Glossary / Technology

Rockets Glossary

Ablative: To wear away under stresses of heat, oxidation, and high velocity gas erosion.
Acceleration: Increasing velocity with time.
Additive: Propellant ingredient used to enhance physical or ballistic properties.
Aft: Tail end of vehicle.
Ammonium Perchlorate: Ammonium Perchlorate is used as an oxidizer in many composite rocket fuels. It is also the oxidizer
Barricade: Sturdy structure meant to stop or deflect high velocity objects created in a test stand explosion.
Bates Grain: Tubular grain uninhibited on the ends which can provide a nearly neutral burning characteristic (BAt
Binder: The rubbery fuel used in solid propellants - also in Hybrid fuels.
Blockhouse: Strong construction used to house personnel and instruments in a static or flight test. Generally ha
Blowdown: Pressurizing gas flowing through a fixed orifice with no other regulation to expel liquid propellant
Boiler Plate Motor: A very solid overdesigned thrust chamber used to test new propellants or new injector concepts.
Bolt Circle: A ring of bolts used to hold a closure in place.
Bulkhead: A wall between two areas - in rocketry usually between two tanks, instrumentation sections or betwee
Bunker: Less sophisticated observation area than a blockhouse. Generally has overhead protection to qualify
Burn Area: The actively burning surface of a rocket grain, either solid or hybrid.
Burning Rate: In solids, the rate at which the burning surface recedes as it combusts. Affected by pressure, tempe
Burst Diaphragm: A thin (metal) disc which fails at a known pressure, releasing pressurant, fuel or oxidizer into flo
Cables: In instrumentation, the shielded electrical lines which conduct signals from the transducers to the
Canadian Association of Rocketry (CAR): CAR is the Canadian Association of Rocketry and it's essentially the Canadian version of the NAR and
Case Bonded: A propellant grain cast directly into a chamber and made to bond securely to the chamber wall.
Center of Gravity (CG): The center of gravity is the balance point of an object. For example, if you throw a stick, it will
Center of Pressure (CP): The center of pressure is the point in an object at which all forces acting upon it are centered. In
Centuri: Centuri was Estes' main competitor in the model rocket business until Estes bought them out in the e
Chamber: Generally a tubular section of a rocket motor (solid, liquid, or hybrid) in which combustion takes p
Chamber Pressure: The pressure generated within a motor by the combustion of the rocket propellant(s).
Chuff: A low frequency instability in rocket motors in periods of up to several seconds - dangerous in that
Chug: Low frequency instability in a liquid motor.
Closure: Any mechanical part which seals a port or chamber.
Composite rocket motor: A composite rocket motor is any rocket motor which doesn't use black powder as it's propellant. Ofte
Core: The cavity within a solid or hybrid grain - often shaped to offer higher burning surface or a consta
Cryogenic: Temperature at which gases liquefy at atmospheric pressure.
Density: Specific weight per volume unit.
Discharge Coefficient: Downrating of the area of an orifice or nozzle due to flow separation or friction.
Electric Match: An electric igniter similar to a model rocket igniter.
End Burner: A 'cigarette burning' grain inhibited or case bonded on the external surface burning only on its fac
Erosive Burning: Increased burning rate in solids and hybrids created by the action of high velocity gases.
Estes: Estes is one of the first companies that started it all way back in 1959 when they introduced the Sc
Exit Area: Largest section of a divergent cone on the exhaust section of a rocket nozzle.
Exit Cone: Applies to the exit or expansion section of a rocket nozzle.
Expansion Ratio: The ratio of the area of the exit diameter of the exhaust portion of a nozzle to the area of the thr
Flex Hose: Used in test stands to feed propellants to liquid or hybrid motors without imposing major loads on t
Flex Member: Spring steel leaf used in supporting test stand table at four corners.
Forward: Towards the nose of the rocket.
Fuel: Component(s) of the propellant which are Oxidized or burned.
Gimbal: Used in attitude controlled vehicles to support motor so it can be deflected to produce control vect
Grain: Any size of monolithic propellant structure designed to be combusted as rocket propellant.
Half-Angle: The divergence of the exhaust cone referring to the angle one side makes with the centerline. Conven
Hold Down: A mechanical clamp for securing a motor to a test stand or to secure an entire vehicle to a launch p
Hoop Stress: The circumferential loading of a cylindrical mechanical body. Mustbe kept well below the yield stren
