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Rocketry Glossary

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1010 Extrusion

1010 extrusion is is a 1.0" x 1.0" T-slotted aluminum rail produced by 80/20. Rocketry hobbyists use the extrusion as rails for launching rockets. [Read More]

1515 Extrusion

1515 extrusion is is a 1.5" x 1.5" T-slotted aluminum rail produced by 80/20. Rocketry hobbyists use the extrusion as rails for launching rockets. [Read More]

3-Fold Method

See: Three-Fold Method [Read More]


An acronym for "Three Fins and a Nose Cone," 3FNC is used as slang for a basic model rocket. See also: 4FNC [Read More]


An acronym for "Four Fins and a Nose Cone," 4 FNC is used as slang for a basic model rocket. See also: 3FNC [Read More]


A company that makes aluminum extrusions that work well as DIY rails. The 80/20 1010 Extrusion is compatible with standard rail buttons (such as those from BlackSky and The company's 1515 Extrusion is compatible with larger rail buttons. [Read More]

- A -


The Usenet alt.binaries.models.rockets newsgroup where "binaries" (images, executables, movies, and other file types) are posted. [Read More]


The flaking and vaporization of material undergoing severe heating due to aerodynamic drag. Portions of rockets subjected to high-heat from drag are sometimes covered with ablative coatings which carry away the heat as the flake away or vaporize. [Read More]


Failure of an aerospace vehicle which prevents completion of its mission. [Read More]


Natural or man-made materials used for grinding, sanding or polishing a surface. [Read More]


Acrylonitrile-Butadiene-Styrene (ABS) is a tough, heat-resistant, and impact-resistant thermoplastic. It is used for telephone housings, luggage, sporting helmets, pipe fittings and automotive parts. [Read More]


The Aerodynamic Center (AC) is the point where all the aerodynamic forces on a glider balance, i.e. the Center of Pressure (CP) of the glider. [Read More]


An accelerometer is an electronic device for detecting the presence of 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 ... [Read More]

Acetate Dope

Acetate Dope is a liquid material made from cellulose and acetic acid that shrinks, waterproofs, and protects flexible coverings such as tissue or silk. [Read More]


Acetone is a flammable liquid used as a general solvent for dope, lacquers and epoxy. [Read More]


An acronym is a word formed from the initial letters or groups of letters of the words in a name or phrase. [Read More]

Acrylic Resin

Acrylic resin is a transparent, stiff thermoplastic resin sometimes used for body tubing. [Read More]


An actuator is a mechanical, electrical, or electronic device that sets a mechanism in operation or performs a specific action such as throwing a switch. [Read More]


See: Transition See Also: Motor Adapter [Read More]


An Analog-Digital Converter (ADC) is a device that converts an analog signal to the digital signal that a computer can read. [Read More]


An additive is a substance added to another to modify its properties. For example, micro balloons can be added to epoxy to reduce the weight of the epoxy. [Read More]


An adhesive is a substance added to two components in order to bond them together. [Read More]

Advanced Model Rocket

An advanced model rocket is a model rocket either constructed of exotic materials or designed to perform a function that differentiates it from normal models. [Read More]

Aerial Photography

Aerial Photography is the study and interpretation of photographs taken from well above the earth's surface. [Read More]

Aerobrake Recovery

Aerobrake recovery is a recovery method where the rocket doesn't deploy a recovery system such as a parachute or streamer. Instead, its speed is kept at a safe level by its large amount of drag. Aerobrake recovery is often used in saucer/UFO designs. [Read More]

Aerodynamic Center

The Aerodynamic Center (AC) is the point where all the aerodynamic forces on a glider balance, i.e. the Center of Pressure (CP) of the glider. [Read More]

Aerodynamic Heating

Aerodynamic heating is the heating of a solid object in an airflow caused by the friction of the air against the object. [Read More]


Aerodynamics is the study of the motion and forces of gases moving around solid objects. [Read More]

Aeronautics Act

The Aeronautics Act is Canadian law that regulates all use of airspace in Canada. The actual regulations are contained in the Canadian Aviation Regulations (CARs). [Read More]


An aerosol is a mixture of fine liquid and/or solid particles suspended in a gas or air such as paint from a spray can. [Read More]

Aerospike Nozzle

A nozzle whose main flow is annular about a center, truncated cone, and a secondary flow is introduced through the base of the cone. The circulation of this secondary flow and its interaction with the engine exhaust creates an "aerodynamic spike" that behaves much like the ideal, isentropic spike. ... [Read More]

Aft Closure

The aft (or rear) closure of a motor is a piece that is screwed or otherwise attached to the rear of the motor case to seal the motor and retain the nozzle. [Read More]


Above Ground Level (AGL) is the altitude measured with respect to the underlying ground surface as opposed to above mean sea level. [Read More]


The American Institute of Aeronautics and Astronautics (AIAA) is professional society for the aerospace field. [Read More]


An ailerons is the hinged portion of a wing which is designed to impart roll to the aircraft. [Read More]

Aircraft Dope

Dope is a liquid material applied to a model aircraft to strengthen and seal the covering material. It is sometimes used with talcum powder to make a filler to seal balsa on a model rocket. [Read More]


Airflow is the motion of air past and around an object. [Read More]

Airfoil Section

An Airfoil section is the cross-section of an airfoil in the plane of the common airflow around that part. [Read More]


An airfoil is the 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. [Read More]


The airframe is a rocket's main outer structure, usually the rocket's body tube. [Read More]


Airstart is the practice of starting one or more rocket motors after the rocket is already in the air. [Read More]


Alignment is bringing parts into position and orientation as desired. [Read More]

Aliphatic Resin

Aliphatic resin is a type of carpenter's (or "yellow") glue that, although water-based, penetrates and bonds porous materials forming a waterproof joint. [Read More]

All Thread

All-thread is a metal rod that is threaded through its entire length, a "threaded rod." [Read More]


A device that measures altitude. Altimeters can be used simply to document a rocket's apogee, but they are also commonly used to control electrical devices for airstarting motors or deploying recovery devices. [Read More]


Altitude is the height above the ground or sea level. [Read More]


Academy of Model Aeronautics . American aeromodeling liaison organization to the CIAM through the NATIONAL AERONAUTIC ASSOCIATION. [Read More]

Amateur Rocketry

Although, in the strictest sense, Amateur Rocketry encompasses all hobby rocketry, the phrase is usually used for activites outside the scope of low to high-power rocketry as defined by the model rocket and high-power safety codes as defined by the National Association of Rocketry and the Tripoli ... [Read More]

American Rocketeer

Centuri's attempt to produce a "Model Rocket News" clone in the late '60s. While the contents were fairly typical (product announcements, club news, rocket plans, reports on "real" aerospace events, etc.) it had a curiously over-produced look to it and ran very heavy on the advertising. Someone ... [Read More]

American SpaceModeling

The journal of the National Association of Rocketry. Previously known as The Model Rocketeer, it underwent yet another name change and became Sport Rocketry starting with the Sept/Oct 1993 issue. See Sport Rocketry [Read More]

Ammonium Nitrate

An oxidizer can be used some experimental motors [Read More]

Ammonium Perchlorate

(NH4ClO4) The oxidizer used in most composite rocket motors. Other components are Aluminum powder (fuel) and polybutediene rubber (the binder holding it all together). This is the propellant mixture that the Shuttle SRB's use. See Binder [Read More]


Deprecating but affectionate abbreviations for American Spacemodeling. See American SpaceModeling [Read More]


Animal Motor Works ; a rocket company that makes high power loads. [Read More]


Ammonium Nitrate: a solid rocket oxidizer. [Read More]


An instrument used to measure the speed of an airflow. [Read More]

Angle of Attack

The angle between the long axis of a rocket and the direction of the air flowing past it. [Read More]


Raised spirals found on some non-rocket tubes such as mailing tubes, etc. The opposite of a 'standard' spiral. Spirals and anti-spirals do not cancel one another. [Read More]


Any of several techniques designed to prevent Zippering. [Read More]


See Ammonium Perchlorate [Read More]


Ammonium Perchlorate Composite propellant. [Read More]


In rocketry, the highest point a rocket achieves before beginning its descent. (More literally, the point farthest on the flight path from Earth.) [Read More]


See American Rocketeer [Read More]


Almost Ready to Fly. A designation from kit manufacturers that indicates that their kit only requires a few final assembly steps. [Read More]


Anti-Radiation Missile; An anti-radiation missile (ARM) is a missile which is designed to detect and home in on the emissions of an enemy radar. Also known as a HARM. [Read More]


The Amateur Rocketry Society of America (ARSA) is an organization supporting all forms of amateur rocketry in the United States. [Read More]


American Rocket Society; an early amateur rocketry group. Now called the American Institute of Aeronautics and Astronautics. [Read More]


Almost Ready to Fly. Same as the more common ARF [Read More]

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. [Read More]

Asymmetric Fins

A set of fins that are not identical in size, shape and relative position on an airframe. [Read More]

Asymmetrical Thrust

Consider a rocket with two or more motors; symmetrical thrust is that which you find in most flight operations since an equal amount of thrust is provided by all motors, unless an motor fails [to ignite] or has a different thrust than the other(s). Safe operation of rockets with different motor ... [Read More]


See BATFE [Read More]


The position and orientation of an object relative to a fixed line, plane of axes or reference. [Read More]


A vehicle whose blades rotate in a horizontal plane due to aerodynamic forces alone, creating lift. [Read More]

Average Chord

The chord at the middle of a wing's span. [Read More]

Average Thrust

The total impulse (in Newton-seconds) divided by the length of 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. [Read More]

Away Cell

A set of launch pads that are far away from the flight line and intended for L motor flight and above. [Read More]


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 (f ... [Read More]


An angle on a horizontal plane. See Elevation. [Read More]

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Boost Glider [Read More]

Backslider (Glider)

A small-finned, long slender model rocket with a single ejection port at the front of the tube, whose CG is midway between the BCP and CLA; can function predictably as a no-moving-parts rocket glider; at ejection, the rocket glides fin-first; theory pioneered by Peter and Robert Alway [Read More]


One of a variety of configurations that block the hot ejection particles while allowing the ejection gas to expand into the rocket's body to cause ejection of the recovery system. Some use wire mesh, steel wool, or just a series of misaligned holes in tubing or bulkheads. [Read More]


Mass added to a model to bring the model into balance. [Read More]

Ballistic Coefficient

A measure of a projectile's ability to coast. It is defined as Cb = M/CdA where M is the projectile's mass and CdA is the Drag Form Factor (q.v.). At any given velocity and air density, the deceleration of a rocket from drag is inversely proportional to this value. Intuitively, it is the principle ... [Read More]

Ballistic Recovery

A recovery system that employs simple physics and has no potential for zipper damage to the airframe. See also prang [Read More]

Ballistic Trajectory

The path a rocket takes when descending without benefit of parachute. Normally, unless acted upon by wind a rocket's ballistic trajectory continues to describe a parabolic arc, bringing it to earth nose-first in a relatively predictable location. [Read More]


Study of objects moving through the air that have been given a short lived acceleration. [Read More]


Big A** Load Lifting Suckers: A popular annual launch for amateur and large HPR rocket flyers. [Read More]

Balsa Wood

Fast growing wood from Central America known for strength, low density, and a very porous grain. Frequently used for model rocket fins. [Read More]


A Born Again Rocketeer (BAR) is a person who once pursued rocketry as a hobby and returned to it at a later time in life. A BAR is an individual who has re-discovered the hobby/sport after an absence of several years. See Also: BOR [Read More]

Barrowman Method

A mathematical technique for calculating the center of pressure of a subsonic rocket at low angles of attack. Named for James S. Barrowman, who developed the method in 1966. [Read More]

Base Drag

Base drag is a component of aerodynamic drag caused by a partial vacuum in the rocket's tail area. The vacuum is the hole created by your rocket's passage through the air. Base drag changes during flight. While the motor is firing, the drag is minimal since the tremendous volume of gas generated ... [Read More]


The line between the tracker and the launcher in the single tracker method for finding altitude, or the line between to the tracking stations in the two tracker method. [Read More]


North American hardwood known for very tight even grain and fairly good ease of working. [Read More]


Ballistic and Test Evaluation System; The propellant grain geometry used in most high power reloadable motors; the grain has a central core, the length of each grain is ~1.5 time its diameter and the ends are uninhibited; the grains burn from the ends as well as the core, making each grain shorter ... [Read More]


Bureau of Alcohol Tobacco and Firearms; a federal regulatory agency. What the BATFE was formerly called. Sometimes called ATF. [Read More]


Bureau of Alcohol Tobacco Firearms and Explosives; a federal regulatory agency. Sometimes called ATF, BATF (older acronyms). [Read More]


Part of a model set aside for a specific purpose such as the payload or electronics bay. [Read More]


Barrowman Center of Pressure; see Barrowman Method [Read More]

Beam , Structural

A rigid body designed to transmit loads in shear or bending transversely to its point of support. A fin is actually a structural beam. [Read More]


A device that produces an auditory signal, assisting searchers to find a rocket after it has landed. [Read More]

Bernoulli Effect

A phenomenon first described by the 18th century Swiss scientist Daniel Bernoulli who studied the pressures in moving fluid streams. The effect states that moving air will have a lower pressure than the still air around it. This is the principle behind how airplane wings generate lift and why ... [Read More]

Bernoulli Lock

A phenomenon similar to the Krushnic Effect where the rocket seems to be "glued" to the pad at liftoff. This afflicts larger, flat-bottomed rockets launched too close to pads with flat blast deflectors. The exhaust gasses escape at great speed through the small annular space between the ... [Read More]

Bernoulli Principle

A physics principle that states the pressure exerted by air perpendicular to its direction of travel decreases with an increase in velocity. This is the theoretical principle upon which airplane wings work. An airplane wing's airfoil is unsymmetrical, its upper surface having a greater curve than ... [Read More]

Binder (propellant)

A material which binds the contituent elements of a composite propellant into a solid (usually rubbery); provides the fuel for the composite propellant; see HTPB and PBAN [Read More]


North American hardwood known for its pliancy and tight grain. [Read More]

Black Brant (II, III, IV, V, X)

A commonly-modeled Canadian sounding rocket. [Read More]

Black Powder

Black powder is the original explosive said to have been invented in China. A mixture of carbon, (charcoal), sulfur and potassium nitrate (saltpeter). [Read More]

Black Rock

A famous (at least to us rocketeers) dry lakebed in Nevada, which is home to the BALLS launches (and many others) [Read More]


