EMRR's Glossary

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3FNC		Slang for a basic rocket: "3 Fins and a Nose Cone".
3-Fold Method		The method Estes (and others) use to attach shock cords to the inside of an airframe; consists of a tapered strip of paper that is folded over on itself, with glue and the shockcord. See Three-fold attachment.
4FNC		Slang for a basic rocket: "4 Fins and a Nose Cone".
80/20		A company that makes aluminum extrusions that work well as DIY rails; their "1010" extrusion is compatible with standard railbuttons (BlackSky and railbuttons.com).

A		Show only A's by clicking here
A.B.M.R.		The public domain alt.binaries.models.rockets newsgroup; this is the place to post binaries (graphics, movies, etc)
Ablation		The flaking and vaporization of material undergoing severe heating due to aerodynamic drag.
Abort		Failure of an aerospace vehicle for any reason which prevents completion of its mission. Similar to "scrub", which involves a decision not to launch.
Abrasive		Natural or man-made materials used for grinding, sanding or polishing a surface.
ABS		Acrylonitrile-Butadiene-Styrene; a tough, heat-resistant and impact-resistant thermoplastic; used for telephone housings, luggage, sporting helmets, pipe fittings and automotive parts.
AC		See Aerodynamic Center
Accelerometer		An electronic device for detecting the presence of high acceleration. An accelerometer can be used for flight data gathering, or for controlling flight events. For example, an accelerometer with a memory chip can record the strength and duration of a rocket’s acceleration. This data can be used by a computer to calculate the rocket’s approximate altitude at various points of its descent. An accelerometer can also be combined with a timer to determine the proper time for a deployment charge or sustainer motor to be activated, by counting down a pre-set number of seconds after acceleration ceases (motor burnout).
Acetate Dope		A liquid material made from cellulose and acetic acid that shrinks, waterproofs and protects flexible coverings such as tissue or silk.
Acetone		A flammable liquid used as a general solvent for dope, lacquers and epoxy.
Acronym		A word formed from the initial letters or groups of letters of the words in a name or phrase, as Wac from Women's Army Corps, or loran from long-range navigation.
Acrylic resin		A transparent, stiff thermoplastic resin sometimes used for body tubing.
Actuator		A mechanical, electrical, or electronic device that sets a mechanism in operation or performs a specific action such as throwing a switch.
Adapter		See Transition. See also Motor Adapter.
ADC		Analog-digital converter; a device that converts an analog signal to the digital signal that a computer can read.
Additive		Substance added to another to modify its properties such as microballoons added to epoxy.
Adhesive		Substance added to two components in order to bond them together.
Advanced Model Rocket		Model rockets either constructed of exotic materials or designed to perform a function that differentiates them from normal models.
Aerial Photography		The study and interpretation of photographs taken from well above the earth’s surface.
Aerobrake Recovery		A recovery method where the rocket comes down 'ballistic' but its speed is kept at a safe level by a large amount of drag; used in saucer/UFO designs.
Aerodynamic Center		The point where all the aerodynamic forces on a glider balance, i.e. the CP of a glider
Aerodynamic Heating		Heating of solid objects in an airflow caused by the friction of the air against the objects.
Aerodynamics		The study of the motion of gases and forces applied by the gases to solid objects around which the gases move.
Aeronautics Act		Canadian law that regulates all use of airspace in Canada. The actual regulations are contained in the Canadian Aviation Regulations (CARs). Equiv. to FAR101
Aerosol		A mixture of fine liquid and/or solid particles suspended in a gas or air, such as paint from a spray can.
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. In addition, the secondary flow re-circulates upward pushing on the base to produce additional thrust. It is this artificial aerodynamic spike for which the Aerospike nozzle is named.
Aft Closure		See Rear Closure.
AGL		Above Ground Level. The altitude a rocket attains, not counting the altitude of the launch site. In the United States, waivers are issued by the Federal Aviation Administration (FAA), limiting the maximum altitude permitted.
AIAA		American Institute of Aeronautics & Astronautics.
Aileron		Hinged portion of a wing, designed to impart roll to the aircraft.
Aircraft Dope		Liquid material applied to model aircraft to strengthen and seal the covering material. Sometimes used with talcum powder to make a filler to seal balsa on a model rocket.
Airflow		the motion of air past and around an object.
Airfoil		A streamlined shape given to fins or wings for maximum aerodynamic efficiency in flight. A conventional airfoil - optimized for subsonic flight - has a rounded leading edge tapering to a pointed trailing edge. See Cambered, Diamond, Symmetrical
Airfoil Section		The cross-section of an airfoil in the plane of the common airflow around that part.
Airframe		The rocket’s main outer structure, especially the body tube.
Airstart		The practice of starting one or more rocket motors after the rocket is already in the air; a common technique with clustered motors.
Alignment		Bringing parts into position and orientation as desired. See an EMRR Featured Tip for Aligning Multiple Fins.
Aliphatic Resin		A type of carpenter’s glue, that although waterbased, penetrates and bond porous material forming a waterproof joint. Commonly called "yellow glue".
All Thread		A metal rod that is threaded through its entire length; aka threaded rod
Altimeter		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.
Altitude		Height above the ground. There are several methods of measuring or expressing altitude: (1) Pressure - Read from an altimeter when it is adjusted to 29.92 inches of mercury. All US aircraft flying above 18,000 AGL use pressure altitudes. (2) Actual (also called True) - Height above mean sea level (3) Density - Pressure reading corrected for temperature and humidity. Example: at 2850 feet actual altitude, at 100 degrees F. with 60% humidity and standard pressure, the density altitude is over 6500 feet. (4) Indicated - The altitude indicated by an altimeter. Altitude can be expressed as either Above Mean Sea Level (MSL), or Above Ground Level (AGL).
AMA		Academy of Model Aeronautics. American aeromodeling liaison organization to the CIAM through the NATIONAL AERONAUTIC ASSOCIATION.
Amateur Rocketry		A class of non-professional rocket beyond HPR. Although in the strictest sense it encompasses the non-professional, home made composite and hybrid motors sanctioned under Tripoli Research rules, the use of the term Amateur Rocketry usually implies other technologies: liquid bi-propellant fuels, zinc-sulfur, steam, and even black powder motors. Amateur rockets typically use structural metal parts and very often the motor casing doubles as the airframe (as with professional rockets). These rockets can be very large and powerful, capable of placing payloads many miles up. Activities in this field (one can scarcely call it a hobby) include formulation and manufacture of propellants and thus can be EXTREMELY hazardous. This is the main reason that amateur rocketry is not to be attempted alone. Another is expense as these vehicles can run many hundreds or thousands of dollars and take months to build. The equipment necessary to safely pursue amateur rocketry (sandbagged bunkers, loading pits, standby fire truck, etc.) are quite beyond the resources of most individuals. Not all amateur rockets are so large. Many of the "beginner" vehicles would qualify as HPR or even model rockets in terms of liftoff weight and total impulse, but fail the Tripoli codes due to their metal airframes and type of propellants. Note: There is a fine, but significant, difference between using a metal cased reloadable motor with pre-manufactured fuel slugs and packing a pipe with zinc/sulfur (a common amateur beginner fuel). Liquid fueled vehicles are becoming more popular among amateur groups. These can produce up to 1,000 lbs of thrust for up to a minute from a LOX/Kerosene engine which can propel the vehicle to altitudes of over 40 miles. Some hobby! Neither Tripoli nor the NAR sanction amateur rocket activities. See Experimental Rocketry
American Rocketeer		Centuri's attempt to produce an MRN 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 looking beneath the surface would notice that there was no reader input (e.g. rocket designs or "Idea Box" style tips); that all the rocket plans came from the Centuri design department and the "tips" were for problems that could be solved by items straight from the catalog! While each issue carried a Volume/Number identification, there was only one "Number" for each "Volume." V1, N1 was in 1966 and continued for at least four years.
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
Ammonium Nitrate		An oxidizer can be used some experimental motors
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
AmSpac/AmSpam		Deprecating but affectionate abbreviations for American Spacemodeling. See American SpaceModeling
AMW		Animal Motor Works; a rocket company that makes high power loads. See also Skid Mark
AN		Ammonium Nitrate: a solid rocket oxidizer.
Anemometer		An instrument used to measure the speed of an airflow.
Angle of Attack		The angle between the long axis of a rocket and the direction of the air flowing past it.
Anti-Spiral		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.
Anti-Zipper		Any of several techniques designed to prevent Zippering.
AP		See Ammonium Perchlorate
APCP		Ammonium Perchlorate Composite propellant. APCP is not an "explosive". See Ammonium Perchlorate
Apogee		In rocketry, the highest point a rocket achieves before beginning its descent. (More literally, the point farthest on the flight path from Earth.)
AR		See American Rocketeer
ARF		Almost Ready to Fly. A designation from kit manufacturers that indicates that their kit only requires a few final assembly steps.
ARM		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.
ARS		American Rocket Society; an early amateur rocketry group. Now called the American Institute of Aeronautics and Astronautics.
ARSA		Acronym for the Amateur Rocketry Society of America; this organization is actively involved in an effort to provide regulatory relief for HPR. See also Experimental Rocketry
ARTF		Almost Ready to Fly. Same as the more common ARF
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.
Asymetrical 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 thrusts, in a cluster would be to ensure symetrical thrust around the center vertical axis of the rocket. See also Vectored Thrust
Asymmetric Fins		A set of fins that are not identical in size, shape and relative position on an airframe.
ATF		See BATFE
Attitude		The position and orientation of an object relative to a fixed line, plane of axes or reference.
Autogyro		A vehicle whose blades rotate in a horizontal plane due to aerodynamic forces alone, creating lift.
Average Chord		The chord at the middle of a wing’s span.
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 Newtonseconds, and burns for 7.5 seconds. 1387.5 Newton-seconds divided by 7.5 equals 185 newtons average thrust.
Away Cell		A set of launch pads that are far away from the flightline and intended for 'L' flight and above.
Axis		One of the three lines of reference around which an aircraft can rotate. The three movements an aircraft can make (other than moving straight ahead) all involve rotation around some central point. That point is called an axis. These movements are: Roll: rotation around the longitudinal (front-to-back) axis (nose remains pointed forward, but the rocket spins), Pitch: rotation around the horizontal axis (nose moves up or down), and Yaw: rotation around the vertical axis (nose moves left or right.).
Azimuth		An angle on a horizontal plane. See Elevation.

