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GAO/NSIAD-92-5 -- page 135
Glossary
Aeroballistic
The flight characteristics of projectiles or high-speed vehicles in the atmosphere.Aerothermodynamic
A branch of thermodynamics relating to the heating effects associated with the dynamics of a gas, particularly the physical effects produced in the air flowing over a vehicle during launch and reentry.Air-Breathing
An aerodynamic vehicle engine that requires air for combustion of its fuel.Air-Breathing Propulsion
A ground test facility used to test an aircraft engine that requires air for Test Cell combustion of its fuel.Airflow
A flow or stream of air.Air-Turboramjet
An air-breathing engine similar to a ramjet except that the air is compressed in an axial flow fan before being mixed with hydrogen (or some other hydrocarbon fuel) and burned in the ramburner. Combustion products are passed through a heat exchanger, which heats the hydrogen fuel, and then are expanded through the exhaust nozzle, creating the thrust. The heated hydrogen passes through an axial flow turbine, which drives the fan, and then is injected into the ramburner, where the heated hydrogen is burned. Temperature limitation caused by turbine blade materials is avoided, since combustion products are not passed through the turbine. Air-turboramjets can perform well from Mach O to 6. The term air-turboramjet is a misnomer resulting from the apparent inadvertent contraction of air-turborocket/ramjet.Air-Turborocket
A combined-cycle engine in which the initial acceleration propulsion mode involves a compressor or fan driven by a turbine. The turbine's motive power is not obtained from fuel combustion in the compressed airstream (as in a turbojet) but rather from either fuel-rich bipropellant combustion or exothermic monopropellant decomposition. The (usually) fuel-rich turbine exhaust is then combusted in the compressed airstream and the products exhausted through a nozzle.GAO/NSIAD-92-5 -- page 136
Air-Turborocket/Ramjet
A combined-cycle engine that utilizes an air-turborocket initial mode followed by a conversion to subsonic combustion ramjet mode for high speed acceleration and cruise. The term air-turboramjet is a misnomer resulting from the apparent inadvertent contraction of air-turborocket/ramjet.Algorithm
A step-by-step procedure for solving a mathematical problem.Ambient Temperature
The temperature of the gas around a test model, which is unaffected by the model's presence.Angle of Attack
The acute angle between the direction of the relative airflow and the chord (i.e., the straight line joining the leading and trailing edges of an airfoil) of the test model.Angle of Sideslip
The acute angle between the direction of the relative airflow in a lateral plane and the chord (i.e., the straight line joining the leading and trailing edges of an airfoil) of the test model.Autoclave
An airtight vessel constructed of thick-walled steel alloy for carrying out chemical reactions under pressure and high temperatures. Auto-claves are used for the industrial processing of composite materials.Autoclave Molding
A method of curing reinforced plastics that uses an autoclave with 50 to 100 pounds per square inch steam pressure to set the resin.Biconic Geometry
Two cone structure configuration.Blowdown Wind Tunnel
An open-circuit wind tunnel in which gas stored under pressure is allowed to expand through a test section to provide a stream of gas or air to test a model. The gas then escapes into the atmosphere or into an evacuated chamber. Test times are finite and usually last from a few seconds to minutes.GAO/NSIAD-92-5 -- page 137
Boundary Layer
A region of the flow of a retarded viscous fluid near the surface of a body that moves through a fluid or past which a fluid moves.Canard
An aerodynamic vehicle in which horizontal surfaces used for trim and control are forward of the wing or mainframe lifting surface.Carbon-Carbon
A material that consists of 100-percent carbon fibers in a carbon matrix. The material does not contain any binders or epoxy and is coated with a ceramic material. Carbon-carbon is extremely lightweight and is being considered for use on aerospace plane thermal protection systems.Carbon-Fiber