A trademarked name for thin-walled body tubing made from phenolic impregnated paper and used with model rockets built for competition, especially superrocs. It was prized by some competition rocket flyers because it was stronger than ordinary cardboard tubing, but lighter than fiberglass. ... [Read More]

Blade Twist

The pitch angle variation on a helicopter blade from root to tip. [Read More]


Long thin wing, rotated around a central hub, such as on a propeller. [Read More]

Blast Deflector

A plate or other device that protects flammable materials like grass; surrounding a launch pad, from being ignited by rocket exhaust. [Read More]

Blister (Paint)

Air bubble formed under a skin of paint. Usually caused by heat applied to that spot or improper/incomplete preparation before paint. [Read More]


A building used for the preparation and launching of a commercial or military rocket, usually heavily reinforced. Not needed in hobby rocketry. [Read More]


Blow-by is the hot motor gasses escaping past the delay grain and igniting a motor ejection charge prematurely. [Read More]


The physical ejection of propellant through the front of the rocket body. See CATO [Read More]

Boat Tail

A tapering section which reduces a rocket's tail diameter and improves aerodynamic efficiency through the reduction of base drag. [Read More]

Body Tube

A cylindrical tube that makes up the body of the rocket. Typically made of cardboard, fiberglass or carbon fiber. See Airframe [Read More]

Bonus Delay

Slang for an unexpectedly long delay, sometimes resulting in airframe damage or parachute stripping. See Zippering [Read More]

Boost Glider

A winged aircraft which is powered into flight by a rocket motor, then returns to the ground as a glider after ejecting its motor or motor assembly. See Rocket Glider. [Read More]

Boost Phase

That part of a rocket's flight in which the propellant is generating thrust. Also known as Thrust Phase [Read More]


In a multi-stage rocket, the first stage. In a parallel staged rocket, the pods containing the motors with the shortest burn time. In a complex single-stage rocket, the term sometimes refers to the part that contains the motor assembly. [Read More]


A "Burned Out Rocketeer" (BOR) is the counterpoint to a "Born Again Rocketeer" (BAR). A BOR is someone who has been going at the hobby too intensely such as in preparation for a major contest. Also, "Big Obnoxious Rocket" [Read More]

Boundary Layer

The very thin layer of fluid close to the surface of a solid in an airflow. [Read More]

Bowling Ball Loft

A a contest in which the goal is to launch a bowling ball to the highest altitude; a common contest at LDRS. [Read More]


See Black Powder [Read More]


British SpaceModeling Association [Read More]


Body Tube [Read More]

Bucket Recovery

See Re-Kitted [Read More]


A bend or kink formed by overstressing the airframe. [Read More]


Repeated forces experienced by a model due to disturbed unsteady airflow. [Read More]


A hollow component, such as a fin, made up of a number of structural parts. [Read More]


A solid partition in the rocket, especially one set perpendicular to the rocket's long axis, designed to not allow gases to pass. [Read More]


Round, woven elastic material, often used as shock cord in high power rockets. [Read More]

Burn Rate Catalyst

An additive used to increase the burn rate of a propellant (iron oxide is a typical catalyst) [Read More]

Burn Rate Modifier

An additive used to increase or reduce the burn rate of a propellant [Read More]

Burn Rate Suppressant

An additive used to slow the burn rate of a propellant (oxamide is an example) [Read More]

Burn Rate

The rate at which a substance is consumed by burning, such as propellant or a fuse. [Read More]

Burn String

Helicopter blade deployment method using thin string to hold blades to the body of the rocket. Ejection gases and particles burn through the string, allowing for blade deployment. [Read More]

Burn Time

The time that it takes for a motor to fully expend its fuel. [Read More]


The chemical reaction that occurs within a rocket motor producing a high velocity gas. See also Neutral Burn, Progressive Burn, Regressive Burn [Read More]

Burned Out Rocketeer

A "Burned Out Rocketeer" (BOR) is the counterpoint to a "Born Again Rocketeer" (BAR). A BOR is someone who has been going at the hobby too intensely such as in preparation for a major contest. [Read More]

Burnout Velocity

The velocity achieved by the model at burnout. [Read More]


The point at which propellant is exhausted in a motor. [Read More]

Burst Disk

A thin disk whose purpose is to isolate propellants (or components of the propellant) until the motor is ready for operation [Read More]

Butt Joint

A joint made by gluing an edge to a surface, such as a fin to a body tube. [Read More]

- C -


A fuel grain geometry where the grain has a radial slot cut on its edge; the burn is relatively neutral until the end; an Aerotech G64 reload is a C-slot [Read More]


A super fine silica. Unlike microballoons, which are tiny glass spheres, Cabosil is "cut' glass fibers and very light. Used as a filler in epoxy fin fillets to reduce weight, and control sagging and dripping in thin epoxies. [Read More]


Cyano Acrylate: a thin, very strong adhesive also known as Super Glue. Comes is gel, fast, medium, slow, black, (thicknesses/speedset) for different applications. [Read More]


Computer Aided Design [Read More]


Caliber is used in rocketry as a comparison to the rocket's diameter. Caliber is usually used when refering to some function of length, e.g. "The CP should be behind the CG by at least one caliber." "One caliber" means a distance equal to the diameter of the rocket. Often, the word Caliper will ... [Read More]


A caliper is a device used to measure the distance between two opposing sides of an object. The word caliper is often mistakenly used in place of the word Caliber . It is an easy mistake to make since a caliper is a tool that may be used to measure the diameter of a rocket and the diameter defines ... [Read More]


The increase in curvature of an airfoil along its chord. [Read More]

Cambered Airfoil

An airfoil (wing) on which only the top surface is tapered, the bottom surface remaining flat. [Read More]


A paint scheme used to conceal an object in its background. [Read More]


A fin or wing located at the middle or front of a rocket. Canard fins are often used on guided missiles since they make the missile less stable and easier to steer. Because canard fins move the center of pressure forward and tend to destabilize model or high power rockets, they are only used for ... [Read More]

Candy Motor

See Sugar Motor [Read More]


The fabric of the top of a parachute. [Read More]

Canted Nozzle

A nozzle positioned so that its line of thrust is not parallel to the direction of flight. See Vectored Thrust [Read More]

Cantilever Beam

A projecting member, fixed at one end rigidly and free at the other. Wings and fins are both cantilever beams. [Read More]

Capacitive Discharge

A type of launch controller which uses a large capacitor to store electrical energy from a battery. When commanded by the launch controller, the capacitor discharges a large current into the igniter. These controllers are often used with large cluster rockets to ensure that all of the motors ... [Read More]


Canadian Association of Rocketry reflecting changes in the CARS regarding rocket associations. [Read More]

Cardboard Cutout Method

An old method of determining the Center of Pressure (CP); this is typically the most conservative estimate of CP ; this is the CP at an angle of attack of 90 degrees - the worst possible situation [Read More]


Canadian Armament Research and Development Establishment. Now known as DREV - Defence Research Establishment Valcartier. [Read More]


Canadian Aviation Regulations . Regulations affecting hobby rocketry are in Sections 101.01 (definitions) and start at 602.42 [Read More]

Case Rupture

The splitting of the motor due to excessive pressure in the combustion chamber. [Read More]

Case, Casing

The outside framework of a rocket motor. [Read More]

Cast Propellant

A solid propellant formed by the pouring of a soft propellant into a mold to solidify into a hard grain. See Grain. [Read More]

Casting Tube

A tube in which propellant is cast, typically cardboard [Read More]


A contrived initialism for "Catastrophe At Take Off," the abbreviation CATO is used as a noun and is generally defined as "a catastrophic failure." Although originally used to describe the dramatic malfunction of a rocket motor, the use of CATO has broadened to include a range of calamitous events ... [Read More]


Short for "catastrophe", cato is used as a noun and is generally defined as "a catastrophic failure." Although originally used to describe the dramatic malfunction of a rocket motor, the use of cato has broadened to include a range of calamitous events such as a rocket "shredding" in flight due to ... [Read More]


Contest Director; also Compact Disk if not shooting rockets [Read More]

Center of Gravity

The point at which a rocket balances when completely prepped for flight. [Read More]

Center of Pressure

The point at which the aerodynamic lift on a rocket is centered. See also:'s Center of Pressure Library . [Read More]

Centering Ring

A ring of paper, cardboard, plywood, or other material which connects the motor tube to the airframe, ensuring that the motor remains parallel to the rocket's main axis. A motor tube requires at least two centering rings. More powerful motors sometimes require more. [Read More]


Code of Federal Regulations [Read More]


See Center of Gravity. [Read More]


Slang term meaning "Cheap and Dirty." Most common usage referes to "CHAD-staging" in which a booster motor is attached to the rear of a rocket motor to convert a single-stage rocket into a two-stage rocket. [Read More]


A list of items to be performed; this is highly recommended on complex projects; everyone has heard of them, but many rockets have been lost because it sounded like too basic a procedure. LPR Checklists and HPR Checklists . [Read More]


A class of chemical which is extremely dangerous when used as a rocket propellant [Read More]


The short dimension (front-to-rear) of a glider's wing. See Span. [Read More]


Slang for a condition in which a motor fails to produce maximum thrust. The rocket's speed and altitude suffer as a result. In a serious case, the rocket does not achieve adequate air speed and crashes. [Read More]


Intermittent burning of a rocket motor, accompanied by the sound of a steam engine starting. [Read More]


International Aeromodelling Commission of FAI, which includes among other hobby disciplines, Spacemodelling (model rocketry) [Read More]


Center of Lateral Area; the balance point determined by the Cardboard Cutout Method of determining CP. See Cardboard Cutout Method. [Read More]

Class B Motors

Rocket motors containing more than 62.5 grams of propellant or motors that impart more than 120 newton-seconds of thrust. [Read More]

Class C Motors

Rocket motors contain less than 62.5 grams of propellant or impart 120 newton-seconds of thrust or less. [Read More]


A rocket design that is streamlined and free of projections. [Read More]

Clip Whip

Short extensions at the end of a launch system with microclips. [Read More]


A rocket that is built to exactly replicate another produced rocket, it is often an Out of Production (OOP) rocket [Read More]

Closed Breech

Piston launcher where the piston is mounted on the launcher, the motor is mounted in the model and the piston movement is upwards with the model. [Read More]


The front and rear sections of a reusable motor assembly, which connect to the motor casing by threads, snap rings, or other method. [Read More]


Canadian Launch Safety Office, a division of Transport Canada that governs safety and issues all launch waivers for rocketry in Canada, ranging from approval of the Canadian Model Rocket Safety Code to permitting satellite launches at the Spaceport, Fort Churchill, Manitoba [Read More]


See clustering [Read More]


A boost technique which uses 2 or more motors side by side in the same rocket. Safe operation of rockets with different motor thrusts, in a cluster would be to ensure symetrical thrust around the center vertical axis of the rocket. This is also sometimes accomplished by canting motors toward the ... [Read More]

Coasting Phase

That part of the rocket's flight between burnout and the airstart of the next stage or between burnout and activation of the recovery system. [Read More]

Coefficient of Drag (Cd)

A dimensionless number used in aerodynamics to describe the drag of a shape. This number is independent of the size of the object and is usually determined in a wind tunnel. It is part of the basic drag equation F=.5*rho*V^2*Cd*A where F is the drag force, rho is the air density, V is the air ... [Read More]

Cold Power

A type of rocket motor powered by CFC refrigerant under pressure. All support for this line was discontinued in the mid-seventies because of concern over the effect of CFC's on stratospheric ozone. [Read More]

Combustion Chamber

The part of the motor where the actual combustion occurs. Composite fuels require a set pressure in the combustion chamber to continue burning at the proper rate. Failure to maintain the pressure results in chuffing. [Read More]

Competition Model

Model whose design is optimized expressly for a particular competitive event. [Read More]


A manufactured part required to assemble a model, such as fins. [Read More]

Composite (material)

Two or more separate and distinct materials, the combination of which produces a new material with more desirable properties such as increased strength, lower density or better workability. [Read More]


A solid rocket motor type which uses two or more substances for combustion, neither component being black powder. A typical composite motor in hobby rocketry uses rubber as a fuel and ammonium perchlorate as an oxidizer. [Read More]

Compound Dihedral Angle

A "bent wing", in which a glider's wing describes two straight planes at different vertical angles, with the tip pitched at a steeper angle than the root. See Dihedral [Read More]


Having a common center. [Read More]

Cone Stability

The inherent stability of conic shapes to fly without fins provided the CG is ahead of the CP. [Read More]


See Nose Cone [Read More]


The arrangement of fins, wings and other parts of a rocket or aircraft. [Read More]


Of or pertaining to a cone. [Read More]


An unstable flight condition in which a rocket's spin causes the rear portion of the rocket to describe a circle. Coning greatly increases aerodynamic drag and reduces peak altitude. Stability is often described in units of "Caliber" and a long, thin rocket with small fins may have several ... [Read More]

Contact Cement

An adhesive that is applied to both parts to be joined and allowed to set up. They are bonded on contact, usually permanently. [Read More]

Contest Acronyms

The NAR uses a bewildering number of acronyms to describe its contests. As with most things of this nature, there is a logic to the naming which makes things much easier to understand once learned. The basic structure of an event name is a prefix, the event acronym and a suffix. The prefix is ... [Read More]


The condition of a continuous circuit in a launch system once safety has been closed. A continuous electrical circuit will allow electricity to flow, so in the context of a launch controller "Continuity" means the igniter circuit is correctly connected and the rocket motor is ready to be ignited. [Read More]

Control Surfaces

Surfaces such as flaps and elevons used to control the attitude of a rocket or glider aerodynamically. [Read More]


The trademark name for an igniter produced by AeroTech, Inc. It is a laminated assembly consisting of a two copper foil strips separated by an insulator, with a quantity of pyrogenic compound on one end. It normally requires a special clip for electrical connections, but some rocketeers have ... [Read More]

Core Ejection

Ejection of a central pod holding the motor from the rear of the model. [Read More]

Core Sample

What happens when an airframe devoid of nosecone punches into the ground without benefit of recovery system. Named for the tubular sample of sod and dirt stuffed into the body tube on impact. Also known as "drilling for oil." See Lawn Dart [Read More]


The hole or slot in the grain of propellant in a motor. Alteration of the core's shape determines the thrust characteristics of the motor. [Read More]


The process, usually marked in seconds counting down to zero, of the final preparation and launch of a rocket. [Read More]


A section of tube used to connect 2 sections of larger body tubing. [Read More]


Material covering the framework of a structure. [Read More]


See Center of Pressure. [Read More]


Close Proximity Recovery: an electronically-controlled system that permits highaltitude rockets to have most of their descent controlled with a drogue. The main parachute deploys at lower altitude. [Read More]


