Engineering

Rocket engine nozzle: design, operation, types, and history Rocket engine nozzle Overview of rocket engine nozzles: purpose, main parts, operating physics (de Laval), common configurations (bell, conical, aerospike), materials, cooling, and historical notes.

Rod (unit of length) Rod (unit) A traditional English unit of length also called a perch or pole, equal to 16.5 feet (5.5 yards, about 5.03 m). Used historically in land measurement and still found in some specia…

Rope: types, construction, history, uses and safety Rope Comprehensive overview of rope: materials and construction, historical development, common uses, care and safety, and distinctions between rope types.

Rotor: rotating components in machines, engineering and culture Rotor A rotor is the rotating element in a wide range of machines and devices. This article explains common types, design considerations, historical notes, applications and other meaning…

Rotor (electric machine) Rotor (electric) The rotor is the rotating part of an electric motor or generator. It works with the stator’s magnetic field to produce motion or electrical power.

Rubber band A rubber band is a flexible loop of elastic material used to hold or secure objects together. This article explains its composition, history, common uses, varieties, safety concern…

Rudder A rudder is a movable control surface attached to the stern or tail of a vessel or aircraft, used to steer by redirecting flow of water or air; it appears in many forms across ship…

San Onofre Nuclear Generating Station Coastal nuclear power complex in southern California, historically housing three reactors; known for its role in regional electricity supply and its 2012–2013 shutdown and ongoing…

Sandpaper: composition, grades, history, uses, and safety Sandpaper Sandpaper is a sheet or backing coated with abrasive particles used for smoothing, shaping, and finishing surfaces in woodworking, metalwork and other trades.

Sandwich panel (composite building panel) Sandwich panel Lightweight structural panels formed from two thin facings bonded to a lightweight core. Used for cladding, insulation and stiff, low-weight structural elements in buildings, trans…

Scram: Emergency shutdown of a nuclear reactor Scram A scram is the rapid shutdown of a nuclear reactor, achieved by inserting control rods or using chemical poisons. It stops the chain reaction but still requires cooling to remove d…

Scramjet (supersonic combustion ramjet) Scramjet An air‑breathing engine that burns fuel in supersonic airflow to propel vehicles at hypersonic speeds; largely experimental and used in research and defense projects rather than co…

Screw (fastener): types, parts, history and common uses Screw A screw is a threaded fastener used to join materials; this article explains its parts, materials, common types, history, measurement, and safe use.

Screw thread A screw thread is a helical ridge used to convert rotation to linear motion, join parts, and provide mechanical advantage. This article explains forms, parts, manufacture, uses, an…

Sealed lead–acid battery (gel cell and VRLA) Sealed lead acid battery A sealed lead–acid (SLA) battery contains immobilized sulfuric acid and is a type of valve-regulated lead–acid (VRLA) battery used for backup power, mobility, and portable equipmen…

Seismic analysis: methods, history, and applications in earthquake engineering Seismic analysis Comprehensive overview of seismic analysis: goals, principal methods (response spectra, time-history), history, uses in design and retrofit, limitations and practical guidance for…

Seismic load: definition, types, assessment, and design considerations Seismic load Seismic load refers to forces and motions applied to structures by earthquakes, ground motion, tsunamis or adjacent interaction. Covers types, assessment methods, design implicatio…

Seismic performance of buildings and structures Seismic performance How well a building or structure maintains safety and function during and after earthquakes, including concepts, evaluation methods, design strategies and historical context.

Selectivity (electrical protection) Selectivity (electronic) Selectivity (also called discrimination) is the coordination of protective devices so only the device nearest a fault operates, minimizing outage and damage. It uses time‑current c…

Sengkang LRT Line Automated light rail line serving Sengkang New Town in Singapore. 10.7 km long, opened 18 January 2003, using Mitsubishi Crystal Movers to provide local circulator and feeder servi…

Series and Parallel Circuits: Definitions, Properties, and Applications Series and parallel circuits Overview of series and parallel electrical circuits, their defining rules for voltage, current and resistance, typical applications, advantages and disadvantages, and how they comb…

Sewage treatment: processes, history, and environmental importance Sewage treatment Sewage treatment removes contaminants from wastewater from buildings and industry to protect public health and the environment. Processes include primary, secondary, and tertiary s…

Sewer systems: purpose, types, operation and maintenance Sewer Overview of sewer systems: their function, main components, historical development, types (combined/sanitary), maintenance, treatment stages and environmental considerations.

