Thrust-to-weight ratio is a dimensionless ratio of thrust to weight of a rocket, jet engine, propeller engine, or a vehicle propelled by such an engine that is an indicator of the performance of the engine or vehicle.
The instantaneous thrust-to-weight ratio of a vehicle varies continually during operation due to progressive consumption of fuel or propellant and in some cases a gravity gradient. The thrust-to-weight ratio based on initial thrust and weight is often published and used as a figure of merit for quantitative comparison of a vehicle's initial performance.
https://en.wikipedia.org/wiki/Thrust-to-weight_ratio
In aerodynamics, the lift-to-drag ratio (or L/D ratio) is the amount of lift generated by a wing or vehicle, divided by the aerodynamic drag it creates by moving through air. A greater or more favorable L/D ratio is typically one of the major goals of aircraft design; since a particular aircraft's required lift is set by its weight, delivering that lift with lower drag results directly in better fuel economy in aircraft, climb performance, and glide ratio.
The term is calculated for any particular airspeed by measuring the lift generated, then dividing by the drag at that speed. These vary with speed, so the results are typically plotted on a 2-dimensional graph. In almost all cases the graph forms a U-shape, due to the two main components of drag.
Lift-to-drag ratios can be determined by flight test, by calculation or by testing in a wind tunnel.[citation needed]
https://en.wikipedia.org/wiki/Lift-to-drag_ratio
Thrust-specific fuel consumption (TSFC) is the fuel efficiency of an engine design with respect to thrust output. TSFC may also be thought of as fuel consumption (grams/second) per unit of thrust (kilonewtons, or kN). It is thus thrust-specific, meaning that the fuel consumption is divided by the thrust.
TSFC or SFC for thrust engines (e.g. turbojets, turbofans, ramjets, rocket engines, etc.) is the mass of fuel needed to provide the net thrust for a given period e.g. lb/(h·lbf) (pounds of fuel per hour-pound of thrust) or g/(s·kN) (grams of fuel per second-kilonewton). Mass of fuel is used, rather than volume (gallons or litres) for the fuel measure, since it is independent of temperature.[1]
Specific fuel consumption of air-breathing jet engines at their maximum efficiency is more or less proportional to exhaust speed. The fuel consumption per mile or per kilometre is a more appropriate comparison for aircraft that travel at very different speeds.[citation needed] There also exists power-specific fuel consumption, which equals the thrust-specific fuel consumption divided by speed. It can have units of pounds per hour per horsepower.
This figure is inversely proportional to specific impulse.
https://en.wikipedia.org/wiki/Thrust-specific_fuel_consumption
In aeronautical engineering, overall pressure ratio, or overall compression ratio, is the ratio of the stagnation pressure as measured at the front and rear of the compressor of a gas turbine engine. The terms compression ratio and pressure ratio are used interchangeably.[1] Overall compression ratio also means the overall cycle pressure ratio which includes intake ram.[2]
https://en.wikipedia.org/wiki/Overall_pressure_ratio
In fluid dynamics, stagnation pressure (or pitot pressure) is the static pressure at a stagnation point in a fluid flow.[1] At a stagnation point the fluid velocity is zero. In an incompressible flow, stagnation pressure is equal to the sum of the free-stream static pressure and the free-stream dynamic pressure.[2]
Stagnation pressure is sometimes referred to as pitot pressure because it is measured using a pitot tube.
Compressible flow[edit]
Stagnation pressure is the static pressure a gas retains when brought to rest isentropically from Mach number M.[6]
or, assuming an isentropic process, the stagnation pressure can be calculated from the ratio of stagnation temperature to static temperature:
where:
- is the stagnation pressure
- is the static pressure
- is the stagnation temperature
- is the static temperature
- is the ratio of specific heats
The above derivation holds only for the case when the gas is assumed to be calorically perfect (specific heats and the ratio of the specific heats are assumed to be constant with temperature).
https://en.wikipedia.org/wiki/Stagnation_pressure
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