Consumer Product Safety Commission. Rules restrict use of HPR motors (H and up) to adults 18 years of age and up. [Read More]

Craze (Crazing)

Cracking of paint or fogging of acrylic resin due to incompatibility of paint, primer, adhesive, and/or material. [Read More]

Cross Section

The area exposed if a part is cut through. [Read More]

Cruise Missile

Description of a rocket which for one reason or another turns downrange and for a short time flies parallel to the ground; a stricter definition is a small, pilotless, rocket powered airplane [Read More]


Adhesive developed through the space program. Adhesive hardens very quickly and forms a high strength bond without the mixing of components. Also known as Superglue, Crazyglue, and CA. [Read More]

- D -


An unpowered vehicle, with the same aerodynamic characteristics as a rocket. A dart is one method of propelling a payload package to a maximum altitude. The dart rides on top of a large booster, possessing a higher coefficient of drag. During powered flight the dart acquires all the momentum of ... [Read More]

Data Reduction

The procedure for transforming raw instrumentation data into useful parameters [Read More]

Davis Douche

Variant of the flash pan, where wicks are inserted into each motor and the wick ends are put into the pan of BP. See Flashpan, with Caution. [Read More]


Dual Deploy [Read More]

Death Dive

See Power Prang [Read More]


The difference, in degrees, between the angles of attack of the wings and stabilizer of a aircraft. This difference builds in some inherent stability, allowing the aircraft to recover from dives and stalls. [Read More]


A reduction of velocity. [Read More]


Bending or displacement from the neutral position due to loading from some outside force. [Read More]


See Blast deflector [Read More]


The processing of a propellant using vacuum processing; reduces bubble that may make the burn less uniform or even cause a CATO [Read More]


An electronic, mechanical, or pyrotechnic device that permits the rocket's unpowered ascent between motor burnout and the deployment of the recovery device. Typically, the delay is a pyrotechnic grain which separates the propellant from the deployment charge and which burns at a known rate. The ... [Read More]


A tough resilient plastic (acetal resin) that is used for rail buttons [Read More]

Delta Wing

Wing planform in the shape of a large triangle, used for supersonic flight conditions. [Read More]


Change in velocity [Read More]


Ratio amount of a substance in a set volume. [Read More]

Deployment Bag

A bag constructed of some fireproof material such as Nomex, in which a rocket's parachute is packed. The bag serves to protect the parachute from hot deployment charge gasses, and assists in the orderly deployment of the parachute to prevent shroud tangling. [Read More]

Deployment Charge

The pyrotechnic charge which pressurizes the part of the rocket containing the recovery system, deploying the recovery device. [Read More]


The condition of releasing, or deploying, a parachute or other recovery device. [Read More]


It was started in 1998 by Dave Lee so that modelers, rocketeers, and most specifically readers of the Usenet newsgroup rec.models.rockets could showcase their talents, display their design on the internet, and win the acclaim of their peers. Prizes were donated by those entering the contest or ... [Read More]


A rocket that uses rods in place of fins; typically 8 rods extend out of the rear centering ring at an angle of approximately 30 degrees; some history can be found [here] . [Read More]


A device designed to ruin the aerodynamic properties of a aircraft, enabling it to safely escape a thermal and return to the ground. [Read More]


To be tricked due to suffering a bad case of launch happiness. [Read More]

Diamond Airfoil

An airfoil on which the leading and trailing edges are tapered symmetrically to a point. This airfoil is used on missiles designed for supersonic flight. Sometimes called a Nike airfoil, since the classic example is the Nike family of missiles. [Read More]

Dihedral Angle

The angle at which a glider's wing tips tilt upward from the horizontal plane, to impart roll and yaw control. [Read More]

Direct Staging

Air start of a sustainer motor caused by the burning propellant of the booster motor. [Read More]

Directional Stability

The ability of an aircraft to return to its original flight direction after being forced off course. [Read More]

Display Launcher

A launcher that is not functional and is used to show off a model. [Read More]


Motion of an aircraft in a head down or nose down attitude. [Read More]


Do It Yourself [Read More]

Dog Barf

Slang for flame retardent cellulose insulation, as used as recovery wadding; see wadding [Read More]


A liquid lacquer based paint used to seal the grain of wood. [Read More]

Doppler Effect

Change in sound frequency caused by the source's rapid movement towards or away from the observer. [Read More]


An uncontrollable competitor's disease, the symptoms of which are to impulsively make last minute changes intended to improve a tested competition model's performance, only to have the modification backfire or cause a disqualification. [Read More]


Department of Transportation: A federal agency responsible for laws concerning the roads, especially the interstate highway system. Transportation of motors and propellants is often regulated by DOT regulations. [Read More]

Double Base Propellant

A solid propellant consisting of two monopropellants (usually nitroglycerin and nitrocellulose) and various additives. Double base propellants are used as smokeless powders in ammunition. They are also used in smaller military rockets but have been largely replaced by composites in larger ... [Read More]

Douche Plate

Metal centering plate on the bottom of a cluster motor model to prevent damage caused by the BP flare-up using a flashpan or Davis Douche. [Read More]


The movement of a column of cooler air downwards, opposite to a thermal. [Read More]


The practice of building smaller versions of larger model rockets. See Downscale Rocket Articles . [Read More]


Slang for disqualification [Read More]

Drag Coefficient

See Coefficient of Drag [Read More]

Drag Form Factor (CdA)

The Drag Coefficient of an object multiplied by its cross sectional area. This is used to scale the drag value for a particular object from the dimensionless Cd. Theoretically, every object of a similar shape will have the same Cd regardless of its size, meaning that both a grain of rice and a ... [Read More]

Drag Race

An event, usually informal, in which multiple rockets are launched simultaneously. [Read More]

Drag Recovery

Recovery method using the shape of the model to slow the model down enough for safe recovery. [Read More]

Drag Separation

A phenomenon where the nose cone is apparently "sucked" out of the body right at motor burnout. It is more prevalent on parabola, ogive and other low drag nose shapes. The theory (as yet unproven) is that since the nose cone has much less drag than the body, its momentum tends to carry it forward ... [Read More]


Defence Research Establishment Valcartier. Formerly known as Canadian Armament Research and Development Establishment. [Read More]

Drilling For Oil

See Core Sample [Read More]

Drogue Parachute

Small, heavily reinforced parachute designed to slow the craft so safe release of the larger main chutes are possible. [Read More]


Detectable Seismic Event; see Power Prang also know as Death Dive [Read More]

Dual Deployment

See Dual Recovery [Read More]

Dual Recovery

A process by which a rocket is recovered by means of a streamer or drogue parachute which opens at apogee, followed by a main parachute which opens at lower altitude. See Single-Stage Recovery. [Read More]


A spray coating from Testor's Corp. that protects the finish of a model while removing the sheen of the finish. [Read More]

- E -


Slang for electric match [Read More]

Easy Access

A term coined by Aerotech for their HPR motors which have individual grains that are 62.5 grams or lighter (29mm and 38mm). This was during the period when the BATFE attempted to regulate rocket motors with more than 62.5 grams of propellant. For a short period, Aerotech clamed to have an ... [Read More]


A line of econonomical composite F and G motors produced my Aerotech; they are sold in pairs and are slightly less expensive than their other motors in a given class, they are also slighly less powerful. [Read More]

Egg Lofter

A rocket designed to carry one or more eggs as payload. Used in competition in which the object is to boost the egg to the maximum possible altitude and recover it without breaking. [Read More]

Ejection Baffle

A physical or mechanical barrier ahead of a motor mount designed to absorb the heat and hot particles of the ejection charge while allowing the gas to pressurize the airframe. [Read More]

Ejection Cannon

A tube or fitting that holds the ejection charge and is attached to the rocket [Read More]

Ejection Charge

A small charge of pyrotechnic matter, usually BP, triggered either by the delay train, timer or an altimeter, used to deploy the recovery device. [Read More]

Electric Match

1.) A type of igniter (see igniter). 2.) although sometimes used synonymously with the term igniter, an electric match usually refers to an igniter with the following attributes: requires low current to fire and has a short burn with little flame; these are generally used to fire ejection charges ... [Read More]


Any of a number of electronic devices used in rocket flight, e.g. Altimeters, Timers, etc. [Read More]


An angle on a vertical plane. See Azimuth [Read More]


A moveable surface on the horizontal stabilizer of an aircraft. The surface is responsible for pitch control. [Read More]

Elliptical Dihedral

A curved wing, in which the tip of a glider's wing curves up at a higher angle than the rest of the wing. The angle is the form of an arc rather than a sharp turn. See Dihedral [Read More]


Acronym for Essence's Model Rocketry Reviews, that's here [Read More]

End Burner

A solid motor that does not have a core and therefore burns only from its end, giving a neutral burn profile; a shallow core can be used to provide an initial thrust spike [Read More]

Engine Block

A ring which is glued into the motor tube to contain the motor during thrust, preventing it from moving forward into the motor tube while allowing ejection charge to pass into the body of the rocket; typically a cardboard ring or section of a used motor casing; normally only used in LPR. Often ... [Read More]

Engine Hook

See Motor Hook. [Read More]


An engine is a device that converts potential energy into mechanical work. Our rocket motors are engines because they convert the chemical energy stored in the propellant into the motion of the rocket. Rocket motors based on solid propellants are generally called "motors" rather than "engines" ... [Read More]

Entrance Cone

The inside portion of a rocket nozzle, which funnels gasses from the expansion chamber to the throat; in most small nozzles is cone chaped [Read More]


A two-part adhesive used extensively in applications requiring high strength. Chemically, a compound in which an oxygen atom is joined to two carbon atoms in a chain to form a bridge. Specifically, a resin containing epoxy groups, that polymerizes spontaneously when mixed with a phenol (see ... [Read More]

Erosion, nozzle

The wearing or burning away of the throat of the motor nozzle caused by the hot gases ejecting from the motor. Also called Ablation. [Read More]


Acronym for Experimental Rocketry [Read More]

Exhaust Clearance

On some models, the amount of offset required to prevent damage to parts below the motor nozzle from the motor exhaust. [Read More]

Exhaust Velocity

The speed of the gases ejected from the motor nozzle. Exhaust velocity is an important consideration in motor design because, according to Newton's third law of Motion, the thrust of the motor is at least partially dependent on the velocity of the motor's exhaust. [Read More]

Expansion Cone

The section of the nozzle that increases thrust via the force exerted by the expanding exhaust gasses; may be a simple cone (typical for hobby rocketry) or a more complex shape [Read More]

Experimental Rocketry

A class of non-professional rocketry beyond HPR. Although some consider this term synonymous with Amateur Rocketry, it generally has a somewhat different connotation. Experimental Rocketry normally implies the use of composite solid fuels (such as AP, AN, and sugar motors) and hybrids. Although ... [Read More]

Explosives Act

Canadian law defining and governing the use of all explosive substances outside the Canadian Armed Forces. [Read More]

- F -


Federal Aviation Administration. This is the organization that governs airspace in the U.S. HPR hobbyists must obtain a waiver from the FAA for permission to fly large or high (2000+') altitude rockets. Equivalent to Transport Canada and the Air Ministry in the United Kingdom. [Read More]


Federation Aeronautique International [Read More]


Rigid or semi-rigid coating used to streamline the airflow around a rocket component sticking out in the airflow. [Read More]


FAA regulations regarding airspace use for hobby rocketry. [Read More]


Fin Can [Read More]

Featherweight Recovery

A recovery method used by very light model rockets. Typically, the rocket ejects its motor and then floats to the earth like a feather, its extremely low weight never allowing it to become aerodynamically stable. [Read More]


A man-made material consisting of glass fibers spun and woven into a mat-like cloth adhered to a rocket with epoxy resins. It is used to add strength to high power rockets, so that they can withstand higher-powered motors than they otherwise could. Although fiberglass is a commonly used word, it ... [Read More]

Fill 'n Finish

Elmer's brand Carpenter's Wood Filler; a common filler for balsa fins, fillets, etc. [Read More]


A substance applied to a surface to fill gouges in the surface or help shape the surface. See Wood Filler. [Read More]


A smooth line of adhesive which is built up at the root of a fin to strengthen the joint formed by the fin and the body tube. [Read More]

Fin Alignment Jig

A device used to align and hold in place fins to a body tube. [Read More]

Fin Can

1.) A subassembly consisting of the motor tube, centering rings and fins, 2.) A single component consisting of the fins and a tubular sleeve which fits over a body tube (e.g. the ACME Fin Canister). [Read More]

Fin Canister

A section of tubing with fins mounted on it, intended to slide over the airframe. Also called a fin can. [Read More]

Fin Flutter

See Flutter [Read More]

Fin Span

1.) Distance from fin root (where it attaches to the body) to the fin tip (outter edge); 2.) More commonly used as the total span from fin tip to fin tip (might think of this as the maximum width of the rocket) [Read More]

Fin Wraps

See Paper Lamination [Read More]


A surface at the rear of a rocket that serves to stabilize it in flight. Fins are usually planar surfaces placed at right angles to the body tube. [Read More]


The art of giving a model a smooth, streamlined outside surface. Click here for some great finishing ideas. [Read More]


A bulkhead designed to prevent fire from passing that point. [Read More]

Flame Bucket

An opening at the base of a launch pad to allow the exhaust to vent. One side is angled to form a blast deflector. [Read More]


a movable control surface on an aircraft or rocket that deflects air. Ailerons, elevators and rudders are all flaps. Flaps are also used as airbrakes. [Read More]


A magnesium-filled glass bulb, once commonly used in photography. In rocketry, flashbulbs are used to ignite thermalite fuses or BP charges for second stage ignition or recovery device deployment. They have the advantage of requiring very low electrical impulses to activate them. However, this ... [Read More]


A type of ignition sometimes used for BP clusters. The rocket is placed in a pan covered with a thin layer of black powder. When the rocket is to be launched, the powder is ignited with an electrical igniter. The resulting flash sends burning particles into the motor nozzles and fires all the ... [Read More]

Flat Spin

A spin around the short axis of a rocket while the craft is descending in a horizontal attitude. [Read More]

Flex Wing

A wing that employs a thin flexible for the main lifting surface stretched over a semi-rigid frame. [Read More]

Flight Card

A card (sometimes a log book entry) that is used to record the pertinent details of a flight at organized launches [Read More]

Flight Line

The area at a launch site where rockets are prepared by participants. The forward-most area where spectators are permitted. [Read More]

Flight Path

The line connecting successive positions of an aircraft while in flight, relative to the ground. [Read More]