Material made by pyrolyzing any spun, felted, or woven raw material to a char at temperatures from 700 degrees to 1,800 degrees Celsius. Carbon-fiber is used as a reinforcing material with epoxy or polyester resins to form composites, which have a higher strength/weight ratio than metals.Celsius
A temperature scale in which the freezing point of water at standard atmospheric pressure is 0 degrees Celsius and the corresponding boiling point is 100 degrees Celsius. Zero degrees Celsius equals 273.16 degrees Kelvin.Coherent Anti-Stokes Raman Scattering
A phenomenon observed in the scattering of light as it passes through a transparent medium. The light undergoes a change in frequency and a random alteration in phase due to a change in rotational or vibrational energy of the scattering molecules.Columbium
A platinum-gray, ductile metal with brilliant luster that is used in alloys, especially stainless steels. Columbium is also known as the element niobium.Combined-Cycle Engine
Engine concepts using some combination of air-breathing and rocket components which are integrated into a single propulsion system.GAO/NSIAD-92-5 -- page 138
Composite Materials
Structural material made of two or more different materials such as carbon-fiber reinforced epoxy resin.Computational Fluid Dynamics
A tool for predicting the aerodynamics and fluid dynamics of air around flight vehicles by solving a set of mathematical equations with a computer. Also known as numerical aerodynamic simulation, computational fluid dynamics is used in aerospace vehicle research and development programs to improve the understanding of hypersonic flow physics and as an aerospace vehicle design tool.Cryogenic
Operating at extremely low temperatures.Diffusion Bonding
A solid-state process for joining metals by using heat and pressure to achieve atomic bonding.Dynamic Pressure
The pressure of a fluid resulting from its motion when brought to rest on a surface. It is also known as impact pressure, stagnation pressure, and total pressure.Electron Beam Welding
A technique for joining materials in which components to be welded are heated by a concentrated beam of high-velocity electrons in vacuo.Enabling Technology
A critical technology that makes development and demonstration of an aerospace vehicle possible. Enabling technologies may include an air breathing propulsion system; advanced materials that are high-strength, lightweight, able to withstand high temperatures, and fully reusable; a fully integrated engine and airframe; use of computational fluid dynamics and supercomputers for aerodynamic, structural, and propulsion system design; and efficient use of hydrogen both as a fuel and to actively cool the airframe.Enthalpy
The total energy (heat content) of a system or substance undergoing change from one stage to another under constant pressure. Enthalpy is expressed as the sum of the internal energy of a system plus the product of the system's volume multiplied by the pressure exerted on the systemGAO/NSIAD-92-5 -- page 139 by its surroundings. Enthalpy is also known as heat content, sensible heat, and total heat.
Euler Codes
Computer software that is a mathematical representation of the motion of a fluid whose behavior and properties are described at fixed points in a coordinate system.Expander Air-Turboramjet
A combined-cycle propulsion system of the air-turborocket/ramjet type in which the compressor or fan element used in the air-turborocket mode is driven directly (or through a gear train) by a turbine. The turbine is powered by the flow of high-temperature, high-pressure gas (usually hydrogen). The gas is previously pumped to high pressure as a liquid and then heated in a heat exchange rather than in a direct combustion process.Expander Bleed-Cycle Engine
Also known as the open expander-cycle engine, the expander bleed-cycle engine uses heat exchange-heated propellant to drive its turbopump. However, unlike the closed expander-cycle engine, a small amount of propellant (usually hydrogen) is "bled" from the high-pressure (pumped) thrust chamber supply to drive a low-flow, high pressure ratio turbine. Exhausted from the turbine at relatively low pressures, this bleed-flow is discharged overboard (rather than being injected into the thrust chamber for combustion, since its pressure is too low for combustion). The Japanese LE-5A engine for the H-II launch vehicle (currently under development) is an example of an expander bleed-cycle engine.Expansion Tube
