Model Rocketry and Siege Engine Glossary Letter T


Model Rocketry and Siege Engine Glossary Letter T

Glossary
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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
Taper
A uniform decrease in diameter in a cylindrical of near cylindrical part
Telemetering System
The complete measuring, transmitting, and receiving apparatus for remotely indicating, recording, and/or integrating information
Telemetry
The transmission of data to a remote receiver, usually through the use of radio frequency broadcast
Tempera
A powdered paint substance often used as tracking powder
Template
The outline of a part, made of a tough material used as a stencil to produce multiple parts of that size and shape
Terrestrial Space
Space comparatively near the earth in which the attraction of the earth is predominant
Terminal Velocity
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
Theodolite
A optical instrument or device for determining altitude by measuring both elevation and azimuth angles. More accurate than a simple inclinometer, which measures only the elevation angle
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
Throat
In rocket and jet engines, the most restricted part of an exhaust nozzle
Throat Area
The cross-sectional area of the nozzle at its smallest inner diameter
Thrust
The result ant force in the direction of motion, owing to the components of the pressure forces in excess of ambient atmospheric pressure, acting on all inner surfaces of the vehicle parallel to the direction of motion. Thrust less drag equals accelerating force
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 Decay
The gradual loss of thrust at the end of a motor’s burn
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
Total Impulse
The total thrust produced by a rocket motor across its full burn time. Usually expressed in Newton-seconds
TRA
Tripoli Rocketry Association
Tracking Powder
A dense, colored powder, usually chalk or tempera, which is added to the recovery bay of a high-altitude rocket. When the recovery system deploys, the powder disperses into a colored cloud which aids trackers to spot the rocket in the sky
Trailing Edge
The rear edge of a wing or fin
Trajectory
The path that a rocket or missile travels from point of launch to point of impact, usually refers to ballistic missiles. Also the route of the course
Transition
See Adapter
  • The condition of crossing the sonic barrier. This is the period of maximum aerodynamic stress in a supersonic flight
  • The intermediate speed in which the flow patterns change from the subsonic flow to supersonic, i.e., from Mach numbers of about .8 to 1.2, or vice versa
Trimming
The act of adjusting surfaces on an aircraft through warping or shifting trim tab angles to achieve stable controllable flight
Troposhere
The lower layer of the earth's atmosphere, extending to about 60,000 feet at the equator and 30,000 feet at the poles
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
Through The Wall; a technique for increasing the strength of a fin-to-airframe mounting joint. The airframe is slotted at the point where the fin is to be mounted. The fin is extended or tabbed so that it can pass through the body tube instead of bonding to its surface. Commonly the root of the fin bonds to the surface of the motor tube, then fillets are built up where the fin passes through the airframe
Tube Fins
Tubes attached to the trailing end of a rocket airframe, used in place of fins
Tube Launched
A rocket - often having some form of folding fins - which is supported at launch by a tube or box rather than by a launch rod or rail
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.
Turbo-Jet
A jet motor whose air is supplied by a turbine driven compressor; the turbine being activated by exhaust gases from the motor
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-Stage 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


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