B		Show only B's by clicking here
B/G		Boost Glider
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
Baffle		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 mis-aligned holes in tubing or bulkheads.
Ballast		Mass added to a model to bring the model into balance.
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 behind why a tightly crumpled piece of paper can be thrown farther than a loosely crumpled one.
Ballistic Recovery		A recovery system that employs simple physics and has no potential for zipper damage to the airframe. See also prang
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.
Ballistics		Study of objects moving through the air that have been given a short lived acceleration.
BALLS		Big A** Load Lifting Suckers: A popular annual launch for amateur and large HPR rocket flyers.
Balsa Wood		Fast growing wood from Central America known for strength, low density, and a very porous grain. Frequently used for model rocket fins.
BAR		Born Again Rocketeer. 1.)A person who once pursued rocketry as a hobby, and returned to it at a later time in life. 2.) An individual who has re-discovered the hobby/sport after an absence of several years. Contrast BOR
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.
Base Drag		1.) Drag produced by the airflow moving from the sides to the rear of a model; 2.) 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 by the motor fills thisvoid. The drag takes a sharp jump at burnout when this gas disappears (note: tracking smoke has very little effect on base drag due to its low density). Base drag can be reduced by the use of a boattail to transition the main body diameter down to the motor diameter which helps direct air into the evacuated area. When properly designed, a boattail can reduce base drag below zero (i.e. actually generate a small amount of forward thrust) by making use of the "Pumpkin Seed" effect. See Watermelon Seed Effect
Baseline		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.
Basswood		North American hardwood known for very tight even grain and fairly good ease of working.
BATES Grain		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 as the burn progresses; the shortening of the grain makes the burn more regressive, almost exactly balancing the progressive nature of the core expansion
BATF		Bureau of Alcohol Tobacco and Firearms; a federal regulatory agency. What the BATFE was formerly called. Sometimes called ATF.
BATFE		Bureau of Alcohol Tobacco Firearms and Explosives; a federal regulatory agency. Sometimes called ATF, BATF (older acronyms).
Bay		Part of a model set aside for a specific purpose such as the payload or electronics bay.
BCP		Barrowman Center of Pressure; see Barrowman Method
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.
Beeper		A device that produces an auditory signal, assisting searchers to find a rocket after it has landed.
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 beach balls stay "balanced" on top of fans in those hardware store displays :-) The effect is significant in rocketry when using altimeters or any other kind of payload that senses the ambient pressure around the rocket. The air moving by the payload section could cause the payload to indicate a lower pressure than the ambient still air, thus giving a false altitude reading. The effectdrops to zero at apogee when your rocket stops moving, but thealtitude vs. time curve will be wrong.
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 rocket and the pad creating a venturi which generates a low pressure region at the base. This pressure deficit can be significant, and if it is greater than the thrust being generated by the motor, the rocket won't go anywhere! This is quite possible as a 2" dia.rocket has, potentially, over 45 lbs (200 N) of "suction" available to hold it back, while a 3" rocket has over 100 lbs (460 N)! The old Centuri "Point" was an infamous Bernoulli locker when launched from an Estes Porta-Pad with its perfectly matching round blast deflector.
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 its lower surface. This causes air flowing across the upper portion of the wing to speed up, since it must cross a greater surface area in the same length of time. The increase in air velocity on the upper surface causes the air pressure in the region just above the wing to be reduced. The higher pressure below the wing presses upward on it, creating lift.
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
Birch		North American hardwood known for its pliancy and tight grain.
Black Brant (II, III, IV, V, X)		A commonly modeled Canadian sounding rocket; included since its spelling is often a point of discussion
Black Powder		The original explosive, said to come from China. A mixture of carbon, (charcoal), sulfur and potassium nitrate (saltpeter).
Black Rock		A famous (at least to us rocketeers) dry lakebed in Nevada, which is home to the BALLS launches (and many others)
Blackshaft(tm)		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. Blackshaft tubing – so called because it was black in color - was sold by Apogee Components. In some circles it earned the derogatory name "blackshatter" due to its inability to absorb any lateral shock without breaking. Manufacture of blackshaft tubing was discontinued in 1994.
Blade		Long thin wing, rotated around a central hub, such as on a propeller.
Blade Twist		The pitch angle variation on a helicopter blade from root to tip.
Blast Deflector		A plate or other device that protects flammable materials like grass; surrounding a launch pad, from being ignited by rocket exhaust.
Blister (Paint)		Air bubble formed under a skin of paint. Usually caused by heat applied to that spot or improper/incomplete preparation before paint.
Blockhouse		A building used for the preparation and launching of a commercial or military rocket, usually heavily reinforced. Not needed in hobby rocketry.
Blow-by		Can merely be the hot motor gasses escaping past the delay grain and igniting a motor ejection charge prematurely. Frequently caused in AT motors (if not assembled according to instructions) by the omission of that rubber washer on the front end of the forward closure.
Blowthrough		The physical ejection of propellant through the front of the rocket body. See CATO
Boat-Tail		A tapering section which reduces a rocket’s tail diameter, to improve aerodynamic efficiency through the reduction of base drag.
Body Tube		A cylindrical tube that makes up the body of the rocket. Typically made of cardboard, fiberglass or carbon fiber. See Airframe
Bonus Delay		Slang for an unexpectedly long delay, sometimes resulting in airframe damage or parachute stripping. See Zippering
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.
Boost Phase		That part of a rocket’s flight in which the propellant is generating thrust. Also known as Thrust Phase
Booster		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.
BOR		1.) Burned Out Rocketeer (facetious). Counterpoint to BAR. Someone who has been going at the hobby too intensely, such as in preparation for a major contest; 2.) Big Obnoxious Rocket
Boundary Layer		The very thin layer of fluid close to the surface of a solid in an airflow.
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.
BP		See Black Powder
BSMA		British SpaceModeling Association
Bucket Recovery		See Re-Kitted
Buckle		A bend or kink formed by overstressing the airframe.
Buffeting		Repeated forces experienced by a model due to disturbed unsteady airflow.
Built-Up		A hollow component, such as a fin, made up of a number of structural parts.
Bulkhead		A solid partition in the rocket, especially one set perpendicular to the rocket’s long axis, designed to not allow gases to pass.
Bungee		Round, woven elastic material, often used as shock cord in high power rockets.
Burn		The chemical reaction that occurs within a rocket motor producing a high velocity gas. See also Neutral Burn, Progressive Burn, Regressive Burn
Burn Rate		The rate at which a substance is consumed by burning, such as propellant or a fuse.
Burn Rate Catalyst		An additive used to increase the burn rate of a propellant (iron oxide is a typical catalyst)
Burn Rate Modifier		An additive used to increase or reduce the burn rate of a propellant
Burn Rate Suppressant		An additive used to slow the burn rate of a propellant (oxamide is an example)
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.
Burn Time		The time that it takes for a motor to fully expend its fuel.
Burnout		The point at which propellant is exhausted in a motor.
Burnout Velocity		The velocity achieved by the model at burnout.
Burst Disk		A thin disk whose purpose is to isolate propellants (or components of the propellant) until the motor is ready for operation
Butt Joint		A joint made by gluing an edge to a surface, such as a fin to a body tube.