A wind tunnel for conducting tests at hypervelocity speeds in which fluid (such as air or some other test gas) at high pressure, usually involving rapid combustion to increase energy, is released by rupturing a diaphragm and accelerating through an evacuated working section (test chamber) containing the model. The major difference between a shock tube and an expansion tube is that in an expansion tube the isentropic flow is exact.Fairing
A structure or surface on an aircraft or rocket that reduces drag, such as the streamlined nose of a satellite-launching rocket.GAO/NSIAD-92-5 -- page 140
Free-Piston Driver Technique
A technique in which a single stroke of a heavy piston in a shock tunnel compresses the driver gas to raise its pressure and temperature before rupturing the main shock tube diaphragm. When helium driver gas is used, this technique allows routine operation of the shock tunnel in the reflected shock mode with test section stagnation enthalpy values approaching orbital velocities (8 kilometers per second).Gas Generator Air Turboramjet
A combined-cycle propulsion system of the air-turborocket/ramjet type in which the compressor or fan element used in the air-turborocket mode is driven directly (or through a gear train) by a turbine. The turbine is powered by the flow of high-temperature, high-pressure gas produced in a bipropellant, monopropellant, or solid propellant combustion type gas generator.Gas Generator-Cycle Rocket
A pump-fed liquid-propellant rocket engine in which a low-flowrate, high pressure-ratio pump-drive turbine is powered by a bipropellant (or monopropellant) gas generator. The low-pressure exhaust is expelled overboard through separate ducts or through the exit section of the main exhaust nozzle, since its pressure is too low to admit it into the combustion chamber. Examples of the gas generator-cycle rocket engine include the Aerojet TechSystems liquid engines for the Titan 4 booster (LR-87 and LR-91), the European Vulcain rocket engine for the Ariane 5 launch vehicle, and the Japanese LE-5 engine for the H-I launch vehicle.Geostationary
A satellite orbit traveling from west to east at speeds that allow it to remain fixed over a given place on the earth's equator at approximately 22,300 miles in altitude. A geostationary satellite makes one revolution in 24 hours, synchronous with the earth's rotation.Gigabyte
One billion bytes.Gigaflop
One billion floating-point operations per second. Gigaflop is used as a measurement of the processing capability of very large computers.Global Positioning System
A positioning or navigation system designed to use 18 to 24 satellites, each carrying atomic clocks, to provide a receiver anywhere on earthGAO/NSIAD-92-5 -- page 141 with extremely accurate measurements of its three-dimensional position, velocity, and time.
Graphite-Polyimide Composites
A composite material composed of a mixture of whisker-thick graphite fibers that add stiffness and an organic (polyimide) resin matrix, which has more heat resistance than conventional epoxies.Heat Exchanger
Any device that transfers heat from one fluid to another or to the environment.Heat Transfer
The transfer or exchange of heat by radiation, conduction, or convection within a substance and between the substance and its surroundings.High-Pressure Expander Cycle Engine
Generically, a liquid propellant rocket engine that usually uses hydrogen for its fuel. Its turbopump is powered by a high-pressure propellant flow that is heated by propellant heat exchange in the thrust chamber cooling jacket. The turbine-drive flow is then injected into the thrust chamber where combustion takes place. The Japanese high-pressure expander cycle engine augments the conventional jacket heat pickup in the turbine-drive propellant (hydrogen) with an adjunct cylindrical heat exchanger inserted directly into the combustion volume of the thrust chamber. Thus, the engine is able to achieve higher chamber pressure levels than could otherwise be achieved. In the 1950s, Pratt & Whitney developed a prototype of a unique hydrogen-fueled air-breathing engine (Model 304) based on this expander-cycle.Hypersonic
A range of speed that is five times or more the speed of sound in air.Hypersonics