Flight Profile

A graphic representation of a aircraft's flight as seen from the side, showing its position and altitude. [Read More]


An aircraft or rocket, having undergone inspection and possibly testing, that has been determined to be ready and sound to fly. [Read More]

Floating Injector

Refers to a type of hybrid motor wherein the nitrous chamber is integral to the motor casing; the injector is then free to move within the casing based on the pressure of the contained gas; Ratt Works hybrids are examples of a floating injector design [Read More]


An oscillation of regular period but irregular amplitude caused by a momentary disturbance but maintained by the characteristics of the fluttering component. [Read More]

Flying Wing

An aircraft, whose wing is designed and balanced for stable flight, that does not rely on stabilizers or canards to maintain the flight stability. [Read More]


see Fill 'n Finish [Read More]

Foam Board

Paper-backed syrofoam sheets used for displays and posters; may be used for fins and centering rings [Read More]

Foam Core

A built up wing using shaped Styrofoam rather than the classic sticks and ribs, then covered with a thin cover of wood such as balsa. [Read More]

Form Drag

Drag resulting from the shape of an object, causing turbulence of the airflow. An example is a square wing edge versus a rounded streamlined edge. [Read More]

Forward Closure

The portion of the motor which seals the top end; in single use motors this is glued in; in reloadable motors it is typically an aluminum housing that either screws into the case (AT style) or is held in with a snap ring (Kosdon style); in motors K and below, this closure usually provides for an ... [Read More]

Free Flight

Unconstrained and unassisted flight of a rocket, relying on the rocket's inherent stability. [Read More]


The fall of an object without guidance or retardation other than through drag. [Read More]

Friction Fit

The joining of two objects, relying not on adhesive but on the tight fit caused by one object being inserted into another, such as the nose cone inserted into a body tube. [Read More]


The resistance an object encounters while moving across the surface of another object. [Read More]

Frontal Area

the surface area of a rocket which faces directly into the airflow. [Read More]


Family Radio Service; these 2-way radios are commonly used at launches both for voice and occasionally telemetry [Read More]


The structure or airframe that houses payload, crew or passengers. Although not inaccurate, this term is used more commonly with regard to airplanes than to rockets. [Read More]


Fast White Lightning; a fast version of Aerotech's White Lightning propellant [Read More]

- G -


A mechanical device which detects the presence of acceleration through the movement of a weighted electrical contact. g-switches are normally used in combination with other electronic devices such as timers. For example, an electronic timer can be programmed to count down a certain number of ... [Read More]


A grade of fiberglass commonly used for fins on high power rockets. G10 designates a laminate made of fiberglass cloth laid in epoxy resin. [Read More]


A crane and scaffolding arrangement, mounted on rails, used to service a fullsized rocket while on the launch pad. [Read More]

Giant Scale

A Sport Scale event where the models cannot be smaller than a given minimum size. Contrast Peanut Scale [Read More]

Glandular Conditions

a general, less common, term for upscaling and downscaling [Read More]


The process of laminating rocket components, such as fins and bodytubes, in fiberglass cloth which is soaked in epoxy resin; polyester resin may be used, but is not recommended. See Fiberglass and Pseudo-Glassing [Read More]

Glide path

The descent of a gliding air vehicle as viewed from the side. [Read More]

Glide Ratio

The ratio between distance traveled horizontally and the amount of vertical drop. [Read More]


The controlled descent of an air vehicle using control surfaces, not rockets to maintain control. The descent is a result of gravity and lifting forces generated by the shape of the air vehicle. [Read More]

Gliding Booster

A booster stage whose fins are placed asymmetrically and is balanced to achieve a glide after ejecting from the rocket. [Read More]

Global Positioning System

See GPS [Read More]


Gross Lift Off Weight - The mass of a rocket completely prepped for flight. [Read More]

Glue Rivets

A method of strengthening the attachment of balsa fins by poking small holes through the body tube fo allow glue to seep through and form "rivets" [Read More]


A rocket design series sold by Estes from 1973 -1975. They were described as the "Zaniest flying freaks in the universe". [Read More]


The rounded triangular section of fabric between two longitudinal seams or shrouds in a parachute canopy. [Read More]

Gorilla Glue

A popular brand of polyurethane glue, alternative to Elmer's ProBond Polyurethane glue. Learn more [Read More]


Gaseous Oxygen [Read More]


Global Positioning System; a position/location service provided by the US Government via a constellation of LEO satellites; good for identifying the exact location of your launch site; some newer flight computers are providing a GPS interface. [Read More]


In rocketry, any pellet or cast section of propellant or other combustible material. The black powder propellant packed and shaped into a single-use model rocket motor is referred to generically as a grain. Also, the direction of the fibers in a piece of wood, such as balsa. See Wood Grain [Read More]


Ground Support Equipment [Read More]


A roughly triangular shaped piece of material added to reinforce a joint, often in a corner. [Read More]


A well balanced flywheel, rotating at high speed and generating a high moment of rotation. Gyroscopes work to maintain their original orientation, and so are used to provide stability to rockets. [Read More]

- H -


A small robust glider designed to be launched by hand. [Read More]


High-Speed Anti-Radiation Missile. See ARM. [Read More]


A door in the side of a spacecraft or aircraft. [Read More]


hazardous materials; term normally used in relation to shipping/transportation [Read More]


See Helicopter Duration. [Read More]

Head-end Igniter

An igniter that is intalled on the top of the motor; this type of igniter is currently non-standard in our hobby, but is being used experimentally for Aerotech 75mm and 98mm motors; this arrangement is not uncommon on professional rockets [Read More]


An alert called by the Launch Control Officer if one of three conditions prevail: (1) A model using an advanced technique such as a cluster is about to be launched. (2) An untried rocket design is about to launch and the results are uncertain. (3) A recovery system has failed, and it is possible ... [Read More]


Wind blowing generally into the front of an aircraft, thereby slowing its ground speed. [Read More]

Heat Shrink Tape

A heat sensitive tape that shrinks when heat is applied; used in place of vacuum bagging for laminating tubes [Read More]

Helicopter Duration

A competitive event in NAR-sanctioned launches, using rockets with helicopter recovery. [Read More]

Helicopter Recovery

A method of model rocket recovery in which long blades are deployed at apogee so that the rocket descends gently through auto-rotation. See Helicopter Rocket Reviews . [Read More]

Hershey Bar Wing

A rectangular wing, with no taper on either the leading or trailing edge. [Read More]

High Velocity Gas

The high velocity gas generated by rocket motors is the principal mechanism for generating thrust. These gasses produce thrust due to conservation of momentum. See Momentum Thrust. [Read More]


See Hand-Launch-Glider [Read More]

Honeycomb Core

A diamond-pattern woven material which looks and behaves somewhat like the inside of corrugated cardboard; used for making light composite structures [Read More]

Hot Wire Cutting

A technique for cutting styrofoam using a wire which is electrically heated. [Read More]


High Power Rocketry. High power rockets are defined as having: a single motor with more than 160 Newton-seconds total impulse or an installed impulse of 320 Newton-seconds and no more than 40,960 Newton-seconds, and an average thrust in excess of 80 Newtons. (H through N range); Depending on ... [Read More]


Homeland Security Act; this Act made changes to Title 18 of the U.S. Code in sections 841 through 844; the primary change is the new requirement making a LEUP or LUP required for in-state purchase and use HPR motors (over 62.5 grams of propellant); such permits were previously required only if the ... [Read More]


Hydroxyl-terminated polybutadiene; a common binder used in composite fuels. See Binder [Read More]


A type of reusable rocket motor in which the fuel and oxidizer are kept separate and in different material states (such as a compressed liquid and a solid) until combustion occurs. A typical hybrid motor currently uses nitrous oxide gas as an oxidizer, and cardboard or plastic as fuel. See Micro ... [Read More]


An arrangement of liquid fuel and oxidizer which ignites spontaneously when combined. [Read More]


Term used to describe a vehicle exceeding Mach 5. [Read More]

- I -


Independent Association of Rocketry. [Read More]


Intercontinental Ballistic Missile. [Read More]


Inner diameter; the ID is what is specified in standard tube sizes; i.e. 18mm, 29mm. Contrast OD [Read More]

Igniter Plug

Plug of paper or plastic forced into the motor nozzle after insertion of the igniter, designed to keep the igniter pressed against the propellant. [Read More]


A length of high-resistance wire, sometimes coated with a flammable material, which is placed in contact with the motor propellant prior to the rocket's launch. When an electrical current is passed through the igniter by the launch controller, the wire's high resistance causes it to become very ... [Read More]


In My Humble [Honest] Opinion [Read More]

Impulse (Relative)

A measure of the efficiency of a rocket engine. Similar to Specific Impulse, it is defined as the Total Impulse divided by the mass of the propellants. A little dimensional juggling shows that this gives the same units as velocity (ft/sec or m/sec) hence is sometimes called "Effective Exhaust ... [Read More]

Impulse (Specific)

A measure of the efficiency of a motor/propellant system. It is determined by taking the Total Impulse and dividing by the weight of propellants. This carries the potentially confusing units of "seconds" (as if it had something to do with the burn duration) but is due to weight and ... [Read More]

Impulse (Total)

A measure of the total momentum imparted to the rocket by the motor. It is defined (for those who know calculus) as the integrated area under the thrust-time curve. For the rest of us, it can be thought of as the motor's average thrust times the duration of the burn. Measured in N-sec or Lb-sec. [Read More]


Thrust force multiplied by time. The units of measurement are usually Newtons and Seconds. [Read More]


A device for determining a rocket's apogee without the use of electronics. A distance is measured off from the launch pad prior to launch. At the time of launch, an observer stands at the measured point and keeps the inclinometer aimed at the rocket. The inclinometer mechanically records the angle ... [Read More]

Indian Fire Brigade

derisive term for stomping out grass that has caught fire. [Read More]

Indirect Staging

Air start of the motor on a sustainer stage by some means other than using the forward-shot bit of propellant from the booster motor. (pictured rockets have their own electronics to start each stage, second picture shows an actual separation and the upper stage has just ignited.) [Read More]

Induced Drag

Drag resulting from lift generated by the foils and lifting body of a aircraft or rocket. [Read More]

Injector Throat

The opening in the Injector housing. See also Throat [Read More]


In a hybrid motor, the unit that introduces the nitrous oxide into the combustion chamber [Read More]

Instrumentation Amplifier

An device that amplifies the low level signal from a device such as a load cell into a useful signal; often also conditions/filters the signal; may be incorporated into a computer interface card [Read More]


A section of a rocket in between two stages, such as the interstage spacing ring between the first and second stage of the Saturn V. [Read More]


Symbol for Specific Impulse [Read More]

- J -


A self-inflating parachute airfoil developed by Domini C. Jalbert. It is very maneuverable and is the current standard airfoil in skydiving parachutes. [Read More]

Japanese Tissue

A thin tissue used by aeromodelers to cover the frames of model aircraft; often used to cover the surface of balsa fins [Read More]


Jet Assited Take Off; despite the term 'jet', this is basically the same as RATO; this may be the more common term [Read More]

Javelin In

See Lawn Dart [Read More]

Jet Deflector

See Blast Deflector [Read More]


Just In Case: Any precaution taken to avoid trouble, such as sanding residue off igniter clips. [Read More]


A tool that uses dowel, blocks of wood, clamps and/or forms to allow precise shaping and/or construction of hard to assemble parts, or mass production of commonly used parts such as centering rings. [Read More]


The identifier for Aerotech's Black Jack propellant; "provides the high visibility tracking of dense black exhaust"; the most difficult Aerotech propellant to ignite [Read More]

- K -

Kaplow Clip

A popular type of motor retainer designed by Bob Kaplow. [Read More]


A synthetic fiber, originally woven into mats for use in bullet-resistant body armor. Kevlar is highly resistant to tearing or burning. Kevlar thread is used in some model rockets as a shock cord. In model rockets, this provides the advantage of allowing the cord to be anchored to the motor mount ... [Read More]


A liquid, usually of the Freon family, used to accelerate the set time of cyanoacrylate adhesive. [Read More]


1.) The practice of modifying a rocket kit to achieve some result other than that intended by the manufacturer; 2.) Taking two (or more) kits and combining ("bashing") them into a new design. Often used as a contest event (Team Kitbash, where teams compete, Kitbash Duration, Scale Kitbash, etc) ... [Read More]

Kitchen Sink

To launch every flyable rocket in one's inventory at a single event or within the span of one day. Usually results in or is the result of launch happiness. [Read More]


Potassium nitrate (KNO3); the oxidizer used in 'sugar' motors [Read More]

Kraft Tubing

AKA paper/cardboard tubing, a common rocket airframe and motor mount material. This material is impregnated to make things like phenolic and phlexible phenolic tubing. [Read More]

Krushnic Effect

A very dramatic phenomenon where your rocket makes a tremendous amount of noise and smoke but doesn't go anywhere! This happens when the motor is recessed into the body tube by more than one tube diameter. If so recessed, the cylindrical volume below the motor forms a secondary expansion chamber ... [Read More]

- L -

L1, L2, L3

Levels one through three: reference to the three levels of high power rocketry certification. Unless you are in Canada, Eh? [Read More]

Lake Stake

A lawn dart or core sample on the playa. [Read More]

Laminar Flow

A smooth flow of air, noted for lack of turbulence. In current theory , it is modeled as consisting of layers of air having similar speed and density. [Read More]

Laminated Wood

Wood made from of multiple layers, commercially made plywood being the most common example. [Read More]

Land Shark

The condition in which a rocket, for whatever reason, fails to attain air flight and slides along the ground under power. [Read More]

Landis Loop

A ring used in a tower launcher to keep the back end of a egglofter centered during launch. Invented by Geoff Landis and named for him by Bob Kaplow. [Read More]

Launch Controller

An electrical device used to activate the motor igniter, which in turn ignites the motor. The launch controller should always incorporate a lock-out device such as a key, to prevent accidentally activating the igniter before the rocket is ready to be launched. [Read More]

Launch Happy

Euphoria from being overly addicted to burnt fuel fumes on a particular day. Symptoms include repeatedly launching a model on increasingly more powerful motors until there are no motors left or the rocket shreds. [Read More]

Launch Lug

Usually, a tube attached to the side of the rocket to accommodate a launch rod, to stabilize the rocket while building up air speed. [Read More]

Launch Pad

An assembly containing the launch rod or tower and blast deflector if any, which permits the rocket to remain steady until launched. [Read More]

Launch Rail

A stiff rail, often with a cross section in the shape of a square letter C or I. Lugs on the rocket ride on the rail. Using a rail rather than a rod provides the advantage that a rail can be made much stiffer than a rod, providing better wind resistance and preventing vibration-induced whipping of ... [Read More]

