-section of an airfoil in the plane of the common airflow around that part.
Airframe
The rocket’s main structure, especially the body tube.
Airstart
The practice of starting rocket motors after the rocket is already in the air. Commonly used with clustered motors
Aliphatic Resin
A type of carpenter’s glue, that although water based, penetrates and bond porous material forming a waterproof joint. Commonly called "yellow glue"
Alignment
Bringing parts into position and orientation as desired.
Altimeter
A device used to measures altitude. Altimeters can be used simply to document a rocket’s path or also used to control electrical devices for airstarting motors or deploying recovery devices.
Altitude
Height measured above the ground.
There are several methods of measuring or expressing altitude:
Pressure - Read from an altimeter when it is adjusted to 29.92 inches of mercury. All US aircraft flying above 18,000 AGL use pressure altitudes.
Actual (also called True) - Height above mean sea level
Density - Pressure reading corrected for temperature and humidity. Example: at 2850 feet actual altitude, at 100 degrees F. with 60% humidity and standard pressure, the density altitude is over 6500 feet.
Indicated - The altitude indicated by an altimeter.
Altitude can be expressed as either Above Mean Sea Level (MSL), or Above Ground Level (AGL).
Amateur Rocketry
Rocketry activities not including model, mid-power, or high-power rocketry. Not professionally funded
Ammonium Perchlorate (NH4CIO4)
The oxidizer used in most composite rocket motors.
AN - Ammonium Nitrate
A solid rocket oxidizer
Analogue Computer
A computing machine that works on the principle of measuring, as distinguished from counting, in which the measurements obtained, as voltages, resistance, etc., are translated into desired data.
Anemometer
instrument used to measure the speed of an airflow
Angle of Attack
The angle between a reference line fixed with respect to an airframe and the apparent relative flow line of the air.
Antenna
A device such as a conductor, horn, dipole-for transmitting or receiving radio waves, exclusive of the means of connecting its main portion with the transmitting or receiving apparatus.
Antimissile Missile
An explosive missile launched to intercept and destroy another missile in flight.
AP
Ammonium Perchlorate
Apogee
In rocketry, the highest point a rocket achieves before beginning its descent
ARF
Almost Ready to Fly. A rocket which is sold almost pre-built, as opposed to a kit. Requires very little assembly in order to fly.
ARS
American Rocket Society; an early amateur rocketry group. Now called the American Institute of Aeronautics and Astronautics.
Aspect Ratio
The ratio of length to width. In rocketry, a rule of thumb is that the aspect ratio of a model rocket’s length to its body diameter must be at least 10:1
Arming
As applied to fuses , the changing from a safe condition to a state of readiness. Generally a fuse is caused to arm by acceleration, rotation, clock mechanism, or air travel, or by combinations of these.
Aspect Ratio
The ratio of length of the rocket to the width. The width is usually the width of the fins. Generally, model rockets have aspect ratio of a about at least 10:1 for stable flight.
Astronaut
One concerned with flying through space, or one who navigates through space.
ASTRONAUTICS
The art, skill, or activity of operating space vehicles. Or in a broader sense, the art or science of designing, building, and operating space vehicles.
Asymmetric Fins
A set of fins that are not identical in size, shape and relative position on an airframe.
ATF
See BATF
Atmosphere
The body of air which surrounds the earth, defined at its outer limits by the actual presence of air particles.
Attitude
The position and orientation of an object relative to a fixed line, plane of axes or reference
Authority Having Jurisdiction
An entity or organization having authority to certify rocket motors under the terms of NFPA 1122 and NFPA 1127.
Autogyro
A vehicle whose blades rotate in a horizontal plane due to aerodynamic forces alone, creating lift
Automatic Pilot
An automatic control mechanism for keeping an aircraft in level flight and on a set course or for executing desired maneuvers. Sometimes called gyropilot, mechanical pilot , robot pilot, or auto pilot.
Average Chord
The chord at the middle of a wing’s span
Average Thrust
The total impulse (in Newton-seconds) divided by the burn time. Example; a K185 motor has a total impulse of approximately 1400 Newton-seconds, and burns for 7.5 seconds. 1387.5 Newton-seconds divided by 7.5 equals 185 newtons average thrust
Axis
One of the three lines of reference around which an aircraft can rotate. The three movements an aircraft can make (other than moving straight ahead) all involve rotation around some central point. That point is called an axis. These movements are: Roll - rotation around the longitudinal (front-to-back) axis (nose remains pointed forward, but the rocket spins), Pitch - rotation around the horizontal axis (nose moves up or down), and Yaw - rotation around the vertical axis (nose moves left or right.)
Azimuth
An angle on a horizontal plane. See Elevation.


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