A branch of aerodynamics that deals with the flow of air and other gas eous fluids at speeds greater than five times the speed of sound in air. Hypersonics may also refer to the technologies associated with aero space vehicles flying at such speeds.Hypervelocity
A range of speed that is about 12 times or more the speed of sound in air.GAO/NSIAD-92-5 -- page 142
Interferometry
The design and use of optical interferometers to conduct, for example, precise measurements of wavelength, very small distances and thick ness, and indices of refraction, and to study the hyperfine structure of spectral lines.Intermittent Wind Tunnel
A wind tunnel in which energy is stored, usually as compressed air, and then released suddenly to force a large quantity of air through the small throat of the nozzle and over the test model in the test section in a short period of time. The test gas is then captured in a vacuum dump tank or released into the atmosphere.Isentropic
Constant entropy or without change in entropy (a measure of the unavailability of energy).Kinetics
A branch of science that deals with the effects of forces on the motion of material bodies or with changes in a physical or chemical system.Liquefaction
A change in the phase of a substance to the liquid state. Liquefaction usually involves a change from the gaseous to the liquid state, especially of a substance that is a gas at normal pressure and temperature.Liquid Air Cycle Engine
Basically a rocket engine in which the oxidizer is liquid air obtained by liquefaction of the air entering the air-breathing inlet. The heat sink capacity of liquid hydrogen is used in a heat exchanger to liquefy the flow of air. The liquid air is then pumped to a conventional rocket combustion chamber, which is used to burn the liquid hydrogen. This engine has variations in the method used to obtain the power to pump the air and hydrogen to high pressures. Theoretically, this engine can perform well from Mach 0 to 8. A liquid air cycle engine is the same as a liquid air rocket engine.Liquid Air Rocket
Basically a rocket engine in which the oxidizer is liquid air obtained by liquefaction of the air entering the air-breathing inlet. The heat sink capacity of liquid hydrogen is used in a heat exchanger to liquefy the flow of air. The liquid air is then pumped to a conventional rocket com bustion chamber, which is used to burn the liquid hydrogen. This engine has variations in the method used to obtain the power to pump the airGAO/NSIAD-92-5 -- page 143 and hydrogen to high pressures. Theoretically, this engine can perform well from Mach 0 to 8. A liquid air rocket engine is the same as a liquid air cycle engine.
Mach Number
A number representing the ratio of the speed of an object to the speed of sound in the surrounding atmosphere. An object traveling at the local speed of sound is traveling at Mach 1.Mach-Zehnder
The design and use of a type of optical interferometer that depends on Interferometr amplitude splitting of the wavelength. It is used mainly in measuring the Y spatial variation of the index of refraction of a gas. The device has two semitransparent mirrors and two wholly reflecting mirrors at alternate corners of a rectangle. Half the beam of light travels along each side of the rectangle. The major application of the Mach-Zehnder interferometer is studying the airflow around models of aircraft, missiles, and projectiles.Magnetic Levitation
A train or sled launch vehicle that travels at high speed at some distance above an electrically conducting track or magnetic field by means of levitation (the use of physical force that does not involve physical contact to balance gravity).Mass Spectrometry
An analytical technique for identification of chemical structures, deter mination of mixtures, and quantitative elemental analysis, based on application of the mass spectrometer.Massively Parallel Computing
The simultaneous computation of several parts of a problem on a computing puter that can carry out more than one logic or arithmetic operation at one time. The computer usually consists of 100 or more processors.Megabyte
One million bytes. A megabyte is a unit of information content equal to 1,048,576 bytes.Megaflop
One million floating-point operations per second. Megaflop is used as a measurement of the processing capability of very large computers.GAO/NSIAD-92-5 -- page 144
Microgravity