Launch Rod

A stiff rod, whose diameter can be from 1/8" to 1" depending on the size and weight of the rocket, along which a rocket flies for the first few feet of its travel. The launch rod stabilizes the rocket's flight while it builds up air speed. [Read More]

Launch Tower

A launch pad containing any sort of stabilizing device other than a launch rod. In model rocketry, a tower commonly consists of 3 or 4 smooth rods which support the rocket on all sides, eliminating the need for a launch lug. [Read More]

Laundry, The

Slang term for recovery components, especially the parachute(s) [Read More]

Lawn Dart

Similar to a Core Sample but requires the nosecone to remain in place prior to impact. Named after a lawn game of the sixties in which large darts were thrown into the air to land inside rings placed on the ground about 25' apart (as in horse shoes). [Read More]


Live Biological Payload. Transport of any vertebrate animal is currently in violation of all rocketry safety codes. [Read More]


Launch Control Officer. Person in charge of controlling the range and launching rockets. [Read More]


Large and Dangerous Rocket Ships: the name of the annual TRA launch. [Read More]

Leading Edge

The front edge of a wing or fin. [Read More]


Low Earth Orbit; an orbit below 1000km [Read More]


1.)BATFE Low Explosive User Permit for rocket motors with greater than 62.5 grams of propellant, as well as other substances deemed by the government to be low explosives such as Thermalite. 2.) a federal permit required to purchase, use, or store HPR motors whenever interstate commerce or ... [Read More]


One of the toughest and most versatile engineering thermoplastics; often used for clear fins; made by GE Plastics [Read More]


"Local Hobby Shop" [Read More]

Lifting Body

a wingless aircraft whose body generates the lift required to fly [Read More]

Liftoff Mass

See GLOW [Read More]

Linear Aerospike

An approach, pioneered by the Rocketdyne company (now a division of Boeing) in the 1970s, places the combustion chambers in a line along two sides of the nozzle. A Linear Aerospike was planned for the now defunct Lockheed-Martin X-33 project. [Read More]


A model builders plywood, noted for its low density. [Read More]


Loadable Motor System - a new (2007) type of motor system by Aerotech. Essentially a single use motor that is assembled by the consumer. [Read More]

Load Cell

An electro-mechanical sensor that converts force or weight into an electrical signal; used in motor test stands [Read More]

Longneck Rocket

On EMRR, a rocket whose length to width ratio is 30:1 or more [Read More]

Lovelace Effect

See Drag Separation [Read More]

Low Power

Typically rockets flying on motors in the A to D range. [Read More]


Liquid Oxygen [Read More]


See Low Power [Read More]

Lucerne Soft Landing

A condition - experienced only on ground surfaces of cracked playa clay - in which a rocket which has landed remains in a semi-upright position with one fin stuck in a crack in the ground. [Read More]


See Launch Lug. [Read More]


Limited Use Permit; a federal permit which allows limited purchase and use of HPR motors within your state of residence; still requires approved storage [Read More]


Launch Vehicle [Read More]

- M -


Used for Mods, OOP, Plans and Scratch. This was added as a section to the classic EMRR web site to differentiate standard product reviews from these other articles. [Read More]


Model Aeronautics Association of Canada . Equivalent to the AMA. Canadian aeromodelingliaison organization to the CIAM through the AERO CLUB OF CANADA. [Read More]

Mach Buster

A rocket design to break the speed of sound. Here are some of them click here [Read More]

Mach Diamonds

A diamond shaped pattern that develops in the supersonic flow of gas from a rocket nozzle; these are caused by shock waves which reflect off of the pressure boundary between the exhaust plume and the ambient environment. [Read More]

Mach Number

An expression of velocity calculated by dividing the actual velocity by the speed of sound. At sea level this speed is 760 mph. [Read More]


Magnetic Apogee Detector. See scratch-build article click here [Read More]


An ATF-approved storage device for large rocket motors and other lowexplosive devices. [Read More]


A rod or bar used as a core around which a material is molded, cast, or wound; typical uses in rocketry are to form the core in a propellant grain, to make an airframe, or mold a nosecone [Read More]

Marginal Stability

Rockets with a static margin between 0.5 and 1.0 caliber are considered to be 'marginally stable'. These rockets may fly fine, but extra attention must be given to the wind conditions, thrust-to-weight ratio, and launch rod velocity. For example, short stubby rockets with a length-to-diameter ... [Read More]

Mass Ratio

Final mass (after propellant burn) divided by initial mass. [Read More]


The point during the powered flight phase of a rocket's ascent at which acceleration stresses on the airframe are the greatest. This is the point at which a shred is most likely to occur. [Read More]

Maximum Thrust

The peak thrust a motor generates. [Read More]

Maximum Weight

Generally used as the maximum weight of a rocket for a specific motor and delay. This is based on the thrust curve and average thrust of a motor. The main objective is to have the rocket traveling at a velocity where the aerodynamic forces produced by the fins are suffficient to keep the rocket ... [Read More]

Mean Chord

A wing's root chord plus its tip chord, divided by two. [Read More]

Medusa Nozzle

A nozzle which has multiple exit ports. [Read More]


Methyl ethyl ketone; a solvent which, per the manufacturer, is required to rejuvinate Igniterman pyrogen once it has fully dried (acetone is also required) [Read More]

Mercury Switch

An electrical switching device consisting of an oval glass bulb which contains two electrical contacts (penetrating the bulb, and at one end of the oval) and a drop of mercury. In hobby rocketry, mercury switches are used to detect the absence of acceleration in a moving rocket. When the rocket ... [Read More]


Malfunctioning Engine Statistical Survey; the NAR's mechanism for gathering motor failure data [Read More]

Micro Balloons

Tiny glass globules which are sometimes added to epoxy in applications like fin fillets, to reduce weight. [Read More]

Micro Bubbles

See Micro Ballons [Read More]

Micro Engine

The series of 10.5mm engines produced by Apogee Components; production is currently halted [Read More]

Micro Grain

A propellant that consists of finely ground particles or (normally) zinc/sulfur; these propellants are fast burning, VERY volatile and DANGEROUS [Read More]

Micro Hybrid

A small hybrid motor that uses nitrous oxide cylinders which are used in the food service industry; fuel grains are typically paper and the motor's thrust is in the 'D' to low 'E' range. See Hybrid [Read More]


Small, toothless electrical clips commonly used to connect the launch system to the igniter on model rockets. [Read More]

MicroMaxx Engine

The series of 6mm engines produced by Quest Aerospace; the original MMX (0.2N) has been replaced with MMX-2 (0.31N) [Read More]

Mid Power

Typically rockets flying on motors in the E to G range. [Read More]

Mid-body Ejection

The practice of placing a rocket's separation point midway up the body tube, helping to prevent tube zippering. [Read More]


Missing In Flight. A rocket that disappears with no sign of the recovery system deployment, and no other obvious failure mode (e.g. Prang or CATO). Sometimes called "into orbit." [Read More]

Mini Engine

The series of 13mm engines produced by Estes; identified in the engine designation by a trailing 'T'; example: A10-3T [Read More]

Minimum Diameter

a model whose diameter is just large enough to accommodate its motor. [Read More]


Multiple Launch Rocket System [Read More]


Motor Mount [Read More]


acronym for Quest MicroMaxx motors. [Read More]

Model Rocket News

The oldest continuously published rocketry periodical. Started by Vern Estes and his small crew in 1960, it is still sent to all of Estes's active mail order customers. Somewhat sophomoric in style, it contains a great deal of practical information, especially for beginners. It has survived a ... [Read More]

Model Rocket

An aircraft that ascends into the air using some form of reaction motor, without the use of aerodynamic lifting surfaces. Model rockets have the following characteristics: Gross launch weight, including the motor(s), does not exceed 1500 grams. Motor power does not exceed 160 newton seconds of ... [Read More]


Slang for Model Rocket. [Read More]


A combination of parts or components arranged and mounted or packaged as a single unit. The parts work together to perform a specific function or functions. [Read More]


In mechanics, a) the tendancy to cause rotation about a point or axis; b) the measure of this tendency; c) the product of a force or mass and its perpendicular distance from its axis or fulcrum [Read More]

Momentum Thrust

The component of a motor's thrust due to the expulsion of gas [Read More]


Monocopters are single-bladed helicopters. The engine, whether an airplane engine or rocket motor, both drives and counteracts the lift forces produced by the single blade. See Monocopter Reviews [Read More]


Model aviation covering consisting of colored heat shrinkable vinyl, applied with a tacking iron. Often used as trim tape. [Read More]


A grain geometry where the circular core touched the outer wall of the grain; a moonburner is regressive throughout its burn [Read More]

Motor Adapter

A replacable unit which allows a smaller diameter motor to fit in a motor tube. [Read More]

Motor Clip

See Motor Hook [Read More]

Motor Code

[Read More]

Motor Diameter

The diameter of a hobby rocketry motor casing. Most commercially-manufactured motors are made in standard sizes. Motor diameters are most commonly expressed in millimeters. The most commonly seen motor diameters are 10.5mm, 13mm, 18mm, 24mm, 29mm, 38mm, 54mm, 75mm, and 98mm. [Read More]

Motor Hook

1.) A device for retaining the motor on a model rocket. 2.) A section of spring metal, the length of the motor and with tabs bent on either end and attached to the motor tube; the back end is left unconstrained so it can be bent away from the motor casing during insertion and removal; normally ... [Read More]

Motor Mount

The assembly/part of the rocket that the motor(s) is installed into for flight [Read More]


A motor is a device that creates or imparts motion. Rocket motors based on solid propellants are generally called "motors" rather than "engines" though it is not incorrect to call them "rocket engines" as Estes does. The term "engine" is usually reserved for liquid-propellant rocket engines ... [Read More]


See Mid Power [Read More]


See The Model Rocket News [Read More]

Murphy's Law

The guiding principle of Rocketry preparation: "If anything can go wrong, it will." [Read More]

Music Wire

A high grade, stiff wire made to low tolerances that comes in a wide variety of diameters. Commonly used to make springs, it is also known as piano wire. Most often used in model rocketry as launch rods. [Read More]


an extraordinarily strong polyester film made by DuPont; commonly used for parachutes [Read More]

- N -


National Aeronautics Association [Read More]


National Advisory Committee for Aeronautics; predecessor to NASA [Read More]


National Association of Rocketry Annual Meet: The annual week-long launch hosted by the NAR. [Read More]


The annual NAR convention. [Read More]


National Association of Rocketry, Visit NAR [Read More]


National Association of Rocketry Training Rocketeers for Experience and Knowledge. It consists of a series of achievement levels in rocketry, each requiring more skill to complete than the previous one. [Read More]


National Aeronautics and Space Administration [Read More]

National Association of Rocketry

The National Association of Rocketry (NAR - ) is one of the two major organizations representing rocketry hobbyists in the United States. [Read More]


Nose Cone [Read More]

Neck Snapper

A motor & Rocket combination that leaves the pad too fast for the eye to follow. [Read More]

Neutral Burn

When the thrust of the motor is relatively flat throughout the burn. See also Burn, Progressive Burn, Regressive Burn [Read More]

Neutral Point

CG location on a glider, which would result in exactly neutral stability (such that if the glider were disturbed, there would be no pitching moment) [Read More]

Neutral Stability

The condition in which a rocket's CP and CG are at the same spot. Dynamically, this creates a situation in which a rocket may fly steadily in dead air but can't recover if the angle of attack is greater than zero. [Read More]


The typical unit of measurement for rocket thrust. One newtonsecond is one newton of thrust maintained for one second. [Read More]


The amount of force required to accelerate one kg, one meter per second per second. 4.45 newtons equals one pound of force. [Read More]

NFPA 1122

Standards code for U.S. Model Rocketry. [Read More]

NFPA 1127

Standards code for U.S. High Power Rocketry. [Read More]


National Fire Protection Association - Private corporation for setting safety standards. [Read More]


Refers to the metal content (nickel/chromium) of the igniter wire most commonly used in model rockets. Nickel/chromium is chosen as a material because it has high resistance and high strength. When exposed to an electrical current, it will glow yellow-hot before burning through. [Read More]

Night launch

A launch conducted after sunset; requires an FAA waiver [Read More]

Nike Airfoil

See Diamond Airfoil [Read More]

Nitrous Oxide

(N2O)Gaseous oxidizer used in current hybrid rocket motors. See Hybrid and Micro Hybrid [Read More]

No Joy

When a rocket motor fails to ignite. Useage: no joy on pad 13. [Read More]


A lightweight, fire-resistant Nylon fiber, originally woven into fireproof garments for fire fighters, race car drivers and astronauts. Also commonly used in aircraft upholstery. In hobby rocketry, Nomex is used as sheaths and bags to protect elastic shock cords and parachutes. See Deployment Bag [Read More]

Non-Survivable Event

see Prang [Read More]

Nose Block

A turned piece of balsawood used to connect two sections of body tube. Just like a stage coupler, but it is a solid block. This allows you to create a "payload section" that is the same diameter as the main body tube. Essentially a long nosecone shoulder (with no nosecone)used to connect two ... [Read More]

Nose Blow Recovery

Recovery method for light models by simply ejecting the nose cone and having it come down attached on the shock cord. [Read More]

Nose Cone

The pointed object at the front of a rocket. Cones are not always strictly cone-shaped. They are sometimes rounded but are most commonly ogive (a pointed arch). Nose cones are an important consideration in rocket design, since they provide two ways to move the center of gravity forward if needed; ... [Read More]

Nose Heavy

The condition in which a glider is trimmed into a dive or a rocket has excessive mass in the nose. [Read More]

Nose Weight

A weight, often of lead, epoxy or modeling clay, which is added to the nose of a rocket to move its center of gravity forward and improve the rocket's stability. [Read More]


abbreviation for nitrous oxide [Read More]


The part of the rocket motor that smoothly expels gas from the combustion chamber; typically made from phenolic (in SU or AT reloads), graphite (Kosdon-style reloads), or clay (Estes motors). Components of the nozzle include the entrance cone, throat, and expansion cone [Read More]


National Sport Launch: an annual three-day launch hosted by the NAR. [Read More]

- O -


A rubber gasket used to contain gasses in solid rocket motors [Read More]


1) Slang term for a strange-looking rocket. Odd-rocs are often made in the shape of other, non-rocketry-related items. 2) Anything clearly not originally intended to fly. Odd shapes, odd conversions. The antithesis of 3FNC; 3) Are strange looking things that often shouldn't fly. (And ... [Read More]