C		Show only C's by clicking here
CA		Cyano Acrylate: a thin, very strong adhesive also known as Super Glue. Comes is gel, fast, medium, slow, black, (thicknesses/speedset) for different applications.
Cabosil		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.
CAD		Computer Aided Design
Caliber		1.) Ratio of a rocket’s diameter to its length. 2.) In rocketry, the diameter of the main body tube. Usually used when refering to some function of length, e.g. "The CP should be behind the CG by at least one caliber." The term is borrowed from the small arms industry where it refers to the bore of a rifle or pistol barrel, e.g. a .38 caliber pistol has a barrel with a .38" bore. Note that in large artillery, caliber refers to the ratio of barrel length to bore. For example, a 3 inch 40 caliber gun would have a barrel 120 inches long. See One-Caliber
Camber		The increase in curvature of an airfoil along its chord.
Cambered Airfoil		An airfoil (wing) on which only the top surface is tapered, the bottom surface remaining flat.
Camouflage		A paint scheme used to conceal an object in its background.
Canard		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 style or to be true to a scale representation.
Candy Motor		See Sugar Motor
Canopy		The fabric of the top of a parachute.
Canted Nozzle		A nozzle positioned so that its line of thrust is not parallel to the direction of flight. See Vectored Thrust
Cantilever Beam		A projecting member, fixed at one end rigidly and free at the other. Wings and fins are both cantilever beams.
Capacitive Discharge		A type of launch controller which uses a large capacitor to store electrical energy from a battery. When commanded by thelaunch controller, the capacitor discharges a large current into the igniter. These controllers are often used with large cluster rockets to ensure all motors ignite simultaneously.
CAR		Canadian Association of Rocketry reflecting changes in the CARS regarding rocket associations.
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
CARDE		Canadian Armament Research and Development Establishment. Now known as DREV - Defence Research Establishment Valcartier.
CARs		Canadian Aviation Regulations. Regulations affecting hobby rocketry are in Sections 101.01 (definitions) and start at 602.42
Case Rupture		The splitting of the motor due to excessive pressure in the combustion chamber.
Case, Casing		The outside framework of a rocket motor.
Cast Propellant		A solid propellant formed by the pouring of a soft propellant into a mold to solidify into a hard grain. See Grain.
Casting Tube		A tube in which propellant is cast, typically cardboard
CATO		Is short for "catastrophic failure". A violent failure of the rocket motor casing, closures, or nozzle. This usually occurs at lift off, and often results in the destruction of the airframe. The exact meaning of CATO is in dispute. Origin: Opinions on the meaning of the acronym range widely. Some say it's not an acronym at all, but simply a contraction of 'catastrophic' and should be pronounced 'Cat-o'. Others maintain that it is an acronym but disagree on the meaning, offering a broad spectrum of 'CAtastrophic Take Off,' 'Catastrophically Aborted Take Off,' 'Catastrophe At Take Off' and the self referential 'CATO At Take Off.' However, it has also been stated that rockets do not "take off". They either "launch" or "lift off" or (in the distant past) "blast off". Aircraft "take off". The acronym crowd pronounces it 'Kay-Tow', like the Green Hornet's side kick. It has been pointed out, though, that all of the above are 'post-hoc' definitions since LCO's were using the term over range PA systems long before any formal acronym was established. Opinions on the origins say that it is either from the military rocket programs of WW II, the post war development era, or even a modroc-only term which originated with the MESS (Malfunctioning Engine Statistical Survey) performed by NAR's Standards and Testing committee. There is also a claim that it started with the Boston Rocket Club and that the spelling has evolved over the years. It supposedly started out as 'KATO' which, of course, stood for KABOOM At Take Off!
CD		Contest Director; also Compact Disk if not shooting rockets
Center of Gravity		The point at which a rocket balances when completely prepped for flight.
Center of Pressure		The point at which the aerodynamic lift on a rocket is centered. See also EMRR's Center of Pressure Library.
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.
CFR		Code of Federal Regulations
CG		See Center of Gravity.
CHAD		Slang term meaning Cheap and Dirty. Most common usage is CHAD-staging, in which a booster motor is attached to the rear of a rocket motor in a single-stage rocket.
Checklist		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.
Chlorates		A class of chemical which is extremely dangerous when used as a rocket propellant
Chord		The short dimension (front-to-rear) of a glider’s wing. See Span.
Chuff		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.
Chuffing		Intermittent burning of a rocket motor, accompanied by the sound of a steam engine starting.
CIAM		International Aeromodelling Commission of FAI, which includes among other hobby disciplines, Spacemodelling (model rocketry)
CLA		Center of Lateral Area; the balance point determined by the Cardboard Cutout Method of determining CP. See Cardboard Cutout Method.
Class B Motors		Rocket motors containing more than 62.5 grams of propellant or motors that impart more than 120 newton-seconds of thrust.
Class C Motors		Rocket motors contain less than 62.5 grams of propellant or impart 120 newton-seconds of thrust or less.
Clean		A rocket design that is streamlined and free of projections.
Clip Whip		Short extensions at the end of a launch system with microclips.
Clone		A rocket that is built to exactly replicate another produced rocket, it is often an Out of Production (OOP) rocket
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.
Closure		The front and rear sections of a reusable motor assembly, which connect to the motor casing by threads, snap rings, or other method.
CLSO		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
Cluster		See clustering
Clustering		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 center of gravity. See also Vectored Thrust.
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.
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=.5rhoV^2CdA where F is the drag force, rho is the air density, V is the air velocity and A is the cross sectional area. All of these, except Cd, are directly measurable in a wind tunnel so Cd can be thought of the "fudge factor" that accounts for all of the aerodynamic peculiarities of a shape. The Cd for most sport type hobby rockets is in the range of .4 to .5. See also Reynolds Number.
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.
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.
Competition Model		Model whose design is optimized expressly for a particular competitive event.
Component		A manufactured part required to assemble a model, such as fins.
Composite		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.
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.
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
Concentric		Having a common center.
Cone		See Nose Cone
Cone Stability		The inherent stability of conic shapes to fly without fins provided the CG is ahead of the CP.
Configuration		The arrangement of fins, wings and other parts of a rocket or aircraft.
Conic		Of or pertaining to a cone.
Coning		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.
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.
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 always the motor code (currently 1/4A thru G) and the suffix is either an "A" for altitude events or "D" for duration events if such a distinction needs to be made (some events, such as parachute duration, have the suffix "built in" to its name, thus don't use one). A futher appendage is the use of "MR" for "Multi-Round" events where you make several flights and pick the best ones. Lastly, there is a set of scoring acronyms used in judging the events, but are not part of the event itself. Event Acronyms: BG - Boost Glider DEL- Dual Eggloft DR - Drag Race EL - Eggloft Single FW - Flexwing BG HD - Helicopter Duration OSL - Open Spot Landing PAY - Payload PD - Parachute Duration PMC - Plastic Model Conversion PRA - Predicted Altitude PRD - Predicted Duration PSL - Parachute Spot Landing R&D - Research & Development RDA - Random Altitude RDD - Random Duration RC/RG - Radio Controlled Rocket Glider RG - Rocket Glider SC - Scale (often seen written out) SCA - Scale Altitude (sometimes seen as Sc.Alt) SD - Streamer Duration SL - Spot Landing SPSC - Sport Scale SPSY - Space Systems SR - Superroc SSL - Streamer Spot Landing STA - Set Altitude STD - Set Duration SUSC - Super Scale Note that there is an ambiguity in the Eggloft event notation. "DELA" could mean the generic Dual Eggloft Altitude event or D Eggloft Altitude. For this reason, the prefixes are normally separated from the event acryonym by spaces. Flight Card/Results Acronyms: BRK - Broken Egg or EGG - Broken Egg CATO - obvious, I hope DQ - Disqualified flight NC - Track Not Closed NG - No Glide NR - No Return PRG - Prang ROT - No Rotation SHR - Shread TL - Track Lost
Continuity		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.
Control Surfaces		Surfaces such as flaps and elevons used to control the attitude of a rocket or glider aerodynamically.
Copperhead ™		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 mastered the "Z-Fold" which allows use of normal alligator clips.
Core		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.
Core Ejection		Ejection of a central pod holding the motor from the rear of the model.
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
Countdown		The process, usually marked in seconds counting down to zero, of the final preparation and launch of a rocket.
Coupler		A section of tube used to connect 2 sections of larger body tubing.
Covering		Material covering the framework of a structure.
CP		See Center of Pressure.
CPR		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.
CPSC		Consumer Product Safety Commission. Rules restrict use of HPR motors (H and up) to adults 18 years of age and up.
Craze (Crazing)		Cracking of paint or fogging of acrylic resin due to incompatibility of paint, primer, adhesive, and/or material.
Cross Section		The area exposed if a part is cut through.
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
C-Slot		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
Cyanoacrylate		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.