The condition of near weightlessness induced by free-fall or unpowered space flight. It also refers to the scientific discipline concerned with the evaluation of the processes in a near-zero gravity environment, particularly those of fluid physics, life, and material sciences.Microsecond
One-millionth of a second.Mini-Supercomputer
Basically a vector-architecture supercomputer with relatively few central processing units capable of attaining performance levels that are 30 to 70 percent of the largest supercomputer systems, or about 100 to 300 megaflops (for the 1990 to 1991 time frame). Mini-supercomputers are sometimes referred to as "departmental" supercomputers, in contrast to larger "corporate" systems.Navier-Stokes Codes
Computer software that contains the mathematical equations of motion for a viscous fluid.Nozzle
The exit duct of a wind tunnel or exhaust duct of an engine used for accelerating a fluid and producing a desired direction, velocity, or shape of discharge. The fluid's pressure decreases as it leaves the nozzle. The nozzle usually has an increasing cross-section in the direction of the flow.Observables
Characteristics of a flight vehicle (such as distance, speed, and shape) that can be seen electronically, optically, or thermally. Composite mater ials can absorb radar waves, thus reducing the returned radar signal.Parabolized Navier-Stokes Codes
Computer codes that use detailed equations for predicting viscous flows in which the equations have been simplified to act on the supersonic outer inviscid flow and with no reverse-flow in the viscous regions on the body.Piston-Driven
A type of shock tunnel in which energy is created by a piston being fired (or driven) down a cylinder, compressing the test gas ahead of it. The pressure and temperature of the test gas is increased, creating a shock.GAO/NSIAD-92-5 -- page 145
Platelet Technology
Very small and intricate passages for transporting a cooling fluid through a hot aerospace vehicle component by constructing the component from a series of very thin sheets of the desired material. Each sheet is photoetched to create the holes or passages desired. The sheets are then placed on top of one another and fused together. The advantage of this technique, particularly for development and experimental work, is that the designs can be easily modified and a new part can be made very quickly. Platelet technology is being considered for use in aerospace vehicles as a thermal control system.Polyimides
Natural or synthetic fibers composed of natural or synthetic polymers (a material built up from a series of smaller units) having the same imide group repeated along the chain.Pre-Burner Cycle Cryogenic Engine
Also known as the staged-combustion and topping cycle engine, this class of rocket engine features a turbopump drive in which some (or all) of the propellants undergo combustion at conditions considerably above thrust chamber combustion pressure (and at acceptable turbine inlet temperature conditions). The propellants pass through the turbine driving the pumps and are then injected into the thrust chamber where maximum cycle temperatures are achieved. Like the expander-cycle engine, and unlike the gas generator-cycle rocket engine and expander bleed-cycle engine, the pre-burner cycle cryogenic engine has no separate low-pressure turbine exhaust discharge. Prior Steady Flow A technique whereby the prior establishment of steady flow in a hyper Technique sonic nozzle is used to ensure rapid starting of a subsequent shock-initi ated flow. This technique is used to allow operation of a free-piston shock tunnel in the non-reflected shock mode. It also permits high-stag nation enthalpy shock tube flows that can be produced with the free piston driver resulting in a hypersonic flow. Thus, test section stagna tion enthalpies exceeding orbital escape velocity (11 kilometers per second) can be produced.Ramjet
An air-breathing engine that compresses (or rams) the high-speed air entering the inlet by efficiently slowing it down to subsonic speeds, at which time it is burned with the fuel in a combustion chamber (ramburner). High-temperature combustion gases are expanded throughGAO/NSIAD-92-5 -- page 146 an exhaust nozzle at high speed, creating the thrust. A ramjet is capable of efficient operation at supersonic speeds of about Mach 2 to 6.