Outer (or outside) diameter. Contrast ID [Read More]


o-give (oh'jiev, oh jiev') - In rocketry, the shape of a common type of nose or tail cone. If the sides of the cone are curved rather than straight, the geometric shape of the cone is actually an ogive rather than a cone. [Read More]

One-Caliber Stability

A widely-accepted rule of thumb for rocket stability: The center of gravity should be approximately one body width (one "caliber") ahead of the center of pressure. [Read More]


Out Of Production. This is a reference to a rocket that was once but is no longer produced by a commercial manufacturer. Reproduction of plans, parts lists, and scaling information for once-popular out-of-production model rockets has become an Internet cottage industry. [Read More]


An propellant additive which makes the propellant opaque; a translucent propellant will absorb ultraviolet light from the flame, which may cause combustion to start deeper in the grain, causing a Cato. [Read More]

Open Breech

A piston launcher in which the motor travels up the piston tube and engages the motor mount. See Piston Launcher [Read More]

Optimum Mass (Weight)

The mass required to lift a rocket to the highest possible altitude on a given motor. [Read More]

Orange Book

BATFE explosives rule book. See BATFE [Read More]

Oscillation, Parachute

The swinging from side to side of a payload under a parachute. [Read More]


Direction parallel to the lateral axis of the rocket and perpendicular to the centerline. [Read More]

Over Stability

Rockets with a static margin over two calibers are considered 'over stable'. These rockets will tend to weathercock badly and may oscillate or even become unstable. Care should be given to the thrust-to-weight ratio, launch rod velocity, and wind conditions. [Read More]


See Krushnic Effect. [Read More]


A substance which provides oxygen to a combustion process, aiding in the speed and efficiency of combustion. The addition of an oxidizer to the chemical process of combustion can cause a fuel that would barely burn under normal atmospheric conditions to burn so enthusiastically that it can be used ... [Read More]

- P -

Pad Manager

Person responsible for assigning pads and controlling the launch pad area. Helps rocket flyers set up pads and rockets for flight. [Read More]


Atmospheric pressure, 14.6 psi [Read More]

Paper Lamination

A techique used to laminate fins (primarily balsa) to cover the grain and add strength; the practice of putting layer(s) of paper over balsa fins to add strength across the surface and create an additional shock absorption layer. [Read More]

Parachute Duration

A popular competitive event in NAR-sanctioned launches. [Read More]


A piece of plastic, cloth, nylon, or other material, shaped something like an umbrella when deployed, which slows the descent of a rocket. [Read More]


A parachute-like device which has an airfoil structure; may be steerable. [Read More]


A flexible, kite-like glider deployed like a parachute and designed to be a recovery device. [Read More]

Parallel Staging

A practice similar to clustering, in which two or more "stages" mounted parallel to the main motor ignite simultaneously. The "stages" usually contain shorter-burning, higher-thrust motors than the main airframe (or sustainer), and drop off when their motors burn out. [Read More]


A flat piece of plastic or other material, formed into a circle or polygon, which is used as a parachute. This is the most common type of parachute used with model rockets. [Read More]


Usually, a glider which is boosted into flight by being attached to the airframe of a model rocket which is modified to accept it. [Read More]

Pay Forward

A Harry Stine expression. To pay back the mentors of our youth, not by tangible means to the mentors, but by acting as mentor to the next generation. [Read More]

Payload Section

A portion of rocket airframe set aside for payloads. Also called payload bay. [Read More]


A package or thing placed in a rocket, which normally does not contribute directly to the success of the flight. For example, an altimeter used to record a rocket's maximum altitude is an example of a payload. [Read More]


Polybutadiene Acrylic Acid Acrylonitrile Prepolymer; another binder used in composite propellant. See Binder [Read More]


See Parachute Duration [Read More]

Peanut Scale

A Sport Scale event where the models cannot be larger than a given maximum size. Contrast Giant Scale [Read More]

Pendulum Rocket Fallacy

The mistaken belief that a rocket will be stable if the motor is ABOVE the rocket's center of mass, so that the rocket is "hanging" below the center of thrust and will try to remain upright, like a hanging pendulum. It doesn't work; even Robert Goddard learned that the hard way. See the following ... [Read More]


The measure of diffusion or "leakage" of gas through a fabric. The permeability determines the rate of descent. [Read More]

Phase Transition

Changes in the crystal structure of a composition resulting in expansion and contraction; in AN motors, temperature induced phase changes cause crystals to break away from the binder and causes erratic burning. See Binder [Read More]


Literally, anything containing phenol, which is a petroleum distillate having many industrial applications. Phenolic resin, with which phenolic airframes are impregnated, is made by mixing phenol with an aldehyde such as formaldehyde, and is used for forming all sorts of molded and cast items. ... [Read More]

Phlexible Phenolic

Introduced by Red Arrow Hobbies as an alternative to the Phenolic airframe. It is offered as being chip and crack resistant from hard landings, etc. (even in cold weather) and as strong or stronger laterally than standard phenolic tubes. [Read More]

Piano Wire

See Music Wire [Read More]

Pilot Chute

A small parachute attached to the apex of a large main parachute, and so oriented that it emerges from the airframe first. Air drag from the inflating pilot chute assists the main chute to exit the airframe, pulling it out apex-first so that it is less likely to tangle. [Read More]

Pink Book

The common name for the NAR Contest Rules Manual. See NAR and Contest Acronyms [Read More]


A condition in which a rocket spins on its horizontal axis. Usually caused by a split in a motor casing. This condition is highly dangerous, as the rocket's trajectory is completely unpredictable. [Read More]

Piston Ejection

Ejection of the recovery device through the use of a solid sliding bulkhead inside the airframe. The use of a piston eliminates the need for wadding. [Read More]

Piston Launcher

A type of launcher used with small competition model rockets. At the moment of motor ignition, a piston assists the motor in launching the rocket. [Read More]


A back-and-forth motion of the nose of a rocket in flight, on the axis determined as "up-and-down". See Yaw. [Read More]


A tool to shave thin slices of material in order to shape or smooth the material. [Read More]


The geometric shape of a wing or fin. [Read More]

Plastic Model Cement

A mixture of solvent and styrene plastic used to adhere plastic to plastic or plastic to paper. [Read More]

Plastic Model Conversion

A refitting of a static plastic model kit to allow it to fly as a model rocket. See Plastic Model Conversion Articles . [Read More]


An additive which makes a composite propellant softer and more flexible [Read More]

Playa (or pan)

(pronounced /ˈplaɪə/) is a dry or ephemeral lakebed, generally extending to the shore, or a remnant of, an endorheic lake. Home to many big launches in the Western US. Black Rock Desert, home of TRA's BALLS launch, is the quintessential example of a rocketry playa. [Read More]

Plugged Motor

A motor made with a solid bulkhead in the front end, blocking any passage of ejection gases into the airframe. [Read More]


See Plastic Model Conversion [Read More]


A wing broken up into multiple panels, angled in relation to each other. [Read More]


A solid plastic made from polymerised styrene [Read More]

Polyurethane Glue

a strong versatile waterproof glue; expands while curing and tends to be messy; the most common rocket use is for inside surfaces such as centering rings [Read More]

Pond Dart

Same as Lawn Dart but in the Pond [Read More]

Pop Pod

The motor mount on a conventional boost glider. When the motor deployment charge fires, the pop pod separates from the glider, deploys a streamer and returns to earth, leaving the glider free to glide. [Read More]


A launch lug affixed the model in such a way that it comes off the model as it clears the launch rod or rail. Pop 'n Go Ignition: A technique whereby a powdered chemical accelerant is poured over an igniter placed in the nozzle to insure ignition. Typical accelerants include Black Powder, ... [Read More]

Potassium Nitrate

An oxidizer used in black powder and 'sugar' motors; see Sugar Motor [Read More]

Power Prang

(See Prang) Slang term for a condition in which an unstable rocket reverses course and moves toward the ground while still under power. Also called a Death Dive. [Read More]


Slang for any condition in which a rocket contacts the ground without benefit of recovery system. The origin of the term is in dispute. Stine claims (Handbook of Model Rocketry, 6th ed., p. 196) that it is a British term, originally used in the aircraft industry to describe deformation of an ... [Read More]


The head of a TRA Prefecture, or the designated person, to maintain a line or communications with, or to see compliance to, the TRA. [Read More]


A club or group affiliated with the TRA. [Read More]

Pressure Relief Hole

A hole in the airframe of an HPR model to relieve the difference in pressure between the inside of the model and the atmosphere, so as not to prematurely eject the nose section. [Read More]

Pressure Thrust

The component of a motor's thrust due to the difference in the chamber and ambient pressures [Read More]


A special mix of paint, applied directly as a first coat, that is formulated to have excellent adhesion and a uniform colour over various materials such as body filler. [Read More]


Pyro Release Mechanism; a mechanical actuator used to depoy a parachute; activated by an electronic match and a small black powder or Pyrodex (or equivalent) [Read More]


A 38mm reloadable solid propellant motor system produced by Cesaroni Technology Incorporated (CTI). [Read More]


A 54mm reloadable solid propellant motor system produced by Cesaroni Technology Incorporated (CTI). [Read More]

Progressive Burn

When the thrust of the motor increases throughout the burn. See also Burn, Neutral Burn, Regressive Burn [Read More]

Propellant Mass Fraction

The propellant mass divided by initial mass. [Read More]


1. a propelling or being propelled, 2. something that propels, a driving force (Webster) [Read More]

Propulsive Chaff

(Brit.) The remains of a shredded rocket while still airborne. [Read More]


Pacific Rocket Society - An amateur rocketry organization. [Read More]


Phase Stabilized Ammonium Nitrate; AN that contains a small amount of nickle salt that eliminates the phase transitions typically associated with AN motors; sold by CP Technologies [Read More]


The process of laminating body tubes in polyester hose soaked in MinWax(tm) PolyCrylic(tm); this adds some strength and resiliency, but is not as sturdy as standard fiberglass laminations. See Fiberglass [Read More]


A model designed and decorated to appear to be a scale model. [Read More]


Tetrafluoroethylene; See Teflon(tm) [Read More]

Pumpkin Seed Effect

See: Watermelon Seed Effect [Read More]


Polyvinyl Chloride; a common plastic usually associated with plumbing pipe; rocket uses have included body tubes, ejection cannons, motor casings, and even as a propellant binder [Read More]


A black powder substitute made by Hodgton; intended for muzzle loading firearms, it is actually considered a propellant and does not require a LEUP for purchase or storage; if contained properly, the 'P' version shows promise for ejection charges [Read More]


1.)Liquid solution that is used to make igniters. 2.)A highly flaamable substance used to ignite rocket motors; typically a liquid that igniters are dipped in; one common commercial pyrogen is Magnalite by Rocketflite [Read More]


Of or pertaining to fire or explosion. The term is most commonly used with reference to fireworks. [Read More]

- Q -

Quantum Tube

An aiframe introduced by Public Missiles: These tubes are made in the USA from a special blended polymer that is extremely durable and easy to use. Most epoxies and paints will readily adhere to this material. It has been tested and found compatible with the following paints: lacquer, enamel, ... [Read More]


See Pseudo-Glassing [Read More]

Quick Link

A metal loop with a captive nut, which is used to connect chains, or in our case recovery system components; also known as a threaded connector; typically oval, but may be square, pear, or delta-shaped [Read More]

Quik Tube

A brand of tubular concrete forms which are often used for large inexpensive airframes [Read More]

- R -

R.M.R. Descon

an on-line rocket design contest started by Dave Lee; Descon Website [Read More]


The public domain rec.models.rockets newsgroup See for yourself click here [Read More]

Rack Rocket

A multi-staged rocket design where the motors are held in a rack that also supports a single set of fins; as successive engines ignite, they eject the previous used motor; the rack may consist of 3 or 4 rods, or slotted tubing [Read More]

Rail Button

A piece of plastic or metal that mates with a Launch Rail; forms a 'H' shape when viewed from the side. [Read More]


See Launch Rail [Read More]

Range Box

A box used to carry everything that you need for flying rockets. Controller, motors, ignitors, wadding, pliers, masking tape, screw drivers, hobby knife, CA glue, parachutes, etc. [Read More]


The part of a launch site where the pads are located. [Read More]


The launch site; or, the distance from an observer to a tracked object [Read More]


Rocket Altitude Simulation Program; a public domain program that simulates the flight of a rocket in one dimension [Read More]


Rocket Assisted Take-Off. RATO refers to a rocket booster that is attached to a conventional aircraft to reduce the distance required for take-off. [Read More]


radio controlled rocket glider [Read More]


radio controlled [Read More]


A (painfully) humorous term that refers to any situation where a rocket goes to pieces such as a prang or a CATO. Thought to have originated at LDRS XIII. Typical usage: "That E-15 sure re-kitted my Black Brant!" [Read More]

Rear Closure

In AeroTech-style cases, an aluminum housing that screws into the case to seal the motor and retain the nozzle; not required per-se for single-use or Kosdon-style reloadble motors. See also Forward Closure. [Read More]

Rear Ejection

The ejection of recovery device through the rear of a model. [Read More]

Recovery Harness

Everything that is used to connect rocket components which separate at ejection; may or may not include a shock cord per-se; term is usually used in HPR where the cords are made from tubular nylon or Kevlar(tm) and do not stretch appreciably. [Read More]

Recovery Wadding

See: Wadding [Read More]

Red Baron

The condition in which a boost glider's motor pod and recovery system gets tangled with the glider portion, causing the glider to spiral down as if it had been "shot down". [Read More]


A propellant by Aerotech that produces a bright scarlet red flame with white exhaust smoke. Only available in H-M sizes at the present time. [Read More]

Reefed Parachute

A parachute whose shroud lines are restricted to prevent full opening of the canopy. [Read More]

Regressive Burn

When the thrust of the motor diminished throughout the burn. See also Burn, Neutral Burn, Progressive Burn [Read More]


A launch controller that controls electrical current to the igniter through an electrical relay. This arrangement allows the power source to be placed close to the rangehead, reducing the voltage drop through long wires. [Read More]


an organic compound consisting of a non-crystalline or viscous liquid substance; see Epoxy [Read More]


A device for keeping the rocket motor from being ejected by the force of the deployment charge. [Read More]

Reynolds Number (Rn)

1.) A nondimensional co-efficient that measures the compression of air due to scaling. This allows scale models to be tested in wind tunnels; 2.) A dimensionless number used by fluid flow engineers to characterize the way a fluid (gas or liquid) will behave when passing over a solid surface. The ... [Read More]


See Rocket Glider [Read More]

Rigid Wing

A glider with wings using rigid airfoils rather than a parafoil or flexible wing. [Read More]