D		Show only D's by clicking here
Dart		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 the entire vehicle. As the booster begins to slow during the coasting phase, its greater drag causes it to fall away from the dart which continues to ascend to a higher altitude.
Data Reduction		The procedure for transforming raw instrumentation data into useful parameters
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.
Death Dive		See Power Prang
Decalage		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.
Deceleration		A reduction of velocity.
Deflection		Bending or displacement from the neutral position due to loading from some outside force.
Deflector		See Blast deflector
Degassing		The processing of a propellant using vacuum processing; reduces bubble that may make the burn less uniform or even cause a CATO
Delay		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 delay grain begins to burn either at the same time the propellant grain is ignited (composite motors), or at the end of propellant ignition (black powder motors). When the delay grain burns through, it ignites the deployment charge. Also, the period of time between propellant burnout and recovery system deployment.
Delrin ™		A tough resilient plastic (acetal resin) that is used for rail buttons
Delta Wing		Wing planform in the shape of a large triangle, used for supersonic flight conditions.
DeltaV		Change in velocity
Density		Ratio amount of a substance in a set volume.
Deployment		The condition of releasing, or deploying, a parachute or other recovery device.
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.
Deployment Charge		The pyrotechnic charge which pressurizes the part of the rocket containing the recovery system, deploying the recovery device.
DESCON		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 readers of the newsgroup who had extra goodies underfoot and wanted to put them to good use.
Desert-Squid		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].
Dethermalizer		A device designed to ruin the aerodynamic properties of a aircraft, enabling it to safely escape a thermal and return to the ground.
Dhanook		To be tricked due to suffering a bad case of launch happiness.
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.
Dihedral Angle		The angle at which a glider’s wing tips tilt upward from the horizontal plane, to impart roll and yaw control.
Direct Staging		Air start of a sustainer motor caused by the burning propellant of the booster motor.
Directional Stability		The ability of an aircraft to return to its original flight direction after being forced off course.
Display Launcher		A launcher that is not functional and is used to show off a model.
Dive		Motion of an aircraft in a head down or nose down attitude.
DIY		Do It Yourself
Dog Barf		Slang for flame retardent cellulose insulation, as used as recovery wadding; see wadding
Dope		A liquid lacquer based paint used to seal the grain of wood.
Doppler Effect		Change in sound frequency caused by the source’s rapid movement towards or away from the observer.
Dorcasitis		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.
DOT		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.
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 vehicles. Double base propellants are not used in hobby rocketry. See also Composite
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.
Downdraft		The movement of a column of cooler air downwards, opposite to a thermal.
Downscale		The practice of building smaller versions of larger model rockets. See Downscale Rocket Articles.
DQ		Slang for disqualification
Drag Coefficient		See Coefficient of Drag
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 Zeppelin would be the same. Multiplying by the area allows comparisons of the true drag between dissimilar objects. For example, the original Honda Civic had a horrible Cd, and makers of large luxury cars, with a little edge rounding, were easily able to beat it and proclaim "Lower drag than a Honda Civic!" in their ads. This is patently absurd as the Honda had such a tiny cross section, thus much lower actual drag. See also Optimum Mass
Drag Race		An event, usually informal, in which multiple rockets are launched simultaneously.
Drag Recovery		Recovery method using the shape of the model to slow the model down enough for safe recovery.
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 faster (or, more correctly, the body's drag decelerates it more quickly) putting tension on the nose-body joint. The condition is exacerbated by any nose weights added for stability (which also raise the momentum of the nose) and/or a loose fit of the nose in the body. Another possible contributing factor could be the denser air (trapped in the body tube from ground level) exerting pressure on the nose cone once the rocket reaches a higher altitude.
DREV		Defence Research Establishment Valcartier. Formerly known as Canadian Armament Research and Development Establishment.
Drilling For Oil		See Core Sample
Drogue Parachute		Small, heavily reinforced parachute designed to slow the craft so safe release of the larger main chutes are possible.
DSE		Detectable Seismic Event; see Power Prang also know as Death Dive
Dual Deployment		See Dual Recovery
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.
Dullcote ™		A spray coating from Testor’s Corp. that protects the finish of a model while removing the sheen of the finish.

E		Show only E's by clicking here
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); See also HSA, LEUP, and LUP
Econojet		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.
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.
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.
Ejection Cannon		A tube or fitting that holds the ejection charge and is attached to the rocket
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.
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 and may not reliably ignite composite motors unless dipped in additional pyrogen.
Electronics		Any of a number of electronic devices used in rocket flight, e.g. Altimeters, Timers, etc.
Elevation		An angle on a vertical plane. See Azimuth
Elevator		A moveable surface on the horizontal stabilizer of an aircraft. The surface is responsible for pitch control.
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
E-Match		Slang for electric match
EMRR		Acronym for Essence's Model Rocketry Reviews, that's here
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
Engine		A device that uses energy to produce mechanical motion. In rocketry, the term is often used interchangeably with Motor, though Motor is the more accurate term. See Motor
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 unsed interchangeably with Thrust Ring. Without a engine block (or thrust ring), the friction fit technique would need to be used.
Engine Hook		See Motor Hook.
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
Epoxy		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 phenolic), forming a strong, hard, resistant adhesive. Epoxy is probably the most commonly used adhesive in high power rocket construction. It comes in several formulations, mostly having to do with the time it takes to cure. Epoxy’s only disadvantages as a rocketry adhesive are its relatively high weight and its low (approx. 200o F.) melting point.
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.
EX		Acronym for Experimental Rocketry
Exhaust Clearance		On some models, the amount of offset required to prevent damage to parts below the motor nozzle from the motor exhaust.
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.
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
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 some clubs and launches operate outside of the TRA, most organized Experimental Rocketry is performed at TRA-sanctioned launches and follow the Tripoli Research Safety Code. Because making your own propellant is potentially dangerous, people who enter this field should study and understand the theory and follow safety precautions. See also Amateur Rocketry
Explosives Act		Canadian law defining and governing the use of all explosive substances outside the Canadian Armed Forces.

F		Show only F's by clicking here
FAA		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.
FAI		Federation Aeronautique International
Fairing		Rigid or semi-rigid coating used to streamline the airflow around a rocket component sticking out in the airflow.
FAR101		FAA regulations regarding airspace use for hobby rocketry.
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.
Fiberglass (tm)		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 is actually a trade mark of Owen-Corning Inc. See Pseudo-Glassing
Fill 'n Finish		Elmer's brand Carpenter's Wood Filler; a common filler for balsa fins, fillets, etc.
Filler		A substance applied to a surface to fill gouges in the surface or help shape the surface. See Wood Filler.
Fillet		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.
Fin		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.
Fin Alignment Jig		A device used to align and hold in place fins to a body tube.
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).
Fin Canister		A section of tubing with fins mounted on it, intended to slide over the airframe. Also called a fin can.
Fin Flutter		See Flutter
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)
Fin Wraps		See Paper Lamination
Finishing		The art of giving a model a smooth, streamlined outside surface. Click here for some great finishing ideas.
Firewall		A bulkhead designed to prevent fire from passing that point.
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.
Flap		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.
Flashbulb		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 attribute also makes them susceptible to accidental activation by static electricity.
Flashpan		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 motors in the cluster simultaneously. CAUTION: This technique presents dangers when used with black powder, and must NEVER be used with composite motors which ignite from the front.
Flat Spin		A spin around the short axis of a rocket while the craft is descending in a horizontal attitude.
Flex Wing		A wing that employs a thin flexible for the main lifting surface stretched over a semi-rigid frame.
Flight Card		A card (sometimes a log book entry) that is used to record the pertinent details of a flight at organized launches
Flight Line		The area at a launch site where rockets are prepared by participants. The forward-most area where spectators are permitted.
Flight Path		The line connecting successive positions of an aircraft while in flight, relative to the ground.
Flight Profile		A graphic representation of a aircraft’s flight as seen from the side, showing its position and altitude.
Flightworthy		An aircraft or rocket, having undergone inspection and possibly testing, that has been determined to be ready and sound to fly.
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
Flutter		An oscillation of regular period but irregular amplitude caused by a momentary disturbance but maintained by the characteristics of the fluttering component.
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.
FnF		see Fill 'n Finish
Foam Board		Paper-backed syrofoam sheets used for displays and posters; may be used for fins and centering rings
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.
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.
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 intergral black powder ejection charge. See also Rear Closure
Free Flight		Unconstrained and unassisted flight of a rocket, relying on the rocket’s inherent stability.
Freefall		The fall of an object without guidance or retardation other than through drag.
Friction		The resistance an object encounters while moving across the surface of another object.
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.
Frontal Area		the surface area of a rocket which faces directly into the airflow.
FRS		Family Radio Service; these 2-way radios are commonly used at launches both for voice and occasionally telemetry
Fuselage		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.
FWL		Fast White Lightning; a fast version of Aerotech's White Lightning propellant

G		Show only G's by clicking here
G10		A grade of fiberglass commonly used for fins on high power rockets. G10 designates a laminate made of fiberglass cloth laid in epoxy resin.
Gantry		A crane and scaffolding arrangement, mounted on rails, used to service a fullsized rocket while on the launch pad.
Giant Scale		A Sport Scale event where the models cannot be smaller than a given minimum size. Contrast Peanut Scale
Glandular Conditions		a general, less common, term for upscaling and downscaling
Glassing		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
Glide		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.
Glide path		The descent of a gliding air vehicle as viewed from the side.
Glide Ratio		The ratio between distance traveled horizontally and the amount of vertical drop.
Gliding Booster		A booster stage whose fins are placed asymmetrically and is balanced to achieve a glide after ejecting from the rocket.
Global Positioning System		See GPS
GLOW		Gross Lift Off Weight - The mass of a rocket completely prepped for flight.
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"
Goonybird		A rocket design series sold by Estes from 1973 -1975. They were described as the "Zaniest flying freaks in the universe".
Gore		The rounded triangular section of fabric between two longitudinal seams or shrouds in a parachute canopy.
Gorilla Glue		A popular brand of polyurethane glue, alternative to Elmer's ProBond Polyurethane glue. Learn more
GOX		Gaseous Oxygen
GPS		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.
Grain		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
GSE		Ground Support Equipment
g-Switch		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 seconds after the Gswitch closes an electrical circuit, at the end of which time the timer closes a second circuit which activates a deployment charge or sustainer motor igniter.
Gusset		A roughly triangular shaped piece of material added to reinforce a joint, often in a corner.
Gyroscope		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.