Hybrid: Refers to the use of mixed states of matter in a bi-propellant system - solid-liquid, gas-solid, etc
Hydrostatic Test: Important operation used to determine the suitability of a vessel or motor chamber for pressure cont
Hypergolic: Propellants which ignite on contact.
Hysteresis: Shift in calibration of transducer when on 'return' from actuation load.
Igniter: An igniter is a small device which is used to ignite the propellant of a rocket motor. It's usually
Inhibit: Bonding non-propellant material to restrict the burning surface of a propellant grain.
Injector: A system of orifices used to direct propellant to create mixing and fog production for combustion.
Insulation: Thermal protection used in motors to prevent heat transfer to temperature sensitive materials.
Liner: An insulated sleeve made from phenolic, EPDM, fiberglass, impregnated cardboard, or any number of ma
Liquid: Refers to liquid propellant in rocket terminology.
Load Cell: Transducer which measures force as a function of resistance or voltage.
National Association of Rocketry (NAR): NAR is the National Association of Rocketry which is the organization which regulates the industry b
Neutral: Pressure curve which is nearly constant with time.
Newton: The Newton (named after Sir Isaac Newton) is a measure of force and is used to indicate the thrust o
Newton-Second (N-s): The Newton-second is a measure of total impulse and is the product of applied force multiplied by ti
Nichrome: An alloy of nickel and chromium drawn into a wire of varying gauges typically used to heat a pyrogen
Nozzle: The portion of the rocket motor which accelerates the gases to sonic velocity at the narrowest part
Oxidizer: All things need oxygen to burn. When a pile of wood burns in an open fire, it sucks in oxygen from t
Oxidizer: The component of a propellant which provides the combustion supporting element (generally Oxygen, bu
Perforation: Another term for core.
Plumbing: Refers to tubing and hoses used as conduits for propellants and pressurants in a liquid or hybrid pr
Port Area: The cross section of a core, perforation or port - used in Hybrid tocalculate G (Mass Flux Rate).
Pressure: Measure of unit of force per unit area exerted by combustion products during rocket motor operation,
Pressure Port: A threaded orifice which can be fitted with a pressure gauge or pressure transducer for determining
Pressure Transducer: Outputs electrical signal proportional to pressure.
Progressive: Pressure time curve which shows increased pressure with duration.
Propellant: Refers to a mixture of oxidizer and fuel or to either oxidizer or fuel used in rocket motors.
Recorder: Any device which creates a semi-permanent display of data, generally on magnetic tape, chart paper,
Regressive: Pressure vs Time curve in which the pressure decreases with duration.
Restrict: Inhibiting a grain.
Rocket: Device which provides propulsion through the expulsion of some mediumat high velocity.
Screech: High frequency instability of liquid motors, generally destructive.
Sliver: Remnant of propellant or fuel in solid or hybrid motors as a consequence of initial geometry.
Solid: Fuel and/or oxidizer in a condensed, solid state of matter.
Solid Rocket Booster (SBR): Solid Rocket Boosters are boosters which are strapped onto the side of a rocket to assist in liftoff
Specific Impulse: Specific impulse refers to the power per unit of propellant. For instance, when Aerotech says that
Specific Impulse: The force per unit mass per unit time generated by a rocket propellant under fixed conditions of pre
Static Test: Firing a rocket motor in a restrained, protected area for purposes of recording chamber pressure, th
Strand Burner: A strand burner measures the burn rate of an energetic composition in an elevated pressure environme
Tailoff: Refers to gradual reduction in pressure and thrust at end of burning of a rocket motor.
Tank: Vessel which contains oxidizer, fuel or pressurant for a rocket motor.
Tap: Referring to either threading of a hole or to the port in a chamber designed to take pressure measur
Test Stand: Designed to restrain a motor during test and permit enough motion to actuate a load cell - see stati
Thrust: Force produced by a rocket motor by the efflux of matter at high velocity.
Total Impulse: The total impulse of a rocket motor is the measure of its power which is measured in Newton seconds.
Transducer: Outputs electrical signal proportional to a force or pressure input.
Ullage: Unfilled volume of a propellant tank and rarely the unfilled volume in a solid motor.
Unrestricted: Refers to a free-standing grain which burns on all surfaces. This method leaves the chamber wall unp
Wall Thickness: Is equal to 1/2 the difference between the inside diameter and outside diameter of a chamber or tank

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