Ring Fin

A fin which is comprised of a ring of tubing, typically larger than the rockets airframe and usually supported by standard fins. [Read More]

Rip-Stop Nylon

a common parachute material; it is distinguished by a fine pattern of boxes (barely noticeable) that are designed to keep fabric from tearing [Read More]


See R.M.R. [Read More]


Reloadable Motor System (has also been called Reusable Motor System). A solid rocket motor which can be re-fueled and reused. [Read More]

Rocket Caviar

Mixture of lead shot and epoxy used for adding nose weight [Read More]

Rocket Eating Tree

Any tree within the launch field; see Murphy's Law. [Read More]

Rocket Eatumupuses

See Rocket Eating Tree. [Read More]

Rocket Glider

A type of boost glider that has the characteristics of a model rocket when ascending, then changes its configuration to have the characteristics of a glider when descending. All parts remain with the model other than the spent fuel. [Read More]

Rocket Mail

Mail that is flown in a rocket to commemorate its launch; may then be sent to recipients via snail mail Rockets were apparently used as early as 1902 to deliver mail from ship to shore in the Fiji islands. No known covers survive. On February 2, 1931 Friedrich Schmiedl successfully launched a ... [Read More]

Rocket Rotisserie

A home made device used to slowly rotate a rocket or component during painting, glassing, or sanding. [Read More]


A computer program that allows you to design any size rocket, and then simulate its flight to see how high, and how fast it will fly. Even before you start building your creation, you'll find out if it is stable and safe to launch. Just image how much money you'll save by doing all your test ... [Read More]

Rod Whip

The flexing of a rod during lift-off, which may cause the rocket to head off at an undesireable angle [Read More]

Rogallo Wing

A flexible delta wing platform developed by Francis Rogallo that is popular for kites, hang-gliders and ultralights. [Read More]


A passive, mechanical roll damper mounted a rocket's fins. Consists of independently acting wing-tip aelerons with enclosed airstream-impelled gyros wheels. [Read More]


Rotational motion of a rocket through the long (flight) axis. [Read More]


Acronym for Rocketry Online , one of the most comprehensive rocketry sites [Read More]

Root Chord

The chord at the root of a wing or fin. See Chord. [Read More]

Root Edge

The edge of a fin or wing that is glued to the airframe. [Read More]

Rotor Blades

Wing-like extensions, rotating around a central hub of a helicopter or autogyro. [Read More]

Rotor Disc

The disc of space formed by the rotation of rotor blades. [Read More]

Rotor Hub

The central attachment point for the blades of a rotor. The attachment usually determines the pitch angle of the blades. The hub can be of 2 types: fixed or rotating. [Read More]


A multi-bladed propeller used to produce lift or control the orientation of an aircraft. [Read More]


Acronym for the book "Rockets of the World", by Pete Alway [Read More]


Reaction Research Society - The oldest continuously-running amateur rocketry group in the United States. [Read More]


Range Safety Officer. Person(s) responsible for field safety. Determines suitability of rockets to fly at a particular site. Inspects rockets prior to flight. [Read More]


Ready to Fly. A rocket which is sold pre-built, as opposed to a kit. [Read More]

- S -


Standards and Testing; name of the NAR's committee that tests and certifies motors [Read More]


A spacer which is used to align a rocket in a tube launcher; may also seal the breach; is discarded after launch. [Read More]


Surface-to-Air Missile [Read More]


The practice of building model rockets which are replicas of existing rockets or other aircraft, which models are constructed to a size that is a particular percentage of the original aircraft's size. Scale models are often built for competition, and their level of detail can be very exact. See ... [Read More]

Scissors Wing

A variable geometry wing planform used on rocket gliders, where the wing unit rotates and aligns with the fuselage when not in glide mode. [Read More]


Safety Check Officer (Deputy RSO) [Read More]

Scott Towel Special

A cheap rocket costing less than $1, made of a tube taken from paper towels, toilet paper or gift wrap, a hand rolled paper nose cone, and card fins or tube fins or other recycled material. The use of balsa for fins or any other conventional model parts immediately disqualifies the model as a ... [Read More]


A a rocket that is built from individual parts, as opposed to being bought as a kit. Many times these are original designs. [Read More]


A really, obnoxiously loud beeper. [Read More]

Screw Eye

A headless screw on which the shaft is extended and formed into a circular eye. [Read More]


to cancel a launch attempt due to problems, technical or otherwise. [Read More]


See Shock Cord [Read More]


See Streamer Duration. [Read More]


Paint-like substance to cover wood parts. Sealer seals the wood grain, preventing any penetration of moisture, allowing a smoother finish, and the use of less paint. [Read More]


A series of nose cones designed and used for maximum aerodynamic efficiency on very high-speed rockets. The most commonly encountered cone in this series is a Von Karmon cone. [Read More]

Self Packing

See Re-Kitted [Read More]


A small mechanical device, which upon receiving a signal from a radio or timer will perform an action such as the movement of a pushrod. [Read More]

Shear Pin

A pin(s) that retain a nosecone to avoid drag separation; they are sheared off by the force of the ejection charge; often nylon screws are used. [Read More]

Shock Cord Mount

The attachment point for a shock cord. [Read More]

Shock Cord

A length of elastic or bungee which provides shock absorption for the rocket components at the point of flight where the deployment charge fires and the parachute opens. [Read More]

Shotgun Recovery

A method of getting your rocket out of rocket eating trees using, well, a shotgun; recommended only as a last resort [Read More]


A slight sharp indentation at the base of a nose cone or top or base of a transition, allowing the part to be slid into a tube while allowing alignment of the rocket sections to be maintained. [Read More]


UK Term: A town in the UK through which rockets pass through during a shred. [Read More]


The condition in which a rocket's airframe fails during launch. This is caused when the force applied by a rocket motor exceeds the tensile strength of the rocket airframe. The effect of a shred is similar to an explosion. [Read More]

Shroud (Transition)

A piece of material, often card stock, used to smoothly allow the airframe to go from one diameter to another. [Read More]

Shroud Line (Parachute)

Lines or strings which pull down on the edges of a parachute. The shrouds come together at their bottom ends to provide a point of attachment between the parachute and the rocket. [Read More]

Single-Stage Recovery

A process by which a rocket is recovered by means of a single parachute, streamer, or group of parachutes which deploy at one time. See Two-Stage Recovery [Read More]

Sink Rate

The rate of vertical drop during the recovery phase of a flight, in feet or metres per second. Sink rate used to specify parachute or streamer size for a rocket. [Read More]

Skid Mark

A motor by Animal Works that produces a lot of flame, black smoke and sparks. [Read More]


The thin outside surface of a hollow part or object. [Read More]


Slang term for the smoke trail left by an unstable rocket which does not fly straight. [Read More]

Smoke Point

The maximum height in millimeters of a smokeless flame of fuel being burned in a laboratory apparatus. This test method provides an indication of the relative smoke producing [Read More]

Snap Ring

A spring metal ring that is intended to snap into a groove either inside or outside a pipe or shaft; inner snap rings are used to retain nozzles and forward closures in Kosdon-style reloadable motors, and an outer ring is usually used as a thrust ring; requires a special set of pliers to ... [Read More]

Snap Swivel

A small device, originally developed to connect fishing lures to leaders.,which is attached to a model rocket's parachute shrouds. This permits the parachute to be easily removed and replaced on the rocket, and permits the parachute to rotate in relation to its connection point, which reduces ... [Read More]


Slimy NAR Insider. A person who associates with (either professionally or casually) members of the NAR board of trustees, thus being privy to the "inner workings" of the organization. Said to have originated during "flame wars" on the CompuServe Sport Rocketry SIG. [Read More]


Slimy NAR Politician. Coined by NAR President Mark "Bunny" Bundick, it refers to an SNI who actually manages to get elected to the NAR board. [Read More]

Snuffer Tube

A small metal tube used to extinguish a wick such as in a dethermalizer. [Read More]

Solar Igniter

Estes Industries brand of Igniter. Made from two wire conductors with a piece of Nichrome wire connecting them at one end. The nichrome wire tip of the igniter is dipped in a pyrogenic compound which flares to ignite the rocket motor. [Read More]

Solids Loading

The proportion of solids in a propellant formulation; increasing the solids loading has several effects, including increasing the Isp [Read More]

Sonic Barrier

The zone of high air density caused by the compression wave of an object traveling near the speed of sound. [Read More]

Sonic Boom

1.) Sonic boom is an impulsive noise similar to thunder. It is caused by an object moving faster than sound, about 750 miles per hour at sea level. An aircraft traveling through the atmosphere continuously produces air-pressure waves similar to the water waves caused by a ship's bow. When the ... [Read More]

Sonic Speed

The speed of sound at the current conditions of air density. humidity and temperature. [Read More]

Sono Tube

A brand of tubular concrete forms which are often used for large inexpensive airframes [Read More]


An artificial sweetener, very similar in appearance and with similar physical characteristics to both sucrose and dextrose sugars; see Sugar Motor [Read More]

Sounding Rocket

A professional rocket used to perform atmospheric experiments. Sounding rockets take their name from the nautical term "to sound," which means to take measurements [Read More]


SpaceCAD makes it easy for you to design rockets. You can view them in 2D and 3D, you can zoom into your design and you can get see how your rocket will look like - before you even start building it. Just think of the hours saved by tweaking your design to the max without sacrificing valuable ... [Read More]


UK Term: A town in the UK where crashed rockets are said to end up. As in "It wasn't a great flight, she bought a first class ticket to Spackington via Shredbury and Zipperfield. [Read More]


1.) (Brit.) Slang for the sound of a model rocket hitting the ground from high altitude. See Prang 2.) Slang term for a crash. Derived from the sound of balsa and cardboard hitting the ground. 3.) Event following catastrophic failure of recovery device [Read More]


The long (side-to-side) dimension of a wing. See Chord. [Read More]


A long, thin, structural member of a airframe. Also, SPAR [Read More]


Special Projects And Research, formerly a department of DeHaviland Canada (now Bombardier), maker of satellites and the original robotic arm for use by the shuttle in space. Now an aircraft maintenance company, the robotics and space devisions were sold to MacDonald-Dettwiller. [Read More]

Specific Impulse (Isp)

The total impulse of a motor divided by unit weight of propellant. [Read More]

Speed Of Balsa

That speed at which a rocket's balsa fins shred. The speed varies with thickness of balsa, thrust gradient, type of glue used and mostly quality of building technique. [Read More]

Spill Hole

A hole in the center of the canopy of a hemispherical parachute, designed to reduce payload oscillations caused by the canopy spilling air unevenly from its edges. [Read More]

Spin Stabilization

The use of spin along the long axis of a rocket to stabilize the flight, thus making the rocket act as a gyroscope. [Read More]


Tabs attached to fins and set at an angle, intended to spin the rocket in order to stabilize it. [Read More]


The small (or larger) grooves in paper tubes that spiral up-down the length. They are induced by the tube wrapping manufacturing process [Read More]

Spool Rocket

A rocket variation made from wire, cable, rope, etc. spools. [Read More]

Sport Model

A model rocket designed and built with no specific purpose in mind other than to fly it. [Read More]

Sport Rocketry

Rocketry activities pursued as a pastime, diversion, or personal enjoyment. Term is often used as a contrast to "competition rocketry." [Read More]

Spot Landing

A competition event in which the goal is to land the model closest to a predetermined spot on the launch field. [Read More]


Abbreviation for Sport Rocketry magazine [Read More]


A small charge of black powder or other propellant, contained in a hollow tube and set off with an electrical igniter. The term is usually used in connection with an electronically-actuated deployment charge for a rocket's recovery system. [Read More]


Space Research Facilities Branch. National Research Council of Canada. Operator of the Black Brants in the 1960s and '70s [Read More]


Single Stage To Orbit. [Read More]


The tendency of a rocket to move in a straight line in the direction it is pointed at launch. A hobby rocket employs "passive" stability, in that it depends on its inherent stability (the relationship of its centers of pressure and gravity) and the counterbalancing pressure of the airflow on its ... [Read More]


Stabilizer: Usually refers to the fin-like structures at the rear of a conventional boost glider. [Read More]


See Booster and Sustainer. [Read More]


The angle of maximum lift for an airfoil. Stalls are dangerous because lift dramatically decreases (often to near zero) at any angle past the stall point Static Balance - A state in which a model's center of gravity can be demonstrated to be in a proper relationship to the center of pressure by ... [Read More]

Stand-Off Scale

A scale model where the degree of accuracy should be judged from a distance (i.e. not too accurately) [Read More]

Static Firing

The firing of a motor, mounted in such a way that the motor can not move. Used usually with instrumentation, to permit performance measurement. [Read More]

Static Inertia

In mechanics, inertia is the resistance to change in velocity. Static Inertia is the resistance of a motionless object to begin to move. [Read More]

Stine's Law

The guiding principle of Rocketry construction and flight: "If at first you don't succeed, try following instructions." [Read More]

Strand Burner

An apparatus that provides for burn rate measurements of a solid rocket propellant in an environment of elevated pressure; sometimes referred to as the Crawford Strand Burner [Read More]

Streamer Duration

(SD) A contest event whose purpose is to maximize the flight duration of models with streamers; a common competitive event in NAR-sanctioned launches. [Read More]


A device for slowing the descent of a rocket, sometimes used in place of a parachute in smaller rockets. The streamer consists of one or more long, narrow lengths of plastic, fabric or paper which are connected to the rocket in the same fashion as a parachute, and which deploy and flutter to slow ... [Read More]

String Test

See Swing Test [Read More]


A condition in which a rocket's fins, or a glider's wings, are pulled off the airframe by excess thrust. [Read More]


The "act" of having wings or fins stripped off an airframe. Also, a pop-pod glider that separates from the booster pod prematurely. [Read More]

Stubby Rocket

On EMRR, a rocket whose length to width ratio is 10:1 or less [Read More]

Stuffer Tube

A small-diameter tube - commonly an extension of the motor tube - which is used in large-diameter rocket airframes to duct deployment charge gases to the recovery system storage area. This reduces the internal area which must be pressurized by the deployment charge. [Read More]


A very light material made of expanded polystyrene plastic. Though Styrofoam has little structural strength, is easily shaped into shapes, such as large nose cones and glider wings, that can be skin-reinforced by fiberglassing or lamination of thin wood veneers. [Read More]


Speeds where no local supersonic flow occurs (such as around tip of nose or leading edge of fin), typically up to Mach 0.8 to 0.9, depending on the shaping of the vehicle [Read More]

Suction Lock

The Mother of all Base Drag. See Bernoulli Lock [Read More]