H		Show only H's by clicking here
Hand-Launch-Glider		A small robust glider designed to be launched by hand.
HARM		High-Speed Anti-Radiation Missile. See ARM.
Hatch		A door in the side of a spacecraft or aircraft.
HAZMAT		hazardous materials; term normally used in relation to shipping/transportation
HD		See Helicopter Duration.
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
Heads-up		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 that the rocket will crash in an area containing people.
Headwind		Wind blowing generally into the front of an aircraft, thereby slowing its ground speed.
Heat Shrink Tape		A heat sensitive tape that shrinks when heat is applied; used in place of vacuum bagging for laminating tubes
Helicopter Duration		A competitive event in NAR-sanctioned launches, using rockets with helicopter recovery.
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.
Hershey Bar Wing		A rectangular wing, with no taper on either the leading or trailing edge.
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.
HLG		See Hand-Launch-Glider
Honeycomb Core		A diamond-pattern woven material which looks and behaves somewhat like the inside of corrugated cardboard; used for making light composite structures
Hot Wire Cutting		A technique for cutting styrofoam using a wire which is electrically heated.
HPR		1.) 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); 2.)Depending on the context, may also refer to the title of the TRA's journal.
HSA		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 purchase and/or use involved interstate commerce or transportation. See also LEUP
HTPB		Hydroxyl-terminated polybutadiene; a common binder used in composite fuels. See Binder
Hybrid		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 Hybrid
Hypergolic		An arrangement of liquid fuel and oxidizer which ignites spontaneously when combined.
Hypersonic		Term used to describe a vehicle exceeding Mach 5.

I		Show only I's by clicking here
IAR		Independent Association of Rocketry.
ICBM		Intercontinental Ballistic Missile.
ID		Inner diameter; the ID is what is specified in standard tube sizes; i.e. 18mm, 29mm. Contrast OD
Igniter		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 hot and ignite the surrounding propellant.
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.
IMHO		In My Humble [Honest] Opinion
Impulse		Thrust force multiplied by time. The units of measurement are usually Newtons and Seconds.
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 Velocity." How quickly the reaction mass leaves the nozzle is a good measure of efficiency.
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 thrust both being force parameters hence canceling out (e.g. lb-sec/lb or N-sec/N). This is actually very handy since it makes the term independent of the units system (metric or English) since they both use "seconds" for time.
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.
Inclinometer		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 at which it is held. Since two angles and the distance between the rocket’s point of origin and the inclinometer are known (assuming that the rocket is launched vertically), a triangle can be graphed which will indicate the apogee attained by the rocket. See Theodolite
Indian Fire Brigade		derisive term for stomping out grass that has caught fire.
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.)
Induced Drag		Drag resulting from lift generated by the foils and lifting body of a aircraft or rocket.
Injector		In a hybrid motor, the unit that introduces the nitrous oxide into the combustion chamber
Injector Throat		The opening in the Injector housing. See also Throat
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
Interstage		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.
Isp		Symbol for Specific Impulse

J		Show only J's by clicking here
J		The identifier for Aerotech's Black Jack propellant; "provides the high visibility tracking of dense black exhaust"; the most difficult Aerotech propellant to ignite
Japanese Tissue		A thin tissue used by aeromodelers to cover the frames of model aircraft; often used to cover the surface of balsa fins
JATO		Jet Assited Take Off; despite the term 'jet', this is basically the same as RATO; this may be the more common term
Javelin In		See Lawn Dart
Jet Deflector		See Blast Deflector
J-Foil		A self-inflating parachute airfoil developed by Domini C. Jalbert. It is very maneuverable and is the current standard airfoil in skydiving parachutes.
JIC		Just In Case: Any precaution taken to avoid trouble, such as sanding residue off igniter clips.
Jig		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.

K		Show only K's by clicking here
Kaplow Clip		A popular type of motor retainer designed by Bob Kaplow.
Kevlar (TM)		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 rather than to the open end of the airframe. This design is less susceptible to zippering and burning. Larger-diameter Kevlar cord is increasingly being used as shock cords on high-power rockets for the same reason, and because Kevlar is stronger than bungee or elastic straps. Kevlar is also woven into sheaths or bags, and used to protect elastic shock cords and parachutes in larger rockets. See Deployment Bag
Kicker		A liquid, usually of the Freon family, used to accelerate the set time of cyanoacrylate adhesive.
Kitbash		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) where the idea is to be creative in a limited amount of time. See Kitbash Articles.
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.
KN		Potassium nitrate (KNO3); the oxidizer used in 'sugar' motors
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.
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 which allows the exhaust gasses to expand below atmospheric pressure before leaving the rocket. Surrounding air aspirated into the exhaust stream causes turbulence which negates much of the thrust, along with creating the characteristic roar. A multi-stage model that ejects its booster motor, but not the airframe, is a perfect example. Very damaging; it almost always destroys the lower body tube beyond use. Named for Richard Krushnic, the rocketeer who characterized the effect in the late '60s. Not to be confused with Suction Lock

L		Show only L's by clicking here
L1, L2, L3		Levels one through three: reference to the three levels of high power rocketry certification.
Lake Stake		A lawn dart or core sample on the playa.
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.
Laminated Wood		Wood made from of multiple layers, commercially made plywood being the most common example.
Land Shark		The condition in which a rocket, for whatever reason, fails to attain air flight and slides along the ground under power.
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.
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.
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.
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.
Launch Pad		An assembly containing the launch rod or tower and blast deflector if any, which permits the rocket to remain steady until launched.
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 the launch rod.
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.
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.
Laundry, The		Slang term for recovery components, especially the parachute(s)
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).
LBP		Live Biological Payload. Transport of any vertebrate animal is currently in violation of all rocketry safety codes.
LCO		Launch Control Officer. Person in charge of controlling the range and launching rockets.
LDRS		Large and Dangerous Rocket Ships: the name of the annual TRA launch.
Leading Edge		The front edge of a wing or fin.
LEO		Low Earth Orbit; an orbit below 1000km
LEUP		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 transportation is involved
LEXAN(tm)		One of the toughest and most versatile engineering thermoplastics; often used for clear fins; made by GE Plastics
Lifting Body		a wingless aircraft whose body generates the lift required to fly
Liftoff Mass		See GLOW
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.
Lite-ply		A model builders plywood, noted for its low density.
LMS		Loadable Motor System - a new (2007) type of motor system by Aerotech. Essentially a single use motor that is assembled by the consumer.
Load Cell		An electro-mechanical sensor that converts force or weight into an electrical signal; used in motor test stands
Longneck Rocket		On EMRR, a rocket whose length to width ratio is 30:1 or more
Lovelace Effect		See Drag Separation
Low Power		Typically rockets flying on motors in the A to D range.
LOX		Liquid Oxygen
LPR		See Low Power
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.
Lug		See Launch Lug.
LUP		Limited Use Permit; a federal permit which allows limited purchase and use of HPR motors within your state of residence; still requires approved storage
LV		Launch Vehicle

Show only M's by clicking here

M.O.P.S.

Used for Mods, OOP, Plans and Scratch. This was added as a section to EMRR to differentiate stand product reviews from these other articles.

MAAC

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

Mach Buster

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

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.

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.

MAD (tm?)

Magnetic Apogee Detector. See scratch-build article click here

Magazine

An ATF-approved storage device for large rocket motors and other lowexplosive devices.

Mandrel

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

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 ratio of under 10 typically will be stable with under one caliber of static margin.

Mass Ratio

Final mass (after propellant burn) divided by initial mass.

Maximum Thrust

The peak thrust a motor generates.

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 pointed in the intended direction. When it is windy the angle of attack of the fins is not zero and under some circumstances where the thrust to weight ratio is low and the velocity is too low, the fins will stall and the rocket will do funny things. Underpowered rockets may pinwheel in the air in moderate crosswinds. A good rule of thumb is a 5:1 thrust to weight ratio on windless days, and a 10:1 ratio on a windy day. Also the longer the launch rod, the higher the allowable weight all other factors being equal. See also Stability and EMRR's Maximum Liftoff Weight Calculator

Max-q

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.

Mean Chord

A wing’s root chord plus its tip chord, divided by two.

Medusa Nozzle

A nozzle which has multiple exit ports.

MEK

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

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 launches, acceleration forces hold the mercury drop at the bottom of the bulb, away from the electrical contacts. When the rocket’s acceleration ceases, the mercury - which is a heavy metal and stores considerable momentum - moves forward in the bulb, bridges the gap between the contacts, and closes the electrical circuit. The electrical circuits controlled by mercury switches are most commonly used to activate recovery system deployment charges or sustainer motor igniters.

MESS

Malfunctioning Engine Statistical Survey; the NAR's mechanism for gathering motor failure data

Micro Balloons

Tiny glass globules which are sometimes added to epoxy adhesive in applications like fin fillets, to reduce weight.

Micro Bubbles

See Micro Ballons

Micro Engine

The series of 10.5mm engines produced by Apogee Components; production is currently halted

Micro Grain

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

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

Microclips

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

MicroMaxx Engine

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

Mid Power

Typically rockets flying on motors in the E to G range.

Mid-body Ejection

The practice of placing a rocket’s separation point midway up the body tube, helping to prevent tube zippering.

MIF

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."

