Thrust-to-weight ratio is, as its name suggests, the ratio of instantaneous thrust to weight (where weight means weight at the Earth’s surface). It is a dimensionless parameter characteristic of rockets and jet engines, and of vehicles propelled by such engines (typically space launch vehicles and jet aircraft). It is used as a figure of merit for quantitative comparison of engine or vehicle design. Thrust is a reaction force described quantitatively by Newtons Second and Third Laws. ... For other uses, see Weight (disambiguation). ... This article is about Earth as a planet. ... This article is about vehicles powered by rocket engines. ... A Pratt and Whitney turbofan engine for the F-15 Eagle is tested at Robins Air Force Base, Georgia, USA. The tunnel behind the engine muffles noise and allows exhaust to escape. ... A Saturn V launch vehicle sends Apollo 15 on its way to the moon. ... Flying machine redirects here. ... A Figure of merit is a quantity used to characterize the performance of a device relative to other devices of the same type. ...

The value is larger for an engine than for a whole launch vehicle; the engine thrust-weight is of use since it determines the maximum acceleration that any vehicle using that engine could theoretically achieve with minimum propellant and structure attached.

For a takeoff using pure thrust and no wings, the thrust-weight ratio for the vehicle has to be more than one (for launch from the Earth's surface, for launch from the Moon it only needs to be more than 0.1654). In general, the thrust-to-weight ratio is numerically equal to the g-force that the vehicle can pull, provided the g-force exceeds local gravity then takeoff can occur. This article is about Earths moon. ... The term g force or gee force refers to the symbol g, the force of acceleration due to gravity at the earths surface. ...

Many factors affect a thrust-to-weight ratio, and it typically varies slightly over the flight. For valid comparison, thrust should be measured under controlled conditions. The main factors that affect thrust include freestream air temperature, pressure, density, and composition. Depending on the engine or vehicle under consideration, the actual performance will often be affected by progressive fuel consumption (causing a rise in thrust-weight ratio), buoyancy, and local gravitational field strength. For other uses, see Temperature (disambiguation). ... This article is about pressure in the physical sciences. ... For other uses, see Density (disambiguation). ... In physics, buoyancy is the upward force on an object produced by the surrounding fluid (i. ... ʐIn physics, the field strength of a field is the magnitude of its vector (spatial) value. ...

Example

The Russian-made RD-180 rocket engine (which powers Lockheed Martin’s Atlas V) produces 3,820 kN of sea-level thrust and has a dry mass of 5,307 kg. Using the Earth surface gravitational field strength of 9.80665 m/s², the sea-level thrust-to-weight ratio is computed as follows: (1 kN = 1000 N = 1000 kg⋅m/s²) RD-180 Engine The RD-180 is a dual-combustion chamber, dual nozzle, Russian-developed rocket engine which is essentially a cut-down version of a larger Russian engine with four combustion chambers, the RD-170 (rocket engine). ... Lockheed/BAE/Northrop F-35 Lockheed Trident missile C-130 Hercules; in production since the 1950s, now as the C-130J Lockheed Martin (NYSE: LMT) is an aerospace manufacturer formed in 1995 by the merger of Lockheed Corporation with Martin Marietta. ... Launch of the Mars Reconnaissance Orbiter, 7:43:00 a. ...