Shake-table (earthquake simulation device) Shake-table A shake-table is an experimental platform that reproduces ground motion to test structures and components under seismic loading, used to study damage, validate designs, and develop…

Sheave (mechanical): definition, parts, history and uses Sheave (mechanical) A sheave is a grooved wheel or roller that guides belts, ropes or cables; used alone or in blocks to change direction, support loads and form pulleys in machines and rigging.

Sheet A sheet is a thin, flat form of material or concept found in textiles, paper, metal, glass, music, sailing, computing and glaciology; this entry describes types, manufacture, prope…

Sheet bend A simple, reliable bend knot for joining two ropes, especially of unequal thickness; widely used in sailing, camping and general ropework.

Simple machine (basic mechanical devices) Simple machine A simple machine alters the direction, magnitude, or point of application of a force to make work easier. The six classical types, their mechanics, history, examples and how they f…

Smith (metalwork) A smith (metalsmith) shapes and joins metals by heat, force and tools. Historically essential for tools, farm implements and weapons; today smithing continues in repair, bespoke an…

Sodium vapor lamp Gas-discharge lamps using excited sodium to produce very efficient yellow/orange light. Includes low-pressure and high-pressure types, common in street lighting, with distinct spec…

Software architecture High-level structure and organization of software systems: components, interactions, styles, documentation, quality goals, trade-offs, and its role in development and maintenance.

Software engineering: principles, lifecycle, and roles Software engineering A concise guide to software engineering: what it is, core practices, lifecycle stages, quality attributes, history, typical roles and common applications.

Soldering: techniques, materials, tools and applications Soldering Soldering is a metal-joining process that uses a low‑melting filler (solder) and flux. This article explains methods, materials, tools, history, common applications, differences fr…

Source code: definition, structure, execution, history and licensing Source code Source code is the human-readable text of a computer program. This article explains what source code is, how it is organized, how it is executed, historical context, common uses, a…

Speculative execution Speculative execution: a computing technique where code paths are executed before they are known to be needed. Used to improve processor performance; has trade-offs including compl…

Spin welding (rotary friction welding) for thermoplastics Spin welding Spin welding is a friction-based joining method for thermoplastic parts that uses rotation and axial pressure to generate heat, melt the interface, and form a solid bond without ad…

Spindle Spindle: overview of rotating shafts in machinery, textile spinning tools, mitotic microtubule assemblies, and neural/sleep-related phenomena; types, components, history, uses and…

Spring scale (spring balance) Spring scale A mechanical instrument that measures force or weight by the extension of a spring; used for weighing, force measurement and simple dynamometry in science, industry and everyday li…

Standard (measurement, compatibility, and protocol) Standard A standard is an agreed reference that enables consistent measurement, compatibility, safety, or quality across products, processes, systems and communications.

Staple (fastener): design, types, history and common uses Staple (fastener) A staple is a small metal fastener used to join sheets or attach materials. This article explains its design, types, historical development, common applications and practical consi…

Static mixer A static mixer is an inline device with stationary internal elements that blends fluids or gases by repeatedly dividing and recombining flow; used for continuous mixing in industry…

Statistical Process Control (SPC) Statistical process control Statistical Process Control uses statistical methods and visual tools to monitor, control, and improve process stability and product quality in manufacturing and services.

Stator: the stationary element of rotary electrical machines Stator A stator is the stationary component of an electric motor or generator. It supports windings or magnets, provides the magnetic field or armature, and works with the rotor to conver…

Low-observable aircraft: design principles, materials, and operational limits Stealth aircraft Overview of low-observable aircraft: principles of stealth shaping, radar‑absorbent materials and multispectral signature control, plus operational trade‑offs, maintenance challeng…

Steam engine: principles, history, design, and uses Steam engine A clear, concise overview of the steam engine: how it works, key components, historical development, major uses and variants, and why it shaped industrial technology.

Steam turbine: principles, design, history and applications Steam turbine A steam turbine is a rotary heat engine that converts pressurized steam energy into mechanical work. Used widely for electricity generation, marine propulsion and industrial drives…

Steel — the iron–carbon alloy and its varieties Steel Steel is an alloy of iron and carbon, often with other elements added. It combines strength, ductility, and versatility, and underpins construction, transport, tools, and many indu…

Steel Dragon 2000 Steel Dragon 2000 is a steel roller coaster at Nagashima Spa Land in Mie Prefecture, Japan, notable as the world's longest coaster and a landmark attraction since its 2000 opening.