Ram-Rocket
A rocket engine in which an air-breathing inlet and duct system are added, permitting atmospheric air to be introduced at the exit of the rocket combustion chamber. By operating the rocket engine with more fuel than necessary to use the rocket's oxidizer, the rocket's hot combus tion products can be mixed with the atmospheric air where the excess fuel is burned, creating additional high-temperature combustion products. A ram-rocket engine provides high thrust at subsonic and supersonic conditions while retaining the rocket's ability to produce thrust at static (Mach 0), hypersonic, and orbital conditions.Rapid Solidification Technology
A process in which molten metals such as titanium and aluminum are transformed into a very fine powder, which is then solidified. The resulting alloy (ti-aluminide) demonstrates much higher strength and stiffness at high temperatures compared to conventional titanium alloys. Moreover, ti-aluminide has one-half the weight of the material previously used at these high temperatures.Real Gas Effects
A gas behavior or phenomena resulting from the interactions of gas molecules.Reynolds Number
A dimensionless number used as an indication of scale of fluid flow. It is significant in the design of a model of any system in which the effect of viscosity is important in controlling the velocities or the flow pattern of a fluid. Reynolds Number is equal to the density of a fluid times its velocity times a characteristic length divided by the fluid viscosity.Rockoon
A high-altitude sounding system consisting of a small solid-propellant research rocket carried aloft and launched by a large balloon.Schlieren
An optical technique that detects density gradients occurring in a fluid flow. Schlieren is a German word that means "striations." It refers to various shadowgraphic techniques for optical investigations. Variations in density in flow through shock waves and supersonic flow, for example, are sharply visible in tonal gradations.GAO/NSIAD-92-5 -- page 147
Scramjet
A supersonic combustion ramjet air-breathing engine in which air flows through the combustion chamber at supersonic speeds. Hydrogen is injected into the combustion chamber where it is ignited by the hot air. At very high flight speeds (Mach 6 and above), the supersonic speeds in the combustor reduce the internal pressures and temperatures, allowing efficient combustion of the hydrogen fuel and a reduction in the weight of the combustor. The hot gases are further accelerated through the exhaust nozzle, creating the thrust. Theoretically, scramjets provide efficient operation at hypersonic speeds of about Mach 4 to 25 (orbital velocity).Shock Tube
A wind tunnel for conducting tests at hypervelocity speeds in which fluid (such as air or some other test gas) at high pressure, usually involving rapid combustion to increase energy, is released by rupturing a diaphragm and accelerated through an evacuated working section (test chamber) containing the model.Shock Tunnel
A hypervelocity wind tunnel in which a shock wave generated in a shock tube ruptures a second diaphragm in the throat of a nozzle at the end of a tube. Gases emerge from the nozzle over the model in the test chamber and into a vacuum dump tank. Speeds achieved in a shock tunnel typically range from Mach 6 to 25.Shock Wave
A fully developed compression wave of large amplitude, across which density, pressure, and particle velocity change drastically.Slush Hydrogen
A mixture of liquid and frozen hydrogen that is denser than liquid hydrogen.Slush Oxygen
A mixture of liquid and frozen oxygen that is denser than liquid oxygen.Sonic (Velocity)
The speed of sound in air (761.5 miles per hour at sea level).Sounding Rocket
A rocket that carries aloft equipment for making observations of or from the upper atmosphere.GAO/NSIAD-92-5 -- page 148
Specific Impulse
A performance parameter of a rocket propellant, expressed in seconds, equal to the thrust in pounds divided by the weight flow rate in pounds per second.Stagnation Enthalpy
The total energy or heat content of a system generated when the flow is brought to rest (zero velocity) isentropically at a stagnation point.Subsonic
A range of speed below the speed of sound in air.Supercomputer
A computer with the highest processing speed in any given period of time. A supercomputer is part of a high-performance computing system that is at the forefront of the computing field in terms of computational power, storage capability, input/output bandwidth, and software. These systems include high-speed vector and pipeline machines, special purpose and experimental systems, scalable parallel architectures, and associated mass storage systems, input/output units, and systems software.Superconducting Magnets
An electromagnet whose coils are made of a type II superconductor with a high transition temperature and extremely high critical field.Supersonic
A range of speed between about one and five times the speed of sound in air.Telemetry
Transmitting the readings of instruments to a remote location by means of wires or radio waves.Test Cell