Sugar Motor

An experimental motor that uses a mixture of potassium nitrate and sugar (typ. sucrose, dextrose or sorbitol) as a propellant; also called 'candy motor' [Read More]

Sun Seeker

A rocket with a crude form of guidance that directs it toward the sun [Read More]


Usually, a lengthened version of an existing model rocket design, used in altitude and duration competition. Scoring is based on altitude multiplied by airframe length. Super-Roc has different length limits for different motor classes. For example; A has a range of 75 to 150 cm, C has a range of ... [Read More]


A speed greater than Mach 1 (760 mph at sea level) and less than Mach 5. [Read More]


An additive which improves a composite propellant's mixing by coating the AP particles [Read More]


In a multi-stage rocket, the last or top stage. In a parallel staged rocket, the longest-burning motor. [Read More]


Single Use; a disposable motor which cannot be re-used. [Read More]


The amount of angle that the leading edge of a wing has been shifted back from a line perpendicular to the airframe of a model. [Read More]

Swing Test

A stability test in which a string is attached to a model rocket at the center of gravity and then swung around the head. If the model is stable, it will head nose into the direction of travel. This test has a large margin of error, thus producing models often overly stable. It can not be used for ... [Read More]


A swivel is a connection that allows the connected object, such as a parachute or streamer to rotate horizontally and/or vertically. [Read More]

Symmetrical Airfoil

An airfoil (wing) in which both the top and bottom surfaces are tapered. [Read More]

- T -


The time interval between ignition and maximum thrust. [Read More]


A nut that attaches to a wooden surface; consists of an internally threaded shaft and a flat plate with prongs; commonly used to provide an attachment point for motor retainer clips; see Kaplow Clip [Read More]

Tail Boom

The spar extending past the wings of a aircraft to which the tail or stabilizer surfaces are attached. It is usually cut down to a minimum diameter as required for strength. [Read More]

Tail Drag

See Base Drag [Read More]

Tail Heavy

General description of a model that will require nose weight to achieve the desired CP/CG relationship for stable flight. [Read More]


See Boat-Tail [Read More]


A uniform decrease in diameter in a cylindrical of near cylindrical part. [Read More]


Team America Rocketry Challenge; an aerospace design and engineering event for teams of US secondary school students, sposored by the NAR [Read More]


The polymer PTFE, an extremely slippery material that is inert to almost every known chemical; rocket uses include lubricants, release films, and reusable recovery wadding; patented by DuPont [Read More]


The transmission of data to a remote receiver, usually through the use of radio frequency broadcast. [Read More]


The outline of a part, made of a tough material used as a stencil to produce multiple parts of that size and shape. [Read More]

Terminal Velocity

1.) The highest allowed velocity for a shape or design, any further attempt to accelerate the object will result in drag forces completely eliminating the acceleration. 2.) in our sport, the speed of a Prang or Core Sample [Read More]


A three sided pyramid [Read More]


A device for determining altitude by measuring both elevation and azimuth angles. More accurate than a simple inclinometer, which measures only the elevation angle. [Read More]


A low-explosive device in the shape of narrow string, similar to detonation cord. Thermalite is often used to enhance the efficiency of igniters in large-diameter composite motors, and is sometimes used for airstarting motors. The possession and use of Thermalite now requires a LEUP to be issued ... [Read More]


An upward moving column of air caused by surface heating of the ground; a good thing in duration events [Read More]


A plastic which is solid when cold, but which may flow and be re-formed multiple times with the application of heat. [Read More]

Three-fold Attachment

See: Tri-Fold Attachment [Read More]

Three-Fold Method

The Three-Fold Method is the method Estes (and others) use to attach shock cords to the inside of an airframe. The Three-Fold Method consists of a tapered strip of paper that is folded over on itself with glue and the shock cord. See also: Tri-Fold Mount [Read More]


1.) The narrowest cross-section of a rocket motor's nozzle. 2.) The actual opening in a rockets nozzle; the throat diameter along with the exit cone area play a large role in the motor's performance [Read More]

Through The Tube (TTT)

See Through The Wall [Read More]

Through The Wall (TTW)

An HPR fin attachment technique which provides much greater strength than the typical surface mount used in model rocketry. To use TTW, slots are cut in the body tube where the fins mount and the fins are built with extended tabs on the root edge which fit through these slots. In one form of TTW, ... [Read More]

Thrust Augmentation

A method used in jet engines to increase thrust by injecting/venting air into the exhaust jet; no examples of thrust augmentation in rocket engines are available. [Read More]

Thrust Curve

1.) The propulsive force of a rocket motor plotted against time. See Thrust 2.) ThrustCurve.Org is a website that contains motor specifics include size, weight, average thrust, total thrust, and thrust curves. See also EMRR's Tools [Read More]

Thrust Decay

The gradual loss of thrust at the end of a motor's burn. [Read More]

Thrust Plate

A plate, usually metal, whose purpose is to distribute the force of a motor on the end of the motor tube [Read More]

Thrust Ring

1.) See Engine Block 2.) In some cases, the thrust ring is part of the motor. It may be part of the rear closure, or a flanged permanently mounted on a single-use motor. The purpose is to prevent the motor from pushing up into the motor mount while the rocket is under thrust. In absence of an ... [Read More]

Thrust Stand

An instrumented test stand used to measure motor performance [Read More]


The propulsive force developed by a rocket motor during the rocket's powered ascent. The force produced by a rocket motor is described by Newton's second law of motion "Force equals mass times acceleration" and by Newton's third law of motion "for every acting force, there is an equal reacting ... [Read More]


An electronic device which is used to control events during a rocket's flight, such as sustainer motor ignition or recovery system deployment. A timer is normally combined with another device such as an accelerometer or g-switch, which provides a start signal for the timer. [Read More]

Tip Chord

The chord at the tip of a wing or fin. See Chord. [Read More]


An alteration of a rocket's flight direction caused by interaction of the launcher, rocket, and wind direction as the rocket leaves the launcher. [Read More]

Tomy Timer

A mechanical timer which is used to deploy parachutes in water rocket competitions [Read More]

Total Impulse

The total thrust produced by a rocket motor across its full burn time. Usually expressed in Newton-seconds. [Read More]

Trailing Edge

The rear edge of a wing or fin. [Read More]


Part of an airframe that smooths the airflow from one airframe component to another of different diameter. Also called an Adapter. [Read More]


The condition of crossing the sonic barrier, from the initial appearance of local shock waves (typically around Mach 0.8 to 0.9), extending to speeds where all local airflow becomes supersonic (typically Mach 1.05 to 1.2). This is the period of maximum aerodynamic stress in a supersonic flight. [Read More]


Tripoli Rocketry Association, Visit TRA [Read More]


The Rocketry Forum; an online, graphical discussion forum. Visit TRF [Read More]

Tri-Fold Attachment

A tri-fold attachment or "Three-Fold Method," is the method Estes (and others) use to attach shock cords to the inside of an airframe. The Three-Fold Method consists of a tapered strip of paper that is folded over on itself with glue and the shock cord. See also: Tri-Fold Mount [Read More]

Tri-Fold Mount

A tri-fold mount is a shock cord attachment created using the Three-Fold Method. [Read More]

Trim Monokote

A brand of self-adhesive vinyl trim; unlike regular Monokote, this does not require heat for adhesion [Read More]


The act of adjusting surfaces on an aircraft through warping or shifting trim tab angles to achieve stable controllable flight. [Read More]

Tripoli Rocketry Association

The Tripoli Rocketry Association (TRA - ) represents rocketry hobbyists in the US and around the world. [Read More]


Truely Recyclable Motors; Kosdon's reloadable motor system [Read More]

Troll (Internet)

A person who enjoys unrest, starts arguements, and tries to upset people on media such as R.M.R. and chat forums [Read More]


Two Stage To Orbit. [Read More]


Identifier for Aerotech Blue Thunder propellant; "produces a bright violet-blue flame with a minimum of exhaust smoke"; the easiest Aerotech's propellant to ignite [Read More]


To The Motor Mount: An extension of TTW fin mounting, in which the fin tab which has passed through the airframe wall contacts the motor mount tube and is bonded there with epoxy. [Read More]


"Tip-to-Tip" - the application of Carbon Fiber or Fiberglass over an entire fin's surface to strengthen the fin. [Read More]


See Through The Wall [Read More]

Tube Fin Rocket

A rocket that uses several tubes rather than conventional fins for stability. Tube Fin Rocket - A rocket that uses several tubes rather than conventional fins for stability. [Read More]

Tube Fins

The case where the fins are made of sections of tubing that are tangentially connected to the airframe; 6 sections of tubing, the same diameter as the airframe, will completely enclose an airframe. See also EMRR's Tools . [Read More]

Tumble Recovery

A recovery method where a very light model rocket ejects its motor and shifts its CG behind the CP, thus preventing stable flight and causing the model to tumble end over end. [Read More]


Slang for wind tunnel. Also, a long hollow conduit on the side of a rocket used to protect wiring traveling from the top to the bottom of the rocket. [Read More]


A device used on rockets with conical cross-sections, such as egg lofters, to prevent the extra drag which occurs when the laminar airflow separates from the airframe. This is done by causing the airflow to become turbulent at the point where it would normally separate from the airframe. [Read More]

Two Part Foam

expanding foam that reacts when the two components are mixed; the reaction is chemical in nature and does not require moisture as do the canned aerosol foams. [Read More]

Two-Stage Recovery

See Dual Recovery [Read More]

- U -


Strictly stands for Unidentified Flying Object, but is used for any saucer-like design (e.g. Estes Snitch , Art Applewhite's Saucers ). [Read More]


United Kingdom Rocketry Association [Read More]


The practice of building very large HPR versions of smaller model rockets, several times the size of the original. [Read More]

Umbilical Mast

A mast extending beside a rocket while sitting on its launcher, designed to support wiring or hoses to the rocket. It is often designed to pull the wiring or hose out of the way once the model's motors ignite. [Read More]

Under Stability

See Marginal Stability [Read More]

Unibody Staged

See Rack Rocket [Read More]

Unsymmetrical Thrust

A condition in which the thrust of a motor or motor cluster is not parallel to the axis of the rocket. This is most often caused by the failure of part of a cluster of motors to ignite or a protuberance extending into the exhaust stream of a single motor. [Read More]


The practice of building large versions of smaller model rockets. See Upscale Rocket Articles . [Read More]

- V -


A method of making lightweight plastic components like nose cones by using heated plastic, a mold, and a vacuum pump that is attached to the mold. [Read More]

Vacuum Bagging

A technique used in laminating rocket components in fiberglass or other material; after the material is applied and wetted with resin, the component is placed in a sealed plastic bag and the air is sucked out. The bag places uniform pressure over the part while the resin sets, resulting in a very ... [Read More]


Visual Center of Pressure; a public domain program to graphically determine the CP [Read More]

Vectored Thrust

A condition in which a rocket motor's thrust is not parallel to the motor's axis. This is achieved by canting the motor's exhaust nozzle, and is often done to reduce the unsymmetrical thrust that results from outboard motors failing to ignite on clustered-motor rockets. [Read More]

Vent Hole

A hole in a Body Tube to allow ejection pressure to vent into another tube or into the atmosphere. [Read More]

Von Karmon

A nose cone shape. Von Karmon is a special case of the Sears-Haack series of nose cone shapes, used on very high-speed rockets. It is the most efficient volume per unit nose drag. [Read More]

- W -


Wadding or Recovery Wadding is a non-flammable filler material placed in a model rocket airframe before the parachute is inserted. Recovery wadding acts as piston to help ensure deployment of the recovery system and it protects the parachute and other deployment system components from burning. [Read More]


A permission granted by the FAA to launch large rockets into airspace that it controls, for specific altitudes (usually 5000 or 10,000 feet) and for a specific period of time. [Read More]


A twist, usually undesired, in a normally flat object such as a fin [Read More]

Water Rocket

A rocket whose propulsion is derived by expelling water; the water may be propelled by compressed gas (normally air); the compression may be derived from pumps (most commonly), pressurized tanks, or chemical reactions. Here are some of them click here . [Read More]

Watermelon Seed Effect

The negative base drag (see "base drag") that can result when the rear of a moving projectile is tapered such that the airflow around the projectile expanding into the space behind the projectile presses against the taper, providing a small amount of forward thrust. The effect is similar to ... [Read More]


The tendency of a rocket to fly into a breeze, altering the flight path from vertical. [Read More]


A method of securing fins by forcing the fin root in between tubes in a motor cluster. [Read More]

Wind Tunnel

A specially designed pipe in which moving air can be channeled in a controlled way, producing an air stream of laminar flow and constant velocity, thus allowing testing of a design under constant conditions. [Read More]

Wing Loading

A method for measuring appropriate wing size, calculated by dividing the wing area in inches squared by the mass of the aircraft. [Read More]


Small fin or wing-like extensions attached to the ends of the wings of an aircraft. [Read More]


The linear distance between the extremities of an airfoil; typically the distance between the wing tips of an airplane. [Read More]


In British usage, a rocket's fins. Also, the lifting surfaces of a glider. [Read More]


White Lightning; a propellant made by Aerotech; "A brilliant white flame, dense bright white exhaust, and a throaty roar are the hallmarks of this popular propellant". [Read More]

Wood Filler

A common filler for tube spirals, balsa fins, fillets, etc. [Read More]

Wood Grain

The predominant direction of the fibers in a piece of wood. important to note as the strength of the material is perpendicular to the fiber direction. [Read More]


Windows Rocket Altitude Simulation Program; a public domain program that simulates the flight of a rocket in one dimension [Read More]

- X -

X-form Parachute

A parachute that is formed by connecting together two rectangles of material, forming an 'X' [Read More]


the 'X' stands for experimental; the series of US Government experimental planes starting with the Bell X-1. [Read More]


"The X PRIZE is a $10,000,000 prize to jumpstart the space tourism industry...the $10 Million cash prize will be awarded to the first team that: Privately finances, builds & launches a spaceship, able to carry three people to 100 kilometers (62.5 miles); Returns safely to Earth; Repeats the launch ... [Read More]

- Y -


Yet Another Born Again Rocketeer. See BAR [Read More]


A back-and-forth motion of the nose of a rocket in flight, on the axis determined as "left-and-right". See Pitch. [Read More]

- Z -

Zipper / Zippering

A condition in which a slot is cut in an airframe by a shock cord. This condition is caused by early or late recovery system deployment, in which the recovery system deploys while the airframe is moving at a high rate of speed. [Read More]


UK Term: A town in the UK where rockets have zippers installed. [Read More]

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