decelerators

Decelerators are devices or systems designed to reduce the speed of a moving object. They can act through friction, drag, or energy conversion, and are used in transportation, aerospace, industrial machinery, and experimental physics to control motion and protect people and equipment.

Mechanical braking uses friction to convert kinetic energy into heat. In road vehicles, pads, discs, or shoes pressed by hydraulics or pneumatics slow rotation of wheels. Regenerative braking captures some energy by feeding it back to a power source.

Aerodynamic deceleration relies on increased drag. Parachutes, airbrakes, and spoilers add surface area or deployable fabrics to slow high-speed craft, aircraft, or projectiles. In atmospheric reentry, vehicles use a combination of drag devices and heat shields to reduce speed before landing.

In fluids, deceleration arises from drag forces acting on a body moving through a medium, or from resistive devices such as water brakes used in ships and amusement rides.

In particle physics, decelerators slow charged particle beams for experiments or injection into storage rings. Radio-frequency cavities, dielectric structures, and magnetic fields extract energy from the beam, reducing its velocity while preserving beam quality.

Performance is described by deceleration magnitude (often expressed as g-forces), stopping distance, and energy absorption. Designs address heat dissipation, wear, control reliability, and safety features such as anti-lock systems and fail-safes.

Common applications include automobile braking systems, aviation drag devices, rail brakes, parachutes on skydivers and spacecraft, and various laboratory decelerators used in accelerator facilities.

Decelerators are complementary to accelerators, providing controlled slowing in addition to propulsion and acceleration mechanisms.