A horizontal test stand for an air-breathing or rocket engine surrounded on three sides by a shelter providing protection from weather and lim ited protection from an accidental explosion.Test Chamber
The test section of a wind tunnel.GAO/NSIAD-92-5 -- page 149
Thrust
The force exerted in any direction by a fluid jet.Torch Igniter Module
A self-igniting flame device used to ignite the fuel-air mixture in a com bustor region of a ramjet-type engine.Transonic
A range of speed between about 0.8 and 1.2 times the speed of sound in air.Turbofan
An air-breathing engine, similar to a turbojet, in which a portion of the compressed air bypasses the combustor and turbine. The remaining compressed air enters the combustor. The compressed air is then mixed with the fuel, burned, and expanded through the turbine. The power from the turbine is used to drive the compressor. Hot gases exiting from the tur bine and compressed bypass air can be mixed and expanded through an exhaust nozzle or separate exhaust nozzles to produce the thrust. When fuel is added and burned downstream of the turbine, a turbofan engine can operate efficiently from Mach 0 to 2.5.Turbofan-Ramjet
An air-breathing engine consisting of a turbofan engine mounted within a ramjet duct. At low speeds, the engine operates as a turbofan. Between Mach 1 and 2, the ramburner begins to operate, providing a greater portion of the thrust until the turbofan is shut down at speeds of approximately Mach 3. At that point, the ramjet provides all of the thrust. During all operating modes, the high-temperature combustion gases are expanded through the exhaust nozzle to produce the thrust. A turbofan ramjet engine provides the efficiency of a turbofan during takeoff and low-speed flight and the efficiency and high thrust of a ramjet during high-speed flight (up to Mach 6).Turbojet
An air-breathing engine in which air is compressed by a compressor before it enters a combustor. Air is then mixed with fuel, burned, and expanded through a turbine. The power from the turbine is used to drive the compressor. Hot gases exiting from the turbine are expanded through an exhaust nozzle to produce thrust. When fuel is added and burned downstream of the turbine, a turbojet engine can operate efficiently from Mach 0 to 3.GAO/NSIAD-92-5 -- page 150
Turbojet-Ramjet
An air-breathing engine consisting of a turbojet engine mounted within a ramjet duct. At low speeds, the engine operates as a turbojet. Between Mach 1 and 2, the ramburner begins to operate and provides a greater portion of the thrust until speeds of approximately Mach 3.5, when the turbojet is shut down and the ramjet provides all of the thrust. During all operating modes, high-temperature combustion gases are expanded through the exhaust nozzle to produce thrust. A turbojet-ramjet engine provides the efficiency of a turbojet during takeoff and low-speed flight and the efficiency and high thrust of a ramjet during high-speed flight (up to Mach 6).Turboramjet
An air-breathing engine consisting of a turbojet engine mounted within a ramjet duct. Intake air is compressed at low speeds by a compressor driven by a turbine and at high speeds by the ram effect of the engine moving through the air. At low speeds, the engine operates as a turbojet. Between Mach 1 and 2, the ramburner begins to operate and provides a greater portion of the thrust until speeds of approximately Mach 3.5, when the turbojet is shut down and the ramjet provides all of the thrust. During all operating modes, high-temperature combustion gases are expanded through the exhaust nozzle to produce thrust. Like the turbojet-ramjet, the turboramjet engine provides the efficiency of a turbojet during takeoff and low-speed flight and the efficiency and high thrust of a ramjet during high-speed flight (up to Mach 6). A turboramjet engine is the same as a turbofan-ramjet engine or turbojet-ramjet engine.Turborocket
A combined-cycle engine in which hot gases from a rocket operating with excess fuel are used to energize a turbine, which, in turn, drives a compressor for operation at speeds of Mach 0 to approximately 5. Gases exiting the turbine are mixed with air from the compressor, which burns the excess fuel. The resulting high-temperature gases are expanded through an exhaust nozzle, causing the thrust. A turborocket engine significantly reduces the need to carry oxidizer, thus reducing the weight of propellant needed to accelerate a vehicle to high Mach numbers and altitudes. A turborocket engine is a variant of an air-turboramjet engine.Vacuum Test Chamber
A pressure vessel, typically spherical or cylindrical, that can be pumped down to a near vacuum. A vacuum test chamber can be used in engine testing to provide a low-pressure reservoir for receiving discharged engine exhaust.GAO/NSIAD-92-5 -- page 151
Wind Tunnel
A ground test facility used to test flight characteristics of an aircraft by directing a controlled stream of air around a scale model and measuring the results with attached instrumentation.|
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