Mini Engine

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

Minimum Diameter

a model whose diameter is just large enough to accommodate its motor.

MLRS

Multiple Launch Rocket System

MMX

acronym for Quest MicroMaxx motors.

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 impulse and/or contain more than 62.5 grams of propellant each, and no more than 125 grams of propellant in multiple motor configurations. All components of model rockets must be of wood, paper, rubber, breakable plastic or similar material and without substantial metal content.

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 bewildering array of changes in format over the years, but is still published three or four times annually.

Modroc

Slang for Model Rocket.

Module

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.

Moment

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

Momentum Thrust

The component of a motor's thrust due to the expulsion of gas

Monocopter

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

Monokote

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

Moonburner

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

Motor

A device that imparts motion through reaction.

Motor Adapter

A replacable unit which allows a smaller diameter motor to fit in a motor tube.

Motor Clip

See Motor Hook

Motor Code

The accepted method of expressing the characteristics of a particular motor. Motor power ranges (total impulse) are expressed with letters A through N. Each letter expresses a power range twice as powerful as the preceding range. The power ranges are as follows:

MOTOR CLASS	MINIMUM NEWTON-SECS	MAXIMUM NEWTON-SECS
¼ A	0.0	0.625
½ A	0.626	1.25
A	1.26	2.5
B	2.51	5
C	5.01	10
D	10.01	20
E	20.01	40
F	40.01	80
G	80.01	160
H	160.01	320
I	320.01	640
J	640.01	1280
K	1280.01	2560
L	2560.01	5120
M	5120.01	10,240
N	10,240.01	20,480

The motor code is expressed as a letter followed by a series of numbers. For example, C6-3, in which C is the power range (5.01-10 Newtons), 6 is the average thrust in Newtons, and 3 is the delay time in seconds(counting from propellant burn-out).

Motor Diameter

The diameter of a hobby rocketry motor casing. Most commerciallymanufactured 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.

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 only used in LPR.

Motor Mount

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

MPR

See Mid Power

MRN

See The Model Rocket News

Murphy’s Law

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

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.

Mylar (tm)

an extraordinarily strong polyester film made by DuPont; commonly used for parachutes

N		Show only N's by clicking here
NAA		National Aeronautics Association
NACA		National Advisory Committee for Aeronautics; predecessor to NASA
NAR		National Association of Rocketry, Visit NAR
NARAM		National Association of Rocketry Annual Meet: The annual week-long launch hosted by the NAR.
NARCON		The annual NAR convention.
NARTREK		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.
NASA		National Aeronautics and Space Administration
Neck Snapper		A motor & Rocket combination that leaves the pad too fast for the eye to follow.
Neutral Burn		When the thrust of the motor is relatively flat throughout the burn. See also Burn, Progressive Burn, Regressive Burn
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)
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.
Newton		The amount of force required to accelerate one kg, one meter per second per second. 4.45 newtons equals one pound of force.
Newton-Second		The typical unit of measurement for rocket thrust. One newtonsecond is one newton of thrust maintained for one second.
NFPA		National Fire Protection Association - Private corporation for setting safety standards.
NFPA 1122		Standards code for U.S. Model Rocketry.
NFPA 1127		Standards code for U.S. High Power Rocketry.
Nichrome		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.
Night launch		A launch conducted after sunset; requires an FAA waiver
Nike Airfoil		See Diamond Airfoil
Nitrous Oxide		(N2O)Gaseous oxidizer used in current hybrid rocket motors. See Hybrid and Micro Hybrid
No Joy		When a rocket motor fails to ignite. Useage: no joy on pad 13.
Nomex (tm)		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
Non-Survivable Event		see Prang
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 sections together.
Nose Blow Recovery		Recovery method for light models by simply ejecting the nose cone and having it come down attached on the shock cord.
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; by using a longer cone, or by adding weight to the cone.
Nose Heavy		The condition in which a glider is trimmed into a dive or a rocket has excessive mass in the nose.
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.
NOX		abbreviation for nitrous oxide
Nozzle		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
NSL		National Sport Launch: an annual three-day launch hosted by the NAR.

O		Show only O's by clicking here
OD		Outer (or outside) diameter. Contrast ID
Oddroc		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 sometime don't!)
Ogive		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.
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.
OOP		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.
Opacifier		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
Open Breech		A piston launcher in which the motor travels up the piston tube and engages the motor mount. See Piston Launcher
Optimum Mass (Weight)		The mass required to lift a rocket to the highest possible altitude on a given motor.
Orange Book		BATFE explosives rule book. See BATFE
O-Ring		A rubber gasket used to contain gasses in solid rocket motors
Oscillation, Parachute		The swinging from side to side of a payload under a parachute.
Outboard		Direction parallel to the lateral axis of the rocket and perpendicular to the centerline.
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.
Over-Expansion		See Krushnic Effect.
Oxidizer		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 as a rocket propellant.

P		Show only P's by clicking here
Pa		Atmospheric pressure, 14.6 psi
Pad Manager		Person responsible for assigning pads and controlling the launch pad area. Helps rocket flyers set up pads and rockets for flight.
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.
Parachute		A piece of plastic, cloth, nylon, or other material, shaped something like an umbrella when deployed, which slows the descent of a rocket.
Parachute Duration		A popular competitive event in NAR-sanctioned launches.
Parafoil		A parachute-like device which has an airfoil structure; may be steerable.
Paraglider		A flexible, kite-like glider deployed like a parachute and designed to be a recovery device.
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.
Parasheet		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.
Parasite		Usually, a glider which is boosted into flight by being attached to the airframe of a model rocket which is modified to accept it.
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.
Payload		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.
Payload Section		A portion of rocket airframe set aside for payloads. Also called payload bay.
PBAN		Polybutadiene Acrylic Acid Acrylonitrile Prepolymer; another binder used in composite propellant. See Binder
PD		See Parachute Duration
Peanut Scale		A Sport Scale event where the models cannot be larger than a given maximum size. Contrast Giant Scale
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 links for more information: http://en.wikipedia.org/wiki/Pendulum_Rocket_Fallacy and http://www.geocities.com/jim_bowery/pendrock.html
Permeability		The measure of diffusion or "leakage" of gas through a fabric. The permeability determines the rate of descent.
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
Phenolic		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. Phenolic airframes are made by impregnating paper with phenolic resin, then tightly winding it into a tube and allowing the resin to cure. The word phenolic is often used to describe any body tube which contains phenolic resin.
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.
Piano Wire		See Music Wire
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.
Pink Book		The common name for the NAR Contest Rules Manual. See NAR and Contest Acronyms
Pinwheel		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.
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.
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.
Pitch		A back-and-forth motion of the nose of a rocket in flight, on the axis determined as "up-and-down". See Yaw.
Planer		A tool to shave thin slices of material in order to shape or smooth the material.
Planform		The geometric shape of a wing or fin.
Plastic Model Cement		A mixture of solvent and styrene plastic used to adhere plastic to plastic or plastic to paper.
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.
Plasticizer		An additive which makes a composite propellant softer and more flexible
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.
Plugged Motor		A motor made with a solid bulkhead in the front end, blocking any passage of ejection gases into the airframe.
PMC		See Plastic Model Conversion
Polyhedral		A wing broken up into multiple panels, angled in relation to each other.
Polystyrene		A solid plastic made from polymerised styrene
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
Pond Dart		Same as Lawn Dart but in the Pond
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.
Pop-Lug		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, Photographer’s Flash Powder etc. So called because of the distinctive "pop" that occurs when the mixture is ignited. Can be dangerous if too much powder is used since this can potentially damage the nozzle and thereby cause a catastrophic motor failure (CATO).
Potassium Nitrate		An oxidizer used in black powder and 'sugar' motors; see Sugar Motor
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.
Prang		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 airframe by ground impact.
Prefect		The head of a TRA Prefecture, or the designated person, to maintain a line or communications with, or to see compliance to, the TRA.
Prefecture		A club or group affiliated with the TRA.
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.
Pressure Thrust		The component of a motor's thrust due to the difference in the chamber and ambient pressures
Primer		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.
PRM		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)
Pro38		A 38mm reloadable solid propellant motor system produced by Cesaroni Technology Incorporated (CTI).
Pro54		A 54mm reloadable solid propellant motor system produced by Cesaroni Technology Incorporated (CTI).
Progressive Burn		When the thrust of the motor increases throughout the burn. See also Burn, Neutral Burn, Regressive Burn
Propellant Mass Fraction		The propellant mass divided by initial mass.
Propulsion		1. a propelling or being propelled, 2. something that propels, a driving force (Webster)
Propulsive Chaff		(Brit.) The remains of a shredded rocket while still airborne.
PRS		Pacific Rocket Society - An amateur rocketry organization.
PSAN		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
Pseudo-Glassing		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
Pseudo-Scale		A model designed and decorated to appear to be a scale model.
PTFE		Tetrafluoroethylene; See Teflon(tm)
Pumpkin Seed Effect		See Watermelon-Seed Effect
PVC		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
Pyrodex (tm)		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
Pyrogen		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
Pyrotechnic		Of or pertaining to fire or explosion. The term is most commonly used with reference to fireworks.

