Model Rocketry and Siege Engine Glossary Letter P


Model Rocketry and Siege Engine Glossary Letter P

Glossary
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Pad Manager
Person responsible for assigning pads and controlling the launch pad area. Helps rocket flyers set up pads and rockets for flight
Parachute
A piece of plastic, cloth, nylon, or other material, shaped something like an umbrella when deployed, which slows the descent of a rocket
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
Payload
A package or thing placed in a rocket, which normally does not perform a function and or 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
PD
Parachute Duration; a popular competitive event in NAR-sanctioned launches
Perigee
The point in an orbit which is closest to the center of the earth
Perihelion
That point on a planet's or comet's orbit nearest the sun
Permeability
The measure of diffusion or "leakage" of gas through a fabric. The permeability determines the rate of descent
Phenolic
Literally, anything containing phenol, which is a petroleum distillate having many industrial applications
Phenolic airframes
Paper body tubes impregnated 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
Phenolic resin
A mixture of phenol with an aldehyde such as formaldehyde, and is used for forming all sorts of molded and cast items
Phototheodolite
A device for measuring and recording the horizontal and vertical angles to a missile while photographing its flight
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
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
  • A back-and-forth motion of the nose of a rocket in flight, on the axis determined as "up-and-down". See Yaw
  • An angular displacement about an axis parallel to the lateral axis of an airframe
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
PMC
See Plastic Model Conversion
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
Plugged Motor
A motor made with a solid bulkhead in the front end, blocking any passage of ejection gases into the airframe
Polyhedral
A wing broken up into multiple panels, angled in relation to each other
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)
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
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. May refer to the sound made when a wing strikes the ground
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 (P)
The result of the impact of molecules on their surroundings, measured as a force per unit area such as pounds per square inch absolute (psia) or pounds per square inch gage (psig)
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
Primer
A special mix of paint, applied directly as a first coat, that is formulated to have excellent adhesion and a uniform color over various materials such as body filler
PROPELLANT
Material consisting of fuel and oxidizer, either separate or together in a mixture or compound which if suitably ignited changes into a larger volume of hot gases, capable of propelling a rocket or other projectile
Propellant Mass Fraction
The propellant mass divided by initial mass
Propulsive Chaff
(Brit.) The remains of a shredded rocket while still airborne
Pseudo Scale
A model designed and decorated to appear to be a scale model
Pulse
A single disturbance of definite amplitude and time length, propagated as a wave or electric current
Pyrogen
The flammable substance placed at the head of an igniter, to assist in igniting rocket motor propellant
Pyrotechnic
Of or pertaining to fire or explosion. The term is most commonly used with reference to fireworks


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