Q		Show only Q's by clicking here
Quantum Tube (tm)		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, epoxy and urethane, as well as many different primers. The Quantum Tube can be squeezed, dropped, or even thrown and will not suffer any damage as can sometimes occur to cardboard or phenolic tube. The Quantum Tubes are molded in medium gray and have a glass smooth finish. The Quantum Tube does have one thing missing: the spiral groove!
Quasi-Glassing		See Pseudo-Glassing
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
Quik Tube		A brand of tubular concrete forms which are often used for large inexpensive airframes

R		Show only R's by clicking here
R.M.R.		The public domain rec.models.rockets newsgroup See for yourself click here
R.M.R. Descon		an on-line rocket design contest started by Dave Lee; Descon Website
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
Rail		See Launch Rail
Rail Button		A piece of plastic or metal that mates with a Launch Rail; forms a 'H' shape when viewed from the side.
Range		The launch site; or, the distance from an observer to a tracked object
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.
Rangehead		The part of a launch site where the pads are located.
RASP		Rocket Altitude Simulation Program; a public domain program that simulates the flight of a rocket in one dimension
RATO		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.
RC		radio controlled
RC/RG		radio controlled rocket glider
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.
Rear Ejection		The ejection of recovery device through the rear of a model.
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.
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".
Redline		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.
Reefed Parachute		A parachute whose shroud lines are restricted to prevent full opening of the canopy.
Regressive Burn		When the thrust of the motor diminished throughout the burn. See also Burn, Neutral Burn, Progressive Burn
Re-Kitted		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!"
Relayer		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.
Resin		an organic compound consisting of a non-crystalline or viscous liquid substance; see Epoxy
Retainer		A device for keeping the rocket motor from being ejected by the force of the deployment charge.
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 number combines the fluid's density, viscosity and velocity with the length it's traveled along the surface. No matter what the fluid is or what size the surface, the flow conditions (laminar, turbulent, detached, etc.) should be the same at the same Rn. Discovered by Osborne Reynolds inthe 19th Century while studying the flow of water in pipes andchannels, it has proven most useful to aerodynamic engineers and naval architects in scaling up wind/water tunnel test results to full size. Carl Dowd, a model aviator and NASA engineer, found it helpful to think of Rn as the "coarseness" of the air seen by a body. Move the body faster, and more particles will pass over it in a given unit of time, increasing Rn. Make the body larger, and there will be more particles over the body at any instant, increasing Rn.
RG		See Rocket Glider
Rigid Wing		A glider with wings using rigid airfoils rather than a parafoil or flexible wing.
Ring Fin		A fin which is comprised of a ring of tubing, typically larger than the rockets airframe and usually supported by standard fins.
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
RMR		See R.M.R.
RMS		Reloadable Motor System (has also been called Reusable Motor System). A solid rocket motor which can be re-fueled and reused.
Rocket Caviar		Mixture of lead shot and epoxy used for adding nose weight
Rocket Eating Tree		Any tree within the launch field; see Murphy's Law.
Rocket Eatumupuses		See Rocket Eating Tree.
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.
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 rocket containing 102 covers and cards from the Austrian town of Schöckl to the village of Radegund. This date is regarded as the beginning of rocket mail usage. On September 9, 1931 Schmiedl initiated the world's first official rocket mail service. Many countries soon followed suit. However, a number of spectacular failures, including the explosion of a canister containing some 30,000 pieces of mail in Northern Scotland, doomed rocket mailed service as a viable entity. Today rocket mail is primarily used for commemorative purposes.
Rocket Rotisserie		A home made device used to slowly rotate a rocket or component during painting, glassing, or sanding.
RockSIM		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 flights on your computer!
Rod Whip		The flexing of a rod during lift-off, which may cause the rocket to head off at an undesireable angle
Rogallo Wing		A flexible delta wing platform developed by Francis Rogallo that is popular for kites, hang-gliders and ultralights.
ROL		Acronym for Rocketry Online, one of the most comprehensive rocketry sites
Roll		Rotational motion of a rocket through the long (flight) axis.
Rolleron		A passive, mechanical roll damper mounted a rocket's fins. Consists of independently acting wing-tip aelerons with enclosed airstream-impelled gyros wheels.
Root Chord		The chord at the root of a wing or fin. See Chord.
Root Edge		The edge of a fin or wing that is glued to the airframe.
Rotor		A multi-bladed propeller used to produce lift or control the orientation of an aircraft.
Rotor Blades		Wing-like extensions, rotating around a central hub of a helicopter or autogyro.
Rotor Disc		The disc of space formed by the rotation of rotor blades.
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.
ROTW		Acronym for the book "Rockets of the World", by Pete Alway
RRS		Reaction Research Society - The oldest continuously-running amateur rocketry group in the United States.
RSO		Range Safety Officer. Person(s) responsible for field safety. Determines suitability of rockets to fly at a particular site. Inspects rockets prior to flight.
RTF		Ready to Fly. A rocket which is sold pre-built, as opposed to a kit.

S		Show only S's by clicking here
S&T		Standards and Testing; name of the NAR's committee that tests and certifies motors
Sabot		A spacer which is used to align a rocket in a tube launcher; may also seal the breach; is discarded after launch.
SAM		Surface-to-Air Missile
SC		See Shock Cord
Scale		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 also Stand-Off Scale
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.
SCO		Safety Check Officer (Deputy RSO)
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 Scott Towel Special.
Scratch-Built		A a rocket that is built from individual parts, as opposed to being bought as a kit. Many times these are original designs.
Screamer		A really, obnoxiously loud beeper.
Screw Eye		A headless screw on which the shaft is extended and formed into a circular eye.
Scrub		to cancel a launch attempt due to problems, technical or otherwise.
SD		See Streamer Duration.
Sealer		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.
Sears-Haack		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.
Self Packing		See Re-Kitted
Servo		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.
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.
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.
Shock Cord Mount		The attachment point for a shock cord.
Shotgun Recovery		A method of getting your rocket out of rocket eating trees using, well, a shotgun; recommended only as a last resort
Shoulder		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.
Shred		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.
Shredbury		UK Term: A town in the UK through which rockets pass through during a shred.
Shroud (Transition)		A piece of material, often card stock, used to smoothly allow the airframe to go from one diameter to another.
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.
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
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.
Skid Mark		A motor by Animal Works that produces a lot of flame, black smoke and sparks.
Skin		The thin outside surface of a hollow part or object.
Skywriting		Slang term for the smoke trail left by an unstable rocket which does not fly straight.
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
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 install/remove
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 shroud tangling.
SNI		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.
SNP		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.
Snuffer Tube		A small metal tube used to extinguish a wick such as in a dethermalizer.
Solar Igniter (tm)		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.
Solids Loading		The proportion of solids in a propellant formulation; increasing the solids loading has several effects, including increasing the Isp
Sonic Barrier		The zone of high air density caused by the compression wave of an object traveling near the speed of sound.
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 aircraft exceeds the speed of sound, these pressure waves combine and form shock waves which travel forward from the generation or "release" point. The sound heard on the ground as a "sonic boom" is the sudden onset and release of pressure after the buildup by the shock wave or "peak overpressure." 2.) Loud report caused by the passing of the compression front generated by an object as it exceeds the speed of sound.
Sonic Speed		The speed of sound at the current conditions of air density. humidity and temperature.
Sono Tube		A brand of tubular concrete forms which are often used for large inexpensive airframes
Sorbitol		An artificial sweetener, very similar in appearance and with similar physical characteristics to both sucrose and dextrose sugars; see Sugar Motor
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
SpaceCAD		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 material!
Spack		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
Spackington		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.
Span		The long (side-to-side) dimension of a wing. See Chord.
Spar		A long, thin, structural member of a airframe. Also, SPAR
SPAR		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.
Specific Impulse (Isp)		The total impulse of a motor divided by unit weight of propellant.
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.
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.
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.
Spinerons		Tabs attached to fins and set at an angle, intended to spin the rocket in order to stabilize it.
Spirals		The small (or larger) grooves in paper tubes that spiral up-down the length. They are induced by the tube wrapping manufacturing process
Spool Rocket		A rocket variation made from wire, cable, rope, etc. spools.
Sport Model		A model rocket designed and built with no specific purpose in mind other than to fly it.
Sport Rocketry		Rocketry activities pursued as a pastime, diversion, or personal enjoyment. Term is often used as a contrast to "competition rocketry."
Spot Landing		A competition event in which the goal is to land the model closest to a predetermined spot on the launch field.
SpRocketry		Abbreviation for Sport Rocketry magazine
Squib		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.
SRFB		Space Research Facilities Branch. National Research Council of Canada. Operator of the Black Brants in the 1960s and '70s
SSTO		Single Stage To Orbit.
Stab		Stabilizer: Usually refers to the fin-like structures at the rear of a conventional boost glider.
Stability		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 fins to keep it moving in the correct attitude. Missiles and spacecraft usually employ "active" stability schemes, in which attitude jets or movable vanes help correct the rocket’s course in flight. Stability involves a rocket’s ability to continue to fly straight when the angle of attack is greater than zero. A stable rocket continues to fly in its intended direction, even if moderate wind or other influences try to change its course. A poorly-designed rocket can be either unstable, marginally stable [under stable] or excessively stable [over stable]. An unstable rocket (whose center of gravity is behind its center of pressure) will fly erratically when launched. A marginally stable rocket (whose center of gravity is less than one diameter ahead of its center of pressure) might be able to maintain a straight flight attitude if there is no side wind (angle of attack is zero.) However, if outside forces such as wind intervene (angle of attach greater than zero), the rocket can be thrown off its flight path and behave in an erratic manner. An excessively stable rocket (whose center of gravity is much more than one diameter ahead of its center of pressure) will tend to turn toward those outside forces rather than remain on the intended line of flight. See Weathercocking, Over Stability, Marginal or Under Stability
Stages		See Booster and Sustainer.
Stall		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 actually balancing the model on a narrow surface.
Stand-Off Scale		A scale model where the degree of accuracy should be judged from a distance (i.e. not too accurately)
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.
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.
Stine’s Law		The guiding principle of Rocketry construction and flight: "If at first you don’t succeed, try following instructions."
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
Streamer		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 and stabilize the falling rocket. Since streamers do not slow the descent as much as a parachute, they are normally only used on relatively small or very robustly-built model rockets. However, they are useful in windy conditions since they will not allow the descent to drift as much as a parachute will.
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.
String Test		See Swing Test
Strip		A condition in which a rocket’s fins, or a glider’s wings, are pulled off the airframe by excess thrust.
Striptease		The "act" of having wings or fins stripped off an airframe. Also, a pop-pod glider that separates from the booster pod prematurely.
Stubby Rocket		On EMRR, a rocket whose length to width ratio is 10:1 or less
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.
Styrofoam		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.
SU		Single Use; a disposable motor which cannot be re-used.
Subsonic		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
Suction Lock		The Mother of all Base Drag. See Bernoulli Lock
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'
Sun Seeker		A rocket with a crude form of guidance that directs it toward the sun
Superroc		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 125-250cm. The rockets can be longer but the excess length is not counted into the length factor. In the altitude category the rocket may be recovered in more than one section.
Supersonic		A speed greater than Mach 1 (760 mph at sea level) and less than Mach 5.
Surficant		An additive which improves a composite propellant's mixing by coating the AP particles
Sustainer		In a multi-stage rocket, the last or top stage. In a parallel staged rocket, the longest-burning motor.
Sweepback		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.
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 large rockets, unless King Kong consents to twirl the string. Sometimes called a string test.
Swivel		A swivel is a connection that allows the connected object, such as a parachute or streamer to rotate horizontally and/or vertically.
Symmetrical Airfoil		An airfoil (wing) in which both the top and bottom surfaces are tapered.
T		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

T		Show only T's by clicking here
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.
Tail Drag		See Base Drag
Tail Heavy		General description of a model that will require nose weight to achieve the desired CP/CG relationship for stable flight.
Tail-Cone		See Boat-Tail
Taper		A uniform decrease in diameter in a cylindrical of near cylindrical part.
TARC		Team America Rocketry Challenge; an aerospace design and engineering event for teams of US secondary school students, sposored by the NAR
Teflon (tm)		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
Telemetry		The transmission of data to a remote receiver, usually through the use of radio frequency broadcast.
Template		The outline of a part, made of a tough material used as a stencil to produce multiple parts of that size and shape.
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
Tetrahedron		A three sided pyramid
Theodolite		A device for determining altitude by measuring both elevation and azimuth angles. More accurate than a simple inclinometer, which measures only the elevation angle.
Thermal		An upward moving column of air caused by surface heating of the ground; a good thing in duration events
Thermalite		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 from the BATF.
Thermoplastic		A plastic which is solid when cold, but which may flow and be re-formed multiple times with the application of heat.
Three-fold attachment		The method Estes (and others) use to attach shock cords to the inside of an airframe; consists of a tapered strip of paper that is folded over on itself, with glue and the shockcord
Throat		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
Through The Tube (TTT)		See Through The Wall
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, the tabs are short and just provide a surface to build up epoxy fillets on the inside as well as the outside. In a stronger version of TTW, the tabs reach all the way to the motor tube where they are glued forming a very rigid box structure (also known as TTW-GTMT for "Glued To the Motor Tube).
Thrust		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 force in the opposite direction." The amount of forward thrust generated by a motor is defined by the second law (F-MXA), the third law merely says that it must move. In obedience to the second law, the two variables which must be known in predicting a motor’s thrust is the mass of exhaust gas expelled at any given moment, and the exhaust’s velocity.
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.
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
Thrust Decay		The gradual loss of thrust at the end of a motor’s burn.
Thrust Plate		A plate, usually metal, whose purpose is to distribute the force of a motor on the end of the motor tube
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 engine block or built in thrust ring, many rocketeers will make a thrust ring by wrapping masking tape around the last 1/4" to 1" section of the motor (depending on motor size). Without a thrust ring (or engine block), the friction fit technique would need to be used.
Thrust Stand		An instrumented test stand used to measure motor performance
Timer		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.
Tip Chord		The chord at the tip of a wing or fin. See Chord.
Tip-Off		An alteration of a rocket’s flight direction caused by interaction of the launcher, rocket, and wind direction as the rocket leaves the launcher.
T-Max		The time interval between ignition and maximum thrust.
T-Nut		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
Tomy Timer		A mechanical timer which is used to deploy parachutes in water rocket competitions
Total Impulse		The total thrust produced by a rocket motor across its full burn time. Usually expressed in Newton-seconds.
TRA		Tripoli Rocketry Association, Visit TRA
Trailing Edge		The rear edge of a wing or fin.
Transition		Part of an airframe that smooths the airflow from one airframe component to another of different diameter. Also called an Adapter.
Transonic		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.
TRF		The Rocketry Forum; an online, graphical discussion forum. Visit TRF
Trim Monokote		A brand of self-adhesive vinyl trim; unlike regular Monokote, this does not require heat for adhesion
Trimming		The act of adjusting surfaces on an aircraft through warping or shifting trim tab angles to achieve stable controllable flight.
TRM		Truely Recyclable Motors; Kosdon's reloadable motor system
Troll (Internet)		A person who enjoys unrest, starts arguements, and tries to upset people on media such as R.M.R. and chat forums
TSTO		Two Stage To Orbit.
TTMM		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.
TTW		See Through The Wall
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.
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.
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.
Tunnel		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.
Turbulator		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.
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.
Two-Stage Recovery		See Dual Recovery

U		Show only U's by clicking here
UFO		Strictly stands for Unidentified Flying Object, but is used for any saucer-like design (e.g. Estes Snitch, Art Applewhite's Saucers).
UKRA		United Kingdom Rocketry Association
Ultrascale		The practice of building very large HPR versions of smaller model rockets, several times the size of the original.
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.
Under Stability		See Marginal Stability
Unibody Staged		See Rack Rocket
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.
Upscale		The practice of building large versions of smaller model rockets. See Upscale Rocket Articles.

V		Show only V's by clicking here
Vacu-form		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.
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 smooth, uniform surface. Typically also requires a breather material and a release agent.
VCP		Visual Center of Pressure; a public domain program to graphically determine the CP
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.
Vent Hole		A hole in a Body Tube to allow ejection pressure to vent into another tube or into the atmosphere.
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.

W		Show only W's by clicking here
Wadding		A non-flammable filler material placed in a model rocket airframe before the parachute is inserted, and serving two purposes: (1) To act as a piston for deployment charge gases (2) To protect the parachute and other deployment system components from burning.
Waiver		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.
Warp		A twist, usually undesired, in a normally flat object such as a fin
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.
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 squeezing a watermelon seed between your fingertips and sending it flying. It is also similar to the way a spike (or aerospike) nozzle provides thrust. Sometimes called the "Pumpkin-Seed Effect".
Weathercocking		The tendency of a rocket to fly into a breeze, altering the flight path from vertical.
Wedging		A method of securing fins by forcing the fin root in between tubes in a motor cluster.
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.
Wing		In British usage, a rocket’s fins. Also, the lifting surfaces of a glider.
Wing Loading		A method for measuring appropriate wing size, calculated by dividing the wing area in inches squared by the mass of the aircraft.
Winglets		Small fin or wing-like extensions attached to the ends of the wings of an aircraft.
Wingspan		The linear distance between the extremities of an airfoil; typically the distance between the wing tips of an airplane.
WL		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".
Wood Filler		A common filler for tube spirals, balsa fins, fillets, etc.
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.
wRASP		Windows Rocket Altitude Simulation Program; a public domain program that simulates the flight of a rocket in one dimension

X		Show only X's by clicking here
X-form Parachute		A parachute that is formed by connecting together two rectangles of material, forming an 'X'
X-Planes		the 'X' stands for experimental; the series of US Government experimental planes starting with the Bell X-1.
X-Prize		"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 with the same ship within 2 weeks"; X-Prize Foundation.

Y		Show only Y's by clicking here
YABAR		Yet Another Born Again Rocketeer. See BAR
Yaw		A back-and-forth motion of the nose of a rocket in flight, on the axis determined as "left-and-right". See Pitch.

Z		Show only Z's by clicking here
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.
Zipperfield		UK Term: A town in the UK where rockets have zippers installed.

The words in the glossary (initial) were compiled from various resources throughout the web and rocketry handbooks. We appreciate the efforts of individuals who have previously compiled some of this information including, but not limited to, Randy Culp, Joel Simon, John H. Boyd, Dick Stafford, and UncaMykul.